Dual fuel engine system and method for controlling a dual fuel engine system

Abstract

A method for controlling a dual fuel engine system includes estimating a total indicated engine load, where the total indicated engine load is based on a sum of a measured engine power and a power loss estimate. The method further includes determining a total fueling amount based on the engine speed and the total indicated engine load, wherein the total fueling amount includes a fueling amount for the first fuel and a fueling amount for the second fuel. The method also includes controlling the dual fuel engine system using the total fuel charge.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Patent Applications No. 17 / 944,910, No. 17 / 944,900, and No. 17 / 944,905, filed on September 14, 2022, the entire contents of each of which are incorporated herein by reference.

[0003] Background

[0004] This disclosure generally relates to methods for controlling a dual - fuel engine system.

[0005] Typically, a dual - fuel engine system can include an original equipment manufacturer (OEM) machine control system, an engine control system or module (ECM) operably coupled to the OEM's base engine, and a gas control system operably coupled to both the OEM machine control system and the base engine control system.

[0006] Summary

[0007] One aspect of the present disclosure relates to a method for controlling a dual - fuel engine system. The method includes estimating a total indicated engine load, the total indicated engine load being based on the sum of a measured engine power and an estimated power loss. The method also includes determining a total fueling amount based on the engine speed and the total indicated engine load, the total fueling amount including a fueling amount for a first fuel and a fueling amount for a second fuel. The method also includes using the total fueling amount to control the dual - fuel engine system.

[0008] Another aspect of the present disclosure relates to a method for controlling a dual - fuel engine system. The method includes estimating a total indicated engine load, wherein the total indicated engine load is based on the sum of a measured engine power, an estimated friction power, and an estimated accessory power. The method also includes determining a total fueling amount from a first look - up table, wherein the look - up table is based on the engine speed and the total indicated engine load. The method also includes determining at least one updated total fueling amount based on the total fueling amount and an operating state of a dual - fuel mode switch within the dual - fuel engine system. The method also includes determining a control input for at least one actuator within the dual - fuel engine system, wherein the control input is based on selecting a corresponding set of look - up tables associated with the at least one actuator, wherein the set of look - up tables includes a plurality of look - up tables, and wherein each look - up table in the plurality of look - up tables is based on the engine speed and at least one updated total fueling amount.

[0009] Another aspect of the present disclosure relates to a dual-fuel engine system. The system includes an internal combustion engine operable in a dual-fuel mode, at least one actuator operably coupled to the internal combustion engine, and at least one controller in communication with the internal combustion engine and the at least one actuator. The at least one controller is configured to perform the following: receive a first input corresponding to engine speed and a second input corresponding to measured engine power, calculate a power loss estimate, determine a total fuel injection amount based on the measured engine power and the power loss estimate, determine a first fuel command for a first fuel associated with the internal combustion engine based at least on a calculated governor command and the power loss estimate, and determine at least one updated total fuel injection amount based on the total fuel injection amount and the first fuel command for the first fuel. The at least one controller is further configured to select a set of look-up tables associated with the at least one actuator based on a second fuel substitution rate associated with the internal combustion engine, wherein the set of look-up tables is based on engine speed and at least one updated total fuel injection amount, and send an input to the at least one actuator based on the set of look-up tables.

[0010] One aspect of the present disclosure relates to a method for controlling a dual-fuel engine system configured to operate using a first fuel and a second fuel. The method includes determining an amount of friction power loss of an internal combustion engine of the dual-fuel engine system, wherein the amount of friction power loss is based on the engine speed of the internal combustion engine and a friction torque estimate. The method further includes determining an amount of accessory power loss of the power of the internal combustion engine, wherein the amount of accessory power loss is based on the engine speed and an accessory torque estimate. The method further includes estimating a net engine power amount based on the amount of accessory power loss of the internal combustion engine and a brake power amount. The method further includes estimating an indicated power of the first fuel, and estimating a first indicated engine power and a first power of the second fuel based on the estimated net engine power.

[0011] Another aspect of the present disclosure relates to a method for controlling a dual-fuel engine system configured to operate using a first fuel and a second fuel. The method includes estimating a net engine power amount of an internal combustion engine of the dual-fuel engine system based on an amount of accessory power loss of the power of the internal combustion engine and an estimated brake power of the internal combustion engine. The method further includes determining a first total indicated engine power based on the net engine power of the internal combustion engine and the amount of friction power loss. The method further includes determining a lower heating value (LHV) of a second fuel within the internal combustion engine, wherein the LHV is a measured value or an estimated value. The method further includes estimating a second total indicated engine power based on the LHV, an estimated total flow rate of the second fuel, and an estimated power of the first fuel. The method further includes activating at least one engine protection measure based on a difference between the first total indicated engine power and the second total indicated engine power being greater than a predetermined threshold.

[0012] Another aspect of the present disclosure relates to a dual - fuel engine system operable in a dual - fuel mode. The system includes at least one controller in communication with an internal combustion engine, where the internal combustion engine is configured to operate using a first fuel and a second fuel. The at least one controller is configured to: receive an input corresponding to the engine speed of the internal combustion engine, receive an input for calculating a net engine power estimate, and calculate a percentage rated power of the internal combustion engine based on the engine speed and the net engine power estimate. The at least one controller is further configured to determine a base substitution rate target for the second fuel of the internal combustion engine based on the engine speed, the percentage rated power, the intake manifold temperature within the internal combustion engine, and an estimate of a knock propensity index within the internal combustion engine. The at least one controller is further configured to determine a second fuel power target for the internal combustion engine based on the base substitution rate target of the second fuel and a first indicated engine power estimate.

[0013] One aspect of the present disclosure relates to a method for controlling a dual - fuel engine system configured to operate using a first fuel and a second fuel. The method includes determining a flow target for a second fuel of an internal combustion engine of the dual - fuel engine system, where the flow target for the second fuel is based on a power target for the second fuel of the internal combustion engine, an estimate of the thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine. The method further includes adjusting the flow target for the second fuel based on at least one of a measured second fuel temperature or a measured second fuel injector pressure. The method further includes determining at least one base second fuel injector command based on the adjusted flow target for the second fuel, an estimate of a second fuel substitution rate, and a second fuel substitution rate target. The method further includes determining a second fuel injector command for at least one engine bank based on the at least one base second fuel injector command.

[0014] Another aspect of the present disclosure relates to a dual - fuel engine system for an internal combustion engine, the dual - fuel engine system being configured to operate using a first fuel and a second fuel. The dual - fuel engine system includes at least one injector for the second fuel, the at least one injector being operably coupled to the internal combustion engine, which has a left bank and a right bank, wherein the internal combustion engine can operate in a dual - fuel mode. The dual - fuel engine system further includes at least one proportional - integral - derivative (PID) controller, the at least one proportional - integral - derivative (PID) controller being communicatively coupled to the internal combustion engine and at least one injector for the second fuel. The at least one PID controller is configured to receive a feed - forward input, an estimated second - fuel substitution rate, and a second - fuel substitution - rate target. The at least one PID controller is further configured to output at least one injector command for the second fuel based on the feed - forward input and to bias the at least one injector command for the second fuel to each of the left bank and the right bank based on an exhaust - temperature difference associated with each of the right bank and the left bank.

[0015] Another aspect of the present disclosure relates to a dual - fuel engine system that can operate in a dual - fuel mode. The dual - fuel engine system includes an internal combustion engine having at least one engine bank, wherein the internal combustion engine is configured to operate using a first fuel and a second fuel. The dual - fuel engine system further includes at least one injector for the second fuel operably coupled to the internal combustion engine, and at least one controller communicatively coupled to the internal combustion engine and at least one injector for the second fuel. The at least one controller is configured to determine a second - fuel flow target for the internal combustion engine, wherein the second - fuel flow target is based on a second - fuel power target of the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine. The at least one controller is further configured to adjust the second - fuel flow target based on at least one of a measured second - fuel temperature or a measured second - fuel injector pressure to determine an adjusted second - fuel flow target for the dual - fuel mode. The at least one controller is further configured to determine at least one basic second - fuel injector command based on the adjusted second - fuel flow target, an estimated substitution rate of the second fuel, and a second - fuel substitution - rate target. The at least one controller is further configured to determine an injector command for the second fuel for at least one engine bank based on the at least one basic second - fuel injector command.

[0016] This summary is merely illustrative and should not be considered restrictive. Brief Description of the Drawings

[0018] The present disclosure will be more fully understood from the following detailed description in conjunction with the accompanying drawings, in which like reference numerals refer to like elements, wherein:

[0019] Figure 1It is a block diagram of a dual-fuel engine system according to an exemplary embodiment.

[0020] Figure 2 is according to an exemplary embodiment Figure 1 of a control system of a dual-fuel engine system.

[0021] Figure 3 is a flowchart showing a method performed by a Figure 2 control system according to an exemplary embodiment.

[0022] Figure 4 is a flowchart showing a method performed by a Figure 2 control system according to an exemplary embodiment.

[0023] Figure 5 is a flowchart showing a method performed by a Figure 2 control system according to an exemplary embodiment.

[0024] Figure 6 is a flowchart showing a method performed by a Figure 2 control system according to an exemplary embodiment.

[0025] Figure 7 is a flowchart showing a method performed by a Figure 2 control system according to an exemplary embodiment.

[0026] Figure 8 is a flowchart showing a method performed by a Figure 2 control system according to an exemplary embodiment.

[0027] Figure 9 is a flowchart showing a method performed by a Figure 2 control system according to an exemplary embodiment.

[0028] Detailed description

[0029] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, like reference symbols generally identify like components unless the context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized and other changes may be made without departing from the spirit or scope of the subject matter described herein. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the figures, can be arranged, substituted, combined, and designed in a variety of different configurations, all of which are contemplated and form a part of the present disclosure.

[0030] The present disclosure relates at least in part to systems and methods for providing reduced operating costs, improved efficiency, and / or improved performance of a dual fuel engine system. In some embodiments, such systems and methods allow meeting target emission levels. In some embodiments, the schemes for controlling the dual fuel system are adjustable to simplify the interfacing between, for example, a diesel engine ECM, a gas controller, and an OEM controller. In various embodiments, the dual fuel engine system (and associated operating methods) are customized to maximize the use of the cheaper gaseous fuel and minimize the use of diesel fuel while meeting performance requirements and emission requirements and maintaining robust engine protection. In particular, to meet Tier 4 emission regulations with a dual fuel engine system, precise and robust control of the dual fuel engine system is required. Such precise and robust control includes, but is not limited to, control of: a gaseous or liquid fuel system, a second fuel type system (e.g., diesel, gas, etc.), and an aftertreatment system included within the dual fuel engine system. The present disclosure outlines a system and method for precise and robust control of a dual fuel engine system, including accurately determining (e.g., by measurement or estimation) a plurality of engine parameters (e.g., brake power, friction power, accessory power, first fuel (e.g., diesel, gas, liquid fuel) power, second fuel (e.g., gas, liquid) power, second fuel (e.g., gas, liquid) substitution rate, fuel quality parameters associated with the second fuel (e.g., methane number), LHV, second fuel (e.g., gas, liquid) temperature, second fuel (e.g., gas, liquid) pressure, knock intensity, exhaust temperature, etc.), and using the determined parameters as inputs for determining appropriate commands for one or more actuators within the dual fuel engine system. The systems and methods described herein are applicable to new engine configurations or for retrofitting to existing Tier 4 diesel engine systems. Advantageously, the systems and methods described herein are lower in cost and complexity compared to typical port gas injection or cylinder pressure sensing systems.

[0031] Reference Figure 1, which shows a block diagram of a dual - fuel engine system 10 according to an exemplary embodiment. The dual - fuel engine system 10 is configured as an engine having a dual - fuel operation mode, and the engine is configured to operate using two different fuels. The engine can be configured to operate using a first fuel and a second fuel, where the first fuel and the second fuel have different properties and / or chemical compositions. These characteristics can include auto - ignition temperature, flame speed, etc. The fuels can include, for example, diesel and natural gas. For example, the first fuel can be diesel fuel. The second fuel can be, for example, natural gas, e - fuel, or liquid biofuel. The liquid biofuel can be, for example, methanol and / or ethanol. The first fuel or the second fuel can be any one of high cetane number fuels, such as diesel, gas - to - liquid (GTL) diesel, heavy fuel oil (HFO), low - sulfur fuel oil (LFSO), hydrotreated vegetable oil (HVO), marine gas oil (MGO), renewable diesel, biodiesel, paraffin diesel, dimethyl ether (DME), F - 76 fuel, F - 34 fuel, jet A fuel, JP - 4 fuel, JP - 8 fuel, or oxymethylene ether (OME), or low cetane number fuels (e.g., high octane number fuels, high methane number fuels). The low cetane number fuels can be natural gas, hydrogen, ethane, propane, butane, syngas, ammonia, methanol, ethanol, or gasoline. The first fuel and / or the second fuel can optionally be a mixture of fuels. It should be recognized that the foregoing are merely examples of fuels and do not exclude other types of first and second fuels. In various embodiments, the dual - fuel engine system 10 is configured for one or more oil and gas production applications (e.g., land - based oil and / or gas drilling and hydraulic fracturing).

