Virtual gas quality sensor for an internal combustion engine

Abstract

Procedure, comprehensive: Operating an internal combustion engine (30) to burn a gaseous fuel; Receiving inputs from a variety of sensors associated with the engine with a controller (150), including inputs from a gaseous fuel mass flow sensor (83), an intake fresh air mass flow sensor (81) and an exhaust O2 sensor (82); Determining a stoichiometric fuel-air ratio (SFAR) value with the controller (150) using the received inputs; Determining a lambda parameter G-value with the controller (150) that indicates the quality of the gaseous fuel based on a predetermined relationship between the SFAR value and the lambda parameter G-value, directly from the SFAR value and without intermediate determinations, wherein the lambda parameter G-value is described by the equation G=((H / C)+(4 × Inert / C)) / ((H / C)+4), where H / C is a hydrogen-carbon ratio, and Inert / C is a ratio between inert components and carbon; and Controlling the operation of the engine (30) with the control unit (150) using the lambda parameter G-value.

Description

FIELD OF THE INVENTION

[0001] The present disclosure relates generally to a virtual gas quality sensor for an internal combustion engine, and more particularly, but not exclusively, to systems and methods for virtually sensing one or more qualities of wellbore natural gas. STATE OF THE ART

[0002] An example of an internal combustion engine is a dual-fuel engine, which includes a first fuel type that can be used as the sole fuel during certain operating conditions and a second fuel type that can be used in varying proportions in combination with the first fuel type during other operating conditions. In certain applications, the first fuel source is diesel fuel and the second fuel source is natural gas. Replacing diesel fuel with natural gas can reduce the cost of operating the engine, particularly if the engine is used in locations where natural gas is abundant or available at a low cost. For example, in high-pressure applications, such as fracking platforms and equipment, internal combustion engines can burn wellhead natural gas, which is often unprocessed or slightly processed.Wellhead natural gas can exhibit a wide range of quality characteristics resulting from a varying combustible mixture of hydrocarbon gases, including varying proportions of methane, ethane, propane, butane, and / or pentane. Previous efforts to provide control for dual-fuel engines have several disadvantages, limitations, and weaknesses. German Offenlegungsschrift DE 10 2014 216 874 A1 discloses a method for operating a dual-fuel internal combustion engine based on a characteristic value representing the stoichiometric air demand of a gaseous fuel. German Offenlegungsschrift DE 196 54 699 A1 discloses an internal combustion engine with air-fuel ratio control. US Patent Publication US 2014 / 0 303 876 A1 discloses a control system for an internal combustion engine powered by compressed natural gas.Thus, it is disclosed that the inert gas concentration in compressed natural gas is inversely proportional to the theoretical air-fuel ratio and also inversely proportional to the Wobbe index. There continues to be a significant need for the unique devices, methods, systems, and techniques disclosed herein. SUMMARY

[0003] Unique systems, methods, and apparatus for controlling the operation of dual-fuel engines are disclosed, including estimation of one or more parameters related to natural gas quality. In one embodiment, natural gas quality parameters are estimated from natural gas properties derived from various sensed parameters of the dual-fuel engine.

[0004] This summary is provided to introduce a selection of concepts that are described in more detail below in the illustrative embodiments. This summary is not intended to be interpreted as identifying principal or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. Other embodiments, forms, objects, features, advantages, aspects, and benefits will become apparent from the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 and Fig. 2 are schematic representations of certain aspects of an exemplary dual-fuel engine and fuel delivery system. Fig. Figure 3 is a diagram of a control device for a dual-fuel internal combustion engine. Fig. 4A-4F are exemplary natural gas property parameter graphs. Fig. 5 is a flowchart of a method for dual-fuel operation of an internal combustion engine. DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0005] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It should be understood, however, that this is not to be interpreted as a limitation on the scope of the invention, and that any changes and further modifications to the illustrated embodiments, as well as any further applications of the principles of the invention as illustrated therein, as would normally occur to one skilled in the art to which the invention pertains, are contemplated herein.

[0006] In relation to Fig. 1 and Fig. 2, an internal combustion engine system 20 is shown in schematic form. A fuel supply system 21 ( Fig. 2) may be operated with the internal combustion engine system 20 to provide fuel supply from a first fuel source 102 and a second fuel source 104 to a dual-fuel engine 30. The internal combustion engine system 20 includes a dual-fuel engine 30 connected to an intake system 22 for providing charge flow to the engine 30 and an exhaust system 24 for expelling exhaust gases. In certain embodiments, the dual-fuel engine 30 includes a lean-burn engine, such as a diesel cycle engine, that utilizes a primary fuel, or first fuel, that is a liquid fuel, such as diesel fuel, and a secondary fuel, or second fuel, that is a gaseous fuel, such as natural gas.The second fuel may be, for example, natural gas, biogas, commercial gas, methane, ethane, propane (LPG), butane, ethanol, producer gas, field gas, nominally treated field gas, well gas, nominally treated well gas, liquefied natural gas (LNG), compressed natural gas, landfill gas, condensate, coal bed methane (CBM), a pre-vaporized liquid fuel (such as gasoline), and a mixture thereof. However, other types of first and second fuels are not excluded, such as any suitable liquid fuel and gaseous fuel. In certain embodiments, the first fuel is a lean-burn fuel, and the second fuel is a fuel that utilizes stoichiometric or near-stoichiometric combustion, unless combined with the first fuel during dual-fuel operation.In the illustrated embodiment, the dual-fuel engine 30 includes six cylinders 31a-31f in an in-line arrangement. However, the number of cylinders (collectively referred to as 31) may be any number, and the arrangement of the cylinders 31 may be any arrangement and is not limited to that shown in FIG. Fig. 1 Number and arrangement shown.

[0007] The dual-fuel engine 30 includes an engine block 70 that at least partially defines the cylinders 31a, 31b, 31c, 31d, 31e, 31f (collectively, cylinder 31). A plurality of pistons (not shown) may be slidably disposed within the respective cylinders 31 to reciprocate between a top dead center position and a bottom dead center position. Each of the cylinders 31, its corresponding piston, and the cylinder head form a combustion chamber. In the illustrated embodiment, the engine 30 includes six such combustion chambers. However, it is contemplated that the engine 30 may include a greater or lesser number of cylinders and combustion chambers, and that the cylinders and combustion chambers may be arranged in an "in-line" configuration, a "V" configuration, or any other suitable configuration.

[0008] In one embodiment, the dual-fuel engine 30 is a four-stroke engine. This means that for each complete engine cycle (i.e., for every other complete crankshaft revolution), each piston of each cylinder 31 undergoes an intake stroke, a combustion stroke, and an exhaust stroke. Thus, during each complete cycle of the depicted six-cylinder engine, there are six strokes in which air is drawn from an intake supply line 26 into individual combustion chambers, and six strokes in which exhaust gases are provided to an exhaust manifold 32.

[0009] The dual-fuel engine 30 includes cylinders 31 connected to the intake system 22 to receive a charge flow and connected to the exhaust system 24 to exhaust gases generated by combustion of the first and / or second fuels. The exhaust system 24 may provide exhaust gases to a turbocharger 46, although a turbocharger is not required. In still other embodiments, multiple turbochargers are included to provide high-pressure and low-pressure turbocharging steps that compress the intake flow.

[0010] Furthermore, the exhaust system 24 may be connected to the intake system 22 via one or both of a high-pressure exhaust gas recirculation (EGR) system 51 and a low-pressure EGR system 60. The EGR systems 51, 60 may each include a cooler 52, 62 and a bypass 54, 64. In other embodiments, one or both of the EGR systems 51, 60 are not provided. If provided, the EGR system(s) 51, 60 provide exhaust gas recirculation to the engine 30 under certain conditions. In any EGR arrangement, at least a portion of the exhaust output of the cylinder(s) 31 is recirculated to the engine intake system 22 under certain operating conditions.In the high-pressure EGR system 51, the exhaust gases of cylinder(s) 31 exit the exhaust system 24 upstream of a turbine 48 of the turbocharger 46 and are mixed with the intake flow at a position downstream of a compressor 50 of the turbocharger 46 and upstream of an intake manifold 28 of the engine 30. In the low-pressure EGR system 60, the exhaust gases of cylinder(s) 31a-31f exit the exhaust system 24 downstream of the turbine 48 of the turbocharger 46 and are mixed with the intake flow at a position upstream of the compressor 50 of the turbocharger 46. The recirculated exhaust gases may be combined with the intake gases in a mixing device (not shown) of the intake system 22 or by any other arrangement. In certain embodiments, the recirculated exhaust gases return directly to the intake manifold 28.

