System and method having reference sensor for reciprocating engine with exhaust gas recirculation

Abstract

A system includes a reciprocating engine having one or more piston-cylinder assemblies. The reciprocating engine is configured to output an exhaust gas. The system also includes an intake system coupled to the reciprocating engine. The intake system includes an intake flow path. The system also includes an exhaust gas recirculation (EGR) system coupled to the intake system and the exhaust system. The system also includes a first sensor coupled to an exhaust system coupled to the reciprocating engine. The first sensor is configured to obtain feedback indicative of a first oxygen value in the exhaust flow path. The system also includes a second sensor coupled to the multi-stage EGR cooler system. The second sensor is configured to obtain feedback indicative of a second oxygen value in the EGR flow path, and the second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

Description

SYSTEM AND METHOD HAVING REFERENCE SENSOR FOR RECIPROCATINGENGINE WITH EXHAUST GAS RECIRCULATIONBACKGROUND

[0001] The subject matter disclosed herein relates to reciprocating engines having sensors for various controls.

[0002] A reciprocating engine may include a sensor disposed in an exhaust system coupled to the reciprocating engine. The sensor may measure a value reflective of an oxygen value associated with the exhaust gas flowing through the exhaust system and adjust a fuel intake into the engine based on the oxygen value measured by the sensor. There may be times when the sensor provides an inaccurate value and / or provides a value that drifts over time. Accordingly, a need exists to verify the oxygen value provided by the sensor in the exhaust system.BRIEF DESCRIPTION

[0003] Certain embodiments commensurate in scope with the originally claimed subj ect matter are summarized below. These embodiments are not intended to limit the scope of the claimed subject matter, but rather these embodiments are intended only to provide a brief summary of possible forms of the subject matter. Indeed, the subject matter may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0004] In certain embodiments, a system includes a reciprocating engine having one or more piston-cylinder assemblies. The reciprocating engine is configured to output an exhaust gas. The system also includes an intake system coupled to the reciprocating engine. The intake system includes an intake flow path configured to route air into the reciprocating engine. The system also includes an exhaust system coupled to the reciprocating engine. The exhaust system includes an exhaust flow path of the exhaust gasfrom the reciprocating engine to an exhaust outlet. The system also includes an exhaust gas recirculation (EGR) system coupled to the intake system and the exhaust system. The EGR system includes an EGR flow path from the exhaust system to the intake system. The system also includes a multi-stage EGR cooler system coupled to the EGR flow path. The multi-stage EGR cooling includes a plurality of EGR coolers. The system also includes a first sensor coupled to the exhaust system. The first sensor is configured to obtain feedback indicative of a first oxygen value in the exhaust flow path. The system also includes a second sensor coupled to the multi-stage EGR cooler system. The second sensor is configured to obtain feedback indicative of a second oxygen value in the EGR flow path, and the second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

[0005] In certain embodiments, a system includes a reciprocating engine controller having a processor, a memory, and instructions stored on the memory and executable by the processor to control a reciprocating engine coupled to an intake system and an exhaust system. An exhaust gas recirculation (EGR) system is coupled to the intake system and the exhaust system. The intake system includes an intake flow path configured to route air into the reciprocating engine. The exhaust system includes an exhaust flow path of an exhaust gas from the reciprocating engine to an exhaust outlet. The EGR system includes an EGR flow path from the exhaust system to the intake system. A multi-stage EGR cooler system is coupled to the EGR flow path and includes a plurality of EGR coolers. The reciprocating engine includes one or more piston-cylinder assemblies. The reciprocating engine controller is configured to obtain feedback indicative of a first oxygen value in the exhaust flow path from a first sensor coupled to the exhaust system. The reciprocating engine controller is also configured to obtain feedback indicative of a second oxygen value in the EGR flow path from a second sensor coupled to the multi-stage EGR cooler system. The second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

[0006] In certain embodiments, a method includes controlling, via a controller, a reciprocating engine coupled to an intake system and an exhaust system. An exhaust gas recirculation (EGR) system is coupled to the intake system and the exhaust system. The intake system includes an intake flow path configured to route air into the reciprocating engine. The exhaust system includes an exhaust flow path of an exhaust gas from the reciprocating engine to an exhaust outlet. The EGR system includes an EGR flow path from the exhaust system to the intake system. A multi-stage EGR cooler system is coupled to the EGR flow path and includes a plurality of EGR coolers. The reciprocating engine includes one or more piston-cylinder assemblies. Controlling includes obtaining feedback indicative of a first oxygen value in the exhaust flow path from a first sensor coupled to the exhaust system. Controlling also includes obtaining feedback indicative of a second oxygen value in the EGR flow path from a second sensor coupled to the multi-stage EGR cooler system. The second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0008] FIG. l is a diagram of an embodiment of a combustion system having a plurality of sensors (e.g., oxygen sensors) coupled to an exhaust system of an engine system, wherein at least one of the sensors is disposed along an exhaust gas recirculation (EGR) line after at least some cooling by a heat exchange system (e.g., multi-stage EGR cooler system);

[0009] FIG. 2 is a diagram of an embodiment of the heat exchange system of FIG. 1, further illustrating details of the sensors distributed throughout the heat exchange system (e.g., at or between heat exchangers);

[0010] FIG. 3 is a diagram of an embodiment of the combustion system of FIG. 1, further illustrating a distribution of the plurality of sensors, including sensors upstream and downstream of a catalytic converter along an exhaust line and a sensor along the EGR line in the heat exchange system;

[0011] FIG. 4 is a cross-sectional view of an embodiment of a sensor of the plurality of sensors of FIGS. 1-3, illustrating the sensor coupled to, and partially protruding into, an exhaust conduit;

[0012] FIG. 5 is a cross-sectional view of another embodiment of a sensor of the plurality of sensors of FIGS. 1-3, illustrating the sensor coupled to a sampling line outside of the exhaust conduit;

[0013] FIG. 6 is a flow chart showing an embodiment of a process for controlling the engine system using two sensors; and

[0014] FIG. 7 is a flow chart showing an embodiment of a process for controlling the engine system using three sensors.DETAILED DESCRIPTION

[0015] One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0016] When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0017] As discussed in detail below, a plurality of sensors (e.g., oxygen sensors) may be placed in the both an exhaust line of an exhaust system and a heat exchange system (e g., multi-stage EGR cooler system) of an exhaust gas recirculation (EGR) system of an engine system (e.g., a reciprocating piston-cylinder internal combustion engine). A first sensor (e.g., oxygen sensor) may be coupled to the exhaust system (e.g., along an exhaust flow path leading to an exhaust outlet) and may be configured to obtain feedback indicating a first oxygen value in the exhaust flow path. A second sensor (e.g., oxygen sensor) may be coupled to the heat exchange system (e.g., multi-stage EGR cooler system), such that the second sensor may be configured to obtain feedback indicative of a second oxygen value in an EGR flow path. The second sensor is disposed downstream from at least some cooling provided by a first heat exchange stage (e.g., first EGR cooler) of a plurality of heat exchange stages (e.g., EGR cooler stages) of the heat exchange system. In certain embodiments, a third sensor may be coupled to the exhaust system (e.g., along an exhaust flow path leading to an exhaust outlet) and may be configured to obtain feedback indicating a third oxygen value in the exhaust flow path. As discussed below, the second sensor is subject to less harsh conditions (e.g., lower temperatures) than the first sensor and the third sensor, which are disposed in the exhaust flow path leading to the exhaust outlet (e.g., higher temperatures). Accordingly, the second sensor may be less susceptible to degradation, fouling, aging, and drift in sensor measurements (e.g., oxygen content measurements) due to thermal effects. For example, because the second sensor is disposed downstream of at least the first heat exchange stage, there is a reduced chance of fouling of the second sensor due to the one or more heat exchange stages catching ashy deposits in the exhaust gas. The second sensor may be used to provide a reference value (e.g., reference oxygen value) for use in validating a value provided by the first sensor. In certain embodiments, the controller of the engine system uses sensor feedback (e.g.,oxygen content measurements) from the first sensor for control of the fuel intake, air intake, EGR flow, and other operating parameters, and thus the second sensor helps to maintain accuracy of the first sensor for use in such control. In certain embodiments, the controller may compare sensor measurements from a plurality of sensors (e.g., first, second and / or third sensors) and ultimately use one or more of the sensor measurements for such control, as discussed in further detail below. Thus, the second sensor positioned after at least some cooling in the heat exchange system helps to maintain accurate oxygen feedback to the controller of the engine system, thereby helping to improve control of the power output, engine efficiency, and exhaust gas emissions.

[0018] FIG. 1 is a diagram of an embodiment of a combustion system 10 having a heat exchange system 12 coupled to an exhaust system 14 of an engine system 16, wherein the heat exchange system 12 may include multiple heat exchangers 18 (e.g., EGR coolers) coupled to an exhaust gas recirculation (EGR) system 13 to cool an EGR flow in multiple EGR cooler stages. As discussed in detail below, the combustion system 10 includes a plurality of sensors 256, wherein the sensors 256 may be located in different positions in an exhaust gas to obtain measurements of oxygen content, emissions content, or other parameters. One or more of the sensors 256 (e.g., main sensors) may be disposed in positions with harsh conditions causing aging, fouling, degradation, and / or drift in sensor measurements, whereas one or more of the sensors 256 (e g., reference sensors) may be disposed in positions with less harsh conditions causing less aging, degradation and / or drift in sensor measurements. The reference sensors 256 are configured to provide a reference measurement (e.g., reference oxygen content), which can be used to adjust measurements by the main sensors 256 to account for any drift in the sensor measurements (e.g., oxygen content). For example, the main sensors 256 may be disposed in a main exhaust flow path of the exhaust system 14, whereas the reference sensors 256 may be disposed in an exhaust gas recirculation (EGR) flow path of the EGR system 13 after one or more heat exchangers 18 (e.g., EGR coolers) of the heat exchange system 12. Various aspects of the sensors 256 and their relative positions and control of the combustion system 10 are discussed in detail below.