[0032] As Figure 1As shown, the dual-fuel engine system includes an internal combustion engine 20, which is operably coupled to a control system 11 via at least one controller 18. The control system 11, which includes a machine control system (OEM system) 12, a first fuel control system 14, and a second fuel control system 16, is configured to send one or more inputs to the controller 18, whereupon the controller 18 then controls the internal combustion engine 20. In various embodiments, the first fuel control system 14 and its components are configured to operate using a first fuel. In other embodiments, the second fuel control system 16 and its components are configured to operate using a second fuel. For example, in various embodiments, the first fuel control system 14 is a diesel control system, and the second fuel control system 16 is a gas control system. In other embodiments, the first fuel control system 14 is a first gas control system, and the second fuel control system 16 is a second gas control system. In still other embodiments, one or both of the first fuel control system 14 and the second fuel control system 16 can be a liquid fuel control system.

[0033] In still other embodiments, the first fuel control system 14 and its components are configured to operate using the second fuel, and the second fuel control system 16 and its components are configured to operate using the first fuel. In still other embodiments, each of the first fuel control system 14 and the second fuel control system 16 and their respective components can selectively operate using the first fuel or the second fuel. In various embodiments, the first fuel control system 14 and the second fuel control system 16 operate cooperatively within the internal combustion engine 20.

[0034] In various embodiments, the controller 18 is configured to include a processor and a non-transitory computer-readable medium (e.g., a memory device) storing computer-readable instructions thereon, which, when executed by the processor, cause the at least one controller 18 to perform one or more operations. In various embodiments, the at least one controller 18 is a computing device (e.g., a microcomputer, a microcontroller, or a microprocessor). In other embodiments, the at least one controller 18 is configured to be part of a data cloud computing system that is configured to receive commands from a user control device and / or a remote computing device.

[0035] The following description generally relates to a system in which a first fuel control system 14 operates using a first fuel and a second fuel control system 16 operates using a second fuel. However, it should be understood that in other embodiments, each of the first fuel control system 14 and the second fuel control system 16 may be selectively configured to operate using the first fuel or the second fuel as described above. The controller 18 is also operatively coupled to at least one second fuel injector 28 (to facilitate injection of the second fuel), at least one second fuel heater 32 configured to heat the second fuel, and at least one actuator 33. In some embodiments, the second fuel injector 28 is a gas injector. In other embodiments, the second fuel injector 28 is a liquid fuel injector. In various embodiments, at least one second fuel heater 32 is a gas heater configured to heat a gas. In some embodiments, at least one second fuel heater 32 is a liquid fuel heater configured to heat a liquid fuel. In other embodiments, the dual-fuel engine system 10 does not include a second fuel heater. In some embodiments, each of the second fuel injector 28, the heater 32, and the actuator 33 is operatively coupled to the internal combustion engine 20. In various embodiments, the second fuel injector 28 is configured to control or facilitate injection of the second fuel (e.g., a gas or a liquid, or a second gas) into the internal combustion engine 20. At least one second fuel heater 32 is configured to adjust the temperature of the second fuel flowing within the internal combustion engine 20. The actuator 33 may include one or more first fuel type (e.g., diesel type or other liquid type, first gas type) actuators, an air handling actuator, a post-treatment actuator, or any other type of actuator within the dual-fuel engine system 10. Thus, during operation, the controller 18 may send one or more inputs to one or more of the internal combustion engine 20, the second fuel injector 28, the heater 32, or the actuator 33 to facilitate a desired operating mode of the dual-fuel engine system 10.

[0036] As shown, the internal combustion engine 20 includes an output shaft 24 and may also include one or more accessories 22. The internal combustion engine 20 also includes at least one manifold 26. In various embodiments, at least one manifold 26 includes, but is not limited to, an intake manifold. The internal combustion engine 20 also includes at least one engine cylinder bank. In some embodiments, at least one engine cylinder bank includes a left bank 30 and a right bank 31. During operation of the dual-fuel engine system 10, the control system 11 may receive one or more inputs from a user and / or one or more sensors within the dual-fuel engine system 10 and control the operation of at least one of the internal combustion engine 20, the second fuel injector 28, or the actuator 33 via the controller 18.

[0037] Figure 2It is a block diagram of a control system 11 of a dual - fuel engine system 10 according to an exemplary embodiment. As shown, the OEM system 12 may include one or more sensors 35, each of the one or more sensors 35 being coupled to one or more corresponding components within the dual - engine system 10. In various embodiments, the one or more sensors 35 may be operatively coupled to or in communication with: a frac (“frac”) pump, an accessory, one or more inlets or outlets of the internal combustion engine 20, or any other component within the dual - fuel engine system 10 (e.g., a cooling fan, a flywheel, a brake, etc.). The OEM system 12 may include one or more processors configured to receive inputs from the sensors 35. In various embodiments, the one or more inputs from the sensors 35 may include a power estimate, a frac pump speed, a frac pump discharge pressure, a dual - fuel mode activation request, or any other input detectable by the one or more sensors 35. As shown, the OEM system 12 is communicatively coupled to each of a first fuel control system 14 and a second fuel control system 16, where the OEM system 12 may output information sensed by the one or more sensors 35 or may receive inputs from the first fuel control system 14 and / or the second fuel control system 16.

[0038] As Figure 2 shown, the first fuel control system 14 includes one or more sensors 40, the one or more sensors 40 being coupled to or disposed adjacent to one or more components within the internal combustion engine 20. In various embodiments, the one or more sensors 40 may be configured to determine (e.g., sense, detect, measure) at least one of the following: engine speed, intake manifold temperature, engine coolant temperature, oil temperature, cooling fan duty cycle, a first fuel (e.g., diesel, a first gas, or other liquid) rate, or the operating state of a dual - fuel mode switch 55. In various embodiments, the dual - fuel mode switch 55 may be configured to switch the operation of the internal combustion engine 20 between a single - fuel mode and a dual - fuel mode. Additionally or alternatively, the one or more sensors 40 may be configured to determine the lower heating value (LHV) of a second fuel (e.g., a gas, a liquid, or a second gas). In still other embodiments, the one or more sensors 40 may be configured to determine one or more parameters indicative of the LHV, which may include but are not limited to the density or the speed of sound of the second fuel (e.g., a gas, a liquid, or a second gas). The first fuel control system 14 also includes an engine governor 50. In various embodiments, the engine governor 50 may include one or more controllers configured to control the speed of the internal combustion engine 20.

[0039] The first fuel (e.g., diesel or first gas) control system 14 also includes a first fuel (e.g., diesel or first gas) engine control system (ECM) and a torque fueling calculations module 45. In various embodiments, the torque fueling calculations module 45 can include one or more processors in communication with one or more reference databases or repositories, where the one or more processors are configured to reference data stored within the databases in order to perform torque calculations related to the internal combustion engine 20. For example, in various embodiments, the torque fueling calculations module 45 is configured to calculate torque based on one or more known parameters. In various embodiments, the module 45 is configured to receive inputs corresponding to: dual fuel mode operating conditions, engine friction parameters, accessory ("parasitic") torque parameters, engine speed, OEM machine power estimates, and engine accessory power estimates (e.g., gas controller, liquid fuel controller, flywheel, etc.). In various embodiments, the one or more reference databases or repositories can include a look-up table 65. In various embodiments, the one or more look-up tables 65 include one or more chi-square tables. In various embodiments, the look-up table 65 can include reference information related to: engine torque, engine speed, engine friction parameters, parasitic parameters or accessory torque parameters, the fuel rate of the first fuel (e.g., diesel or first gas), intake manifold temperature, and / or engine coolant temperature. In various embodiments, the engine friction parameters of the look-up table 65 can be based on at least one of oil temperature or coolant temperature. In some embodiments, the parasitic parameters or torque parameters of the look-up table 65 can be based on the cooling fan duty cycle (i.e., the cooling fan duty cycle of the cooling fan within the internal combustion engine 20). In various embodiments, the module 45 is configured to determine at least one of: the total fueling amount of the first fuel (e.g., diesel or first gas), an approximate equivalent total fueling amount, an equivalent total fueling amount (i.e., the fueling equivalent of a second fuel for the fueling amount of the first fuel), a friction torque estimate, or the first fuel rate.

[0040] The first fuel control system 14 further includes a first fuel (e.g., diesel or first gas) air handling, aftertreatment, and fuel system reference determination and control module 60. In various embodiments, the control module 60 may include at least one processor in communication with a database (e.g., a look-up table) 75. In various embodiments, the database 75 includes a data repository associated with engine speed, fuel fill amount (e.g., equivalent total fuel fill amount, approximate equivalent total fuel fill amount), second fuel (e.g., gas, liquid, or second gas) substitution rate (G / D), compressor inlet density (CID), or any other relevant parameter. Accordingly, one or more processors within the control module 60 are configured to reference the data stored within the database 75 to determine one or more system inputs for at least one of the air handling control system 80, the aftertreatment control system 85, or the first fuel control system 90. In various embodiments, one or more system inputs include, but are not limited to, actuator commands or targets (e.g., set points, operating thresholds, etc.) for at least one of the first fuel air handling control system 80, the aftertreatment control system 85, or the first fuel control system 90.

[0041] As Figure 2As shown, a second fuel (e.g., gas, liquid, or second gas) control system 16 can include one or more sensors 95 that are coupled to or disposed adjacent to one or more components within an internal combustion engine 20. In various embodiments, the one or more sensors 95 can be configured to determine (e.g., sense, detect, measure, etc.) at least one of the following: OEM machine torque, accessory torque, fuel mass parameters associated with the second fuel, second fuel injector pressure, second fuel supply pressure, second fuel flow rate, engine set exhaust temperature, aftertreatment system temperature, LHV, second fuel temperature, dual fuel mode input, knock intensity, G / D, or any other relevant parameter. In various embodiments, the fuel mass parameter associated with the second fuel can be a knock propensity indicator or a knock propensity index. In some embodiments, the knock propensity index (KPI) can be an index that correlates the fuel composition (i.e., of the second fuel) with the knock propensity of an engine (i.e., engine 20) operating with the fuel (i.e., the second fuel). In some embodiments, the KPI can be a methane number (MN), octane number, anti-knock index (AKI), or any other parameter known in the art. In various embodiments, when the second fuel is natural gas, the KPI can be the MN. In various embodiments, when the second fuel is gasoline, the KPI can be the octane number or the AKI. In some embodiments, the engine set exhaust temperature can correspond to the left bank average exhaust temperature and / or the right bank average exhaust temperature. In some embodiments, the bank average exhaust temperature can be calculated by averaging measurements from the individual exhaust port temperature sensors. In some embodiments, the exhaust port temperature sensors can be among at least one of sensors 35, 40, and / or 95. The second fuel control system 16 further includes an OEM machine power and accessory power estimation module 130. In various embodiments, the OEM machine power and accessory power estimation module 130 can include one or more processors that are configured to estimate OEM machine power and / or accessory power based on one or more inputs received by the one or more sensors 95 (and / or from sensors 35, 40). In some embodiments, the accessory power can be the power associated with one or more accessory components and / or the output shaft (e.g., output shaft 24) within the dual fuel engine system 10. In various embodiments, the OEM machine power and accessory power estimation module 130 is configured to receive inputs related to OEM machine power estimates, accessory torque measurements, pump speed, pump discharge pressure, and engine speed, whereupon one or more processors then estimate accessory power estimates based on the input. Similarly, the second fuel control system 16 further includes a KPI (e.g., MN) estimation module 125.In various embodiments, the KPI estimation module 125 can include one or more processors configured to estimate KPIs associated with the internal combustion engine 20 based on one or more inputs received by one or more sensors 95 (and / or from sensors 35, 40). In various embodiments, at least one of sensors 35, 40, or 95 can be assigned or partitioned to any of the different control systems (e.g., OEM system 12, first fuel control system 14, second fuel control system 16) within the dual fuel engine system 10 without changing the overall functionality of the sensor. For example, in various embodiments, sensor 95 can be included within or operably coupled to any of the following: OEM system 12, first fuel control system 14, or second fuel control system 16. Similarly, sensor 35 can be included within or operably coupled to any of the following: OEM system 12, first fuel control system 14, or second fuel control system 16. Sensor 40 can also be included within or operably coupled to any of the following: OEM system 12, first fuel control system 14, or second fuel control system 16.

[0042] The second fuel control system 16 also includes an indicated engine power and second fuel (e.g., gas, liquid, or second gas) estimation module 115. The indicated engine power and second fuel estimation module 115 may include one or more processors configured to receive one or more inputs related to the operation of the dual fuel engine system 10. The indicated engine power and second fuel estimation module 115 may also be configured to use the database 170 and / or a torque-to-power calculation system 175 to determine at least one of the following: a thermal efficiency estimate, a first power estimate of the second fuel (e.g., gas, liquid, or second gas), an indicated power estimate of the first fuel (e.g., diesel, first gas, or other liquid), a net engine power estimate, an intake manifold temperature (e.g., maximum intake manifold temperature), and / or other related parameters. In various embodiments, the database 170 is a look-up table. In some embodiments, the torque-to-power calculation system 175 may be computer logic or include computer logic. In various embodiments, the indicated engine power and second fuel estimation module 115 is configured to receive one or more inputs corresponding to the following: a G / D estimate, a friction torque estimate, an accessory (“parasitic”) torque estimate, a first fuel rate, an engine speed, an intake manifold temperature, and / or an MN estimate. In an embodiment, the KPI estimate is determined by the KPI module 125. Although the terms “torque” and “power” are used in various instances throughout the present disclosure, it should be understood that in various embodiments, torque may be used in place of power, or power may be used in place of torque. For example, it should be understood that power may be calculated based on torque and speed, and vice versa. In still other embodiments, any other parameter indicative of load (e.g., alternatively or in addition to torque and / or power) may be determined and / or used in the operations performed by the control system 11.