[0011] The intake system 22 includes one or more intake supply lines 26 connected to an engine intake manifold 28 that distributes the charge flow to the cylinders 31 of the engine 30. The exhaust system 24 is also coupled to the engine 30 via an engine exhaust manifold 32. The exhaust system 24 includes an exhaust conduit 34 extending from the exhaust manifold 32 to an exhaust valve. In the illustrated embodiment, the exhaust conduit 34 extends to the turbine 48 of the turbocharger 46. The turbine 48 includes a valve, such as a controllable bleed valve 70, or other suitable bypass operable to selectively divert at least a portion of the exhaust flow from the turbine 48 to reduce boost pressure and engine torque under certain operating conditions. In another embodiment, the turbine 48 is a variable geometry turbine with an adjustable-size inlet port.In other embodiments, the exhaust valve is an exhaust throttle valve and / or a bleed valve. Although specific examples have been discussed, no particular form of intake or exhaust control valve assembly is required, nor does the use of such a valve preclude it.

[0012] An aftertreatment system 80 may be connected to an exhaust line 68. The aftertreatment system 80 may include, for example, oxidizers (DOC), particulate matter removal devices (DPF, CDPF), component absorbers or reducers (SCR, AMOX, LNT), reduction systems, and other components, if desired.

[0013] In one embodiment, the exhaust conduit 34 is fluidly coupled to the exhaust manifold 32 and may further include one or more intermediate flow channels, conduits, or other structures. The exhaust conduit 34 extends to the turbine 48 of the turbocharger 46. The turbocharger 46 may be any suitable turbocharger known in the art, including fixed geometry turbochargers, variable geometry turbine turbochargers, and bleed valve turbochargers. The turbocharger 46 may further include multiple turbochargers. The turbine 48 is connected via a shaft 49 to the compressor 50, which is fluidly coupled to the intake supply conduit 26.

[0014] The compressor 50 receives a fresh air flow from an intake air supply line 23. The second fuel source 104 may also be fluidly coupled to the compressor 50 at or upstream of the inlet or downstream of the compressor 50, as described further below. The intake system 22 may further include a compressor bypass 72 connecting a downstream, or discharge, side of the compressor 50 to an upstream, or intake, side of the compressor 50. The compressor bypass 72 includes a control valve 74 that is selectively opened to allow charge flow to be redirected to the intake side of the compressor 50 to reduce compressor surge under certain operating conditions, for example, when an intake throttle 76 is closed. The intake supply line 26 may include a charge air cooler 36 downstream of the compressor 50 and the intake throttle 76.In another embodiment, a charge air cooler 36 is located upstream of the intake throttle 76 in the intake system 22. The charge air cooler 36 may be disposed in the intake air supply line 26 between the engine 30 and the compressor 50 and may include, for example, an air-to-air heat exchanger, an air-to-liquid heat exchanger, or a combination of both to facilitate the transfer of heat energy to or from the flow directed to the engine 30.

[0015] During operation of the internal combustion engine system 20, fresh air is supplied through the intake air supply line 23. The fresh air flow or combined flows may be filtered, unfiltered, and / or conditioned in any known manner when provided, either before or after mixing with the EGR flow from the EGR systems 51, 60. The intake system 22 may include components configured to facilitate or control the introduction of the charge flow into the engine 30 and may include an intake throttle 76, one or more compressors 50, and a charge air cooler 36. The intake throttle 76 may be connected upstream or downstream of the compressor 50 via a fluid passage and configured to control a flow of atmospheric air and / or a combined air / EGR flow to the engine 30.Compressor 50 may be a fixed or variable geometry compressor configured to receive air or an air-fuel mixture from fuel source 104 and compress the air or combined flow to a predetermined pressure level prior to engine 30. The charge flow is pressurized by compressor 50 and passed through charge air cooler 36 and provided to engine 30 through intake supply line 26 at engine intake manifold 28.

[0016] With further reference to Fig. 2, the fuel system 21 is configured to provide dual fuel supply to the engine 30. In Fig. 2, only four cylinders 31a, 31b, 31c, 31d are shown; it should be understood that if additional cylinders, such as cylinders 31e and 31f, or fewer cylinders are provided, they will be arranged in a similar manner to the illustrated cylinders 31. The fuel system 21 includes a first fuel source 102 and a second fuel source 104. The first fuel source 102 is configured to provide a flow of a first fuel to the cylinders 31 with one or more injectors at or near each cylinder. The second fuel source 104 is connected to the intake system 22 with a mixing device or connection at or adjacent to an inlet of the compressor 50.In certain embodiments, each of the cylinders 31 includes at least one direct fuel injector for delivering fuel from a primary fuel source, such as the first fuel source 102, to the combustion chamber thereof. Additionally, at least one of a port injector at each cylinder or a mixing device at an inlet of the compressor 50 may be provided for delivering or supplying fuel from the second fuel source 104, delivering the charge flow to the cylinders 31.

[0017] The fuel supply from the first fuel source 102 is controlled to provide the sole fuel supply to the engine 30 under certain operating conditions, and the fuel supply from the second fuel source 104 is provided to replace the fuel supply from the first fuel source 102 under other operating conditions to provide a dual-fuel flow of fuel to the engine 30. In embodiments where the first fuel source 102 is diesel fuel and the second fuel source 104 is natural gas, a control system including a controller 150 is configured to control the flow of liquid diesel fuel from the first source 102 and the flow of gaseous fuel from the second source 104, for example, taking into account engine speed, engine load, intake manifold pressure, and fuel pressure, as described further below.

[0018] A direct injector as used herein includes any fuel injector that injects fuel directly into the cylinder volume and can deliver fuel into the cylinder volume when the intake valve(s) and exhaust valve(s) are closed. The direct injector may be configured to inject fuel at the top of the cylinder or at the side of the cylinder. In certain embodiments, the direct injector may be configured to inject fuel into a combustion pre-chamber. Each cylinder 31 may include one or more direct injectors 116a-116d, respectively. The direct injectors 116a-116d may be the primary fuel supply device for the first fuel source 102 for the cylinders 31.

[0019] A port injector as used herein includes any fuel injector that injects the second fuel outside the engine cylinder into the intake manifold to form the air-fuel mixture. The port injector injects the fuel toward the intake valve. During the intake stroke, the descending piston draws the air-fuel mixture past the open intake valve and into the combustion chamber. Each cylinder 31a, 31b, 31c, 31d may each include one or more port injectors 118a, 118b, 118c, 118d. In one embodiment, port injectors 118a-118d may be the primary fuel delivery device for the second fuel source 104 to the cylinders 31.In another embodiment, the second fuel source 104 may be connected to the intake system 22 with a mixing device 115 at a gaseous fuel port 114 upstream of the intake manifold 28, such as at the inlet of or upstream of the compressor 50. A flow control valve 117 may be provided to control the flow of gaseous fuel from the second fuel source 104 to the engine 30.

[0020] In certain embodiments, each cylinder 31 includes at least one direct fuel injector capable of providing the entire designed fuel delivery amount to the cylinders 31 under any operating conditions from the first fuel source 102. The second fuel source 104 provides a flow of a second fuel to each cylinder 31 through a port injector or natural gas connection upstream of the intake manifold 28 to provide a second fuel flow to the cylinders 31 to achieve desired operating results, such as improved efficiency, improved fuel consumption, improved high-load operation, and other results.