[0019] The engine system 16 may include a reciprocating engine 26 (e.g., reciprocating piston-cylinder internal combustion engine). The reciprocating engine 26 may include a two-stroke engine, a four-stroke engine, or other type of reciprocating engine. In certain embodiments, the reciprocating engine 26 is a four-stroke engine. The reciprocating engine 26 may also include any number of combustion chambers, pistons, and associated cylinders (e.g., 1-24) in one cylinder bank (e.g., inline) or multiple cylinder banks (e.g., left and right cylinder banks) of a V, W, VR (a.k.a. Vee-Inline), or WR cylinder bank configuration. For example, in certain embodiments, the reciprocating engine 26 may include a large-scale industrial reciprocating engine having 6, 8, 12, 16, 20, 24 or more pistons reciprocating in cylinders. In some such cases, the cylinders and / or the pistons may have a diameter of between approximately 13.5-31 centimeters (cm). In certain embodiments, the cylinders and / or the pistons may have a diameter outside of the above range. The fuel utilized by the reciprocating engine 26 may be any suitable gaseous fuel, such as natural gas, associated petroleum gas, hydrogen (H2), propane (CsHs), biogas, sewage gas, landfill gas, coal mine gas, butane (C4H10), ammonia (NH3) for example. The fuel may also include a variety of liquid fuels, such as gasoline, diesel, methanol, or ethanol fuel. The fuel may be admitted through either a high pressure (blow-through) fuel supply system or low pressure (draw-through) fuel supply system or direct injection. In certain embodiments, the reciprocating engine 26 may utilize spark ignition. In other embodiments, the reciprocating engine 26 may utilize compression ignition. The reciprocating engine 26 may vary in the size, number, and arrangement of pistons and cylinders, the ignition type (e.g., spark or compression ignition), the fuel type, the make and model, the exhaust system configuration (e.g., exhaust circuit layout, heat exchanger layout based on cooling requirements, EGR layout, exhaust gas waste heat recovery layout, etc.), and / or any other engine characteristics. The reciprocating engine 26 also may vary in exhaust flow characteristics and cooling needs, such as different EGR cooling needs depending on the engine design and other considerations.

[0020] The exhaust system 14 may include one or more exhaust circuits 28 between the reciprocating engine 26 and the corresponding heat exchange system 12. The exhaustcircuits 28 may be configured to route one or more flows of exhaust gas 30 between the reciprocating engine 26 and the heat exchange system 12. For example, the reciprocating engine 26 may output and route a flow of the exhaust gas 30 along an exhaust line 32 (e.g., exhaust conduit) to the heat exchange system 12 and recirculate the exhaust gas 30 from the heat exchange system 12 back into the reciprocating engine 26 via one or more exhaust gas recirculation (EGR) lines 33 (e.g., EGR conduits).

[0021] The heat exchange system 12 coupled to the exhaust circuit 28 may include one or more heat exchanger assemblies 36 (e.g., multi-stage EGR cooling systems), wherein each of the heat exchanger assemblies 36 includes a plurality of the heat exchangers 18 (e.g., EGR coolers) coupled to one of a plurality of distribution manifolds 38. For example, the heat exchanger assemblies 36 may include heat exchanger assemblies 40, 42, and 44, wherein each of the heat exchanger assemblies 36 includes one of the distribution manifolds 38 (e.g., distribution manifolds 46, 48, and 50). Each of the heat exchanger assemblies 36 may include any number of the heat exchangers 18 disposed in a series arrangement, a parallel arrangement, or a combination thereof. For example, in certain embodiments, the heat exchangers 18 for each of the heat exchanger assemblies 36 having one of the distribution manifolds 38 may include heat exchangers (e.g., EGR coolers) 52, 54, 56, and 58. Although four heat exchangers 52, 54, 56, and 58 are shown, any number of heat exchangers (e.g., up to an Nth heat exchanger) may be disposed in each of the heat exchanger assemblies 36. The heat exchangers 52, 54, 56, and 58 may be arranged in series, in parallel, or a combination thereof. In certain embodiments, the heat exchangers 52 and 54 may be first stage heat exchangers or first stage EGR coolers (e.g., arranged in parallel), the heat exchanger 56 may be a second stage heat exchanger or second stage EGR cooler, and the heat exchanger 58 may be a third stage heat exchanger or third stage EGR cooler. However, the heat exchangers 18 may be arranged in any number of stages, each stage having 1, 2, 3, or more heat exchangers arranged in parallel with one another.

[0022] The illustrated heat exchanger assemblies 40, 42, and 44 each have one of the distribution manifolds 46, 48, and 50 having a plurality of the heat exchangers 18, such asthe heat exchangers 52, 54, 56, and 58. The heat exchanger assemblies 40, 42, and 44 may have the same or different configuration of the heat exchangers 18 and the distribution manifolds 38, such as the same or different numbers of the heat exchangers 18, the same or different numbers of sections making up the distribution manifolds 38, or any combination thereof. Each of the distribution manifolds 38 may represent a single one- piece distribution manifold (e.g., single cast manifold), a multi-piece distribution manifold (e.g., sectional cast manifold) having different manifold portions removably coupled together, or individual conduits coupling together the heat exchangers 18 as a multi-conduit distribution manifold.

[0023] In the illustrated embodiment, each heat exchanger assembly 36 (e.g., multistage EGR cooling system) includes a plurality of the heat exchangers 18 (e.g., EGR coolers), such as a series arrangement of the heat exchangers 52, 54, 56, and 58, coupled to at least one of the distribution manifolds 38. The heat exchangers 18 are also coupled to the exhaust line 32 and the EGR line 33 of the exhaust circuit 28 of the exhaust system 14 through the at least one distribution manifold 38. A flow of the exhaust gas 30 may be configured to flow from one or more of the reciprocating engines 26 through the exhaust line 32 into one of the distribution manifolds 38, through the heat exchangers 18, back through one of the distribution manifolds 38, and then through the EGR line 33 for recirculation into an intake of the reciprocating engine 26. In some embodiments, at least part or all of the exhaust gas 30 may not flow back into the reciprocating engine 26 via the EGR line 33. For example, at least part of the exhaust gas 30 may discharge from the heat exchanger assembly 36 and flow downstream into one of the exhaust gas waste heat recovery systems 106 and / or discharge into the environment as indicated by arrow 140.

[0024] Each distribution manifold 38 may be configured to circulate the exhaust gas 30 from the reciprocating engine 26 through each of the heat exchangers 18, such as in a series arrangement and / or a parallel arrangement, while also circulating one or more heat exchange fluids 142 through the distribution manifold 38 and the heat exchangers 18. For example, the heat exchange fluids 142 may include heat exchange fluids 144, 146, and 148.The heat exchange fluids 142 may include one or more liquids, such as water, antifreeze liquids or additives, coolants, or any combination thereof. For example, the heat exchange fluids 142 may include a main engine fluid and an auxiliary fluid. The main engine fluid may flow to, from, and through the reciprocating engine 26, such that the main engine fluid may be configured to provide cooling of the reciprocating engine 26. Similarly, the auxiliary fluid may pass to and from one or more auxiliary systems, such that the auxiliary fluid may provide cooling. The auxiliary systems may be related and / or unrelated to the reciprocating engine 26, but the auxiliary systems may be outside or separate from the reciprocating engine 26. For example, auxiliary systems may include other power plant equipment, and the auxiliary fluid may be described as a balance of plant (BoP) fluid (e.g., BoP auxiliary water)). Again, for each heat exchanger assembly 36, the distribution manifold 38 may be configured to route inputs and outputs of both the exhaust gas 30 and the heat exchange fluids 142 (e.g., the main engine fluid and / or the auxiliary fluid) through each of the heat exchangers 18.

[0025] Accordingly, the heat exchanger assemblies 36 may transfer heat between the exhaust gas 30 and one or more of the heat exchange fluids 142, such as the main engine fluid and the auxiliary fluid. The heat exchangers 18 may be gas liquid heat exchangers, which are configured to transfer heat between the exhaust gas 30 and the liquid of the heat exchange fluids 142. In some embodiments, each of the heat exchangers 18 may be a plate heat exchanger, a brazed plate heat exchanger, and / or a gas-to-liquid plate heat exchanger, such as manufactured by Alfa Laval of Lund, Sweden. For example, the heat exchangers 18 may be Alfa Laval model GL150 heat exchangers. The heat exchangers 18 may be sealed for life to provide low maintenance, and the heat exchangers 18 may be cleaned via a clean-in-place (C1P) procedure, wherein the heat exchangers 18 are cleaned without any disassembly by flushing a cleaning fluid through the internal flow passages.

[0026] In the illustrated embodiment, the heat exchanger assemblies 36 are disposed in three different locations throughout the exhaust system 14, as indicated by heat exchanger assemblies 40, 42, and 44. The reciprocating engine 26 includes an engine block 170having a plurality of piston-cylinder assemblies 172, each having a piston 174 disposed within a cylinder 176. Each piston 174 may be configured to reciprocate within the cylinder 176 in response to combustion in a combustion chamber of the engine block 170, thereby driving rotation of a crankshaft coupled to a shaft 178 driving a load 180 (e.g., an electric generator). Additionally, the reciprocating engine 26 includes an exhaust manifold 182 and an intake manifold 184. The intake manifold 184 is coupled to an intake circuit 186 of an intake system 188, while the exhaust manifold 182 is coupled to the exhaust circuit 28 of the exhaust system 14. The intake circuit 186 includes one or more intake lines 190 extending between an air intake section 192 and the intake manifold 184, thereby supplying air into the reciprocating engine 26. For example, the air intake section 192 may include an air intake duct, air filters, or other features to process the air coming into the intake system 188.

[0027] The exhaust system 14 has one or more exhaust lines 32 extending between an exhaust section 194 and the exhaust manifold 182. For example, the exhaust section 194 may include a silencer, an emissions control system (e.g., a catalytic converter 197), a discharge duct, or other equipment to facilitate discharge of the exhaust gas into the environment. As noted above, the exhaust system 14 also may include the EGR system 13 (e.g., including EGR circuits 202, 204) having one or more EGR lines 33 to facilitate exhaust gas recirculation between the exhaust circuit 28 and the intake circuit 186. For example, the EGR lines 33 may include one or more EGR lines 33 upstream and / or downstream of a turbocharger 195, which includes a turbine 196 disposed along the exhaust line 32, a compressor 198 disposed along the intake line 190, and a shaft 200 coupling together the turbine 196 and the compressor 198. The turbocharger 195 is driven by exhaust gas passing through the exhaust line 32 and through the turbine 196, which in turn rotates the shaft 200 coupled to the compressor 198. The compressor 198 operates to compress an airflow from the air intake section 192 flowing along the intake line 190 into the intake manifold 184.

[0028] As noted above, the EGR system 13 may include EGR lines 33 both upstream and downstream of the turbocharger 195. For example, the EGR system 13 may include an EGR circuit 202 and an EGR circuit 204 disposed at different positions upstream and downstream relative to the exhaust gas flow through the turbocharger 195. In the illustrated embodiment, the EGR circuit 202 has EGR lines 206 and 208 coupled to the respective exhaust line 32 and the intake line 190, wherein the EGR lines 206 and 208 also couple to one of the heat exchanger assemblies 36 (e.g., the heat exchanger assembly 40). Similarly, the EGR circuit 204 has EGR lines 210 and 212 coupled to the respective exhaust line 32 and the intake line 190, wherein the EGR lines 210 and 212 also couple to one of the heat exchanger assemblies 36 (e.g., the heat exchanger assembly 42). In the illustrated embodiment, the EGR circuit 202 may be described as a high pressure EGR circuit, due to its location upstream from the turbine 196, whereas the EGR circuit 204 may be considered a low pressure EGR circuit based on its position downstream from the turbine 196. The exhaust system 14 may include one or more of the heat recovery systems, such as the exhaust gas waste heat recovery system 106 having one of the heat exchanger assemblies 36 (e.g., the heat exchanger assembly 44).