[0043] The second fuel control system 16 also includes a second fuel (e.g., gas, liquid, or second gas) LHV and G / D estimation module 120. The LHV and G / D estimation module 120 can include a second fuel (e.g., gas, liquid, or second gas) power selector switch 185, an LHV learning algorithm 180 configured to process one or more received inputs, and a power rationality diagnosis and protection module 190. In various embodiments, the LHV learning algorithm 180 includes a filter (e.g., low-pass filter, moving average filter, etc.) and / or an adaptive learning routine. In some embodiments, one or more inputs are received from a sensor 95. The LHV and G / D estimation module 120 can include one or more processors configured to receive inputs including: an estimated total flow rate of the second fuel (i.e., the second fuel flowing within the engine system 10), a thermal efficiency estimate, an indicated power estimate of the first fuel, and a first indicated engine power estimate. In various embodiments, the one or more processors of the LHV and G / D estimation module 120 can receive inputs from sensors 35, 40, and / or 95. The LHV and G / D estimation module 120 can thereby estimate the G / D amount and the LHV amount associated with the internal combustion engine 20. In various embodiments, the one or more processors within the LHV and G / D estimation module 120 can determine the LHV and G / D estimated amounts by: multiplying the estimated total flow rate of the second fuel by the thermal efficiency estimate and using the result to normalize the first power estimate of the second fuel (e.g., by dividing the first power estimate of the second fuel by the product of the estimated total flow rate of the second fuel and the thermal efficiency estimate) to determine an instantaneous LHV amount. The LHV learning algorithm 180 can process the instantaneous LHV amount to then determine (i.e., learn) the LHV estimate. In various embodiments, the second fuel power selector switch 185 can be configured to receive inputs corresponding to the first power estimate and the second power estimate. In some embodiments, the second fuel power selector switch 185 can also be configured to output a final power estimate of the second fuel using the first power estimate and the second power estimate. In various embodiments, the final power estimate of the second fuel is based on the maximum or minimum of the first power estimate and the second power estimate. In various embodiments, the power rationality diagnosis and protection module 190 can include one or more processors configured to receive inputs corresponding to the first indicated engine power estimate and the second indicated engine power estimate. In some embodiments, the power rationality diagnosis and protection module 190 is further configured to initiate one or more diagnostic operations or engine protection protocols based on and in response to a comparison of one or both of the first indicated engine power estimate and the second indicated engine power estimate with one or more thresholds.

[0044] As shown, the second fuel control system 16 also includes a G / D target automatic compensation module 105. In various embodiments, the G / D target automatic compensation module 105 is configured to adjust or compensate the G / D target of the internal combustion engine 20. The module 105 is configured to receive one or more inputs indicating engine speed, engine load (e.g., power, torque, etc.), intake manifold temperature, and / or KPI estimate. In various embodiments, the module 105 receives one or more inputs from sensors 95, 35, and / or 40. In some embodiments, the one or more inputs received by the module 105 are processed by a speed-based G / D target interpolation unit 135 to determine the G / D target based on the indicated engine speed. In various embodiments, the speed-based G / D target interpolation unit 135 uses data stored in one or more databases 145 to determine the G / D target based on the indicated engine speed. In some embodiments, the one or more databases 145 may include one or more look-up tables. The module 105 also includes a G / D target limiter 140, which includes one or more processors configured to determine a G / D target limit value based on one or more inputs. In various embodiments, the one or more inputs may include engine knock, exhaust temperature, and / or the first fuel quantity. In various embodiments, the exhaust temperature corresponds to the exhaust temperature of the engine set. The second fuel control system 16 may use the G / D target limit value and the first indicated engine power estimate to determine a second fuel power target value.

[0045] As Figure 2 shown, the second fuel control system 16 includes a second fuel injector control module 110, which includes at least one G / D proportional-integral-derivative (PID) controller 150. In various embodiments, the PID controller 150 is configured to receive a feedforward input based on a second fuel flow target compensated for second fuel injector pressure and temperature. In various embodiments, the second fuel injector pressure and temperature may be measured by sensors 95, 35, and / or 40. The controller 150 may also receive a feedback input corresponding to the G / D estimate and a target input corresponding to the G / D controller. In response to receiving the feedforward input, feedback input, and target input, the PID controller 150 may output at least one basic second fuel injector command. In various embodiments, the at least one basic second fuel injector command is associated with at least one engine set second fuel injector command. In some embodiments, the at least one engine set second fuel injector command includes a left group second fuel injector command and / or a right group second fuel injector command.

[0046] The second fuel injector command converter 160 can be operably coupled to the PID controller 150. In various embodiments, the second fuel injector command converter 160 can include one or more processors configured to convert a base second fuel injector command into at least one engine bank second fuel injector command. The second fuel injector control module 110 can also include a bank balance PID controller 155. In various embodiments, the PID controller 155 is configured to receive feedback inputs corresponding to the exhaust temperature difference between the left bank (e.g., left bank 30) and the right bank (e.g., right bank 31) of the internal combustion engine 20, and a target value associated with the exhaust temperature difference. In various embodiments, the target value is zero. In response to the feedback input and the target input, the PID controller 155 is configured to output a left bank correction amount and a right bank correction amount. In various embodiments, one or both of the left bank correction amount and the right bank correction amount can be positive or negative values. The output left bank correction amount and right bank correction amount can each be added to the base second fuel injector command (e.g., the output from the PID 150), and the second fuel injector command converter 160 can convert it into a corresponding left bank second fuel injector command and right bank second fuel injector command. The second fuel flow estimator 165 is configured to receive each of the left bank second fuel injector command and the right bank second fuel injector command, as well as the second fuel pressure and the second fuel temperature. In various embodiments, the second fuel flow estimator 165 can include or be coupled to one or more processors within the module 110. In some embodiments, the second fuel pressure and / or the second fuel temperature are measured by sensors 95, 35, and / or 40. In various embodiments, the second fuel flow estimator 165 is configured to output an estimated total second fuel flow associated with the internal combustion engine 20 based on the left bank second fuel injector command and the right bank second fuel injector command, the second fuel pressure, and the second fuel temperature.

[0047] Finally, as Figure 2As shown, the second fuel control system 16 includes a second fuel heater control module 100. In various embodiments, the second fuel heater control module 100 is configured to control the operating state of at least one heater 32 coupled to the internal combustion engine 20. In various embodiments, the second fuel heater control module 100 includes one or more processors configured to receive one or more inputs from at least one controller 18 and / or from other components within the control system 11. The one or more processors within the second fuel heater control module 100 may be configured to cause the second fuel heater control module 100 to change the operating state of at least one heater 32. In some embodiments, changing the operating state of at least one heater 32 may include adjusting the operating settings of the heater control valve 195 to control the operating state of at least one heater 32. In various embodiments, at least one heater 32 may be an electric heater. In other embodiments, at least one heater 32 may be configured to use engine coolant to provide heat.

[0048] In various implementations, the engine control system 11, including the OEM system 12, the first fuel control system 14, and the second fuel control system 16, may cooperate to control the dual fuel engine system 10. Figure 3 A flowchart is shown that illustrates a method 300 for controlling the dual fuel engine system 10 according to an exemplary embodiment. In operation 305, the engine control system 11 estimates the total engine load (e.g., power, torque, etc.) of the internal combustion engine 20. In various embodiments, the OEM system 12 calculates the total engine load by determining a first amount of load (“primary load”) transmitted through the engine (e.g., via the flywheel, frac pump load, etc.) and broadcasting the determined first load (e.g., via a data link) to the first fuel control system 12 and / or the second fuel control system 16. In embodiments where the OEM system 12 controls the accessory load (“secondary load”, e.g., cooling fan load) within the dual fuel engine system 10, the OEM system 12 may estimate the accessory load, add the accessory load to the first amount of load, and then broadcast (e.g., via a data link) the sum indicating the total engine load to systems 14 and / or 16. In operation 310, the control system 11 may determine the total fuel fill amount for the internal combustion engine 20. Then, in operation 315, the control system 11 may use the total fuel fill amount determined in operation 310 to control the dual fuel engine system 10.

[0049] In various implementations, the control system 11 may estimate the total engine load (e.g., power, torque, etc.). In some implementations, the control system 11 estimates the total engine load in operation 305 by measuring the engine power in operation 320, estimating the power loss in operation 325, and determining the sum of the measured engine power and the estimated power loss in operation 330. In some embodiments, the estimated total engine load may be based on inputs received from the OEM system 12 (e.g., from one or more sensors that may sense at least one of pump discharge pressure, rotational speed, current, or voltage) in response to or indicative of an external load. Then, the OEM system 12 may use the inputs (i.e., the sensed information) to calculate the engine load. Then, the OEM system 12 may output the calculated load value to the second fuel control system 16 and / or the first fuel control system 14 using a data link signal and / or an analog signal (e.g., 4 mA - 20 mA). In some embodiments, the external load corresponds to at least one of a generator or a pump operably coupled to the internal combustion engine 20. In various implementations, the engine control system 11 may determine the total fuel injection amount in operation 310. In some implementations, the control system 11 determines the total fuel injection amount in operation 310 based at least in part on the measured engine speed 335 and the calculated indicated torque demand 340 of the governor. As Figure 4 shown, in various implementations, controlling the dual-fuel engine system 10 in operation 315 may include determining an updated total fuel injection amount in operation 345 and determining at least one control input for at least one actuator 33 in operation 350. In various embodiments, the at least one actuator 33 may be a first fuel system actuator. In various implementations, the updated total fuel injection amount determined in operation 345 may be based on determining the operating state of the dual-fuel mode switch 55 in operation 355. In various embodiments, the updated fuel injection amount determined in operation 345 includes a first updated fuel injection amount and a second updated fuel injection amount. In some embodiments, the first updated fuel injection amount corresponds to the maximum value between the total fuel injection amount and the fuel command for the first fuel (e.g., diesel, first gas, or other liquid). In some embodiments, the second updated total fuel injection amount is determined by subtracting the fuel command for the first fuel from the first overall updated fuel injection amount to determine the first fuel equivalent of the fuel injection amount of the second fuel, and adding the first fuel equivalent fuel injection amount to the second fuel command for the first fuel.

[0050] In various implementations, determining a control input for at least one actuator 33 (in operation 350) can be based on selecting a set of look-up tables. Information in the look-up tables can then be referenced when determining the control input. The look-up tables can include information from one or more of the following: a first fuel ECM and torque fueling calculation module 45, a first fuel air handling, aftertreatment, and fuel system reference determination and control module 60, and / or an engine power and second fuel power estimation module 115. Selection of the set of look-up tables can be performed in operation 360. In various embodiments, selecting the set of look-up tables in operation 360 includes determining a compressor inlet density (CID) of the internal combustion engine 20. In some embodiments, selecting the set of look-up tables in operation 360 additionally or alternatively includes determining a G / D within the internal combustion engine 20. In other embodiments, selecting the set of look-up tables in operation 360 additionally or alternatively includes determining an operating state of a dual fuel mode switch 55. In some embodiments, selecting the set of look-up tables in operation 360 includes selecting at least one of an air handling reference table, an aftertreatment reference table, or a fueling reference table.

[0051] In various implementations, the control system 11 can determine a maximum amount between a total fueling amount (from operation 310) and a first fuel command for a first fuel. In various embodiments, the first fuel command for the first fuel is determined from a first fuel control system 14. In some embodiments, the control system 11 can be configured to determine a second updated total fueling amount. In various embodiments, the second updated fueling amount is determined by: subtracting the first fuel command for the first fuel from a first updated total fueling amount to determine a first fuel equivalent of a fueling amount of a second fuel associated with the internal combustion engine, and adding the first fuel equivalent of the fueling amount of the second fuel to a second fuel command for the first fuel to determine the second updated total fueling amount. In various embodiments, the control system 11 can determine at least one actuator command based on at least one of an engine speed and the first updated total fueling amount or the second updated total fueling amount. In some embodiments, the at least one actuator command can be associated with at least one of an air handling control system 80, an aftertreatment control system 85, a first fuel control system 90, or an actuator within the actuator 33.