[0021] An embodiment of the system 20 includes the fuel system 21 having at least one fuel source 102 for providing a first fuel flow to all cylinders 31 and a second fuel source 104 that provides a second fuel flow to all cylinders 31 in addition to the first fuel flow under certain operating conditions. The first fuel source 102 includes a first fuel pump 105 connected to the controller 150, and the second fuel source 104, in one embodiment, includes a second fuel pump 106 connected to the controller 150. Each of the cylinders 31 includes an injector, such as each of the illustrated cylinders 31a-31d of Fig. 2 associated direct injectors 116a-116d. The direct injectors 116a-116d are electrically connected to the controller 150 to receive fueling commands that provide a fuel flow to the corresponding cylinders 31 taking into account a fueling command determined depending on engine operating conditions and an operator input with reference to fueling maps, control algorithms, or another source stored in the controller 150 for determining fueling rate / amount. The first fuel pump 105 is connected to each of the direct injectors 116a-116d by a first fuel line 109. The first fuel pump 105 is operable to provide each of the cylinders 31a-31d with a first fuel flow from the first fuel source 102 at a rate, amount, and timing determined by the controller 150.which achieves a desired power and exhaust emission from cylinders 31.

[0022] If provided, the second fuel pump 106 is connected via a second fuel line 108 to the inlet of the compressor 50, to the gaseous fuel port 114, or to the manifold injectors 118. A shutoff valve 112 connected to the controller 150 may be provided in the fuel line 108 and / or at one or more locations in the fuel system 21. The second fuel pump 106 is operable to provide a second fuel flow from the second fuel source 104 in an amount determined by the controller 150 that achieves a desired power and exhaust emission from the cylinders 31.In another embodiment, the second fuel pump 106 is omitted and fuel is provided to the port 114 or the manifold injectors 118 under pressure from a pressurized second fuel source 104 and the flow of gaseous fuel from the second fuel source 104 is controlled by the flow control valve 117.

[0023] The controller 150 may be connected to actuators, switches, or other devices associated with the fuel pumps 105, 106, the isolation valve 112, the intake throttle 76, the compressor bypass valve 74, the flow control valve 117, the isolation valve 112, the bleed valve 70, and / or the injectors 116, 118 and configured to provide control commands thereto that control the amount, timing, and duration of the flows of the first and second fuels to the cylinders 31, the charge flow, and the exhaust flow to provide the desired power and exhaust emission. The positioning of each of the isolation valve 112, the flow control valve 117, the intake throttle valve 76, the compressor bypass valve 74, the bleed valve 70, the injectors 116, 118 and / or the on / off status of the fuel pumps 105, 106 may be controlled via control commands from the controller 150.

[0024] In other embodiments, a first sub-array of cylinders 31 is associated with a first cylinder bank (not shown), and a second sub-array of cylinders 31 is associated with a second cylinder bank. Accordingly, different gaseous fuel replacement rates may be used for the cylinder banks. In certain embodiments of engines with multiple cylinder banks, the gaseous fuel supply lines to each cylinder bank may be controlled separately to provide the desired gaseous fuel replacement rate for the corresponding cylinder bank.

[0025] In certain embodiments of the systems disclosed herein, controller 150 is configured to perform certain operations to control engine operation and fueling of cylinders 31 with fuel delivery system 21 to provide desired operating results. In certain embodiments, controller 150 forms a portion of a processing subsystem including one or more computing devices having storage, processing, and communication hardware. Controller 150 may be a single device or a distributed device, and the functions of controller 150 may be performed by hardware or instructions provided on a computer-readable storage medium. Controller 150 may be included in or partially included in an engine controller (not shown) or may be completely separate from it.The controller 150 may be in communication with any sensor or actuator throughout the systems disclosed herein, including by direct connection, connection via a data link, and / or by connection to other controllers or portions of the processing subsystem that provide sensor and / or actuator information to the controller 150.

[0026] A number of sensors associated with systems 20 and / or 21 may be configured in operative communication with controller 150. Unless otherwise stated, the sensors disclosed herein may include physical sensors, virtual sensors, and / or combinations thereof. In certain embodiments, controller 150 may be in operative communication with: an intake fresh air mass flow sensor 81 (sometimes referred to as an intake air flow sensor) configured to measure or estimate intake fresh air mass flow, an exhaust O2 sensor 82 (sometimes referred to as an exhaust lambda sensor) configured to measure or estimate exhaust oxygen or related characteristics, and a gaseous fuel mass flow sensor 83 (sometimes referred to as a gas mass flow sensor) configured to measure or estimate the mass flow of gaseous fuel provided for combustion.The exhaust O2 sensor may also be provided and used in conjunction with an exhaust backpressure sensor. The gaseous fuel mass flow sensor 83 may comprise a hot-foil gas mass flow sensor or an orifice-type sensor. The orifice-type sensor may include inlet pressure, temperature, and delta pressure or exhaust pressure sensor components. Either a high-precision gas control valve or a dedicated orifice may be used in conjunction with the orifice-type sensor. In certain embodiments, multiple gas mass flow sensors may be present; for example, a gas mass flow sensor 83 may be an orifice-type sensor, and a hot-foil gas mass flow sensor 83' may also be used.In certain embodiments, the controller 150 may be in operative communication with a sensor 84, which may be a thermal conductivity sensor configured to measure the thermal conductivity characteristics of gaseous fuel. In certain embodiments, the sensor 84 may alternatively be a speed of sound sensor configured to measure the speed of sound in the gaseous fuel. In certain embodiments, the controller 150 may be in operative communication with a methane fraction sensor configured to measure the methane fraction characteristics of gaseous fuel.While each of the sensors 81, 82, 83, 83' and 84 may be present in certain embodiments, it should be appreciated that one or more of the sensors may be omitted in other embodiments, for example, in cases where the information provided by a particular sensor is not needed for the control methods and systems disclosed herein.

[0027] Example and non-limiting implementation elements include: sensors that provide any value defined herein, sensors that provide any value that is a precursor to a value defined herein, data link and / or network hardware, including communication chips, crystal oscillators, communication links, cables, twisted pair wires, coaxial wires, shielded wires, transmitters, receivers and / or transceivers, logic circuits, hard-wired logic circuits, reconfigurable logic circuits in a particular non-transient state configured according to the module specification, any actuator, including at least one electrical, hydraulic or pneumatic actuator, a solenoid, an operational amplifier, analog control elements (springs, filters, integrators, adders, dividers, gain elements) and / or digital control elements.

[0028] One skilled in the art, given the disclosures herein, can appreciate that the controllers, control systems, and control methods disclosed herein are configured to perform operations that enhance various techniques and provide improvements in various technical fields. Exemplary and non-limiting technical improvements include, without limitation, improvements in the combustion performance of dual-fuel internal combustion engines, improvements in engine torque production and torque control, engine fuel consumption performance, improvements in engine noise and vibration control of dual-fuel engines, improvements in the performance or operation of aftertreatment systems and / or components of dual-fuel engines, and / or improvements in emission control of dual-fuel engines.Exemplary and non-limiting technical areas that are improved include, without limitation, the technical areas of dual-fuel internal combustion engines and related devices and systems, as well as vehicles incorporating the same.

[0029] Certain operations described herein include operations for interpreting and / or determining one or more parameters. Interpretation or determination, as used herein, includes: receiving values ​​by any method known in the art, including at least receiving values ​​from a data link or network communication, receiving an electronic signal (e.g.,a voltage, frequency, current, or PWM signal) indicative of the value, receiving a computer-generated parameter indicative of the value, reading the value from a memory location on a non-transient computer-readable storage medium, receiving the value as a runtime parameter by any means known in the art, and / or by receiving a value by which the interpreted parameter can be calculated, and / or by referring to a standard value that is interpreted as the parameter value.

[0030] The following schematic flow descriptions provide illustrative embodiments of methods for controlling fuel delivery during a dual-fuel mode of operation of the internal combustion engine 20. As used herein, a dual-fuel system 21 is a fuel delivery system in which a dual-fuel mode is provided in which each of the cylinders 31 of the engine 30 receives a first fuel flow and, under certain operating conditions, a second fuel flow in addition to the first fuel flow. However, it is contemplated that the dual-fuel system 21 may be operated in a single-fuel mode from the first fuel source 102 upon operator selection or under certain operating conditions.Depicted acts are merely exemplary, and acts may be combined or split, added or removed, and rearranged in whole or in part, unless expressly stated otherwise herein. Certain illustrated acts may be implemented by a computer or control device embodiment of controller 150 executing a computer program product on a non-transient computer-readable storage medium, the computer program product including instructions for causing the computer to perform one or more of the acts or for issuing instructions to another device to perform one or more of the acts.