[0029] The combustion system 10 may include a variety of components along the exhaust system 14 and the intake system 188. As discussed above, the turbine 196 of the turbocharger 195 is disposed along the exhaust line 32 of the exhaust system 14. The turbocharger 195 also may include a bypass valve or waste gate valve 214 configured to open and close to vary a bypass of exhaust gas around the turbine 196. The exhaust section 194 also may include various components, such as the silencer, catalytic converter 197, or other exhaust gas treatment components.

[0030] Similarly, the intake system 188 may include a bypass valve 216 configured to open and close to vary a bypass flow of air intake around the compressor 198. The intake circuit 186 of the intake system 188 may include an intercooler 218 configured to control the temperature of the air intake and a throttle 220 configured to control the flow of the air intake and fuel 221 from a fuel supply 223 into the intake manifold 184. For example, theintercooler 218 may be a heat exchanger configured to transfer heat away from the intake air after compression in the compressor 198, thereby cooling the compressed air to a suitable temperature prior to intake into the reciprocating engine 26 via the intake manifold 184. The throttle 220 also may be configured to control the fluid flows (e.g., air, recirculate exhaust gas, and fuel) into the intake manifold 184 downstream from the Intercooler 218. The air intake section 192, as discussed above, may include air filters, intake ducts, or other equipment to properly intake and route the air flow into the reciprocating engine 26.

[0031] Each of the EGR circuits 202 and 204 may be configured to recirculate an exhaust gas being discharged along the exhaust line 32 into the intake line 190 for return into the intake manifold 184 of the reciprocating engine 26. Each of the EGR circuits 202 and 204 includes an EGR valve, such as EGR valves 222 and 224, configured to regulate the flow of exhaust gas back into the reciprocating engine 26 through the respective circuits 101 and 204. Downstream from the EGR valves, the EGR circuits 202 and 204 may include an EGR mixer, such as EGR mixers 226 and 228. The EGR mixers 226 and 228 are configured to mix the EGR flow (e.g., the exhaust gas) with the incoming air from the air intake section 192. The EGR mixers 226 and 228 mix the exhaust gas and air prior to delivery into the reciprocating engine 26 via the intake manifold 184. The EGR mixer 226 mixes the exhaust gas and air downstream from the compressor 198 of the turbocharger 195, whereas the EGR mixer 228 mixes the exhaust gas in the air upstream from the compressor 198 of the turbocharger 195.

[0032] In certain embodiments, the combustion system 10 may include only one or both of the EGR circuits 202 and 204 and the respective heat exchanger assemblies 36. Each of the heat exchanger assemblies 36, such as the heat exchanger assemblies 40 and 42, may be configured to transfer heat away from the exhaust gas and into one or more heat exchange fluids 142 of a heat exchanger fluid system 229. For example, as discussed above, the heat exchange fluids 142 may include a main engine fluid and / or an auxiliary fluid. The heat exchanger assemblies 36 transfer heat away from the exhaust gas into the heat exchange fluids 142 of the heat exchanger fluid system 229, thereby cooling theexhaust gas prior to recirculating the exhaust gas back into the intake manifold 184 of the reciprocating engine 26. The heat exchanger assemblies 36 (e.g., heat exchanger assemblies 40 and 42) may be described as EGR cooling systems, such as multi-stage EGR cooling systems that provide EGR cooling in a plurality of stages.

[0033] As discussed above, each of the heat exchanger assemblies 36 (e.g., heat exchanger assemblies 40 and 42) includes a plurality of the heat exchangers 18, such as heat exchangers 52, 54, 56, and 58, disposed in series and / or parallel along the EGR circuit 202 or 204. The heat exchangers 18 are coupled to one of the distribution manifolds 38, which in turn couples with the EGR lines 206 and 208 of the EGR circuit 202 or the EGR lines 210 and 212 of the EGR circuit 204. In the EGR circuit 202, the EGR line 206 directs the exhaust gas from the exhaust line 32 into the manifold 38, while the EGR line 208 receives a discharge of the exhaust gas from the distribution manifold 38 and returns the exhaust gas into the intake line 190. The EGR circuit 204 has the EGR line 210 coupled to an intake of the distribution manifold 38, while the EGR line 212 couples to a discharge of the distribution manifold 38 and returns the exhaust gas to the intake line 190. Similarly, the exhaust gas waste heat recovery system 106 has one of the heat exchanger assemblies 36 (e.g., heat exchanger assembly 44) coupled to the exhaust section 194 to facilitate waste heat recovery using the heat exchangers 18. The heat exchanger assembly 44 of the exhaust gas waste heat recovery system 106 may include any number of the heat exchangers 18 in series, in parallel, or a combination thereof, in a similar manner as the heat exchangers 18 in the EGR circuits 202 and 204.

[0034] In operation, each of the heat exchanger assemblies 36 directs the exhaust gas into the distribution manifold 38, which then directs the exhaust gas through each of the heat exchangers 18 in a parallel configuration, a series configuration, or a combination thereof, followed by discharge of the exhaust gas from the distribution manifold 38 back into the intake system 188. Simultaneously, the distribution manifold 38 receives one or more heat exchange fluids 140 from the heat exchanger fluid system 229 via a line 238, circulates the one or more heat exchange fluids 142 through the heat exchangers 18 in aseries arrangement, parallel arrangement, or a combination thereof, followed by discharge of the one or more heat exchange fluids 142 from the distribution manifold 38 back to the heat exchanger fluid system 229 as indicated by line 240. The lines 238 and 240 may represent one or more fluid lines depending on the number of heat exchange fluids 142. For example, if the heat exchanger fluid system 229 incorporates the main engine fluid and auxiliary fluid as two of the heat exchange fluids 142, then the line 238 may include at least two heat exchanger fluid supply lines into the distribution manifold 38, while the line 240 may include at least two or more fluid discharge lines to receive the heat exchange fluids 142 from the distribution manifold 38 back into the heat exchanger fluid system 229. This discussion of the heat exchanger fluid system 229 may be the same or substantially the same for each of the EGR circuits 202 and 204. Similarly, the heat exchanger assembly 36, 44 of the exhaust gas waste heat recovery system 106 may include a similar arrangement of heat exchangers 18, and a similar heat transfer between the heat exchange fluids 142 and the exhaust gas. The differing arrangements of the heat exchanger fluid system 229 (e.g., parallel arrangement, series arrangement, etc.) may provide for variation in functionality of the heat exchange stages of the heat exchanger assemblies 36. For example, a first heat exchange stage may be a non-condensing heat exchange stage, a second heat exchange stage may be a condensing heat exchange stage, and a third heat exchange stage may be a reheat heat exchange stage.

[0035] The heat exchanger fluid system 229 may include one or more components 242, such as components 244, 246, 248, and 250. The components 242 may include any number of components to control fluid flow in and out of the heat exchanger assembly 36. For example, the component 244 may include one or more fluid pumps, the component 246 may include one or more control valves, the component 248 may include one or more filters or fluid treatment units, and the component 250 may include one or more sensors or flow meters. In certain embodiments, one common heat exchanger fluid system 229 may be shared among each of the heat exchanger assemblies 36. However, in some embodiments, a dedicated or independent heat exchanger fluid system 229 may be coupled to each of theheat exchanger assemblies 36, such as each of the heat exchanger assemblies 40, 42, and 44.

[0036] In certain embodiments, the combustion system 10 may include a control system 252 having a controller 254 coupled to a plurality of sensors 256 and actuators 258 distributed about the combustion system 10. For example, the sensors 256, designated as “S,” may be coupled to the combustion system 10 at various locations along the exhaust system 14, the intake system 188, the EGR circuit 202, the EGR circuit 204, the turbocharger 195, the reciprocating engine 26, and the heat exchanger assemblies 36. Each of these sensors 256 may be configured to measure one or more parameters, such as oxygen content, emissions content, temperature, pressure, flow rate, or other engine parameters. The emissions content may include a content of nitrogen oxides (NOx), carbon oxides (COx) such as carbon dioxide (CO2) and carbon monoxide (CO), sulfur oxides (SOx), or the like. For example, the sensors 256 may be used to monitor changes in each of the following parameters at or between inlets and outlets of the heat exchangers 18, at or between inlets and outlets of the distribution manifolds 38, at different heat exchanger stages (e.g., EGR cooler stages), at one or more positions separate from the heat exchangers 18 (e.g., exhaust flow path leading to an exhaust outlet), over a duration of time at any sensor location, or any combination thereof. For example, one more of the sensors 256 (e.g., main sensors) may be disposed in positions within a main exhaust flow path along the exhaust line 32, whereas one or more of the sensors 256 (e.g., reference sensors) may be disposed in positions within or coupled to one or more heat exchangers 18 of the heat exchange system 12 (e.g., along EGR lines 206 and 208). The actuators 258 may include valve actuators, such as valve actuators for the waste gate 214 and the bypass valve 216, pump actuators for the heat exchanger fluid system 229, valve actuators for the EGR valves 222 and 224, or any combination thereof. The controller 254 may include one or processors 260, memory 262, instructions 264 stored on the memory 262 and executable by the processor 260, and communication circuitry 266 configured to communicate with the sensors 256, the actuators 258, and various components throughout combustion system 10. The controller 254 may use local and / or remote computer systems and storage, web-basedinterfaces, cloud-based interface, apps on smart devices (e g., smart phones, tablet computers, etc ), or any suitable use interface. In certain embodiment, the controller 254 may implement a cloud-based platform used for asset management of the reciprocating engines 26, such as myPlant, provided by Innio of Jenbach, Tyrol, Austria.

[0037] FIG. 2 is schematic view of an embodiment of the heat exchange system 12 of FIGS. 1, further illustrating details of the heat exchangers 18 in the heat exchanger assembly 36. In the illustrated embodiment, the heat exchanger assembly 36 is arranged with the heat exchangers 18 both in a series arrangement and a parallel arrangement. In particular, the illustrated embodiment of the heat exchanger assembly 36 has the heat exchangers 52 and 54 disposed in a first heat exchange stage 340 (e.g., first EGR cooler stage), the heat exchanger 56 disposed in a second heat exchange stage 342 (e.g., second EGR cooler stage), and the heat exchanger 58 disposed in a third heat exchange stage 344 (e.g., third EGR cooler stage). The heat exchangers 52 and 54 in the first heat exchange stage 340 are disposed in a parallel arrangement relative to one another. As illustrated in FIG. 2, each of the heat exchangers 18 includes a mounting interface 346, such as mounting interfaces 348, 350, 352, 354 on the respective heat exchangers 52, 54, 56, and 58. Each of the mounting interfaces 346 has connections (e.g., mechanical connections and fluid connections) to facilitate mounting of the heat exchangers 18.