[0052] In various embodiments, determining the total fuel fill in operation 310 may include referring to one or more torque - fuel lookup tables. In various embodiments, one or more torque - fuel lookup tables are determined or referred to from the first fuel ECM and the torque fuel fill calculation module 45. In various embodiments, the lookup table may be based on engine speed and an indicated first fuel torque input. In some embodiments, the indicated first fuel torque input may be determined by sensor 35. In various embodiments, the indicated first fuel torque input determined in operation 310 is based on the sum of a friction power estimate and an engine speed torque demand. In some embodiments, the engine speed torque demand corresponds to the difference between the engine speed and a predetermined engine speed target. In various embodiments, in operation 325, the control system 11 determines a power loss estimate. In some embodiments, in operation 325, the control system 11 determines the power loss estimate by: estimating the amount of friction torque associated with the internal combustion engine 20, estimating the accessory torque amount, determining the boost air pumping torque amount, and determining the engine speed. In various embodiments, the engine speed is determined via sensors 35, 40, and / or 95. In various embodiments, the boost air pumping torque amount is an estimate of the pumping loss associated with the dual - fuel engine system 10, where the pumping loss corresponds to the amount of work the engine does to draw air into the engine to facilitate combustion and then expel the combustion products into the atmosphere. In some embodiments, cylinder pressure data determined during engine development may be used to measure the boost air pumping torque. In various embodiments, the data determined during engine development may be used to calibrate a pumping torque virtual sensor (i.e., operatively coupled to the OEM system 12, the first fuel control system 14, and / or the second fuel control system 16), which is configured to sense the boost air pumping torque amount.

[0053] In some implementations, the friction torque estimate may be determined from a lookup table. In various embodiments, the lookup table is determined or referred to from the first fuel ECM and the torque fuel fill calculation module 45. In some embodiments, the lookup table is based on engine speed and engine friction parameters. In some embodiments, the engine friction parameters may correspond to the oil temperature or coolant temperature within the internal combustion engine 20 of the dual - fuel engine system 10. In various embodiments, the control system 11 may be configured to determine an accessory torque estimate from the lookup table. In various embodiments, the lookup table is determined or referred to from the first fuel ECM and the torque fuel fill calculation module 45. In some embodiments, the lookup table is based on engine speed and accessory torque parameters. In various embodiments, the accessory torque parameters may correspond to the amount of cooling fan power (e.g., measured or estimated) or duty cycle commanded by the internal combustion engine 20 of the dual - fuel engine system 10.

[0054] In various embodiments, the control system 11 is configured to determine a first fuel command for a first fuel from a torque - fuel lookup table. In various embodiments, the torque - fuel lookup table is determined or referenced from the first fuel ECM and the torque fueling calculation module 45. In some embodiments, the torque - fuel lookup table is based on the engine speed (i.e., of the internal combustion engine 20) and the sum of an estimated friction power and a torque demand associated with the internal combustion engine 20. In various implementations, the torque demand is set by the engine governor 50.

[0055] In various embodiments, the control system 11 may be configured to activate one or more protection measures associated with the internal combustion engine 20. In some embodiments, the control system 11 is configured to activate one or more protection measures via the power rationality diagnosis and protection module 190. Figure 5 A method 400 is shown that may be implemented by the control system 11 to activate one or more engine protection measures. In operation 405, the control system 11 is configured to determine an amount of friction power loss. In various implementations, the amount of friction power loss may be determined by measuring the speed of the internal combustion engine 20 in operation 425 and estimating an amount of friction torque in operation 430. After determining the amount of friction power loss in operation 405, the control system 11 may determine an amount of accessory power loss in operation 410. In various embodiments, the amount of accessory power loss may be associated with the loads imposed by the OEM system 12 (e.g., cooling fans, pumps, alternators, etc.) and / or any other accessory components within or coupled to the internal combustion engine 20.

[0056] In various embodiments, the amount of accessory power loss may be based on the measured engine speed (determined in operation 425) and on an estimated accessory torque amount determined in operation 435. Using the amount of accessory power loss and the amount of friction power loss, in operation 415 the control system 11 may estimate a net engine power amount. In various embodiments, the net engine power amount may also be based on a braking power amount (e.g., engine dynamometer measurements) determined by the control system 11 in operation 440. Using the estimated net engine power amount determined in operation 415, in operation 420 the control system 11 may estimate a first indicated engine power and a first power amount for the first fuel. In various embodiments, the control system 11 may also estimate an indicated first fuel power. In some embodiments, the control system 11 is configured to estimate the indicated first fuel power by multiplying a determined heat efficiency correction amount by a determined first fuel power estimate.

[0057] In some embodiments, determining the first fuel power estimate includes using a first look-up table. In various embodiments, the first look-up table is determined or referenced from the first fuel ECM and the torque fuel injection calculation module 45. In some embodiments, the first look-up table is based on the first fuel rate and the engine speed. In various embodiments, determining the heat efficiency correction amount includes referencing a first set of look-up tables. In some embodiments, the first set of look-up tables is determined or referenced from the first fuel ECM and the torque fuel injection calculation module 45. In various embodiments, the first set of look-up tables is based on the G / D of the internal combustion engine 20, the KPIs associated with the internal combustion engine 20, and / or the intake manifold temperature within the internal combustion engine 20. In various embodiments, estimating the first power amount for the second fuel includes subtracting the indicated first fuel power from the indicated engine power.

[0058] Then, at operation 450, the control system 11 may estimate the second indicated engine power and the second power amount for the second fuel. In various embodiments, the second total indicated engine power and the second power amount for the second fuel may be at least partially based on the second fuel LHV value determined at operation 445. In various embodiments, the LHV determined at operation 45 may be based on the first power amount of the second fuel (determined at operation 420), the total second fuel flow rate estimate, and the heat efficiency correction amount. In some implementations, the LHV may be determined by an estimate. In various embodiments, the control system 11 may determine the LHV estimate by dividing the first power amount of the second fuel by a multiple of the second fuel flow rate estimate and the heat efficiency correction amount. In various implementations, the resulting LHV is an instantaneous LHV amount. In some embodiments, the control system 11 may be configured to implement a learning algorithm to determine the LHV estimate based on the instantaneous LHV amount.

[0059] In other embodiments, the second total indicating engine power and the second power amount of the second fuel can additionally or alternatively be based on the estimated engine second fuel flow rate (determined in operation 453) and the estimated first fuel power amount (determined in operation 455). In various embodiments, determining the second total indicating engine power includes determining the product of the total second fuel flow rate estimate and the LHV estimate, and adding the product of the total second fuel flow rate estimate and the LHV estimate to the first fuel power estimate. In some embodiments, the control system 11 can be configured to determine a first power estimate of the second fuel based on the first total indicating engine power, and determine a second power estimate of the second fuel based on the LHV estimate and the product of the thermal efficiency parameter and the estimated engine second fuel flow rate. In various embodiments, the thermal efficiency parameter corresponds to a thermal efficiency correction amount. Then, the control system 11 can determine a final second fuel power estimate based on the first power estimate and the second power estimate of the second fuel. In various embodiments, the control system 11 can be configured to estimate the G / D of the internal combustion engine 20. In various embodiments, the control system 11 is configured to estimate the G / D of the internal combustion engine 20 by dividing the final second fuel power estimate by the first total engine power estimate.

[0060] As Figure 5 shown, in operation 460, the control system 11 can then calculate the difference between the first total indicating engine load (e.g., power, torque, etc.) (determined in operation 420) and the second total indicating engine load (e.g., power, torque, etc.) (determined in operation 450). Then, in operation 465, the control system 11 can compare the difference between the first total indicating engine load and the second total indicating engine load (calculated in operation 460) with a predetermined threshold. For example, in various implementations, the control system 11 can determine the difference between the predetermined threshold and: the difference between the first total indicating engine load and the second total indicating engine load (i.e., the total indicating engine load increment). In various embodiments, the predetermined threshold can be set by the OEM and / or the user of the dual fuel engine system 10.

[0061] Thus, if the difference between the total indicated engine load increase and a predetermined threshold is greater than a predetermined amount, the control system 11 may determine that the dual-fuel engine system 10 is operating under abnormal or adverse conditions. In various embodiments, the predetermined threshold is associated with a predetermined time period. In various embodiments, the predetermined threshold may be set, such as by the controller 18. For example, if the difference between the total indicated engine load increase and the predetermined threshold is greater than the predetermined amount within a predetermined time period, the control system 11 may determine that the dual-fuel engine system 10 is operating in an abnormal or adverse state. Thus, in response to the control system 11 determining that the difference between the first total indicated engine load and the second total indicated engine load meets the predetermined threshold (or the total indicated engine load increase exceeds the predetermined amount), the control system 11 may activate one or more engine protection measures 470. For example, the control system 11 may disable dual-fuel operation, perform a shutdown, and / or reduce the engine speed, etc.

[0062] In other embodiments, the control system 11 may be configured to determine one or more second fuel power targets associated with the internal combustion engine 20. Figure 6 A method 500 for determining a second fuel power target associated with the internal combustion engine 20 is shown. In operation 505, the control system 11 measures the engine speed, and in operation 510, estimates the engine power amount. In various embodiments, the engine speed is sensed by sensors 95, 35, and / or 40. In some embodiments, the engine power amount is the net engine power amount. In operation 515, the control system 11 may calculate a percentage of the rated power of the internal combustion engine 20 (“percentage power”) based on the estimated engine power from operation 510. The percentage rated power may be calculated by dividing the net engine power by the rated engine power limit and multiplying by 100%. The control unit may also determine the intake manifold temperature (e.g., the maximum intake manifold temperature) in operation 525, and determine an estimated value of the KPI of the second fuel in operation 530. The control system 11 may determine a basic second fuel substitution rate (G / D) target for the internal combustion engine 20 in operation 520. In various embodiments, the control system 11 determines the basic G / D target based on the engine speed of the internal combustion engine 20, the percentage rated power, the intake manifold temperature (determined in operation 525), and the estimated KPI. Then, in operation 535, the control system 11 determines the second fuel power target for the internal combustion engine 20 based on the basic second fuel substitution rate target determined in operation 520. In various embodiments, the second fuel power target is based on the basic G / D target and the first indicated engine power estimate. In some embodiments, the control system 11 determines the first indicated engine power estimate by performing operation 420 of method 400. In various embodiments, the control system 11 is configured to determine (e.g., calculate) the first indicated engine power based on the estimated engine power amount and the friction power loss amount.

[0063] In various embodiments, the base G / D target determined in operation 520 is based on a first speed base G / D target (which may be determined in operation 540) when the engine speed is above a threshold and a speed base G / D target (which may be determined in operation 545) when the engine speed is below the threshold. In various embodiments, at least one of the first speed base G / D target or the second speed base G / D target is determined based on the intake manifold temperature (determined in operation 525) and / or the estimated KPI (such as the methane number) (determined in operation 530). In various embodiments, the first speed base G / D target is a high speed base G / D target, and the second speed base G / D target is a low speed base G / D target (i.e., lower than the first base G / D target). In some embodiments, the high speed base G / D target is based on the percentage of rated power, the intake manifold temperature, and the KPI estimate. Similarly, the low speed base G / D target is based on the percentage of rated power, the intake temperature, and the KPI estimate. Thus, the base G / D target determined in operation 520 is further determined by interpolation based on the engine speed between the high speed base G / D target and the low speed base G / D target. In various embodiments, the high speed base G / D target is determined from a first set of look-up tables, and the low speed base G / D target is determined from a second set of look-up tables (i.e., from look-up table / database 145).

[0064] In various embodiments, the control system 11 may be configured to operate the dual fuel engine system 10 to determine one or more second fuel injector commands for at least one engine bank within the internal combustion engine 20. Figure 7 A method 600 for determining at least one second fuel injector command for at least one engine bank within the internal combustion engine 20 is shown. In operation 605, the control system 11 is configured to determine a second fuel flow target. In various implementations, the second fuel flow target is based on a second fuel power target determined in operation 625, a thermal efficiency estimate determined in operation 630, and a LHV determined in operation 635. In some implementations, the second fuel power target determined in operation 625 is determined by the control system 11 via method 500. In other implementations, the LHV determined in operation 635 is determined by performing one or more operations similar or equivalent to operation 445 via the control system 11. In other embodiments, the LHV determined in operation 635 is determined via an LHV sensor or a look-up table based on measured or estimated KPIs. In various embodiments, determining the second fuel flow target in operation 605 includes dividing the second fuel power target by the thermal efficiency estimate and the LHV.

[0065] The control system 11 is configured to adjust the second fuel flow target in operation 610 based on at least one of the measured second fuel temperature determined in operation 640 and / or the second fuel injector pressure measured in operation 645. In various embodiments, at least one of the second fuel temperature or the second fuel injector pressure is measured by sensors 35, 40, and / or 95. Using the adjusted second fuel flow target determined in operation 610, the control system 11 is configured to determine at least one basic second fuel injector command in operation 615. In various embodiments, the at least one basic second fuel injector command is also determined based on the estimated G / D of the internal combustion engine 20 determined in operation 650 and the G / D target determined in operation 655. In various implementations, the G / D target determined in operation 655 is determined by the control system 11 by implementing one or more operations similar or equivalent to operation 520. Then, in operation 620, the control system 11 may determine at least one second fuel injector command for at least one engine bank of the internal combustion engine 20. In some embodiments, the second fuel power target is based on a first indicated engine power estimate and the G / D target. In various implementations, the first indicated engine power estimate is determined by the control system 11 by performing operation 420. In some implementations, adjusting the second fuel flow target in operation 610 includes calculating the amount of the adjusted second fuel flow target. In various embodiments, the amount of the second fuel flow target is based on the product of the second fuel flow target and at least one of the following: a first ratio of the measured second fuel temperature to a temperature reference amount, or a second ratio of the measured second fuel injector pressure to a pressure reference amount.