[0031] Fig. 3 is a schematic representation of a processing subsystem embodiment 300 of the controller 150 that determines one or more natural gas quality parameters 310. The gas quality parameters 310 may be, for example, one or more of a parameter G (sometimes referred to as a lambda parameter G), a specific gravity associated with a gaseous fuel, a methane number associated with a gaseous fuel, a lower heating value (LHV) associated with a gaseous fuel, and a Wobbe index associated with a gaseous fuel.

[0032] The controller 150 may use the parameter G to determine values ​​for lambda used to control an internal combustion engine. The parameter G may be a significant potential source of control error when high lambda values ​​are encountered, for example, under lean-burn conditions. In certain embodiments, the controller 150 may include closed-loop PI(D) controls configured to determine a target value for exhaust O2 (or a parameter related thereto, e.g., lambda or an equivalent ratio), a current exhaust O2 (or a parameter related thereto, e.g.,Lambda or an equivalent ratio) using a sensor, which may be a physical sensor or a virtual sensor, or a combination thereof; determine an error between the target value and the current value; and process the error using proportional, integral, and / or derivative controls in conjunction with a feedback loop. In other embodiments, the controller 150 may use open-loop or other types of controls.

[0033] The controller 150 may determine a target value for lambda by performing a calculation according to the following equation (1): λ=1+GxO21−AxO2

[0034] The parameter G can be theoretically defined in terms of a hydrogen-carbon ratio and a ratio between inert components and carbon as described, for example, by equation (2) below: G=HC+4InertCHC+4

[0035] In practice, the explicit calculation of the parameter G may not be possible or practical, as the H:C ratio and inert:C ratio may be unknown and difficult to determine or estimate. Even if attempted, the explicit calculation of the parameter G from these ratios can result in computational burden and introduce sources of error.

[0036] In certain embodiments, subsystem 300 may be configured to directly determine or estimate the parameter G without performing any intermediate actions, calculations, or processes, such as determining the HC ratio and Inter:C ratio. In one exemplary form, subsystem 300 may determine a stoichiometric fuel-to-air ratio (SFAR), for example, as described in connection with equation (4) below, and determine the parameter G directly from SFAR without requiring any intermediate calculations or processing steps. The determination may be made based on a predetermined relationship between the parameter G and SFAR, for example, the relationship described in Fig. 4A. Subsystem 300 may be configured to directly determine parameter G using a predetermined relationship between parameter G and SFAR in a number of ways, for example, using a lookup table structure storing values ​​representing the predetermined relationship, using an array, graph, or other data structure to store values ​​representing the predetermined relationship, or by performing a calculation based on a formula representing or approximating the predetermined relationship.

[0037] Parameters x O2is an exhaust gas oxygen value that may be determined by controller 150 using input received from an exhaust gas O2 sensor. Parameter A (sometimes referred to as lambda parameter A) may be determined based on the ratio of N2 to O2 in the intake charge provided to the engine (which may be set to a nominal atmospheric value and, in some forms, adjusted based on indicators of altitude or ambient conditions) and the ratio of H2O to O2 in the intake charge provided to the engine (which may be determined or estimated based on inputs received from a humidity sensor). In certain embodiments, controller 150 may be configured to determine parameter A according to the following equation (3): A=1+N2O2+H2OO2

[0038] In certain embodiments, subsystem 300 may determine a methane number used by controller 150 to control or prevent engine knock by controlling fuel delivery, EGR, and / or airflow parameters. In one exemplary form, subsystem 300 may determine a current sensor ratio (FSR), for example, as described in connection with equation (5) below, determine one of a thermal conductivity (TC) value, such as from the output of a thermal conductivity sensor configured to measure the thermal conductivity characteristics of gaseous fuel, and a speed of sound (SOS) value, such as from the output of a speed of sound sensor configured to measure the speed of sound in the gaseous fuel, and determine the methane number from these values.If the input is received from a thermal conductivity sensor, the determination can be made directly based on a predetermined relationship between the methane number and the product of TC and FSR (TC*FSR), for example the one shown in . Fig. 4C. If the input is received from a sound velocity sensor, the determination can be made directly based on a predetermined relationship between the methane number and the product of SOS and FSR (SOS*FSR), which is one of the Fig. 4B for the thermal conductivity sensor. Subsystem 300 may be configured to directly determine a methane number using such a predetermined relationship in a number of ways, for example, using a lookup table structure storing values ​​representing the predetermined relationship, using an array, graph, or other data structure to store values ​​representing the predetermined relationship, or by performing a calculation based on a formula representing or approximating the predetermined relationship.

[0039] In certain embodiments, subsystem 300 may determine a gas-specific weight parameter that may be used by controller 150 to control engine operation. Controller 150 may use the gas-specific weight parameter to calculate a fresh air flow from charge flow and gas mass flow (e.g., by determining how much fresh air is moved by the gas mass flow) and may control fueling, EGR, and / or air routing decisions based thereon.In one exemplary form, subsystem 300 may determine a current sensor ratio (FSR), for example, as described in connection with equation (5) below, one of a thermal conductivity (TC) value, such as from the output of a thermal conductivity sensor configured to measure the thermal conductivity characteristics of gaseous fuel, and a speed of sound (SOS) value, such as from the output of a speed of sound sensor configured to measure the speed of sound in the gaseous fuel, and determine the methane number from these values. If the input is received from a thermal conductivity sensor, the determination may be made directly based on a predetermined relationship between the specific gravity and the inverse of the product of TC and FSR (1 / (TC*FSR)), for example, as shown in . Fig. 4B. When the input is received from a sound velocity sensor, the determination can be made directly based on a predetermined relationship between the specific gravity and the inverse of the product of SOS and FSR (1 / (SOS*FSR)), which is one of the Fig. 4B for the thermal conductivity sensor. The subsystem 300 may be configured to directly determine a specific gravity using such a predetermined relationship in a number of ways, for example, using a lookup table structure storing values ​​representing the predetermined relationship, using an array, graph, or other data structure to store values ​​representing the predetermined relationship, or by performing a calculation based on a formula representing or approximating the predetermined relationship.

[0040] In certain embodiments, subsystem 300 may determine and use a lower heating value (LHV) for fuel quality monitoring and may control fueling, EGR, and / or airflow decisions based thereon. In one exemplary form, subsystem 300 may determine a stoichiometric fuel-to-air ratio (SFAR), for example, as described in connection with equation (4) below, determine one of a thermal conductivity (TC) value, such as from the output of a thermal conductivity sensor configured to measure the thermal conductivity characteristics of gaseous fuel, and a speed of sound (SOS) value, such as from the output of a speed of sound sensor configured to measure the speed of sound in the gaseous fuel, and determine the LHV from these values.When the input is received from a thermal conductivity sensor, the determination can be made directly based on a predetermined relationship between the LHV and the inverse of the product of TC and SFAR (1 / (TC*SFAR)), for example the one shown in . Fig. 4D. If the input is received from a sound velocity sensor, the determination can be made directly based on a predetermined relationship between LHV and the inverse of the product of SOS and SFAR (1 / (SOS*SFAR)), which is similar to the one shown in Fig. 4D for the thermal conductivity sensor. Alternatively, if the input is received from a thermal conductivity sensor, the determination can be made directly based on a predetermined relationship between the LHV and the quotient of TC and SFAR (TC / SFAR), for example, the relationship shown in Fig. 4F. If the input is received from a sound velocity sensor, the determination can be made directly based on a predetermined relationship between LHV and the quotient of SOS and SFAR (SOS / SFAR), which corresponds to the Fig. 4F for the thermal conductivity sensor. Subsystem 300 may be configured to directly determine a methane number using such a predetermined relationship in a number of ways, for example, using a lookup table structure storing values ​​representing the predetermined relationship, using an array, graph, or other data structure to store values ​​representing the predetermined relationship, or by performing a calculation based on a formula representing or approximating the predetermined relationship.