[0038] As illustrated in FIG. 2, each of the heat exchangers 18 includes exhaust ports 356 and 358, fluid ports 360 and 362, and condensate ports 364 and 366 along the mounting interface 346. Inside of the heat exchanger 18, the exhaust ports 356 and 358 are fluidly coupled together via one or more exhaust passages, the fluid ports 360 and 362 are fluidly coupled together via one or more fluid passages, and the condensate ports 364 and 366 are fluidly coupled together via one or more condensate passages. In the illustrated embodiment, the exhaust ports 356 and 58 are larger than both the fluid ports 360 and 362 and the condensate ports 364 and 366. The fluid ports 360 and 362 also may be larger than the condensate ports 364 and 366. In certain embodiments, the exhaust ports 356 and 358 may be disposed on opposite sides of a plane or axis 368, the fluid ports 360 and 362 maybe disposed on opposite sides of the plane or axis 368, and the condensate ports 364 and 366 may disposed on opposite sides of the plane or axis 368. However, the exhaust ports 356 and 358, the fluid ports 360 and 362, and the condensate ports 364 and 366 may have any suitable arrangement on each of the heat exchangers 18.

[0039] The flows through the heat exchangers 18 may be the same or different in various stages and positions. In certain embodiments, the exhaust flow through the exhaust passage between the exhaust ports 356 and 358 may be opposite to the fluid flow through the fluid passage between the fluid ports 360 and 362. The flows of exhaust gas and fluid may be opposite or counter flow relative to one another. However, in certain embodiments, the exhaust flow and the fluid flow through the heat exchanger 18 may be in the same flow direction as one another.

[0040] The mounting interface 346 may represent a flat surface or planar surface having the exhaust ports 356 and 358, the fluid ports 360 and 362, and the condensate ports 364 and 366. Each of the illustrated ports may have a seal groove supporting a seal ring, such as an elastomeric seal ring, a metal seal ring, or any combination thereof. Although each of the heat exchangers 18 has the mounting interface 346 with the associated ports, the flows through each of the heat exchangers 18 may be the same or different from one another.

[0041] In the illustrated embodiment, the heat exchangers 52 and 54 in the first heat exchange 340 are arranged to receive parallel flows through the respective passages. For example, the heat exchangers 52 and 54 receive an input flow of exhaust gas from an exhaust gas (in) 370 into the exhaust ports 356, the exhaust gas flows through the internal exhaust passages to the exhaust ports 358, and then exhaust gas flows out through the exhaust ports 358 in parallel to one another to the exhaust port 358 in the heat exchanger 56 in the second heat exchange stage 342. The exhaust gas then flows through the internal exhaust passage within the heat exchanger 56 to the exhaust port 356, and then the exhaust gas exits through the exhaust port 356 and flows into the exhaust port 358 in the heat exchanger 58 in the third heat exchange stage 344. The exhaust gas then flows through theinternal exhaust passage in the heat exchanger 58 to the exhaust port 356, and then the exhaust gas flows out from the exhaust port 356 to an exhaust gas (out) 372. The exhaust gas flows through the heat exchangers 18 first in parallel through the heat exchangers 52 and 54 in the first heat exchange stage 340, followed by a series flow through the heat exchangers 56 and 58 in the second and third heat exchange stages 342 and 344. In the illustrated embodiment, the exhaust gas (in) 370 may correspond to the exhaust gas flow discharged from the exhaust manifold 182 of the reciprocating engine 26 of FIG. 2, whereas the exhaust gas (out) 372 may correspond to the exhaust gas discharged from the manifold 38 and directed to the EGR valve 222 or 224 as illustrated in FIG. 2. For example, in certain embodiments, the exhaust gas (in) 370 may include an exhaust gas input port in the distribution manifold 38, and the exhaust gas (out) 372 may include an exhaust gas (out) port in the distribution manifold 38. The distribution manifold 38 may include a matching mounting interface to couple with each of the mounting interfaces 346 of the heat exchangers 18.

[0042] In the first heat exchange stage 340, the heat exchangers 52 and 54 are configured to receive a first fluid flow from a first fluid (in) 374 (e.g., port in the distribution manifold 38), which directs a flow of the first fluid into the fluid ports 362 in the heat exchangers 52 and 54. The first fluid then flows through the heat exchangers 52 and 54, and then the first fluid exits through the fluid ports 360 into the distribution manifold 38 as indicated by first fluid 376 (shown as a box). The first fluid is then routed by the distribution manifold 38 into the heat exchanger 58 in the third heat exchange stage 344 via the fluid port 360. The first fluid then flows through an internal fluid passage in the heat exchanger 58 from the fluid port 360 to the fluid port 362, wherein the fluid port 362 then discharges the first fluid as indicated by a first fluid (out) 378. The first fluid (out) 378 may correspond to a first fluid out port disposed in the distribution manifold 38. In the illustrated embodiment, a second fluid also may be used for heat transfer in addition to the first fluid 376 passing through the heat exchangers 52, 54, and 58.

[0043] For example, the heat exchanger assembly 36 may include a second fluid (in) 380 (e.g., port in the distribution manifold 38), which directs a flow of a second fluid into the fluid port 360 in the heat exchanger 56, wherein the second fluid flows through an internal fluid passage from the fluid port 360 to the fluid port 362, and then exits from the fluid port 362 into a second fluid (out) 382. The second fluid (out) 382 may correspond to a second fluid out port disposed in the distribution manifold 38.

[0044] As noted above, each heat exchanger 18 may include condensate ports 364 and 366. However, one of the condensate ports may be inactive depending on the orientation of the heat exchanger 18. For example, the upper most condensate port 366 may be inactive in each of the illustrated heat exchangers 18, while the lower condensate port 364 may be active in at least one or more of the heat exchangers 18. For example, the condensate ports 364 of the heat exchangers 52 and 54 in the first heat exchange stage 340 may discharge a condensate to a condensate (out) 384, which may include a condensate out port disposed in the distribution manifold 38. Similarly, the condensate ports 364 in the heat exchangers 56 and 58 may discharge a condensate flow to a condensate (out) 386, which may be the same or different than the condensate (out) 384. The condensate (out) 386 may correspond to a condensate (out) port disposed in the distribution manifold 38.

[0045] In the illustrated embodiment, the exhaust flow and the fluid flow through each of the heat exchangers 18 is arranged to provide counter flows, which may facilitate heat transfer in each respective heat exchanger 18. However, in certain embodiments, the exhaust flow and the fluid flow may be parallel or in the same direction relative to one another. In some embodiments, the first heat exchange stage 340 may include only one of the heat exchangers 52 or 54, or the first heat exchange stage 340 may include additional heat exchangers 18. Similarly, the heat exchange stages 342 and 344 are illustrated with only one respective heat exchangers 56 and 58; however, each of the heat exchange stages 342 and 344 may include any number of heat exchangers 18, such as 2, 3, 4, or more heat exchangers 18. In certain embodiments, the first heat exchange stage 340 is a noncondensing heat exchange stage (e.g., non-condensing EGR cooler), the second heatexchange stage 342 is condensing heat exchange stage (e.g., condensing EGR cooler), and the third heat exchange stage 344 is a reheating heat exchange stage (e g., reheating EGR cooler).

[0046] In the illustrated embodiment, one or more of the sensors 256 (e.g., oxygen sensors, pressure sensors, temperature sensors, humidity sensors, etc.) are disposed downstream of the first heat exchange stage 340, such as at, upstream, and / or downstream from the second and third heat exchange stages 342 and 344. For example, one or more of the sensors 256 may be disposed at the second heat exchange stage 342, at the third heat exchange stage 344, between the first and second heat exchange stages 340 and 342, between the second and third heat exchange stages 342 and 344, or downstream from the third heat exchange stage 344. In certain embodiments, if the one or more sensors 256 may be sensitive to moisture, a protective shield (e g., cover) may be used to enclose the one or more sensors 256. In particular, one or more of the sensors 256 may be disposed downstream of the first heat exchange stage 340 and upstream of the second heat exchange stage 342. Additionally, one or more of the sensors 256 may be disposed downstream of the second heat exchange stage 342 and upstream of the third heat exchange stage 344. In certain embodiments, one or more of the sensors 256 may be disposed at or near an outlet (e.g., exhaust ports 358) of the first heat exchange stage 340, at or near an inlet or an outlet (e.g., exhaust ports 356 and 358) of the second heat exchange stage 342, at or near an inlet or an outlet (e.g., exhaust ports 356 and 358) of the third heat exchange stage 344, or any combination thereof. In certain embodiments, the sensor 256 may be disposed between inlets and outlets (e.g., exhaust ports 356 and 358) of the second heat exchange stage 342 and / or the third heat exchange stage 344. In certain embodiments, each of the sensors 256 may include an oxygen sensor configured to measure an oxygen value (e.g., oxygen content) of the exhaust gas flowing through the heat exchanger 18 (e.g., EGR cooler stage). One or more of the foregoing sensors 256 (e g., oxygen sensors) may be a reference sensor (e.g., reference oxygen sensor) used to help validate sensor data acquired by another sensor 256 in a main exhaust flow path, such as along the exhaust line 32.

[0047] FIG. 3 is a diagram of an embodiment of the combustion system 10 of FIG. 1, further illustrating a placement of the sensors 256 (e.g., sensors 402, 404, and 406), each sensor 256 configured to obtain feedback indicative of an oxygen level in the exhaust system 14 of the engine system 16. In the illustrated embodiment, the sensors 256 are electrically coupled to the controller 254 which includes the processor 260, memory 262, instructions 264, and communication circuitry 266. In certain embodiments, the sensor 402 (e.g., first sensor) may be coupled to the exhaust system 14 and may be disposed after or downstream from the turbine 196 in the direction of exhaust gas flow through the exhaust line 32 (e.g., main exhaust flow path extending to an exhaust outlet). The sensor 402 may be configured to obtain feedback (e g., of the exhaust flow) indicative of an oxygen value (e.g., oxygen proportion, oxygen content) in the exhaust lines 32 (e.g., exhaust flow path). In certain embodiments, the exhaust flow path may include the catalytic converter 197, such that the sensor 402 is disposed upstream of the catalytic converter 197 and downstream of the turbine 196. The upstream placement of the sensor 402 means that the sensor 402 measures oxygen content prior to exhaust gas treatment by the catalytic converter 197. In certain embodiments, the sensor 402 may be described as measuring the oxygen content of the exhaust gas without any exhaust gas treatment (e.g., lowering levels of nitrogen oxides (NOx), carbon oxides (COx), sulfur oxides (SOx), or the like) and / or exhaust gas cooling. In other words, the sensor 402 may be described as measuring the oxygen content of the exhaust gas as a raw output from the reciprocating engine 26.