[0066] In various implementations, the control system 11 may also be configured to estimate the total second fuel flow rate. In various embodiments, the estimated total second fuel flow rate is based on the measured second fuel injector pressure (determined in operation 645), the measured second fuel temperature (determined in operation 640), and at least one second fuel injector command for at least one engine bank. In some implementations, at least one second fuel injector command for at least one engine bank includes a left bank second fuel injector command (i.e., for left bank 30) and a right bank second fuel injector command (i.e., for right bank 31). In other implementations, determining the left bank second fuel injector command and determining the right bank second fuel injector command includes: biasing at least one second fuel injector command for at least one engine bank to each of the left bank 30 and the right bank 31. In various embodiments, biasing at least one second fuel injector command for at least one engine bank to each of the left bank 30 and the right bank 31 is based on the exhaust temperature difference associated with each of the left bank 30 and the right bank 31. In some embodiments, the exhaust temperature difference is measured by sensors 35, 40, and / or 95. In other embodiments, the exhaust temperature difference corresponds to the difference between the exhaust temperature measured at the left bank 30 and the exhaust temperature measured at the right bank 31. Thus, during operation of the twin-engine system 10, the control system 11 may measure the exhaust temperature of the left bank 30, measure the exhaust temperature of the right bank 31, and determine the difference between the exhaust temperature of the left bank 30 and the exhaust temperature of the right bank 31. Then, the control system 11 may add a left bank adjustment amount to at least one second fuel injector command for at least one engine bank. In various embodiments, the control system 11 adds a left bank adjustment amount to at least one second fuel injector command to determine a first adjusted base second fuel injector command based on the difference between the left bank exhaust temperature and the right bank exhaust temperature. Similarly, the control system 11 may then add a right bank adjustment amount to at least one second fuel injector command for at least one engine bank. In various embodiments, the control system 11 adds a right bank adjustment amount to at least one injector command for the second fuel to determine a second adjusted base second fuel injector command based on the difference between the left bank exhaust temperature and the right bank exhaust temperature. Then, the control system 11 may convert each of the first adjusted base second fuel injector command and the second adjusted base second fuel injector command into a left bank second fuel injector command and a right bank second fuel injector command, respectively.

[0067] In some implementations, determining at least one second fuel injector command for at least one engine group in operation 615 includes determining a feedforward input for a G / D PID controller that is operably coupled to the internal combustion engine 20. In various embodiments, the G / D PID controller is the controller 150. In some embodiments, the feedforward input is based on a look-up table. In various embodiments, the look-up table is determined or referenced from the first fuel ECM and torque fueling calculation module 45, the first fuel air handling, aftertreatment, and fuel system reference determination and control module 60, and / or the indicated engine power and second fuel power estimation module 115. In various embodiments, the look-up table is based on at least one of the following: the measured second fuel injector pressure, the measured second fuel temperature, or the adjusted second fuel flow target amount. In some embodiments, the control system 11 is further configured to determine at least one hot control valve command. In various embodiments, the at least one hot control valve command is associated with the heater control valve 195. In some embodiments, the at least one hot control valve command is based on the measured second fuel temperature and / or the measured second fuel mass flow rate within the internal combustion engine 20. In still other embodiments, the control system 11 is further configured to adjust at least one second fuel temperature setpoint based on the measured KPIs and / or the estimated KPI numbers. In various embodiments, the measured KPIs are measured by the sensors 35, 40, and / or 95. In some embodiments, the estimated KPI numbers are determined by the KPI estimation module 125. In some implementations, at least one second fuel temperature setpoint is based on an engine protection setpoint. In various embodiments, the engine protection setpoint is determined or set by the OEM system 12, the first fuel control system 14, or the second fuel control system 16.

[0068] Figure 8A method 700 performed by a dual fuel engine system 10 is shown. In various embodiments, the dual fuel engine system 10 includes at least one PID controller coupled to an internal combustion engine 20 and a second fuel injector 28. In operation 705, the control system 11 determines a G / D estimate value. In various embodiments, the G / D estimate value is determined from an LHV and G / D estimation module 120. Then, the control system 11 determines a G / D target in operation 710. In various embodiments, in operation 710, the control system 11 determines the G / D target by performing one or more operations similar or equivalent to operation 520 in method 500. In operation 715, at least one PID controller is configured to receive a feedforward input in addition to the G / D estimate value and the G / D target. In various embodiments, the feedforward input is based on a look-up table that can be determined or referenced from: a first fuel ECM and torque fueling calculation module 45, a first fuel air handling, aftertreatment, and fuel system reference determination and control module 60, and / or an engine power and second fuel power estimation module 115. In some embodiments, the G / D target is determined from the LHV and G / D estimation module 120. In operation 720, at least one PID controller is configured to output at least one second fuel injector command. In operation 725, at least one PID controller then biases at least one second fuel injector command to each of a left group 30 and a right group 31. In various embodiments, at least one PID controller biases at least one second fuel injector command to each of the left group 30 and the right group 31 based on the difference between each of a left group exhaust temperature (determined in operation 730) and a right group exhaust temperature (determined in operation 735). In various embodiments, an exhaust temperature difference is determined in operation 740. In some embodiments, at least one PID controller includes a first PID controller and a second PID controller. For example, the first PID controller can be configured to receive a feedforward input, a G / D estimate value, and a G / D target (i.e., PID controller 150), and the second PID controller can be configured to bias at least one second fuel injector command to each of the left group 30 and the right group 31 (i.e., group balance PID 155).

[0069] In some embodiments, the dual-fuel engine system 10 includes an aftertreatment system (i.e., controlled by an aftertreatment control system 85) operably coupled to an internal combustion engine 20, a second fuel injection system (i.e., controlled by a second fuel injector control module 110) including at least one second fuel injector 28, and an air handling system (i.e., controlled by an air handling control system 80) operably coupled to the internal combustion engine 20. In some implementations, the aftertreatment system is a selective catalytic reduction (SCR) and oxidation catalyst (OC) system. In some embodiments, the second fuel injection system is configured to independently control second fuel injection on each of a left group 30 and a right group 31 (i.e., via at least one second fuel injector 28). In other embodiments, the air handling system is configured to control the air flow through the internal combustion engine 20. In some embodiments, the air handling system controls the air flow independent of the operating conditions of the internal combustion engine 20. In other embodiments, the air flow is based on a predetermined value obtained from a look-up table. In various embodiments, the look-up table is determined by or corresponds to a database 75 in a module 60. In various embodiments, the predetermined value is associated with a target temperature in at least one location of the aftertreatment system.

[0070] In various embodiments, the dual-fuel engine system 10 includes one or more heaters operably coupled to at least one second fuel injector 28 and the internal combustion engine 20. The at least one heater is configured to adjust the temperature of the second fuel flowing within the internal combustion engine 20 (i.e., heat). Figure 9A method 800 for controlling the operating state of a heater coupled to an internal combustion engine 20 is shown. In operation 805, the control system 11 is configured to determine a second fuel flow target. For example, the control system 11 is configured to determine the second fuel flow target via one or more operations similar or equivalent to operation 605. In various implementations, the second fuel flow target determined in operation 805 may be based on one or more of a second fuel power target, an estimated thermal efficiency, and an LHV. For example, the second fuel flow target may be based on the second fuel power target determined in operation 820, the estimated thermal efficiency of the internal combustion engine 20 determined in operation 825, and the LHV determined in operation 830. In operation 810, the control system 11 may adjust the second fuel flow target based on at least one of a measured second fuel temperature or a measured second fuel injector pressure. For example, in operation 810, the control system 11 is configured to adjust the second fuel flow target based on at least one of the measured second fuel temperature determined in operation 835 or the measured second fuel injector pressure determined in operation 840. In various implementations, the measured second fuel temperature determined in operation 835 is determined by the control system 11 by performing one or more operations similar or equivalent to operation 640. In some embodiments, the measured second fuel temperature is determined via sensors 35, 40, and / or 95. In various embodiments, the measured second fuel injector pressure determined in operation 840 is determined by the control system 11 by performing one or more operations similar or equivalent to operation 645. In some embodiments, the measured second fuel injector pressure is determined via sensors 35, 40, and / or 95. Then, the control system 11 may control the operating state of the heater 32 based on at least one of a measured second fuel temperature or a measured engine coolant temperature. In some embodiments, at least one of the measured second fuel temperature or the measured engine coolant temperature is determined via sensors 35, 40, and / or 95.

[0071] In some embodiments, the control system 11 is configured to perform on / off control of the heater 32 in response to a determination regarding the measured second fuel temperature relative to one or more threshold temperatures. For example, the control system 11 is configured to control the operation of the heater 32 in response to determining that the measured second fuel temperature is less than a first threshold temperature during a first period. Specifically, in some embodiments, the control system 11 is configured to operate (i.e., turn on) the heater 32 in response to determining that the measured second fuel temperature (determined in operation 835) is less than the first threshold temperature during the first period. In various embodiments, the first threshold temperature is set by the OEM system 12, the first fuel control system 14, or the second fuel control system 16. In other embodiments, the control system 11 is configured to control the operation of the heater 32 in response to determining that the measured second fuel temperature is greater than a second threshold temperature during a second period. For example, the control system 11 is configured to operate (i.e., turn off) the heater 32 in response to determining that the measured second fuel temperature (determined in operation 835) is greater than the second threshold temperature during the second period. In various embodiments, the second threshold temperature is set by the OEM system 12, the first fuel control system 14, or the second fuel control system 16.

[0072] Although the embodiments are described above with reference to Figures 1 - 9 those embodiments, various modifications and incorporations are contemplated within the scope of the present disclosure.

[0073] The present technology may also include, but is not limited to, the features and combinations of features recited in the following lettered paragraphs, and it should be understood that the following paragraphs should not be construed as limiting the scope of the appended claims or requiring that all such features be included in those claims:

[0074] A. A method for controlling a dual-fuel engine system, the method comprising:

[0075] estimating a total indicated engine load based on a sum of a measured engine power and an estimated power loss value; and

[0076] determining a total fuel injection amount based on an engine speed and the total indicated engine load, the total fuel injection amount including a fuel injection amount of a first fuel and a fuel injection amount of a second fuel; and

[0077] using the total fuel injection amount to control the dual-fuel engine system.

[0078] B. The method according to paragraph A, wherein the method further comprises determining a first updated total fuel injection amount based on a maximum value between the total fuel injection amount and a first fuel command for the first fuel.

[0079] C. The method according to paragraph B, wherein the method further includes determining a second updated total fuel filling amount, and wherein determining the second updated total fuel filling amount includes: subtracting the first fuel command for the first fuel from the first updated total fuel filling amount to determine a first fuel equivalent of a second fuel filling amount; and adding the first fuel equivalent of the second fuel filling amount to a second fuel command for the first fuel.

[0080] D. The method according to paragraph A, wherein controlling the dual fuel engine system includes determining a first fuel system actuator command.

[0081] E. The method according to paragraph A, wherein determining the total fuel filling amount includes referring to a torque - fuel lookup table, the torque - fuel lookup table being based on the engine speed and indicating a first fuel torque input.

[0082] F. The method according to paragraph A, wherein the method further includes determining the power loss estimate based on a friction torque estimate, an accessory torque estimate, a supercharged air pumping torque, and the engine speed.

[0083] G. The method according to paragraph F, wherein the method further includes:

[0084] determining the friction torque estimate from a second lookup table, the second lookup table being based on the engine speed and engine friction parameters;

[0085] wherein the engine friction parameters are based on at least one of the oil temperature or coolant temperature within the dual fuel engine system.

[0086] H. The method according to paragraph E, wherein the method further includes determining the accessory torque estimate from a third lookup table, the third lookup table being based on the engine speed and accessory torque parameters.

[0087] I. The method according to paragraph H, wherein the method further includes determining the accessory torque parameters based on the cooling fan power or duty cycle commanded by the dual fuel engine system.

[0088] J. The method according to paragraph B, wherein the method further includes determining at least one actuator command based on at least one of the first updated total fuel filling amount or the second updated total fuel filling amount and the engine speed.

[0089] K. A method according to paragraph A, wherein the method further includes determining a first fuel command for the first fuel from a torque - fuel lookup table, the torque - fuel lookup table being based on the sum of a friction power estimate and a torque demand, and the engine speed, the torque demand being set by an engine governor within the dual - fuel engine system.

[0090] L. A method for controlling a dual - fuel engine system, the method comprising:

[0091] estimating a total indicated engine load, the total indicated engine load being based on the sum of a measured engine power, a friction power estimate, and an accessory power estimate;

[0092] determining a total fuel injection quantity from a first lookup table, the lookup table being based on the engine speed and the total indicated engine load;

[0093] determining at least one updated total fuel injection quantity based on the total fuel injection quantity and an operating state of a dual - fuel mode switch within the dual - fuel engine system; and

[0094] determining a control input for at least one actuator within the dual - fuel engine system;

[0095] wherein the control input is based on selecting a corresponding set of lookup tables associated with the at least one actuator, the set of lookup tables including a plurality of lookup tables, each of the plurality of lookup tables being based on the engine speed and the at least one updated total fuel injection quantity.

[0096] M. A method according to paragraph L, wherein the at least one actuator is at least one of an air - handling actuator, a post - treatment actuator, or a first - fuel - system actuator.