[0041] In certain embodiments, subsystem 300 may determine and use a Wobbe index for fuel quality monitoring and may control fueling, EGR, and / or airflow decisions based thereon. In one exemplary form, subsystem 300 may determine a stoichiometric fuel-to-air ratio (SFAR), for example, as described in connection with equation (4) below, and determine the Wobbe index from the SFAR. The determination may be made directly based on a predetermined relationship between the Wobbe index and the SFAR, for example, as described in Fig. 4E. Subsystem 300 may be configured to directly determine parameter G using a predetermined relationship between parameter G and SFAR in a number of ways, for example, using a lookup table structure storing values ​​representing the predetermined relationship, using an array, graph, or other data structure to store values ​​representing the predetermined relationship, or by performing a calculation based on a formula representing or approximating the predetermined relationship.

[0042] In certain embodiments, the controller 150 may determine a plurality of gas quality parameters, such as those described above. In certain forms, two or more of a lambda parameter G, a gas specific gravity, a methane number, a lower heating value (LHV), and a Wobbe index may be determined and used to control operation of the engine as described herein. In certain forms, three or more of a lambda parameter G, a gas specific gravity, a methane number, a lower heating value (LHV), and a Wobbe index may be determined and used to control operation of the engine as described herein. In certain forms, four or more of a lambda parameter G, a gas specific gravity, a methane number, a lower heating value (LHV), and a Wobbe index may be determined and used to control operation of the engine as described herein.In certain forms, any of the lambda parameter G, a gas specific gravity, a methane number, a lower heating value (LHV), and a Wobbe index may be determined and used to control the operation of the engine as described herein.

[0043] The processing subsystem 300 includes a natural gas properties measurement module 302 configured to receive engine parameter inputs from a plurality of sensors associated with the dual-fuel engine 30 and / or the systems 20 and 21 and to determine one or more properties of the natural gas 304 using the sensor inputs. The sensor inputs may include inputs from one or more of the sensors described herein. It is understood that the terms "sensor input" and "sensor inputs" refer to inputs received at the processing subsystem 300 from one or more sensors and may alternatively be referred to as "received sensor outputs."In certain embodiments, the sensor inputs include an input from a charge flow or airflow sensor configured to measure or estimate the charge flow or airflow, and an input from a gas mass flow sensor configured to measure characteristics of the gaseous fuel provided for combustion. As previously described, the mass flow sensor may include a hot foil gas mass flow sensor and / or an orifice integral with intake pressure, temperature, and delta pressure or exhaust pressure sensor components. The sensor inputs may further include inputs from a thermal conductivity sensor and a methane fraction sensor. In certain embodiments, the sensor inputs include inputs from a charge airflow sensor, an exhaust O2 sensor, an exhaust backpressure sensor, an orifice gas mass flow sensor, a hot foil mass flow sensor, a thermal conductivity sensor, and a methane fraction sensor.

[0044] The natural gas properties measurement module 302 is configured to determine one or more natural gas properties 304 using the received sensor inputs. The natural gas properties 304 may include a stoichiometric fuel-to-air ratio (SFAR) and a flow sensor ratio (FSR). The module 302 may be configured to determine an SFAR value by receiving inputs from a gas mass flow sensor, a fresh air flow sensor, and an exhaust O2 or lambda sensor and perform a calculation according to the following equation (4): SFAR=(Gas mass flow sensor input / Fresh air mass flow sensor input)*(Exhaust O2 or Lambda sensor input)

[0045] The gas mass flow sensor input may be provided by a muzzle gas mass flow sensor or a hot foil gas mass flow sensor or a combination thereof and / or other gas mass flow sensors.

[0046] The module 302 may be further configured to determine an FSR value by performing a calculation according to the following equation (5): FSR=(muzzle gas mass flow sensor input) / (hot foil gas mass flow sensor input)

[0047] It should be noted that for the predetermined (e.g., nominal or ideal) gas for which both sensors are calibrated, FSR = 1 and that FSR changes according to the gas quality, since different sensor types (e.g., orifice-type sensors and hot foil sensors) are based on different physics and are affected by different physical properties.For example, hot foil sensors are affected by a variation in thermal conductivity and viscosity, while orifice-type sensors are affected by a variation in density and specific heat ratio. It should also be recognized that FSR can be determined as the ratio between two different types of sensors, generally referred to as gas mass flow sensor 1 and gas mass flow sensor 2, where sensor 1 can be a orifice-type sensor, a hot foil sensor, or another type of sensor, and sensor 2 can be another of a orifice-type sensor, a hot foil sensor, or another type of sensor.

[0048] The subsystem 300 further includes a natural gas quality parameter estimation module 306 configured to output one or more natural gas quality parameters 310 for operation and control of the systems 20 and 31 by the controller 150 in response to the natural gas properties 304. The natural gas quality parameters 310 may include, for example, one or more of a lambda (λ) parameter G, a gas specific gravity, a methane number, a lower heating value (LHV), and a Wobbe index. The module 306 may be configured to determine the parameters 310 using one or more predetermined relationships between a natural gas quality parameter and a natural gas property, such as those generally described above in connection with the controller 150. The predetermined properties may be implemented in one or more lookup tables or one or more calculation algorithms.The predetermined relationships can be determined based on empirically observed relationships, theory-based relationships, or combinations thereof.

[0049] In certain embodiments, the natural gas quality parameter estimation module 306 stores or has access to predetermined relationships based on one or more empirical natural gas quality parameter extrapolation graphs 308 that provide a relationship between the natural gas quality parameter(s) 310 in response to the natural gas properties 304. The natural gas quality parameter extrapolation graphs 308 may provide relationships for a number of natural gas quality parameters.

[0050] Examples of empirically determined relationships between the natural gas quality parameters 310 and the natural gas properties 304 are given in Fig. 4A-4F. The data plots shown therein represent results for 10,000 uniformly random gas compositions (CO2, N2, CH4, C2H6, C3H8, C a H 10 ). Actual field samples of gas compositions (CO2, N2, CH4, C2H6, C3H8, C4H 10 , C5H 12 , C6H 14) can also be used. The gas compositions were tested assuming that the internal combustion engine system was configured to burn CH4 at maximum calculated power with a hot-foil sensor voltage of 3.5. Using these conditions, an empirically based mass flow was determined whose lambda value is the same for each gas. A hot-foil sensor flow and a port-type sensor flow were calculated that correspond to the actual mass flow for each gas. The gas quality parameters were mapped to functions of physical or derived gas properties measured by sensor sets that yielded the best correlation.

[0051] The graph from Fig. Figure 4A shows a relationship between the lambda parameter G and the stoichiometric fuel-air ratio (SFAR). As in Fig. As shown in Figure 4A, a linear relationship between the lambda parameter G and SFAR may be determined, for example, using a regression technique to determine a best-fitting curve. As described above, this relationship may be implemented in module 304 using one or more lookup tables and / or computational algorithms. In certain embodiments, the relationship may be partially linear, linear over different intervals or ranges, or nonlinear, and may fit a higher-order polynomial or an exponential expression.

[0052] The graph from Fig. Figure 4B shows a linear relationship between a gas specific gravity and the inverse of the product of the thermal conductivity (TC) and the current sensor ratio (FSR) (1 / (TC*FSR)). The graph from Fig. Figure 4C shows a linear relationship between a methane number and the product of TC and FSR (TC*FSR). The graph from Fig. Figure 4D represents a linear relationship between a lower heating value by standard volume (LHV) and the product of TC and SFAR of a finish-type sensor (1 / (TC*SFAR Orifice )). The graph from Fig. Figure 4E shows a linear relationship between a Wobbe index and the inverse of a SFAR of a muzzle-type sensor (1 / SFAR Orifice ). The graph from Fig. Figure 4F shows a linear relationship between a lower heating value by mass (LHV) and the quotient of TC and SFAR of a mouth-type sensor (TC / SFAR Orifice ). The relationship described above may be implemented in module 304 using one or more lookup tables and / or calculation algorithms. In certain embodiments, the relationships may be partially linear or nonlinear, linear over different intervals or ranges, and may fit a higher-order polynomial or exponential expression.