[0048] As shown in the illustrated embodiment, the sensor 404 (e.g., second sensor) may be coupled to the EGR system 13 (e.g., EGR circuits 202, 204, 408) of the exhaust system 14 at the heat exchange system 12 (e.g., a multi-stage EGR cooler system 259). The EGR circuits 202 and 204 are described in detail above with reference to FIG. 1. The EGR circuit 202 (e.g., high-high pressure circuit) includes an EGR line 33 (e.g., EGR lines 206, 208) from the exhaust flow path upstream from the turbine 196 (e.g., higher pressure exhaust gas) to the air intake flow path downstream from the compressor 198 (e.g., higher pressure air intake) of the turbocharger 194. The EGR circuit 204 (e.g., low-low pressurecircuit) includes an EGR line 33 (e.g., EGR lines 210, 212) from the exhaust flow path downstream from the turbine 196 (e g., lower pressure exhaust gas) to the air intake flow path upstream from the compressor 198 (e.g., lower pressure air intake) of the turbocharger 194. The EGR circuit 408 (e.g., high-low pressure circuit) includes an EGR line 33 from the exhaust flow path upstream from the turbine 196 (e.g., higher pressure exhaust gas) to the air intake flow path upstream from the compressor 198 (e.g., lower pressure air intake) of the turbocharger 194. The heat exchange system 12 (e.g., a multi-stage EGR cooler system 259) with the sensor 404 (or multiple sensors 404) may be disposed only or independently along the EGR circuit 202, only or independently along the EGR circuit 204, only or independently along the EGR circuit 408, or any combination of the EGR circuits 202, 204, and 408. Thus, the sensor 404 may be used in a variety of configurations of the EGR system 13 with one or more of the EGR circuits 202, 204, and / or 408.

[0049] In certain embodiments, the sensor 404 may be disposed after (e.g., downstream of) the first heat exchange stage 340 and, in certain embodiments, before (e.g., upstream of) the second heat exchange stage 342. In certain embodiments, the sensor 404 may be disposed between the first heat exchange stage 340 and the second heat exchange stage 342. In some embodiments, the sensor 404 may be disposed after the third heat exchange stage 344. In certain embodiments, the sensor 404 may be coupled to an exhaust inlet, an exhaust outlet, or between the exhaust inlet and the exhaust outlet of the heat exchanger 18 (e.g., EGR cooler) of the second heat exchange stage 342 and / or the third heat exchange stage 344. In some embodiments, the sensor 404 may be coupled to an exhaust outlet of the heat exchanger 18 (e.g., EGR cooler) of the first heat exchange stage 340, or between the exhaust outlet of the heat exchanger 18 (e.g., EGR cooler) of the first heat exchange stage 340 and an exhaust inlet of the heat exchanger 18 (e.g., EGR cooler) of the second heat exchange stage 342. Although the present embodiments may exclude placement of the sensor 404 upstream and / or within the heat exchanger 18 (e.g., EGR cooler) of the first heat exchange stage 340, some embodiments may include the sensor 404 upstream and / or within the heat exchanger 18 (e.g., EGR cooler) of the first heat exchange stage 340. Furthermore, the sensors 256 (e.g., sensor 404) may include or exclude any of the sensorpositions described above. The sensor 404 may be configured to obtain feedback indicative of an oxygen value in the EGR line 33 (EGR circuits 202, 204, 408) of the EGR system 13. As discussed in further detail below, the oxygen value obtained via the sensor 404 at any one or more of the foregoing positions may be a reference value for validation (e.g., comparison, calibration) of the oxygen value obtained via the sensor 402. Advantageously, the sensor 404 is disposed along the EGR line 33 after at least some EGR cooling by the heat exchange system 12, such that the sensor 404 is less susceptible to heat degradation, thermally driven aging, and associated drift in sensor measurements (e.g., oxygen content measurements), or sensor fouling by ashy exhaust combustion byproducts. Unlike the sensor 402, the sensor 404 may have a longer useful life with accurate sensor measurements, which can then be used to validate and / or compare (e.g., calibrate) a value provided by the sensor 402.

[0050] In the illustrated embodiment, the sensor 406 (e.g., third sensor) may be coupled to the exhaust system 14 and configured to obtain feedback indicative of an oxygen value in the exhaust lines 32 (e.g., exhaust flow path). In certain embodiments, the exhaust lines 32 may include the catalytic converter 197, wherein the sensor 402 is disposed upstream of the catalytic converter 197 (e.g., and downstream of the turbine 196) and the sensor 406 is disposed downstream of the catalytic converter 197, or vice versa.

[0051] In certain embodiments, the catalytic converter 197 may include a two-way catalytic converter and / or a three-way catalytic converter. The two-way catalytic converter 197 is configured to provide oxidation of carbon monoxide (CO) to carbon dioxide (CO2) and to provide oxidation of hydrocarbons (e.g., unburnt or partially burned fuel) to carbon dioxide (CO2) and water. The three-way catalytic converter 197 is configured to provide reduction of nitrogen oxides (NOx), such as nitrogen oxide (NO) and nitrogen dioxide (NO2), to nitrogen (N2). Additionally, the three-way catalytic converter 197 is configured to provide oxidation of carbon, hydrocarbons, and carbon monoxide (CO) to carbon dioxide (CO2). In certain embodiments, the catalytic converter 197 includes one or more catalyst materials, such as one or more precious metals (e.g., platinum, palladium, rhodium,etc ). For example, rhodium may be used as a reduction catalyst, palladium may be used as an oxidation catalyst, and platinum may be used for both reduction and oxidation. In certain embodiments, the catalytic converter 197 may be part of an emissions control system, which may include other exhaust gas treatment systems. For example, the exhaust gas treatment systems may include a selective catalytic reduction (SCR) system configured to convert nitrogen oxides (NOx), such as nitrogen oxide (NO) and nitrogen dioxide (NO2), to nitrogen (N2) using a catalyst and a reductant. The catalyst may include metallic or ceramic substrates, zeolites, or various precious metals. The reductant may include anhydrous ammonia (NHi), aqueous ammonia (NH4OH), or a urea (CO(NH2)2) solution. Accordingly, in certain embodiments, the sensors 402 and 406 may be disposed upstream and downstream (or vice versa) relative to element 197, which may include one or more catalytic converters, SCR systems, and / or other exhaust gas treatment systems. In contrast to the sensor 402, the downstream placement of the sensor 406 means that the sensor 406 measures oxygen content after exhaust gas treatment by the catalytic converter 197. In other words, the sensor 406 may be described as measuring the oxygen content of the exhaust gas as a treated exhaust gas (e.g., with partially lowered levels of nitrogen oxides (NOx), carbon oxides (COx), sulfur oxides (SOx), or the like). It should be recognized that a first signal indicative of an oxygen value output by the sensor 402 (e.g., upstream of the catalytic converter 197) may differ from a second signal indicative of an oxygen value output by the sensor 406 (e.g., downstream of the catalytic converter 197) due to chemical reactions that may take place in the catalytic converter 197.

[0052] In certain embodiments, the sensors 256 may each be oxygen sensors. In other embodiments, the sensor 402 and / or the sensor 404 may include an oxygen sensor, a nitrogen oxides (NOx) sensor, or a combination thereof. It should be recognized that an NOx sensor may implicitly provide a signal indicative of an oxygen value during normal operation. Of the sensors 256 that are oxygen sensors, the oxygen sensors may be narrow band sensors, wide band sensors, or a combination thereof. In certain embodiments, other types of sensors may be placed in the proximity of each of the sensors 256 so as to augment an accuracy of the oxygen value output by each of the sensors 256. For example, a pressuresensor, a temperature sensor (e.g., resistance temperature detector [RTD]), a water vapor sensor, or a combination thereof, may be disposed proximate to each of the sensors 256. In certain embodiments, a water vapor sensor may be disposed after the third heat exchange stage 344 and may be configured to infer a humidity (e.g., water vapor content) of the flow in the EGR line 33 after the first heat exchange stage 340. The inferred humidity of the flow in the EGR line 33 after the first heat exchange stage 340 may be used to determine an estimated oxygen value after the first heat exchange stage 340 that is compensated for water vapor. In certain embodiments, the controller 254 may be configured to adjust the feedback received by each of the sensors 256 based on a signal received by a temperature sensor disposed proximate to each of the sensors 256. For example, the controller 254 may be configured to use a lookup table to lookup an oxygen value based on a signal received from the sensors 256 (e.g., sensor 404) for a given temperature received by the temperature sensor.

[0053] As discussed in further detail below, the controller 254 may be configured to receive sensor feedback from the sensors 256 (e.g., 402, 404, and 406), compare the sensor feedback, validate (e.g., compare, calibrate) and / or adjust one or more values output by the sensors 256 based on the sensor feedback from the other sensors 256, and / or control the combustion system 10 (e.g., reciprocating engine 26) based on the sensor feedback from one or more of the sensors 256. For example, the oxygen measurements may be used to control various operating parameters of the reciprocating engine 26, such as an air intake flow, an EGR flow, a fuel intake or injection flow, a spark ignition timing, a fuel injection timing, a fuel / air ratio, or any combination thereof. In certain embodiments, one of the sensors 256 (e.g., 402, 404, or 406) may be designated as a main, primarily, or lead sensor, whereas one of the other sensors 256 (e.g., 402, 404, or 406) may be designated as a reference sensor. In one embodiment, the sensor 402 is the main sensor and the sensor 404 is the reference sensor. In another embodiment, the sensor 406 is the main sensor and the sensor 404 is the reference sensor. In another embodiment, the sensor 402 is the main sensor and the sensors 404 and 406 are both reference sensors. However, the sensors 256 (e.g., 402, 404, and 406) may be used in a variety of ways by the controller 254 for controlof the combustion system 10. For example, the controller 254 may use the main sensor for all control functions, while using the reference sensor for validation of a value output by the main sensor. By further example, the controller 254 may compare the sensor feedback of all sensors 256 (e.g., 402, 404, and 406) and use the sensor feedback from at least two of the sensors that generally agree (e.g., sensor values within a tolerance range of one another). Various uses of the sensors 256 are discussed in further detail below.

[0054] FIG. 4 is a cross-sectional view of an embodiment of a sensor 256 of FIGS. 1-3 coupled to an EGR line 33 of the EGR system 13 (e.g., EGR circuits 202, 204, or 408). In the illustrated embodiment, the sensor 256 may include a sensor housing 410 having a sensor mount 411 (e.g., mounting flange), and a sensing element 412 (e.g., oxygen sensing element) coupled to the sensor housing 410. The sensing element 412 may include a heating element 414 (e.g., heating coil) disposed inside the sensing element 412. In the illustrated embodiment, the sensor 256 is coupled to an outer wall 416 (e.g., exterior surface, outer annular wall) of the EGR line 33 via the sensor mount 411, such that the sensing element 412 protrudes radially through an opening 417 in the outer wall 416 into the interior 418 of the EGR line 33. The sensor mount 411 may be coupled to the outer wall 416 via a fixed connection (e.g., welded joint) or a removable connection (e.g., threaded fasteners, clamps, straps, snap-fit couplings, etc.). As the exhaust gas flows past the sensing element 412, the sensor 256 may be configured to send a signal to the controller 254 indicative of an oxygen value associated with the exhaust gas flowing through the EGR line 33. The heating element 414 may be configured to control a temperature of the sensing element 412 (e.g., oxygen sensing element) to operate within an operating temperature range (e.g., between upper and lower temperature thresholds).