[0097] N. A method according to paragraph L, wherein selecting the corresponding set of lookup tables includes determining a compressor inlet density, a second - fuel substitution rate within the dual - engine system, and the operating state of the dual - fuel mode switch.

[0098] O. A method according to paragraph N, wherein selecting the set of lookup tables further includes selecting at least one of an air - handling reference table, a post - treatment reference table, or a fuel - injection reference table.

[0099] P. According to the method described in paragraph O, wherein the at least one updated fuel injection quantity includes a first updated fuel injection quantity and a second updated fuel injection quantity, wherein the first updated fuel injection quantity corresponds to the maximum value between the total fuel injection quantity and the fuel command for the first fuel, and wherein the second updated fuel injection quantity is determined by: subtracting the fuel command for the first fuel from the first updated total fuel injection quantity to determine the first fuel equivalent of the fuel injection quantity for the second fuel, and adding the fuel injection quantity of the first fuel equivalent to the second fuel command for the first fuel.

[0100] Q. A dual - fuel engine system, comprising:

[0101] An internal combustion engine operable in a dual - fuel mode;

[0102] At least one actuator operably coupled to the internal combustion engine; and

[0103] At least one controller in communication with the internal combustion engine and the at least one actuator;

[0104] Wherein the at least one controller is configured to:

[0105] Receive a first input corresponding to the engine speed and a second input corresponding to the measured engine power;

[0106] Calculate an estimated power loss;

[0107] Determine a total fuel injection quantity based on the measured engine power and the estimated power loss;

[0108] Determine a first fuel command for the first fuel associated with the internal combustion engine based at least on a calculated governor command and the estimated power loss;

[0109] Determine at least one updated total fuel injection quantity based on the total fuel injection quantity and the first fuel command for the first fuel;

[0110] Select a set of lookup tables associated with the at least one actuator based on a second fuel substitution rate associated with the internal combustion engine, the set of lookup tables being based on the engine speed and the at least one updated total fuel injection quantity; and

[0111] Send an input to the at least one actuator based on the set of lookup tables.

[0112] R. The system according to paragraph Q, wherein the at least one controller is further configured to determine an indication of a first fuel torque input based on a sum of a friction power estimate and an engine speed torque demand, the engine speed torque demand corresponding to a difference between the engine speed and an engine speed target.

[0113] S. The system according to paragraph Q, wherein the at least one controller is configured to determine the power loss estimate based on a friction torque estimate, an accessory torque estimate, a boost air pumping torque, and the engine speed.

[0114] T. The system according to paragraph Q, wherein the at least one controller is further configured to select the look-up table based on a compressor inlet density.

[0115] U. A method for controlling a dual-fuel engine system configured to operate using a first fuel and a second fuel, the method comprising:

[0116] Determining an amount of friction power loss of an internal combustion engine of the dual-fuel engine system, the amount of friction power loss being based on an engine speed and a friction torque estimate of the internal combustion engine;

[0117] Determining an amount of accessory power loss of the power of the internal combustion engine, the amount of accessory power loss being based on the engine speed and an accessory torque estimate;

[0118] Estimating a net engine power amount based on the amount of accessory power loss and a brake power amount of the internal combustion engine;

[0119] Estimating an indicated power of the first fuel; and

[0120] Estimating a first indicated engine power and a first power of the second fuel based on the estimated net engine power.

[0121] V. The method according to paragraph U, wherein estimating the indicated power of the first fuel includes multiplying a determined heat efficiency correction amount by a determined power estimate of the first fuel.

[0122] W. The method according to paragraph V, wherein determining the power estimate of the first fuel includes using a first look-up table based on a fuel rate of the first fuel and the engine speed.

[0123] X. The method according to paragraph V, wherein determining the heat efficiency correction amount includes consulting a first set of look-up tables based on at least one of a substitution rate of the second fuel, a knock tendency index, or an intake manifold temperature.

[0124] Y. The method according to paragraph V further includes determining an estimated lower heating value (LHV) of the second fuel based on the first power of the second fuel, the estimated total second fuel flow rate, and the heat efficiency correction amount.

[0125] Z. The method according to paragraph Y, wherein determining the estimated LHV includes:

[0126] Dividing the first power of the second fuel by the product of the estimated second fuel flow rate and the heat efficiency correction amount to determine an instantaneous LHV amount.

[0127] AA. The method according to paragraph Z further includes applying a learning algorithm to the instantaneous LHV amount to determine the estimated LHV.

[0128] BB. The method according to paragraph Y further includes estimating a second total indicated engine power, wherein estimating the second total indicated engine power includes:

[0129] Determining the product of the estimated total flow rate of the second fuel and the estimated LHV; and

[0130] Determining the sum of the product of the total second fuel flow rate and the estimated LHV and the estimated power of the first fuel.

[0131] CC. The method according to paragraph BB further includes determining the difference between the first total indicated engine power and the second total indicated engine power.

[0132] DD. The method according to paragraph CC further includes activating at least one engine protection measure based on the difference between the first total indicated engine power and the second total indicated engine power being greater than a threshold.

[0133] EE. The method according to paragraph DD further includes setting the threshold to correspond to a predetermined time period.

[0134] FF. The method according to paragraph V, wherein estimating the first power of the second fuel includes subtracting the indicated power of the first fuel from the indicated engine power.

[0135] GG. A method for controlling a dual-fuel engine system configured to operate using a first fuel and a second fuel, the method including:

[0136] Estimating a net engine power amount of an internal combustion engine of the dual-fuel engine system based on an accessory power loss amount of the power of the internal combustion engine and an estimated brake power of the internal combustion engine;

[0137] Determine a first gross indicated engine power based on the net engine power and the frictional power losses of the internal combustion engine;

[0138] Determine the lower heating value (LHV) of the second fuel within the internal combustion engine, where the LHV is a measured or estimated value;

[0139] Estimate a second gross indicated engine power based on the LHV, the estimated total flow rate of the second fuel, and the estimated power of the first fuel; and

[0140] Activate at least one engine protection measure based on the difference between the first gross indicated engine power and the second gross indicated engine power being greater than a predetermined threshold.

[0141] HH. The method according to paragraph GG, wherein estimating the second gross indicated engine power includes:

[0142] Determine the sum of the product of the total second fuel flow rate and the LHV and the estimated power of the first fuel.

[0143] II. The method according to paragraph GG, further comprising:

[0144] Determine a first power estimate of the second fuel, the first power estimate of the second fuel being based on the first gross indicated engine power;

[0145] Determine a second power estimate of the second fuel, the second power estimate of the second fuel being based on the product of the estimated thermal efficiency and the estimated total second fuel flow rate and the LHV; and

[0146] Determine a final second fuel power estimate based on the first power estimate of the second fuel and the second power estimate of the second fuel.

[0147] JJ. The method according to paragraph II, further comprising estimating a substitution rate of the second fuel, wherein estimating the substitution rate of the second fuel includes:

[0148] Divide the final second fuel power estimate by the first power estimate.

[0149] KK. A dual-fuel engine system operable in a dual-fuel mode, the dual-fuel engine system comprising:

[0150] At least one controller in communication with an internal combustion engine, the internal combustion engine being configured to operate using a first fuel and a second fuel;

[0151] Wherein the at least one controller is configured to:

[0152] Receiving an input corresponding to the engine speed of the internal combustion engine;

[0153] Receiving an input for calculating an estimated net engine power;

[0154] Calculating a percentage rated power of the internal combustion engine based on the engine speed and the estimated net engine power;

[0155] Determining a basic substitution rate target for the second fuel of the internal combustion engine based on the engine speed, the percentage rated power, the intake manifold temperature in the internal combustion engine, and an estimated knock tendency index in the internal combustion engine; and

[0156] Determining a second fuel power target for the internal combustion engine based on the basic substitution rate target for the second fuel and a first indicated engine power estimate.

[0157] LL. The system according to paragraph KK, wherein the controller is configured to determine the basic substitution rate target for the second fuel by performing the following operations:

[0158] When the engine speed is higher than a threshold, determining a first speed-based basic substitution rate target for the second fuel based on the percentage rated power, the intake manifold temperature, and the estimated knock tendency index;

[0159] When the engine speed is lower than the threshold, determining a second speed-based basic substitution rate target for the second fuel based on the percentage rated power, the intake manifold temperature, and the estimated knock tendency index; and

[0160] Determining the basic substitution rate target for the second fuel based on the engine speed, the high-speed basic substitution rate target for the second fuel, and the low-speed basic substitution rate target for the second fuel.

[0161] MM. The system according to paragraph LL, wherein the first speed-based basic substitution rate target for the second fuel is determined based on a first set of look-up tables, and the second speed-based basic substitution rate target for the second fuel is determined based on a second set of look-up tables.

[0162] NN. The system according to paragraph KK, wherein the controller is configured to determine the first indicated engine power based on the estimated net engine power and the amount of frictional power loss.

[0163] OO. A method for controlling a dual-fuel engine system configured to operate using a first fuel and a second fuel, the method comprising:

[0164] Determine a flow target for a second fuel of an internal combustion engine for the dual - fuel engine system, the flow target for the second fuel being based on a power target for the second fuel of the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine;

[0165] Adjust the flow target for the second fuel based on at least one of a measured second fuel temperature or a measured second fuel injector pressure;

[0166] Determine at least one basic second fuel injector command based on the adjusted flow target for the second fuel, an estimated second fuel substitution rate, and a second fuel substitution rate target; and

[0167] Determine a second fuel injector command for at least one engine bank based on the at least one basic second fuel injector command.

[0168] PP. The method according to paragraph OO, further comprising estimating a total second fuel flow based on the measured second fuel injector pressure, the measured second fuel temperature, and the at least one injector command for the second fuel of the at least one engine bank.

[0169] QQ. The method according to paragraph OO, wherein the at least one engine bank includes a left bank and a right bank, wherein the at least one injector command for the second fuel of the at least one engine bank includes a left - bank second fuel injector command and a right - bank second fuel injector command, and determining the left - bank second fuel injector command and the right - bank second fuel injector command includes:

[0170] Bias the at least one injector command for the second fuel of the at least one engine bank to each of the right engine bank and the left engine bank based on an exhaust temperature difference associated with each of the right engine bank and the left engine bank.

[0171] RR. The method according to paragraph QQ, wherein biasing the at least one basic second fuel injector command to each of the right engine bank and the left engine bank includes:

[0172] Measure the left - bank exhaust temperature;

[0173] Measure the right - bank exhaust temperature;

[0174] Determine the difference between the right - bank exhaust temperature and the left - bank exhaust temperature;

[0175] Add a left set adjustment amount to the at least one injector command for the second fuel of the at least one engine set to determine a first adjusted basic second fuel injector command based on a difference between the right set exhaust temperature and the left set exhaust temperature;

[0176] Add a right set adjustment amount to the at least one injector command for the second fuel of the at least one engine set to determine a second adjusted basic second fuel injector command based on a difference between the right set exhaust temperature and the left set exhaust temperature; and

[0177] Convert each of the first adjusted basic second fuel injector command and the second adjusted basic second fuel injector command into a left set second fuel injector command and a right set second fuel injector command, respectively.

[0178] SS. The method according to paragraph OO, wherein determining the flow target for the second fuel includes dividing the power target for the second fuel by the thermal efficiency estimate and the LHV.

[0179] TT. The method according to paragraph SS, wherein the power target for the second fuel is based on a first indicated engine power estimate and the second fuel substitution rate target.

[0180] UU. The method according to paragraph OO, wherein adjusting the flow target for the second fuel includes:

[0181] Calculating an adjusted second fuel flow target amount that is a product of the flow target and at least one of: a first ratio of the measured second fuel temperature to a temperature reference amount, or a second ratio of the measured pressure to a pressure reference amount.

[0182] VV. The method according to paragraph UU, wherein determining at least one injector command for the second fuel of the at least one engine set includes:

[0183] Determining a feedforward input for a second fuel substitution rate proportional-integral-derivative controller operably coupled to the internal combustion engine, the feedforward input being based on a look-up table that references at least one of: the measured second fuel injector pressure, the measured second fuel temperature, or the adjusted second fuel flow target amount.

[0184] WW. The method according to paragraph VV, further comprising:

[0185] Adjust at least one temperature set point of the second fuel based on at least one of a measured knock tendency index or an estimated knock tendency index.

[0186] XX. The method according to paragraph WW, wherein the at least one temperature set point of the second fuel is based on an engine protection set point.

[0187] YY. A dual-fuel engine system for an internal combustion engine, the dual-fuel engine system being configured to operate using a first fuel and a second fuel, the dual-fuel engine system comprising:

[0188] At least one injector for the second fuel, the at least one injector being operably coupled to the internal combustion engine, the internal combustion engine having a left bank and a right bank, the internal combustion engine being operable in a dual-fuel mode; and

[0189] At least one proportional-integral-derivative (PID) controller, the at least one proportional-integral-derivative (PID) controller being communicatively coupled to the internal combustion engine and the at least one injector for the second fuel;

[0190] Wherein the at least one PID controller is configured to:

[0191] Receive a feedforward input, an estimated second fuel substitution rate, and a second fuel substitution rate target;

[0192] Output at least one injector command for the second fuel based on the feedforward input; and

[0193] Bias the at least one injector command for the second fuel to each of the right bank and the left bank based on an exhaust temperature difference associated with each of the right bank and the left bank.