[0053] With reference to Fig. 5, another embodiment of a method 400 for estimating one or more natural gas quality parameters is shown. In one embodiment, the method 400 is implemented by the processing subsystem 300. The method 400 includes an operation 402 for introducing natural gas into an intake system 22 on an internal combustion engine 30 for an operation 404 of operating the internal combustion engine 30 from a mixture of natural gas and diesel fuel as described hereinbefore. The method 400 continues with an operation 406 for sensing one or more engine parameters through various sensors of the internal combustion engine 30, including a virtual or physical charge / airflow sensor, a wideband exhaust O2 sensor including a backpressure sensor, a hot foil gas mass flow sensor, and / or a muzzle gas mass flow sensor, a thermal conductivity sensor, and / or a methane fraction sensor.

[0054] The method 400 continues with an operation 408 to measure one or more natural gas properties, including a stoichiometric fuel-to-air ratio (SFAR) corresponding to (gas mass flow / fresh air flow) * (exhaust O2 lambda) and / or a flow sensor ratio (FSR) corresponding to (gas mass flow sensor 1) / (gas mass flow sensor 2). The method 400 continues with an operation 410 to estimate the natural gas quality parameter(s) in response to the measured natural gas properties. In one embodiment, a lambda parameter G is estimated from the extrapolation graph shown in Fig. 4A, a gas specific gravity is determined from the Fig. 4B shown extrapolation graph, a methane number is estimated from the value given in the Fig. 4C, an LHV [BUT / SCF] is estimated from the relationship shown in the extrapolation graph in Fig. 4D, a Wobbe index [BTU / SCF] is estimated from the relationship shown in the extrapolation graph in Fig. 4E shown extrapolation graphs and / or an LHV [MJ / kg] is calculated from the relationship shown in the Fig. The relationship shown in the extrapolation graphs in Figure 4F was estimated.

[0055] A number of further exemplary embodiments will now be described. An exemplary embodiment is a first method comprising: Operating an internal combustion engine to combust a gaseous fuel; receiving inputs from a plurality of sensors associated with the engine with a controller, including inputs from a gaseous fuel mass flow sensor, an intake fresh air mass flow sensor, and an exhaust O2 sensor; determining a stoichiometric fuel-to-air ratio (SFAR) value with the controller using the received inputs; determining a lambda parameter G value with the controller that represents the quality of the gaseous fuel based on a predetermined relationship between the SFAR value and the lambda parameter G-value, directly from the SFAR value and without intermediate determinations; and controlling operation of the engine with the controller using the lambda parameter G-value. In certain forms of the first method, the act of controlling operation of the engine with the controller using the lambda parameter G-value includes calculating a lambda control value (λ) using the lambda parameter G-value and controlling operation of the engine using the lambda control value (λ).In certain forms of the first method, the process of calculating the lambda control value (λ) comprises calculating a lambda parameter A based on a ratio of N2 to O2 in the intake charge provided to the engine and a ratio of H2O to O2 in the intake charge provided to the engine, and calculating the lambda control value using the lambda parameter A. In certain forms of the first method, the lambda parameter A is calculated according to the following equation: A = 1 + (N2 / O2) + (H2O / O2); and the lambda control value (λ) is determined according to the following calculation: -λ= (1 + (G × exhaust oxygen)) / (1 + (A × exhaust oxygen)).

[0056] Certain forms of the first method further comprise, following a change in gaseous fuel composition: receiving second inputs from the plurality of sensors with a control sensor; determining a second SFAR value with the controller using the received second inputs; determining a second lambda parameter G value with the controller directly from the second SFAR value and without intermediate determinations; and controlling operation of the engine with the controller using the second lambda parameter G value; wherein the second lambda parameter G value is operative to adapt operation of the engine to the change in gaseous fuel composition.

[0057] Additional exemplary embodiments include systems including an electronic control system configured to perform a control process according to the first method or any of the previously described forms of the first method. Additional exemplary embodiments include non-transitory, controller-readable storage media configured with instructions executable by a controller to perform a control process according to the first method or any of the previously described forms of the first method.

[0058] Another exemplary embodiment is a second method comprising: operating an internal combustion engine to combust a gaseous fuel; receiving, with a controller, an input from one of a thermal conductivity sensor configured to detect the thermal conductivity of the gaseous fuel and a speed of sound sensor configured to detect the speed of sound in the gaseous fuel; receiving, with the controller, inputs from a first gaseous fuel mass flow sensor configured to detect the mass flow of the gaseous fuel and a second gaseous fuel mass flow sensor configured to detect the mass flow of the gaseous fuel, wherein the second gaseous fuel mass flow sensor is a different sensor type than the first gaseous fuel mass flow sensor;Determining a flow sensor ratio (FSR) value with the controller using the inputs received from the first gaseous fuel mass flow sensor and the second gaseous fuel mass flow sensor; determining a calculated value with the controller using the FSR value and the input received from one of the thermal conductivity sensor and the speed of sound sensor; determining a gaseous fuel quality parameter value from the calculated value with the controller based on a predetermined relationship between the calculated value and the gaseous fuel quality parameter; and controlling operation of the engine with the controller using the gaseous fuel quality parameter.

[0059] In certain forms of the second method, the first gaseous fuel mass flow sensor comprises a nozzle-type sensor and the second gaseous fuel mass flow sensor comprises a hot foil sensor. In certain forms of the second method, the calculated value is calculated as the product of a TC value based on the input received from the thermal conductivity sensor and the FSR value, wherein the gaseous fuel quality parameter is a methane number. In certain forms of the second method, the calculated value is calculated as the product of an SOS value based on the input received from the speed of sound sensor and the FSR value, wherein the gaseous fuel quality parameter is a methane number.In certain forms of the second method, the calculated value is calculated as the inverse of the product of a TC value based on the input received from the thermal conductivity sensor and the FSR value, where the quality parameter of the gaseous fuel is a specific gravity of the gaseous fuel. In certain forms of the second method, the calculated value is calculated as the inverse of the product of an SOS value based on the input received from the sound speed sensor and the FSR value, where the quality parameter of the gaseous fuel is a specific gravity of the gaseous fuel.

[0060] Certain forms of the second method further comprise, following a change in the composition of the gaseous fuel: determining a second FSR value with the controller using second inputs received from the first gaseous fuel mass flow sensor and the second gaseous fuel mass flow sensor; determining a second calculated value with the controller using the second FSR value and a second input received from one of the thermal conductivity sensor and the speed of sound sensor; determining a second gaseous fuel quality parameter from the second calculated value with the controller; and controlling operation of the engine with the controller using the second gaseous fuel quality parameter.wherein the second quality parameter of the gaseous fuel is effective to adapt the operation of the engine to the change in the composition of the gaseous fuel;

[0061] Additional exemplary embodiments include systems including an electronic control system configured to perform a control process according to the second method or any of the previously described forms of the second method. Additional exemplary embodiments include non-transitory, controller-readable storage media configured with instructions executable by a controller to perform a control process according to the second method or any of the previously described forms of the second method.

[0062] Another exemplary embodiment is a third method comprising: operating an internal combustion engine to combust a gaseous fuel; receiving, with a controller, an input from one of a thermal conductivity sensor configured to sense the thermal conductivity of the gaseous fuel and a speed of sound sensor configured to sense the speed of sound in the gaseous fuel; receiving, with the controller, inputs from a gaseous fuel mass flow sensor, an intake fresh air mass flow sensor, and an exhaust O2 sensor; determining, with the controller, a stoichiometric fuel-to-air ratio (SFAR) value using the received inputs from the gaseous fuel mass flow sensor, the intake fresh air mass flow sensor, and the exhaust O2 sensor;Determining a calculated value with the controller using the SFAR value and the input received from one of the thermal conductivity sensor and the speed of sound sensor; Determining a gaseous fuel quality parameter value from the calculated value with the controller based on the predetermined relationship between the calculated value and the gaseous fuel quality parameter; and controlling operation of the engine with the controller using the gaseous fuel quality parameter.