[0055] FIG. 5 is a cross-sectional view of another embodiment of the sensor 256 of FIGS. 1-3 coupled to the EGR line 33 of the EGR system 13 (e.g., EGR circuits 202, 204, or 408). In the illustrated embodiment, the sensor 256 may include the sensor housing 410 and the sensing element 412 disposed inside the sensor housing 410. The sensing element 412 may include the heating element 414 (e.g., heating coil) disposed inside the sensingelement 412. In the illustrated embodiment, the sensor 256 is coupled to a sampling channel 440 (e.g., exhaust sampling conduit) that diverges from the outer wall 416 of the EGR line 33 and subsequently reunites with the outer wall 416 of the EGR line 33, such that the sensor 256 measures the exhaust gas flowing through the sampling channel 440. As the exhaust gas flows past the sensing element 412, the sensor 256 may be configured to send the signal to the controller 254 indicative of an oxygen value associated with the exhaust gas flowing through the sampling channel 440.

[0056] FIG. 6 is a flow chart showing an embodiment of a process 460 for controlling the engine system 16 of FIGS. 1-3 using a plurality of sensors 256 (e.g., two oxygen sensors) coupled to the controller 254. In block 462 of the process 460, the controller 254 may be configured to receive sensor feedback indicative of the first oxygen value (e.g., oxygen percentage, oxygen content, etc.) in the exhaust flow path through the exhaust system 14 of the reciprocating engine 26 via a first sensor 256. In certain embodiments, the first sensor 256 may be the sensor 402 disposed downstream of the turbine 196 and upstream of the catalytic converter 197. In other embodiments, the first sensor 26 may be the sensor 406 disposed downstream of the turbine 196 and the catalytic converter 197. However, the first sensor 256 may be disposed anywhere along the exhaust flow path of the exhaust line 32 of the exhaust system 14.

[0057] In block 464, the controller 254 may be configured to obtain sensor feedback indicative of the second oxygen value in the EGR flow path of the EGR system 13 (e.g., EGR circuits 202, 204, 408) via the second sensor 256 downstream from the first heat exchange stage 340 (e.g., first EGR cooler) of the heat exchange system 12 (e.g., multistage EGR cooler system 259) of the EGR system 13. As previously discussed, the second sensor 256 may be the sensor 404 disposed downstream of the first heat exchange stage 340 (e.g., first EGR cooler) and upstream of the second heat exchange stage 342 (e.g., second EGR cooler). In certain embodiments, the second sensor 256 (e.g., 404) may be disposed downstream of the first heat exchange stage 340 and near an outlet of the first heat exchange stage 340 (e.g., outlet leading to the second heat exchange phase 342). Incertain embodiments, the controller 254 may be configured to receive (e.g., request) the second oxygen value from the second sensor 256 (e.g., 404) continuously, at a set frequency (e.g., once every minute, once every hour, etc.), at a set time point (e.g., 30 minutes after activation, full speed load), or a combination thereof. In certain embodiments, the controller 254 may be configured to receive the second oxygen value from the second sensor 256 (e.g., 404) in response to an input provided by an operator (e.g., from a user interface (UI)). The sensor 256 (e.g., 404) may be disposed at any position in the heat exchange system 12 (e.g., multi-stage EGR cooler system 259) of the EGR system 13 as discussed in detail above. In certain embodiments, the controller 254 may be configured to receive the second oxygen value from the second sensor 256 based on one or more operating conditions of the system. For example, the controller 254 may be configured to receive the second oxygen value when the EGR system 13 is in operation and when exhaust gas is detected to be flowing through the EGR system 13. In certain embodiments, a heating coil of the second sensor 256 may be powered down when the EGR system 13 is not in use so that wearing of the heating coil may be reduced. That is, the controller 254 may be configured to activate and / or deactivate the second sensor 256 based on one or more operating conditions of the engine system 16.

[0058] In block 466, the controller 254 may be configured to compare the first and second oxygen values to obtain a comparison. In certain embodiments, the comparing of the first and second oxygen values may include taking the difference between the first and second values. For example, the comparison may include subtracting the second oxygen value (e.g., obtained from the second sensor in the EGR system) from the first oxygen value (e.g., obtained from the exhaust flow), or vice versa.

[0059] In block 468, the controller 254 may be configured to obtain a deviation between the first and second oxygen values based on the comparison. For example, the deviation may include taking the difference between the first and second oxygen values at the same moment in time. In certain embodiments, the deviation may include taking a difference between a first moving average of first oxygen values and a second moving average ofsecond oxygen values, so as to account for fluctuations in the first and second oxygen values over time (e.g., due to noise).

[0060] In block 470, the controller 254 may be configured to determine whether the deviation is less than a threshold value (e.g., threshold deviation). In certain embodiments, the controller 254 may be configured to take the absolute value of the deviation before comparing the deviation to the threshold. If the deviation is greater than or equal to the threshold value, the controller 254 may be configured to output an alert (e.g., block 472). In certain embodiments, the alert may include an audio notification, a visual notification, an email, a short message service (SMS) message, or any combination thereof. For example, the audio notification may include an audio alarm or an audio message. By further example, the visual notification may include a flashing light, a colored light, a text message and / or a visual indicator on an electronic display. In some embodiments, the alert may indicate that there is a deviation (e.g., larger than the threshold) between the first and second oxygen values. In other embodiments, the alert may indicate that either the first oxygen sensor (e.g., or second oxygen sensor) needs to be replaced.

[0061] In block 474, if the deviation is less than the threshold value, the controller 254 may be configured to adjust a value of the first sensor 256 (e.g., sensor disposed in the exhaust flow) based on the deviation to obtain an adjusted first oxygen value. In certain embodiments, the first sensor 256 may be adjusted via adding the deviation (e.g., prior to taking the absolute value) to the first oxygen value. In certain embodiments, the deviation may first be multiplied by a proportional gain and the resulting value may be added to the first oxygen value.

[0062] In block 476, the controller 254 may be configured to control the engine system 16 (e.g., reciprocating engine 26) based on the adjusted first oxygen value. In certain embodiments, the controller 254 may be configured to control a fuel intake valve configured to control the amount of fuel received by the engine system 16. In certain embodiments, a database (e.g., lookup table) may be used to determine the amount by which the fuel intake valve is to be opened / closed based on the adjusted first oxygen value.In certain embodiments, the process 460 iterates back to block 462 in response a completion of the block 476, such that the process 460 may be treated as a feedback control loop (e.g., closed-loop control) for validating and / or adjusting a value provided by the first oxygen sensor. In certain embodiments, a proportional-integral-derivative (PID) control law (e.g., or variations thereof) may be used for controlling the first oxygen sensor.

[0063] FIG. 7 is a flow chart showing an embodiment of a process 500 for controlling the engine system 16 using a plurality of sensors 256 (e.g., three oxygen sensors) coupled to the controller 254. In block 502, the controller 254 may be configured to obtain sensor feedback indicating the first oxygen value in the exhaust flow path through the exhaust system 14 of the engine system 16 (e.g., reciprocating engine 26) via a first sensor 256. In certain embodiments, the first sensor 256 may be disposed downstream of the turbine 196 and, in certain embodiments, upstream or downstream of the catalytic converter 197.

[0064] In block 504, the controller 254 may be configured to obtain sensor feedback indicating a second oxygen value (e.g., oxygen percentage, oxygen content, etc.) in the EGR flow path via a second sensor 256, 404 (e.g., oxygen sensor, NOx sensor, etc.) downstream from the first heat exchange stage 340 (e.g., first EGR cooler) of the EGR system 13 (e.g., multi-stage EGR cooler system 259). In certain embodiments, the second sensor 256 (e.g. 404) may be disposed downstream from the first heat exchange stage 340 and upstream the second heat exchange stage 342. In some embodiments, the second sensor 256 (e.g. 404) may be disposed downstream of the first heat exchange stage 340 and near an outlet of the first heat exchange stage 340 (e.g., outlet leading to the second heat exchange stage 342). In certain embodiments, the second sensor 256 (e.g. 404) may be a wide-band oxygen sensor or a narrow-band oxygen sensor.

[0065] In block 506, the controller 254 may be configured to obtain sensor feedback indicative of a third oxygen value in the exhaust flow path through the exhaust system via a third sensor 256 (e.g., oxygen sensor, NOx sensor, etc.). In certain embodiments, the third sensor 256 may be disposed downstream of the turbine 196 and, in certain embodiments, upstream or downstream of the catalytic converter 197. In someembodiments, the third sensor 256 may be the sensor 402 disposed upstream of the catalytic convert 197 and the first sensor 256 may be the sensor 406 disposed downstream of the catalytic converter, or the second sensor 256 may be the sensor 402 disposed upstream of the catalytic convert 197 and the third sensor 256 may be the sensor 406 disposed downstream of the catalytic converter.

[0066] In block 508, the controller 254 may be configured to compare the first, second, and third oxygen values to obtain a comparison. In certain embodiments, the comparing of the first, second, and third oxygen values may include taking the difference between each combination of two oxygen values (e.g., first and second oxygen values, second and third oxygen values, first and third oxygen values). For example, the comparison may include subtracting the second oxygen value (e.g., obtained from the second sensor in the EGR system) from the first oxygen value (e.g., obtained from the exhaust flow), or vice versa. The subtraction procedure may be performed for each combination of two oxygen values.

[0067] In block 510, the controller 254 may be configured to obtain a first deviation between the first and second oxygen values based on the comparison. For example, the first deviation may include taking the difference between the first and second oxygen values at the same moment in time. In certain embodiments, the first deviation may be determined by taking a difference between a first moving average of first oxygen values and a second moving average of second oxygen values, so as to account for fluctuations in the first and second oxygen values over time (e.g., due to noise).

[0068] In block 512, the controller 254 may be configured to obtain a second deviation between the first and third oxygen values based on the comparison. For example, the second deviation may include taking the difference between the first and third oxygen values at the same moment in time. In certain embodiments, the second deviation may be determined by taking a difference between a first moving average of first oxygen values and a third moving average of third oxygen values, so as to account for fluctuations in the first and third oxygen values over time (e.g., due to noise).