[0194] ZZ. The system according to paragraph YY, wherein the at least one PID controller is configured to bias the at least one injector command for the second fuel to each of the right bank and the left bank by performing operations including:

[0195] Measure the left bank exhaust temperature;

[0196] Measure the right bank exhaust temperature;

[0197] Determine a difference between the right bank exhaust temperature and the left bank exhaust temperature;

[0198] Add a left bank adjustment amount to the at least one injector command for the second fuel to determine a first adjusted injector command for the second fuel;

[0199] Add the right set of adjustment amounts to the at least one injector command for the second fuel to determine a second adjusted injector command for the second fuel; and

[0200] Convert each of the first adjusted injector command for the second fuel and the second adjusted injector command for the second fuel into a left set of injector commands for the second fuel and a right set of injector commands for the second fuel, respectively.

[0201] AAA. The system according to paragraph YY, wherein the at least one PID controller includes a first PID controller and a second PID controller, wherein the first PID controller is configured to receive the feedforward input, the second fuel substitution rate estimate, and the second fuel substitution rate target, and wherein the second PID controller is configured to bias the at least one injector command for the second fuel to each of the right set and the left set.

[0202] BBB. The system according to paragraph YY, further comprising:

[0203] An aftertreatment system, the aftertreatment system being operably coupled to the internal combustion engine, the aftertreatment system being a selective catalytic reduction (SCR) and oxidation catalyst (OC) system;

[0204] An injection system for the second fuel, the injection system being operably coupled to the internal combustion engine, the injection system for the second fuel including the at least one injector for the second fuel, wherein the injection system for the second fuel is configured to independently control the injection of the second fuel on each of the left set and the right set; and

[0205] An air handling system, the air handling system being operably coupled to the internal combustion engine, the air handling system being configured to control the air flow through the internal combustion engine independently of the operating conditions of the internal combustion engine, wherein the air flow is based on a predetermined value obtained from a look-up table, the predetermined value being associated with a target temperature in at least one location of the aftertreatment system.

[0206] CCC. A dual-fuel engine system operable in a dual-fuel mode, the dual-fuel engine system comprising:

[0207] An internal combustion engine having at least one engine group, the internal combustion engine being configured to operate using a first fuel and a second fuel;

[0208] At least one injector for the second fuel, the at least one injector being operably coupled to the internal combustion engine; and

[0209] At least one controller communicatively coupled to the internal combustion engine and to the at least one injector for the second fuel;

[0210] wherein the at least one controller is configured to:

[0211] Determine a second fuel flow target for the internal combustion engine, the second fuel flow target being based on a second fuel power target of the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine;

[0212] Adjust the second fuel flow target based on at least one of a measured second fuel temperature or a measured second fuel injector pressure to determine an adjusted second fuel flow target for the dual fuel mode;

[0213] Determine at least one basic second fuel injector command based on the adjusted second fuel flow target, an estimated substitution rate of the second fuel, and a substitution rate target of the second fuel; and

[0214] Based on the at least one basic second fuel injector command, determine an injector command for the second fuel for the at least one engine bank.

[0215] DDD. The system according to paragraph CCC, wherein the at least one controller is further configured to:

[0216] Determine a left bank second fuel injector command and a right bank second fuel injector command based on the at least one injector command for the second fuel.

[0217] EEE. The system according to paragraph DDD, wherein the at least one controller is further configured to determine the second fuel flow target by dividing the second fuel power target by the estimated thermal efficiency and the lower heating value (LHV), wherein the LHV is determined on a look-up table based on an estimated knock tendency index.

[0218] It should be noted that, as used herein, the term "exemplary" and its variants used to describe various embodiments are intended to indicate that these embodiments are possible examples, representations, or illustrations of possible embodiments (and these terms are not intended to imply that these embodiments are necessarily exceptional or top-level examples).

[0219] As used herein, the term "coupled" and its variants refer to two components being joined directly or indirectly to each other. Such a joining can be stationary (e.g., permanent or fixed) or movable (e.g., removable or releasable). Such a joining can be achieved by two components being directly coupled to each other, where the two components are coupled to each other using a separate intermediate component and any additional intermediate components that are coupled together, or where the two components are coupled to each other using an intermediate component that is integrally formed as a single unit with one of the two components. If "coupled" or its variants are modified by an additional term (e.g., directly coupled), then the general definition of "coupled" provided above is modified by the plain language meaning of the additional term (e.g., "directly coupled" means a joining of two components without any separate intermediate component), resulting in a narrower definition than the general definition of "coupled" provided above. Such coupling can be mechanical, electrical, or fluidic.

[0220] References to element positions herein (e.g., "top", "bottom", "above", "below") are for describing the orientation of the various elements in the drawings only. It should be noted that the orientation of the various elements can be different according to other exemplary embodiments, and such variations are intended to be included in the present disclosure.

[0221] In some embodiments, the hardware and data processing components for implementing the various processes, operations, illustrative logics, logic blocks, modules, and circuits described in connection with the embodiments disclosed herein, such as the hardware and data processing components of a controller (e.g., the memory within controller 18, the memory within OEM system 12, the memory within first fuel control system 14, or the memory within second fuel control system 16), may be implemented or performed by: a general-purpose single-chip or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, certain processes and methods may be performed by circuitry specific to a given function. The memory (e.g., memory, memory unit, storage device) may include one or more devices (e.g., RAM, ROM, flash memory, hard disk storage) for storing data and / or computer code to perform or facilitate the various processes, layers, and modules described in this disclosure. The memory may be or may include volatile memory or non-volatile memory, and may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in this disclosure. According to an exemplary embodiment, the memory (e.g., the memory within controller 18, the memory within OEM system 12, the memory within first fuel control system 14, or the memory within second fuel control system 16) is communicatively coupled to the processor via a processing circuit and includes computer code for performing (e.g., by the processing circuit or the processor) one or more of the processes described herein.

[0222] The present disclosure contemplates methods and systems for implementing various operations (e.g., operations 305 - 360 of method 300, operations 405 - 470 of method 400, operations 505 - 545 of method 500, operations 605 - 655 of method 600, operations 705 - 740 of method 700, and operations 805 - 845 of method 800) on any machine-readable medium. Embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor of a suitable system introduced for this or another purpose, or by a hard-wired system. Embodiments within the scope of the present disclosure include program products that include a machine-readable medium for carrying or having machine-executable instructions or data structures stored thereon. Such a machine-readable medium may be any available medium that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such a machine-readable medium may include RAM, ROM, EPROM, EEPROM, or other optical disk storage, magnetic disk storage, or other magnetic storage devices, or any other medium that can be used to carry or store the desired program code in the form of machine-executable instructions or data structures and that can be accessed by a general purpose or special purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable medium. Machine-executable instructions include, for example, instructions and data that cause a general purpose computer, special purpose computer, or special purpose processing machine to perform a certain function or a group of functions.

[0223] Although the figures and the specification may show a particular order of method steps, the order of these steps may be different from that depicted and described, unless stated otherwise above. In addition, two or more steps may be performed simultaneously or partially simultaneously, unless otherwise specified above.

[0224] It is important to note that any element disclosed in one embodiment may be combined with or used in conjunction with any other embodiment disclosed herein. Although only one example of an element from one embodiment that may be combined or utilized in another embodiment has been described above, it should be understood that other elements of the various embodiments may be combined with or used in conjunction with any other embodiment disclosed herein.

Claims

1. A method for controlling a dual - fuel engine system, the dual - fuel engine system being configured to operate using a first fuel and a second fuel, the method comprises: estimating a total indicated engine load, the total indicated engine load being estimated based on the sum of a measured engine power and a power loss estimate; determining a total fuel injection quantity based on the engine speed and the total indicated engine load, the total fuel injection quantity including a fuel injection quantity for the first fuel and a fuel injection quantity for the second fuel; and using the total fuel injection quantity to control the dual - fuel engine system.

2. The method according to claim 1, further comprising determining a first updated total fuel injection quantity based on a maximum value between the total fuel injection quantity and a first fuel command for the first fuel.

3. The method according to claim 2, further comprising determining a second updated total fuel injection quantity, wherein, determining the second updated total fuel injection quantity comprises: subtracting the first fuel command for the first fuel from the first updated total fuel injection quantity to determine a first fuel equivalent of the fuel injection quantity of the second fuel; and adding the first fuel equivalent of the fuel injection quantity of the second fuel to a second fuel command for the first fuel.

4. The method according to claim 1, wherein, controlling the dual - fuel engine system comprises determining a fuel system actuator command for the first fuel.

5. The method according to claim 1, wherein, determining the total fuel injection quantity includes referring to a torque - fuel lookup table, the torque - fuel lookup table being based on the engine speed and an indicated first fuel torque input.

6. The method according to claim 1, further comprising determining the power loss estimate based on a friction torque estimate, an accessory torque estimate, a supercharged air pumping torque, and the engine speed.

7. The method according to claim 6, further comprises: determining the friction torque estimate from a second lookup table, the second lookup table being based on the engine speed and engine friction parameters; wherein the engine friction parameters are based on at least one of an oil temperature or a coolant temperature within the dual - fuel engine system.

8. The method according to claim 5, further comprising determining the accessory torque estimate from a third lookup table, the third lookup table being based on the engine speed and accessory torque parameters.

9. The method according to claim 8, further comprising determining the accessory torque parameters based on a cooling fan power or duty cycle commanded by the dual - fuel engine system.

10. The method according to claim 2, further comprising determining at least one actuator command based on at least one of the first updated total fuel injection quantity or the second updated total fuel injection quantity and the engine speed.

11. The method according to claim 1 further includes determining a first fuel command for the first fuel from a torque - fuel lookup table, the torque - fuel lookup table being based on the sum of a friction power estimate and a torque demand, and the engine speed, the torque demand being set by an engine governor within the dual - fuel engine system.

12. A method for controlling a dual - fuel engine system, the dual - fuel engine system being configured to operate using a first fuel and a second fuel, the method comprises: estimating a total indicated engine load, the total indicated engine load being based on the sum of a measured engine power, a friction power estimate, and an accessory power estimate; determining a total fuel injection amount from a first lookup table, the lookup table being based on the engine speed and the total indicated engine load; determining at least one updated total fuel injection amount based on the total fuel injection amount and an operating state of a dual - fuel mode switch within the dual - fuel engine system; and determining a control input for at least one actuator within the dual - fuel engine system; wherein the control input is based on selecting a corresponding set of lookup tables associated with the at least one actuator, the set of lookup tables including a plurality of lookup tables, each of the plurality of lookup tables being based on the engine speed and the at least one updated total fuel injection amount.

13. The method according to claim 12, wherein, the at least one actuator is at least one of a fuel system actuator for the first fuel, an air handling actuator, or a post - treatment actuator.

14. The method according to claim 12, wherein, selecting the corresponding set of lookup tables includes determining a compressor inlet density, a substitution rate of the second fuel within the dual - engine system, and the operating state of the dual - fuel mode switch.

15. The method according to claim 14, wherein, selecting the set of lookup tables further includes selecting at least one of an air handling reference table, a post - treatment reference table, or a fuel injection reference table.

16. The method according to claim 15, wherein, the at least one updated fuel injection amount includes a first updated fuel injection amount and a second updated fuel injection amount, wherein the first updated fuel injection amount corresponds to the maximum value between the total fuel injection amount and a fuel command for the first fuel, and wherein the second updated fuel injection amount is determined by: subtracting the fuel command for the first fuel from the first updated total fuel injection amount to determine a fuel equivalent of the first fuel for the fuel injection amount of the second fuel, and adding the fuel injection amount of the equivalent of the first fuel to a second fuel command for the first fuel.

17. A dual - fuel engine configured to operate using a first fuel and a second fuel, the engine system comprises: an internal combustion engine capable of operating in a dual - fuel mode; at least one actuator operably coupled to the internal combustion engine; and at least one controller in communication with the internal combustion engine and the at least one actuator; wherein, the at least one controller is configured to: receive a first input corresponding to engine speed and a second input corresponding to measured engine power; calculate an estimated power loss; determine a total fuel filling amount based on the measured engine power and the estimated power loss; determine a first fuel command for the first fuel associated with the internal combustion engine based at least on a calculated governor command and the estimated power loss; determine at least one updated total fuel filling amount based on the total fuel filling amount and the first fuel command for the first fuel; select a set of look-up tables associated with the at least one actuator based on a second fuel substitution rate associated with the internal combustion engine, the set of look-up tables being based on the engine speed and the at least one updated total fuel filling amount; and send an input to the at least one actuator based on the set of look-up tables.

18. The system according to claim 17, wherein, the at least one controller is further configured to determine an indicated first fuel torque input based on a sum of a friction power estimate and an engine speed torque demand amount, the engine speed torque demand amount corresponding to a difference between the engine speed and an engine speed target.

19. The system according to claim 17, wherein, the at least one controller is configured to determine the estimated power loss based on a friction torque estimate, an accessory torque estimate, a supercharged air pumping torque, and the engine speed.

20. The system according to claim 17, wherein, the at least one controller is further configured to select the look-up table based on a compressor inlet density.