[0063] In certain forms of the third method, the quality parameter value of the gaseous fuel is a lower heating value. In certain forms of the third method, the calculated value is calculated as the inverse of the product of a TC value based on the input received from the thermal conductivity sensor and the SFAR value. In certain forms of the third method, the calculated value is calculated as the inverse of the product of an SOS value based on the input received from the sound speed sensor and the SFAR value. In certain forms of the third method, the calculated value is calculated as a TC value based on the input received from the thermal conductivity sensor divided by the SFAR value. In certain forms of the third method, the calculated value is calculated as an SOS value based on the input received from the sound speed sensor divided by the SFAR value.

[0064] Certain forms of the third method further comprise, following a change in the composition of the gaseous fuel: receiving second inputs from the gaseous fuel mass flow sensor, the intake fresh air mass flow sensor, and the exhaust O2 sensor with a controller; determining a second SFAR value with the controller using the received second inputs; determining a second calculated value with the controller using the second SFAR value and a second input received from the one of the thermal conductivity sensor and the speed of sound sensor; determining a second gaseous fuel quality parameter value from the second calculated value with the controller; and controlling operation of the engine with the controller using the second gaseous fuel quality parameter.wherein the second quality parameter of the gaseous fuel is effective to adapt the operation of the engine to the change in the composition of the gaseous fuel;

[0065] Additional exemplary embodiments include systems including an electronic control system configured to perform a control process according to the third method or any of the previously described forms of the third method. Additional exemplary embodiments include non-transitory, controller-readable storage media configured with instructions executable by a controller to perform a control process according to the third method or any of the previously described forms of the third method.

[0066] Another exemplary embodiment is a fourth method comprising: operating an internal combustion engine to combust a gaseous fuel; receiving, with a controller, inputs from a plurality of sensors associated with the engine, including inputs from a gaseous fuel mass flow sensor, an intake fresh air mass flow sensor, and an exhaust O2 sensor; determining, with the controller, a stoichiometric fuel-to-air ratio (SFAR) value using the received inputs; determining, with the controller, a Wobbe index value indicative of the quality of the gaseous fuel based on a predetermined relationship between the SFAR value and the Wobbe index value, directly from the SFAR value and without intermediate determinations; and controlling operation of the engine using the Wobbe index value.

[0067] Certain forms of the fourth method further include: receiving, with a controller, an input from one of a thermal conductivity sensor configured to sense the thermal conductivity of the gaseous fuel and a speed of sound sensor configured to sense the speed of sound in the gaseous fuel; receiving, with the controller, inputs from the gaseous fuel mass flow sensor and a second gaseous fuel mass flow sensor configured to sense the mass flow of the gaseous fuel, wherein the second gaseous fuel mass flow sensor is a different sensor type than the gaseous fuel mass flow sensor; determining, with the controller, a flow sensor ratio (FSR) value using the inputs received from the gaseous fuel mass flow sensor and the second gaseous fuel mass flow sensor;Determining a calculated value with the controller using the FSR value and the input received from one of the thermal conductivity sensor and the speed of sound sensor; Determining a gaseous fuel quality parameter value from the calculated value with the controller based on the predetermined relationship between the calculated value and the gaseous fuel quality parameter; and controlling operation of the engine with the controller using the gaseous fuel quality parameter.

[0068] Certain forms of the fourth method further include: receiving an input from one of a thermal conductivity sensor configured to sense the thermal conductivity of the gaseous fuel and a speed of sound sensor configured to sense the speed of sound in the gaseous fuel, in addition to the inputs from the gaseous fuel mass flow sensor, the intake fresh air mass flow sensor, and the exhaust O2 sensor; determining a calculated value with the controller using the SFAR value and the input received from the one of the thermal conductivity sensor and the speed of sound sensor; determining a quality parameter value of the gaseous fuel from the calculated

[0069] value with the controller based on the predetermined relationship between the calculated value and the gaseous fuel quality parameter; and controlling operation of the engine with the controller using the gaseous fuel quality parameter.

[0070] Certain forms of the fourth method further comprise, following a change in the composition of the gaseous fuel: receiving second inputs from the plurality of sensors with a control sensor; determining a second SFAR value with the controller using the received second inputs; determining a second Wobbe index value with the controller directly from the second SFAR value and without intermediate determinations; and controlling operation of the engine using the second Wobbe index value; wherein the second Wobbe index value is operative to adapt operation of the engine to the change in the composition of the gaseous fuel.

[0071] Additional exemplary embodiments include systems including an electronic control system configured to perform a control process according to the fourth method or any of the previously described forms of the fourth method. Additional exemplary embodiments include non-transitory, controller-readable storage media configured with instructions executable by a controller to perform a control process according to the fourth method or any of the previously described forms of the first method.

[0072] As is apparent from the foregoing figures and text, a variety of aspects of the present invention are contemplated. In one aspect, a method includes: introducing natural gas into an intake system of an internal combustion engine; operating the internal combustion engine at least partially in response to introducing the natural gas into the internal combustion engine's intake system; sensing at least one engine parameter associated with operation of the internal combustion engine; measuring at least one property of the natural gas in response to sensing the at least one engine parameter; and estimating at least one quality parameter of the natural gas in response to measuring the at least one natural gas property.

[0073] While the invention has been shown and described in detail in the drawings and the foregoing description, it is to be interpreted as illustrative and not restrictive, and it is to be understood that only certain exemplary embodiments have been shown and described. One skilled in the art will recognize that many modifications to the exemplary embodiments are possible without substantially departing from the present invention. All such modifications are accordingly included within the scope of the present disclosure as defined in the following claims.

[0074] When reading the claims, it should be noted that the use of terms such as "a," "an," "at least one," or "at least a part" is not intended to limit the claim to only one element, unless the claim expressly states otherwise. When "at least a part" and / or "a part" is used, the element may include part and / or all of the element, unless expressly stated otherwise.