[0069] In block 514, the controller 254 may be configured to obtain a third deviation between the second and third oxygen values based on the comparison. For example, the third deviation may include taking the difference between the second and third oxygen values at the same moment in time. In certain embodiments, the third deviation may be determined by taking a difference between a second moving average of second oxygen values and a third moving average of third oxygen values, so as to account for fluctuations in the second and third oxygen values over time (e.g., due to noise).

[0070] In block 516, the controller 254 may be configured to determine whether each of the first, second, and third deviations exceed a threshold value (e.g., threshold deviation). In certain embodiments, the controller 254 may be configured to take the absolute value of each of the first, second, and third deviations before comparing each of the first, second, and third deviations to the threshold value. In certain embodiments, the threshold value may be adjustable via the controller 254 (e.g., via a user interface).

[0071] If each of the first, second, and third deviations are greater than or equal to the threshold value, the controller 254 may be configured to output an alert (block 518). In certain embodiments, the alert may include an audio notification, a visual notification, an email, an SMS message, or any combination thereof, as discussed above. For example, the visual notification may include a notification light or, in certain embodiments, a notification on a user interface. In some embodiments, the alert may indicate that there is a deviation (e.g., larger than the threshold) between the first and second oxygen values, the first and third oxygen values, and / or the second and third oxygen values. In other embodiments, the alert may indicate that the first oxygen sensor (e.g., second oxygen sensor, third oxygen sensor) needs to be replaced.

[0072] If any of the first, second, and third deviations are less than the threshold value, the controller 254 may be configured to determine (block 520) whether the first deviation is less than the threshold value. In certain embodiments, the controller 254 may be configured to take the absolute value of the first deviation before comparing the firstdeviation to the threshold value. In some embodiments, the controller 254 may be configured to use the absolute value of the first deviation determined in block 516.

[0073] If the first deviation is less than the threshold value (block 520), the controller 254 may be configured to adjust (block 522) a value output by the first sensor based on the first deviation to obtain an adjusted first oxygen value. For example, the controller 254 may be configured to add / subtract the first deviation to / from the first oxygen value to obtain the adjusted first oxygen value. In certain embodiments, the controller 254 may be configured to multiply the first deviation by a constant (e.g., proportional gain) before adding / subtracting the first deviation to / from the first oxygen value to obtain the adjusted first oxygen value.

[0074] In block 523, the controller 254 may be configured to control the engine system 16 (e.g., reciprocating engine 26) based on the adjusted first oxygen value. In certain embodiments, the controller 254 may be configured to control a fuel intake valve configured to control the amount of fuel received by the engine system 16. In certain embodiments, a database (e.g., lookup table) may be used to determine the amount by which the fuel intake valve is to be opened / closed based on the adjusted first oxygen value. In certain embodiments, the process 500 iterates back to block 502 in response a completion of block 523.

[0075] If the first deviation is greater than or equal to the threshold value (block 520), the controller 254 may be configured to determine (block 524) whether each of the second and third deviations are less than the threshold value. In certain embodiments, the controller 254 may be configured to take the absolute value of each of the second and third deviations before comparing each of the second and third deviations to the threshold value. In some embodiments, the controller 254 may be configured to use the absolute values of the second and third deviations determined in block 516.

[0076] If the second and third deviations are less than the threshold value (block 524), the controller 254 may be configured to adjust (block 526) a value output by first sensorbased on the second deviation to obtain the adjusted first oxygen value. For example, the controller 254 may be configured to add / subtract the second deviation to / from the first oxygen value to obtain the adjusted first oxygen value. In certain embodiments, the controller 254 may be configured to multiply the second deviation by a constant (e.g., proportional gain) before adding / subtracting the second deviation to / from the first oxygen value to obtain the adjusted first oxygen value. In response to a completion of block 526, the controller 254 may be configured to proceed to block 523, as discussed herein.

[0077] If the second and third deviations are greater than or equal to the threshold value (block 524), the controller 254 may be configured to determine (block 528) whether the third deviation is less than the threshold value. In certain embodiments, the controller 254 may be configured to take the absolute value of the third deviation before comparing the third deviation to the threshold value. In some embodiments, the controller 254 may be configured to use the absolute value of the third deviation determined in block 516.

[0078] If the third deviation is less than the threshold value (block 528), the controller 254 may be configured to adjust (block 530) a value output the third sensor based on the third deviation to obtain an adjusted third oxygen value. For example, the controller 254 may be configured to add / subtract the third deviation to / from the third oxygen value to obtain the adjusted third oxygen value. In certain embodiments, the controller 254 may be configured to multiply the third deviation by a constant (e g., proportional gain) before adding / subtracting the third deviation to / from the third oxygen value to obtain the adjusted third oxygen value. In certain embodiments, the controller 254 may be configured to determine an adjustment (e g., offset) to the third deviation based on a map (e.g., lookup table). In some embodiments, the map may include catalytic converter operation and / or condition as an input parameter.

[0079] In block 531, the controller 254 may be configured to control the engine system 16 (e.g., reciprocating engine 26) based on the adjusted third oxygen value. In certain embodiments, the controller 254 may be configured to control a fuel intake valve configured to control the amount of fuel received by the engine system 16. In certainembodiments, a database (e.g., lookup table) may be used to determine the amount by which the fuel intake valve is to be opened / closed based on the adjusted third oxygen value. In certain embodiments, the process 500 iterates back to block 502 in response a completion of block 531.

[0080] If the third deviation is greater than or equal to the threshold value (block 528), the controller 254 may be configured to determine (block 532) whether the second deviation is less than the threshold value. In certain embodiments, the controller 254 may be configured to take the absolute value of the second deviation before comparing the second deviation to the threshold value. In some embodiments, the controller 254 may be configured to use the absolute value of the second deviation determined in block 516.

[0081] If the second deviation is less than the threshold value (block 532), the controller 254 may be configured to control (block 523) the engine system 16 (e.g., reciprocating engine 26) using the first oxygen value from the first oxygen sensor (e.g., without adjustment). In certain embodiments, the controller 254 may be configured to control a fuel intake valve configured to control the amount of fuel received by the engine system 16. In certain embodiments, a database (e.g., lookup table) may be used to determine the amount by which the fuel intake valve is to be opened / closed based on the first oxygen value. In certain embodiments, the process 500 iterates back to block 502 in response a completion of block 523.

[0082] If the second deviation is greater than or equal to the threshold value (block 532), the controller 254 may be configured to output (block 518) an alert. In certain embodiments the alert may include an audio notification, a visual notification, an email, an SMS message, or any combination thereof, as discussed above. For example, the alert may include a notification light or, in certain embodiments, a notification on a user interface. In some embodiments, the alert may indicate that there is a deviation (e.g., larger than the threshold) between the first and second oxygen values. In other embodiments, the alert may indicate that either the first oxygen sensor or second oxygen sensor needs to be replaced.

[0083] Technical effects of the disclosed embodiments include the ability to use redundant oxygen measurements collected from a plurality of sensors to correct the oxygen measurement collected from a sensor disposed an exhaust flow path of a reciprocating engine. The second sensor, which is disposed downstream of at least a first EGR cooler of an EGR system of the reciprocating engine, is subject to less harsh conditions (e.g., lower temperatures) than the first sensor and the third sensor, which are disposed in the exhaust flow path leading to the exhaust outlet (e.g., higher temperatures). Accordingly, the second sensor may be less susceptible to degradation, fouling, aging, and drift in sensor measurements (e.g., oxygen content measurements) due to thermal effects. The second sensor may be used to provide a reference value (e.g., reference oxygen value) for use in validating (e.g., calibrating) and / or adjust a value output by the first sensor. In certain embodiments, the controller of the engine system uses sensor feedback (e.g., oxygen content measurements) from the first sensor for control of the fuel intake, air intake, EGR flow, and other operating parameters, and thus the second sensor helps to maintain accuracy of the first sensor for use in such control. In certain embodiments, the controller may compare sensor measurements from a plurality of sensors (e.g., first, second and / or third sensors) and ultimately use one or more of the sensor measurements for such control, as discussed in further detail below. Thus, the second sensor positioned after at least some cooling in the heat exchange system helps to maintain accurate oxygen feedback to the controller of the engine system, thereby helping to improve control of the power output, engine efficiency, and exhaust gas emissions.

[0084] The subject matter described in detail above may be defined by one or more clauses, as set forth below.

[0085] A system includes a reciprocating engine having one or more piston-cylinder assemblies. The reciprocating engine is configured to output an exhaust gas. The system also includes an intake system coupled to the reciprocating engine. The intake system includes an intake flow path configured to route air into the reciprocating engine. The system also includes an exhaust system coupled to the reciprocating engine. The exhaustsystem includes an exhaust flow path of the exhaust gas from the reciprocating engine to an exhaust outlet. The system also includes an exhaust gas recirculation (EGR) system coupled to the intake system and the exhaust system. The EGR system includes an EGR flow path from the exhaust system to the intake system. The system also includes a multistage EGR cooler system coupled to the EGR flow path. The multi-stage EGR cooling includes a plurality of EGR coolers. The system also includes a first sensor coupled to the exhaust system. The first sensor is configured to obtain feedback indicative of a first oxygen value in the exhaust flow path. The system also includes a second sensor coupled to the multi-stage EGR cooler system. The second sensor is configured to obtain feedback indicative of a second oxygen value in the EGR flow path, and the second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

[0086] The system of the preceding clause, wherein the second oxygen value is a reference value for validation of the first oxygen value.

[0087] The system of any preceding clause, including a controller having a processor, a memory, and instructions stored on the memory and executable by the processor to validate the first sensor based on the second oxygen value of the second sensor, and control the reciprocating engine based on the validated first oxygen value.

[0088] The system of any preceding clause, wherein the controller is configured to compare the first and second oxygen values, obtain a deviation between the first and second oxygen values based on the comparison, and adjust the first sensor value based on the deviation.

[0089] The system of any preceding clause, wherein the controller is configured to compare the deviation with a threshold, adjust the first sensor value based on the deviation when the deviation is less than the threshold, and output an alert when the deviation is equal to or greater than the threshold.

[0090] The system of any preceding clause, including a third sensor coupled to the exhaust system, wherein the third sensor is configured to obtain feedback indicative of a third oxygen value in the exhaust flow path.

[0091] The system of any preceding clause, including a controller having a processor, a memory, and instructions stored on the memory and executable by the processor to compare the first, second, and third oxygen values, wherein the controller is configured to evaluate an accuracy of the first sensor based on the comparison.

[0092] The system of any preceding clause, including a catalyst disposed along the exhaust flow path, wherein the first sensor is disposed upstream from the catalyst and the third sensor is disposed downstream from the catalyst.

[0093] The system of any preceding clause, including a turbocharger turbine disposed downstream of the reciprocating engine, wherein the first sensor is disposed downstream of the turbocharger turbine.

[0094] The system of any preceding clause, including a turbocharger turbine disposed downstream of the reciprocating engine, wherein the first sensor is disposed upstream of the turbocharger turbine.