21. A method for controlling a dual-fuel engine system, the dual-fuel engine system being configured to operate using a first fuel and a second fuel, the method comprises: determining an amount of frictional power loss of an internal combustion engine of the dual-fuel engine system, the amount of frictional power loss being based on an engine speed of the internal combustion engine and a friction torque estimate; determining an amount of accessory power loss of the power of the internal combustion engine, the amount of accessory power loss being based on the engine speed and an accessory torque estimate; estimating a net engine power amount based on the amount of accessory power loss and a brake power amount of the internal combustion engine; estimating an indicated power of the first fuel; and estimating a first indicated engine power and a first power of the second fuel based on the estimated net engine power.

22. The method according to claim 21, wherein, estimating the indicated power of the first fuel includes multiplying a determined heat efficiency correction amount by a determined power estimate value of the first fuel.

23. The method according to claim 22, wherein, determining the power estimate value of the first fuel includes using a first look-up table, the first look-up table being based on a fuel rate of the first fuel and the engine speed.

24. The method according to claim 22, wherein, determining the heat efficiency correction amount includes looking up a first set of look-up tables, the first set of look-up tables being based on at least one of a substitution rate of the second fuel, a knock tendency index, or an intake manifold temperature.

25. The method according to claim 22 further includes determining an estimated value of the lower heating value (LHV) of the second fuel based on the first power of the second fuel, the estimated total second fuel flow rate, and the heat efficiency correction amount.

26. The method according to claim 25, wherein, determining the estimated LHV value includes: dividing the first power of the second fuel by the product of the estimated second fuel flow rate and the heat efficiency correction amount to determine an instantaneous LHV amount.

27. The method according to claim 26 further includes applying a learning algorithm to the instantaneous LHV amount to determine the estimated LHV value.

28. The method according to claim 25 further includes estimating a second total indicated engine power, wherein, estimating the second total indicated engine power includes: determining the product of the estimated total flow rate of the second fuel and the estimated LHV value; and determining the sum of the product of the total second fuel flow rate and the estimated LHV value and the estimated power value of the first fuel.

29. The method according to claim 28 further includes determining the difference between the first total indicated engine power and the second total indicated engine power.

30. The method according to claim 29 further includes activating at least one engine protection measure based on the difference between the first total indicated engine power and the second total indicated engine power being greater than a threshold.

31. The method according to claim 30 further includes setting the threshold to correspond to a predetermined time period.

32. The method according to claim 22, wherein, estimating the first power of the second fuel includes subtracting the indicated power of the first fuel from the indicated engine power.

33. A method for controlling a dual-fuel engine system, the dual-fuel engine system being configured to operate using a first fuel and a second fuel, the method includes: estimating a net engine power amount of an internal combustion engine of the dual-fuel engine system based on an accessory power loss amount of the power of the internal combustion engine and an estimated value of the brake power of the internal combustion engine; determining a first total indicated engine power based on the net engine power of the internal combustion engine and a friction power loss amount; determining a lower heating value (LHV) for the second fuel within the internal combustion engine, the LHV being a measured value or an estimated value; estimating a second total indicated engine power based on the LHV, the estimated total flow rate of the second fuel, and the estimated power value of the first fuel; and activating at least one engine protection measure based on the difference between the first total indicated engine power and the second total indicated engine power being greater than a predetermined threshold.

34. The method according to claim 33, wherein, estimating the second total indicated engine power includes: determining the sum of the product of the total second fuel flow rate and the LHV and the estimated power value of the first fuel.

35. The method according to claim 33 further includes: determining a first power estimated value of the second fuel, the first power estimated value of the second fuel being based on the first total indicated engine power; Determine a second power estimate of the second fuel, the second power estimate of the second fuel being based on the product of a thermal efficiency estimate and a total second fuel flow estimate and the LHV; and Determine a final second fuel power estimate based on the first power estimate of the second fuel and the second power estimate of the second fuel.

36. The method according to claim 35, further comprising estimating a substitution rate of the second fuel, wherein estimating the substitution rate of the second fuel comprises: Dividing the final second fuel power estimate by the first power estimate.

37. A dual-fuel engine system capable of operating in a dual-fuel mode, the dual-fuel engine system comprising: At least one controller in communication with an internal combustion engine, the internal combustion engine being configured to operate using a first fuel and a second fuel; wherein the at least one controller is configured to: Receive an input corresponding to the engine speed of the internal combustion engine; Receive an input for calculating a net engine power estimate; Calculate a percentage rated power of the internal combustion engine based on the engine speed and the net engine power estimate; Determine a basic substitution rate target of the second fuel of the internal combustion engine based on the engine speed, the percentage rated power, an intake manifold temperature within the internal combustion engine, and a knock tendency index estimate within the internal combustion engine; and Determine a second fuel power target of the internal combustion engine based on the basic substitution rate target of the second fuel and a first indicated engine power estimate.

38. The system according to claim 37, wherein the controller is configured to determine the basic substitution rate target of the second fuel by performing the following operations: When the engine speed is higher than a threshold, determine a first speed basic substitution rate target of the second fuel based on the percentage rated power, the intake manifold temperature, and the knock tendency index estimate; When the engine speed is lower than the threshold, determine a second speed basic substitution rate target of the second fuel based on the percentage rated power, the intake manifold temperature, and the knock tendency index estimate; and Determine the basic substitution rate target of the second fuel based on the engine speed, the high speed basic substitution rate target of the second fuel, and the low speed basic substitution rate target of the second fuel.

39. The system according to claim 38, wherein the first speed basic substitution rate target of the second fuel is determined based on a first set of look-up tables, and the second speed basic substitution rate target of the second fuel is determined based on a second set of look-up tables.

40. The system according to claim 37, wherein the controller is configured to determine the first indicated engine power based on the net engine power estimate and a frictional power loss amount.

41. A method for controlling a dual-fuel engine system, the dual-fuel engine system being configured to operate using a first fuel and a second fuel, the method comprising: Determine a flow target for a second fuel of an internal combustion engine for the dual-fuel engine system, the flow target for the second fuel being based on a power target for the second fuel of the internal combustion engine, an estimated value of the thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine; Adjust the flow target for the second fuel based on at least one of a measured second fuel temperature or a measured second fuel injector pressure; Determine at least one basic second fuel injector command based on the adjusted flow target for the second fuel, an estimated second fuel substitution rate, and a second fuel substitution rate target; and Determine a second fuel injector command for at least one engine bank based on the at least one basic second fuel injector command.

42. The method according to claim 41, further comprising estimating a total second fuel flow based on the measured second fuel injector pressure, the measured second fuel temperature, and the at least one injector command for the second fuel of the at least one engine bank.

43. The method according to claim 41, wherein, the at least one engine bank includes a left bank and a right bank, wherein the at least one injector command for the second fuel of the at least one engine bank includes a left bank second fuel injector command and a right bank second fuel injector command, and determining the left bank second fuel injector command and the right bank second fuel injector command includes: Biasing the at least one injector command for the second fuel of the at least one engine bank to each of the right bank and the left bank of the engine based on an exhaust temperature difference associated with each of the right bank and the left bank of the engine.

44. The method according to claim 43, wherein, biasing the at least one basic second fuel injector command to each of the right bank and the left bank of the engine includes: Measuring the left bank exhaust temperature; Measuring the right bank exhaust temperature; Determining a difference between the right bank exhaust temperature and the left bank exhaust temperature; Adding a left bank adjustment amount to the at least one injector command for the second fuel of the at least one engine bank to determine a first adjusted basic second fuel injector command based on the difference between the right bank exhaust temperature and the left bank exhaust temperature; Adding a right bank adjustment amount to the at least one injector command for the second fuel of the at least one engine bank to determine a second adjusted basic second fuel injector command based on the difference between the right bank exhaust temperature and the left bank exhaust temperature; and Converting each of the first adjusted basic second fuel injector command and the second adjusted basic second fuel injector command into the left bank second fuel injector command and the right bank second fuel injector command, respectively.

45. The method according to claim 41, wherein, determining the flow target for the second fuel includes dividing the power target for the second fuel by the estimated thermal efficiency and the LHV.

46. The method according to claim 45, wherein, The power target of the second fuel is based on a first indicated engine power estimate and the second fuel substitution rate target.

47. The method according to claim 41, wherein, adjusting the flow target of the second fuel includes: calculating an adjusted second fuel flow target amount, the adjusted second fuel flow target amount being the product of the flow target and at least one of: a first ratio of the measured second fuel temperature to a temperature reference amount, or a second ratio of the measured pressure to a pressure reference amount.

48. The method according to claim 47, wherein, determining at least one injector command for the second fuel for the at least one engine bank includes: determining a feedforward input for a second fuel substitution rate proportional-integral-derivative controller, the second fuel substitution rate proportional-integral-derivative controller being operatively coupled to the internal combustion engine, the feedforward input being based on a look-up table that references at least one of: the measured second fuel injector pressure, the measured second fuel temperature, or the adjusted second fuel flow target amount.

49. The method according to claim 48, further comprising: adjusting at least one temperature setpoint of the second fuel based on at least one of a measured knock tendency index or an estimated knock tendency index.

50. The method according to claim 49, wherein, the at least one temperature setpoint of the second fuel is based on an engine protection setpoint.

51. A dual fuel engine system for an internal combustion engine, the dual fuel engine system being configured to operate using a first fuel and a second fuel, the dual fuel engine system comprising: at least one injector for the second fuel, the at least one injector being operatively coupled to the internal combustion engine, the internal combustion engine having a left bank and a right bank, the internal combustion engine being capable of operating in a dual fuel mode; and at least one proportional-integral-derivative (PID) controller, the at least one proportional-integral-derivative (PID) controller being communicatively coupled to the internal combustion engine and the at least one injector for the second fuel; wherein the at least one PID controller is configured to: receive a feedforward input, a second fuel substitution rate estimate, and a second fuel substitution rate target; output at least one injector command for the second fuel based on the feedforward input; and bias the at least one injector command for the second fuel to each of the right bank and the left bank based on an exhaust temperature difference associated with each of the right bank and the left bank.

52. The system according to claim 51, wherein, the at least one PID controller is configured to bias the at least one injector command for the second fuel to each of the right bank and the left bank by performing operations including: measuring the left bank exhaust temperature; measuring the right bank exhaust temperature; determining a difference between the right bank exhaust temperature and the left bank exhaust temperature; Add the left set of adjustment amounts to the at least one injector command for the second fuel to determine a first adjusted injector command for the second fuel; Add the right set of adjustment amounts to the at least one injector command for the second fuel to determine a second adjusted injector command for the second fuel; and Convert each of the first adjusted injector command for the second fuel and the second adjusted injector command for the second fuel into a left set of injector commands for the second fuel and a right set of injector commands for the second fuel, respectively.

53. The system according to claim 51, wherein, the at least one PID controller includes a first PID controller and a second PID controller, wherein the first PID controller is configured to receive the feedforward input, the second fuel substitution rate estimate, and the second fuel substitution rate target, and wherein the second PID controller is configured to bias the at least one injector command for the second fuel to each of the right set and the left set.

54. The system according to claim 51, further comprising: a post-treatment system, the post-treatment system being operably coupled to the internal combustion engine, the post-treatment system being a selective catalytic reduction (SCR) and oxidation catalyst (OC) system; an injection system for the second fuel, the injection system for the second fuel being operably coupled to the internal combustion engine, the injection system for the second fuel including the at least one injector for the second fuel, wherein the injection system for the second fuel is configured to independently control the injection of the second fuel on each of the left set and the right set; and an air handling system, the air handling system being operably coupled to the internal combustion engine, the air handling system being configured to control the air flow through the internal combustion engine independently of the operating conditions of the internal combustion engine, wherein the air flow is based on a predetermined value obtained from a look-up table, the predetermined value being associated with a target temperature in at least one location of the post-treatment system.

55. A dual-fuel engine system capable of operating in a dual-fuel mode, the dual-fuel engine system comprising: an internal combustion engine having at least one engine bank, the internal combustion engine being configured to operate using a first fuel and a second fuel; at least one injector for the second fuel, the at least one injector being operably coupled to the internal combustion engine; and at least one controller, the at least one controller being communicatively coupled to the internal combustion engine and the at least one injector for the second fuel; wherein the at least one controller is configured to: determine a second fuel flow target for the internal combustion engine, the second fuel flow target being based on the second fuel power target of the internal combustion engine, the estimated thermal efficiency of the internal combustion engine, and the lower heating value (LHV) within the internal combustion engine; Adjust the second fuel flow target based on at least one of the measured second fuel temperature or the measured second fuel injector pressure to determine an adjusted second fuel flow target for the dual fuel mode; Determine at least one basic second fuel injector command based on the adjusted second fuel flow target, the estimated substitution rate of the second fuel, and the substitution rate target of the second fuel; and Determine an injector command for the second fuel for the at least one engine bank based on the at least one basic second fuel injector command.

56. The system according to claim 55, wherein, the at least one controller is further configured to: Determine a left bank second fuel injector command and a right bank second fuel injector command based on the at least one injector command for the second fuel.

57. The system according to claim 56, wherein, the at least one controller is further configured to determine the second fuel flow target by dividing the second fuel power target by the estimated thermal efficiency and the lower heating value (LHV), wherein the LHV is determined on a look-up table based on the estimated knock tendency index.

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