Claims

[1] Method comprising: Operating an internal combustion engine (30) to combust a gaseous fuel; Receiving inputs from a plurality of sensors associated with the engine with a controller (150), including inputs from a gaseous fuel mass flow sensor (83), an intake fresh air mass flow sensor (81), and an exhaust O2 sensor (82); determining a stoichiometric fuel-to-air ratio (SFAR) value with the controller (150) using the received inputs; Determining a lambda parameter G value with the controller (150) that indicates the quality of the gaseous fuel based on a predetermined relationship between the SFAR value and the lambda parameter G value, directly from the SFAR value and without intermediate determinations, wherein the lambda parameter G value is described by the equation G=((H / C)+(4 × Inert / C)) / ((H / C)+4), where H / C is a hydrogen-to-carbon ratio, and Inert / C is a ratio between inert components and carbon; and Controlling the operation of the engine (30) with the controller (150) using the lambda parameter G value. [2] The method of claim 1, wherein the act of controlling operation of the engine (30) with the controller using the lambda parameter G-value comprises calculating a lambda control value (λ) using the lambda parameter G-value and controlling operation of the engine using the lambda control value (λ). [3] The method of claim 2, wherein: the process of calculating the lambda control value (λ) comprises calculating a lambda parameter A based on a ratio of N2 to O2 in the intake charge provided to the engine (30) and a ratio of H2O to O2 in the intake charge provided to the engine (30), and calculating the lambda control value using the lambda parameter A; and the lambda parameter A is calculated according to the following equation: A = 1 + (N2 / O2) + (H2O / O2); and the lambda control value (λ) is determined according to the following equation: λ = (1 + (G × exhaust oxygen)) / (1 + (A × exhaust oxygen)). [4] The method of claim 1, further comprising, after a change in the composition of the gaseous fuel: Receiving second inputs from the plurality of sensors with the controller (150); determining a second SFAR value with the controller (150) using the received second inputs; Determining a second lambda parameter G value with the controller (150), directly from the second SFAR value and without intermediate determinations; and controlling the operation of the engine (30) with the controller (150) using the second lambda parameter G value; wherein the second lambda parameter G value is effective to adapt the operation of the engine (30) to the change in the composition of the gaseous fuel. [5] Internal combustion engine system (20) including an electronic controller (150) configured to perform the method of any of claims 1-4. [6] Method comprising: Operating an internal combustion engine (30) to combust a gaseous fuel; Receiving an input from one of a thermal conductivity sensor (84) configured to detect the thermal conductivity of the gaseous fuel and a speed of sound sensor (84) configured to detect the speed of sound in the gaseous fuel, with a controller (150); Receiving inputs from a first gaseous fuel mass flow sensor configured to detect the mass flow of the gaseous fuel and a second gaseous fuel mass flow sensor configured to detect the mass flow of the gaseous fuel with the controller (150), wherein the second gaseous fuel mass flow sensor is a different sensor type than the first gaseous fuel mass flow sensor; Determining a flow sensor ratio (FSR) value with the controller (150) using the inputs received from the first gaseous fuel mass flow sensor and the second gaseous fuel mass flow sensor, the FSR value being the ratio of the orifice gas mass flow sensor input to the hot foil gas mass flow sensor input; Determining a calculated value with the controller (150) using the FSR value and the value from the one of the thermal conductivity sensors (84) and the input received by the speed of sound sensor (84); Determining a quality parameter value of the gaseous fuel from the calculated value with the controller (150) based on the predetermined relationship between the calculated value and the quality parameter of the gaseous fuel; and Controlling the operation of the engine (30) with the controller (150) using the quality parameter of the gaseous fuel. [7] The method of claim 6, wherein the first gaseous fuel mass flow sensor comprises a nozzle type sensor (83) and the second mass flow sensor comprises a hot foil sensor (83'). [8] A method according to claim 6, wherein the calculated value is calculated as one of the following: the product of a thermal conductivity (TC) value based on the input received from the thermal conductivity sensor (84) and the FSR value, where the quality parameter of the gaseous fuel is a methane number; and the product of a speed of sound (SOS) value based on the input received from the speed of sound sensor and the FSR value, wherein the quality parameter (310) of the gaseous fuel is a methane number. [9] The method of claim 6, wherein the calculated value is calculated as one of the following: the inverse of the product of a thermal conductivity (TC) value based on the input received from the thermal conductivity sensor (84) and the FSR value, wherein the gaseous fuel quality parameter (310) is a specific gravity of the gaseous fuel; and the inverse of the product of a speed of sound (SOS) value based on the input received from the speed of sound sensor (84) and the FSR value, wherein the quality parameter (310) of the gaseous fuel is a specific gravity of the gaseous fuel. [10] The method of claim 6, further comprising, after a change in the composition of the gaseous fuel: Determining a second FSR value with the controller (150) using second values ​​from the first gaseous fuel mass flow sensor and inputs received by the second gaseous fuel mass flow sensor; determining a second calculated value with the controller (150) using the second FSR value and a second input received from the one of the thermal conductivity sensor (84) and the speed of sound sensor; Determining a second quality parameter (310) of the gaseous fuel from the second calculated value with the controller (150); and Controlling the operation of the engine (30) with the controller (150) using the second quality parameter (310) of the gaseous fuel; wherein the second quality parameter (310) of the gaseous fuel is effective to adapt the operation of the engine (30) to the change in the composition of the gaseous fuel. [11] Internal combustion engine system (20) including an electronic controller (150) configured to perform the method of any of claims 6-10. [12] Method comprising: Operating an internal combustion engine (30) to combust a gaseous fuel; Receiving an input from one of a thermal conductivity sensor (84) configured to detect the thermal conductivity of the gaseous fuel and a speed of sound sensor (84) configured to detect the speed of sound in the gaseous fuel, with a controller (150); Receiving inputs from a gaseous fuel mass flow sensor (83), an intake fresh air mass flow sensor (81), and an exhaust O2 sensor (82) with the controller (150); Determining a stoichiometric fuel-to-air ratio (SFAR) value with the controller (150) using the received inputs from the gaseous fuel mass flow sensor (83), the intake fresh air mass flow sensor (81), and the exhaust O2 sensor (82); Determining a calculated value with the controller (150) using the SFAR value and the value from the one of the thermal conductivity sensors (84) and the input received by the speed of sound sensor (84); Determining a quality parameter value of the gaseous fuel from the calculated value with the controller (150) based on the predetermined relationship between the calculated value and the quality parameter of the gaseous fuel; and Controlling the operation of the engine (30) with the controller (150) using the quality parameter of the gaseous fuel. [13] The method of claim 12, wherein the quality parameter value of the gaseous fuel is a lower heating value. [14] The method of claim 12, wherein the calculated value is calculated as one of the following: the inverse of the product of a thermal conductivity (TC) value based on the input received from the thermal conductivity sensor (84) and the SFAR value; and the inverse of the product of a speed of sound (SOS) value based on the input received from the sound speed sensor (84) and the SFAR value. [15] The method of claim 12, wherein the calculated value is calculated as one of the following: a thermal conductivity (TC) value based on the input received from the thermal conductivity sensor (84) divided by the SFAR value; and a speed of sound (SOS) value based on the input received from the speed of sound sensor (84) divided by the SFAR value. [16] The method of claim 12, further comprising, after a change in the composition of the gaseous fuel: Receiving second inputs from the gaseous fuel mass flow sensor (83), the intake fresh air mass flow sensor (81), and the exhaust O2 sensor (82) with a controller (150); determining a second SFAR value with the controller (150) using the received second inputs; determining a second calculated value with the controller (150) using the second SFAR value and a second input received from the one of the thermal conductivity sensor (84) and the speed of sound sensor (84); Determining a second quality parameter value of the gaseous fuel from the second calculated value with the controller (150); and controlling the operation of the engine (30) with the controller (150) using the second quality parameter of the gaseous fuel; wherein the second quality parameter of the gaseous fuel is effective to adapt the operation of the engine (30) to the change in the composition of the gaseous fuel. [17] Internal combustion engine system (20) including an electronic controller (150) configured to perform the method of any one of claims 12-16. [18] Internal combustion engine system (20), comprising: an engine (30) configured to combust a gaseous fuel; and an electronic controller (150) configured to receive inputs from a plurality of sensors associated with the engine (30), including inputs from a gaseous fuel mass flow sensor (83), an intake fresh air mass flow sensor (81s), and an exhaust O2 sensor (82), wherein the controller (150) is adapted to: determining a stoichiometric fuel-to-air ratio (SFAR) value using the received inputs; Determining a Wobbe index value based on a predetermined relationship between the SFAR value and the Wobbe index value directly from the SFAR value and without intermediate determinations, wherein the Wobbe index value indicates the quality of the gaseous fuel; and Controlling the operation of the motor (30) using the Wobbe index value. [19] The internal combustion engine system (20) of claim 18, wherein the controller (150) is further configured to: Receiving an input from one of a thermal conductivity sensor (84) configured to detect the thermal conductivity of the gaseous fuel and a speed of sound sensor (84) configured to detect the speed of sound in the gaseous fuel; Receiving inputs from the gaseous fuel mass flow sensor and a second gaseous fuel mass flow sensor configured to sense the mass flow of the gaseous fuel, wherein the second gaseous fuel mass flow sensor is a different sensor type than the gaseous fuel mass flow sensor; Determining a flow sensor ratio (FSR) value using the inputs received from the gaseous fuel mass flow sensor and the second gaseous fuel mass flow sensor, wherein the FSR value is the ratio of the orifice gas mass flow sensor input to the hot foil gas mass flow sensor input; Determining a calculated value using the FSR value and the input received from one of the thermal conductivity sensor (84) and the sound velocity sensor (84); Determining a second gaseous fuel quality parameter value from the calculated value based on the predetermined relationship between the calculated value and the second gaseous fuel quality parameter; and Controlling the operation of the engine (30) using the second quality parameter of the gaseous fuel. [20] The internal combustion engine system (20) of claim 18, wherein the controller (150) is further configured to: Receiving an input from one of a thermal conductivity sensor (84) configured to detect the thermal conductivity of the gaseous fuel and a speed of sound sensor (84) configured to detect the speed of sound in the gaseous fuel, in addition to the inputs from the gaseous fuel mass flow sensor (83), the intake fresh air mass flow sensor (81), and the exhaust O2 sensor (82); Determining a calculated value using the SFAR value and the input received from one of the thermal conductivity sensor (84) and the speed of sound sensor (84); Determining a second gaseous fuel quality parameter value from the calculated value based on the predetermined relationship between the calculated value and the second gaseous fuel quality parameter; and Controlling the operation of the engine (30) using the second quality parameter of the gaseous fuel.

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