[0095] The system of any preceding clause, wherein the plurality of EGR coolers includes the first EGR cooler, a second EGR cooler, and a third EGR cooler in series along the EGR flow path.

[0096] The system of any preceding clause, wherein the first EGR cooler is a noncondensing EGR cooler, the second EGR cooler is a condensing EGR cooler, and the third EGR cooler is a reheating EGR cooler.

[0097] The system of any preceding clause, wherein the second sensor is disposed between the first and second EGR coolers.

[0098] The system of any preceding clause, wherein the second sensor is disposed after the third EGR cooler.

[0099] The system of any preceding clause, including a humidity sensor disposed after the third EGR cooler, wherein the humidity sensor is proximate to the second sensor.

[0100] The system of any preceding clause, including a catalyst disposed along the exhaust flow path, wherein the first sensor is disposed upstream from the catalyst.

[0101] The system of any preceding clause, including a turbocharger having a turbine disposed along the exhaust flow path and a compressor disposed along the intake flow path.

[0102] The system of any preceding clause, wherein the EGR flow path includes at least one of: a first EGR circuit from the exhaust flow path upstream from the turbine to the intake flow path downstream from the compressor, a second EGR circuit from the exhaust flow path downstream from the turbine to the intake flow path upstream from the compressor, or a third EGR circuit from the exhaust flow path upstream from the turbine to the intake flow path upstream from the compressor.

[0103] The system of any preceding clause, wherein the first and second sensors include an oxygen sensor, a nitrogen oxides (NOx) sensor, or a combination thereof.

[0104] The system of any preceding clause, wherein the oxygen sensor includes a wide band sensor.

[0105] The system of any preceding clause, wherein the oxygen sensor includes a narrow band sensor.

[0106] The system of any preceding clause, wherein a pressure sensor, a temperature sensor, a water vapor sensor, or a combination thereof is disposed proximate to each of the first and second sensors.

[0107] A system includes a reciprocating engine controller having a processor, a memory, and instructions stored on the memory and executable by the processor to control a reciprocating engine coupled to an intake system and an exhaust system. An exhaust gas recirculation (EGR) system is coupled to the intake system and the exhaust system. The intake system includes an intake flow path configured to route air into the reciprocating engine. The exhaust system includes an exhaust flow path of an exhaust gas from the reciprocating engine to an exhaust outlet. The EGR system includes an EGR flow path from the exhaust system to the intake system. A multi-stage EGR cooler system is coupled to the EGR flow path and includes a plurality of EGR coolers. The reciprocating engine includes one or more piston-cylinder assemblies. The reciprocating engine controller is configured to obtain feedback indicative of a first oxygen value in the exhaust flow path from a first sensor coupled to the exhaust system. The reciprocating engine controller is also configured to obtain feedback indicative of a second oxygen value in the EGR flow path from a second sensor coupled to the multi-stage EGR cooler system. The second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

[0108] The system of the preceding clause, wherein the reciprocating engine controller is configured to validate the first sensor based on the second oxygen value of the second sensor, wherein the controller is configured to control the reciprocating engine based on the validated first oxygen value.

[0109] The system of claim any preceding clause, wherein the controller is configured to compare the first and second oxygen values, obtain a deviation between the first and second oxygen values based on the comparison, and adjust the first sensor value based on the deviation.

[0110] A method includes controlling, via a controller, a reciprocating engine coupled to an intake system and an exhaust system. An exhaust gas recirculation (EGR) system is coupled to the intake system and the exhaust system. The intake system includes an intake flow path configured to route air into the reciprocating engine. The exhaust systemincludes an exhaust flow path of an exhaust gas from the reciprocating engine to an exhaust outlet. The EGR system includes an EGR flow path from the exhaust system to the intake system. A multi-stage EGR cooler system is coupled to the EGR flow path and includes a plurality of EGR coolers. The reciprocating engine includes one or more piston-cylinder assemblies. Controlling includes obtaining feedback indicative of a first oxygen value in the exhaust flow path from a first sensor coupled to the exhaust system. Controlling also includes obtaining feedback indicative of a second oxygen value in the EGR flow path from a second sensor coupled to the multi-stage EGR cooler system. The second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

[0111] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

[0112] The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function], . or “step for [perform]ing [a function]...”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Claims

CLAIMS1. A system, comprising: a reciprocating engine having one or more piston-cylinder assemblies, wherein the reciprocating engine is configured to output an exhaust gas; an intake system coupled to the reciprocating engine, wherein the intake system comprises an intake flow path configured to route air into the reciprocating engine; an exhaust system coupled to the reciprocating engine, wherein the exhaust system comprises an exhaust flow path of the exhaust gas from the reciprocating engine to an exhaust outlet; an exhaust gas recirculation (EGR) system coupled to the intake system and the exhaust system, wherein the EGR system comprises an EGR flow path from the exhaust system to the intake system; a multi-stage EGR cooler system coupled to the EGR flow path, wherein the multi-stage EGR cooling comprises a plurality of EGR coolers; a first sensor coupled to the exhaust system, wherein the first sensor is configured to obtain feedback indicative of a first oxygen value in the exhaust flow path; and a second sensor coupled to the multi-stage EGR cooler system, wherein the second sensor is configured to obtain feedback indicative of a second oxygen value in the EGR flow path, and the second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

2. The system of claim 1, comprising a controller having a processor, a memory, and instructions stored on the memory and executable by the processor to: validate the first sensor based on the second oxygen value of the second sensor; and control the reciprocating engine based on the validated first oxygen value; wherein the second oxygen value is a reference value for validation of the first oxygen value.

3. The system of claim 2, wherein the controller is configured to: compare the first and second oxygen values; obtain a deviation between the first and second oxygen values based on the comparison; and adjust the first sensor value based on the deviation.

4. The system of claim 3, wherein the controller is configured to: compare the deviation with a threshold; adjust the first sensor value based on the deviation when the deviation is less than the threshold; and output an alert when the deviation is equal to or greater than the threshold.

5. The system of claim 1, comprising: a third sensor coupled to the exhaust system, wherein the third sensor is configured to obtain feedback indicative of a third oxygen value in the exhaust flow path; a controller having a processor, a memory, and instructions stored on the memory and executable by the processor to compare the first, second, and third oxygen values, wherein the controller is configured to evaluate an accuracy of the first sensor based on the comparison; and a catalyst disposed along the exhaust flow path, wherein the first sensor is disposed upstream from the catalyst and the third sensor is disposed downstream from the catalyst.

6. The system of claim 1, wherein the plurality of EGR coolers comprises the first EGR cooler, a second EGR cooler, and a third EGR cooler in series along the EGR flow path.

7. The system of claim 6, wherein the first EGR cooler is a non-condensing EGR cooler, the second EGR cooler is a condensing EGR cooler, and the third EGR cooler is a reheating EGR cooler.

8. The system of claim 6, wherein the second sensor is disposed between the first and second EGR coolers.

9. The system of claim 6, wherein the second sensor is disposed after the third EGR cooler.

10. The system of claim 9, comprising a humidity sensor disposed after the third EGR cooler.

11. The system of claim 1, comprising a catalyst disposed along the exhaust flow path, wherein the first sensor is disposed upstream from the catalyst.

12. The system of claim 1, comprising a turbocharger having a turbine disposed along the exhaust flow path downstream of the reciprocating engine and a compressor disposed along the intake flow path upstream of the reciprocating engine, wherein the EGR flow path comprises at least one of a first EGR circuit from the exhaust flow path upstream from the turbine to the intake flow path downstream from the compressor, a second EGR circuit from the exhaust flow path downstream from the turbine to the intake flow path upstream from the compressor, or a third EGR circuit from the exhaust flow path upstream from the turbine to the intake flow path upstream from the compressor.

13. The system of claim 1, comprising a turbocharger having a turbine disposed along the exhaust flow path downstream of the reciprocating engine, wherein the first sensor is disposed along the exhaust flow path upstream of the turbine.

14. The system of claim 1, comprising a turbocharger having a turbine disposed along the exhaust flow path downstream of the reciprocating engine, wherein the first sensor is disposed along the exhaust flow path downstream of the turbine.

15. The system of claim 1, wherein each of the first and second sensors comprise at least one of an oxygen sensor, a wide band oxygen sensor, a narrow band oxygen sensor, a nitrogen oxides (NOx) sensor, or a combination thereof.

16. A system, comprising: a reciprocating engine controller having a processor, a memory, and instructions stored on the memory and executable by the processor to control a reciprocating engine coupled to an intake system and an exhaust system, wherein an exhaust gas recirculation (EGR) system is coupled to the intake system and the exhaust system, the intake system comprises an intake flow path configured to route air into the reciprocating engine, the exhaust system comprises an exhaust flow path of an exhaust gas from the reciprocating engine to an exhaust outlet, the EGR system comprises an EGR flow path from the exhaust system to the intake system, a multi-stage EGR cooler system is coupled to the EGR flow path and comprises a plurality of EGR coolers, and the reciprocating engine comprises one or more piston-cylinder assemblies, wherein the reciprocating engine controller is configured to: obtain feedback indicative of a first oxygen value in the exhaust flow path from a first sensor coupled to the exhaust system; and obtain feedback indicative of a second oxygen value in the EGR flow path from a second sensor coupled to the multi-stage EGR cooler system, wherein the second sensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

17. The system of claim 16, wherein the reciprocating engine controller is configured to validate the first sensor based on the second oxygen value of the second sensor,wherein the controller is configured to control the reciprocating engine based on the validated first oxygen value.

18. The system of claim 17, wherein the controller is configured to: compare the first and second oxygen values; obtain a deviation between the first and second oxygen values based on the comparison; and adjust the first sensor value based on the deviation.

19. The system of claim 16, wherein the reciprocating engine controller is configured to: activate the second sensor based on a first operating condition; and deactivate the second sensor based on a second operating condition.

20. A method, comprising: controlling, via a controller, a reciprocating engine coupled to an intake system and an exhaust system, wherein an exhaust gas recirculation (EGR) system is coupled to the intake system and the exhaust system, the intake system comprises an intake flow path configured to route air into the reciprocating engine, the exhaust system comprises an exhaust flow path of an exhaust gas from the reciprocating engine to an exhaust outlet, the EGR system comprises an EGR flow path from the exhaust system to the intake system, a multi-stage EGR cooler system is coupled to the EGR flow path and comprises a plurality of EGR coolers, and the reciprocating engine comprises one or more pistoncylinder assemblies, wherein controlling comprises: obtaining feedback indicative of a first oxygen value in the exhaust flow path from a first sensor coupled to the exhaust system; and obtaining feedback indicative of a second oxygen value in the EGR flow path from a second sensor coupled to the multi-stage EGR cooler system, wherein the secondsensor is disposed downstream from at least a first EGR cooler of the plurality of EGR coolers.

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