WO2016022142A1

WO2016022142A1 - Exhaust gas recirculation flow measurement

Info

Publication number: WO2016022142A1
Application number: PCT/US2014/050281
Authority: WO
Inventors: Ming-Feng Hsieh; V. Phanindra GARIMELLA; Aniket Gupta; Dat D. LE
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2014-08-08
Filing date: 2014-08-08
Publication date: 2016-02-11
Anticipated expiration: 2017-02-08

Abstract

Systems, methods, and apparatus include determining an exhaust gas recirculation (EGR) flow rate. An effective flow area of an EGR system is determined based on a position of an EGR control valve of the EGR system and a pressure differential between an exhaust manifold pressure (EMP) and an intake manifold pressure (IMP) of an internal combustion engine. In response to the effective flow area, the pressure differential between the EMP and the IMP, the EMP, the IMP, and an exhaust manifold temperature the EGR flow rate is determined and a fraction of EGR flow in the charge flow is adjusted in response to the EGR flow rate.

Description

EXHAUST GAS RECIRCULATION FLOW MEASUREMENT

BACKGROUND

[0001] External exhaust gas recirculation (EGR) systems are generally coupled to internal combustion engines. EGR systems recirculate a portion of exhaust gas from an engine exhaust system to an engine intake system, which lower engine combustion chamber temperatures and control emissions. An accurate measurement of EGR flow is desirable to match against engine operating conditions in order to maintain optimal engine performance while meeting emission output standards. Commonly used techniques for measuring an EGR flow include orifice flow measurement techniques and venturi flow measurement techniques. Two drawbacks of the orifice and venturi based flow measurement techniques include high costs and the back pressure that is created, which may result in extra pumping work and a brake specific fuel consumption penalty. In addition, the pressure drop that is caused by the EGR flow measurement system could result in a tendency for natural gas engines to knock. Therefore, further technological developments are desirable in this area.

SUMMARY

[0002] Systems, methods, and apparatus are disclosed for determining an EGR flow rate of an EGR system. The EGR system may include an EGR control valve to control the EGR flow from an exhaust system that includes an exhaust manifold to receive exhaust gases resulting from combustion of a charge flow and fuel in cylinders of an internal combustion engine to an intake system coupled to an intake manifold of the internal combustion engine. One embodiment is a unique system, method, and apparatus for determining an EGR flow rate of an EGR system based on an effective flow area that is determined in response to a position of the EGR control valve and the pressure differential between an exhaust manifold pressure (EMP) and an intake manifold pressure (IMP). The EGR flow rate is then determined in response to the effective flow area and least the pressure differential between the EMP and the IMP. In certain embodiments, the EGR flow rate is further determines in response to the EMP, the IMP, and an exhaust manifold temperature. Control of the EGR fraction in the charge flow is performed in response to the EGR flow rate.

[0003] This summary is provided to introduce a selection of concepts that are further described below in the illustrative embodiments. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The description herein makes reference to the accompanying figures wherein like reference numerals refer to like parts throughout the several views, and wherein:

[0005] FIG. 1 is a schematic block diagram of a system that includes an internal combustion engine connected to an exhaust gas recirculation (EGR) system;

[0006] FIG. 2 is a schematic block diagram of an example controller for operating the system of FIG. 1 ;

[0007] FIG. 3 is a flow diagram of a procedure determining an EGR flow rate for operating the system of FIG. 1 ;

[0008] FIG. 4 is a graph illustrating a comparison of measured EGR flow rates and predicted EGR flow rates using a prior art EGR flow model; and

[0009] FIGS. 5-6 are test results showing the relationship between EGR valve position, effective flow area, and engine differential pressure.

[0010] FIGS. 7- 10 are graphs illustrating measured EGR flow rates and predicted EGR flow rates based on EGR flow models according to the present invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0011] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the invention as illustrated therein as would normally occur to one skilled in the art to which the invention relates are contemplated herein.

[0012] Referring to FIG. 1 , there is shown a schematic view of a system 100 that includes an internal combustion engine 102 that is operable to produce an exhaust gas flow. The engine 102 may be any type of internal combustion engine known in the art, such as a gasoline or a diesel engine, either as a stand-alone power source, in combination with other engines, or part of a hybrid power train including an internal combustion engine for at least one of the power sources. The system 100 can be used for mobile applications including, but not limited to, a vehicle, locomotive, or marine application, or for stationary applications, such as a power generation or a pumping system, for example.

[0013] The engine 102 is in fluid communication with an intake system 108 through which charge air (i.e., pressurized intake air and recirculated exhaust gas) enters an intake manifold 104 of the engine 102 and an exhaust system 1 10 through which exhaust gas resulting from combustion exits by way of an exhaust manifold 106 of the engine 102. Intake valves (not shown) control the admission of charge air into cylinders of the engine 102, and exhaust valves (not shown) control the outflow of exhaust gas through the exhaust manifold 106 and ultimately to the atmosphere, it being understood that not all details of these systems that are typically present are shown. The system 100 includes an intake throttle valve 142 to regulate the charge air flow to the cylinders of the engine 102.

[0014] The system 100 further includes an EGR system 1 12 that includes an EGR conduit 1 18 connecting the exhaust system 1 10 to the intake system 108. In the illustrated embodiment, the EGR system 1 12 is a high pressure system that is connected upstream of a turbine 122 and downstream of a compressor 126 of a turbocharger 120. The EGR system 1 12 includes an EGR control valve 1 14 and an EGR cooler 1 16 disposed in the EGR conduit 1 1 8. In certain embodiments, an EGR bypass (not shown) may be configured in the EGR system 1 12 to bypass all or a portion of the EGR flow around the EGR cooler 1 16. In the embodiment of the EGR system 1 12 illustrated in FIG. 1 , the EGR control valve 1 14 is downstream of the EGR cooler 1 16. It is contemplated that in certain embodiments the EGR control valve 1 14 may be upstream of the EGR cooler 1 16. The EiGR control valve 1 14 can be controlled by a controller 130 to facilitate control of the EGR flow through the EGR system 1 12 to provide a desired EGR fraction in the charge flow.

[0015] The EGR control valve 1 14 and/or the intake throttle valve 142 can include any suitable actuatable valve member that is actuatable between at least two positions, such as an open/on position, and a closed/off position, although full authority actuatable valve members are not precluded. The EGR control valve 1 14 and/or the intake throttle valve 142 may be, for example, a butterfly type valve, a guillotine-type valve, or a ball-type valve. The actuatable valve members may be an electronic actuator, an electric motor, a pneumatic actuator, and/or any other suitable type of actuator to operate the valve member of the EGR control valve 1 14 and/or the intake throttle valve 142.

[0016] The system 100 further includes the turbocharger 120 operable to compress ambient air before the ambient air enters the intake manifold 1 04 of the engine 102 at increased pressure. The turbocharger 120 includes a shaft 124 connecting the turbine 122 in the exhaust system 1 10 and the compressor 126 in the intake system 108. A mixture of compressed air from the compressor 126 and exhaust gas from the EGR system 1 12 is pumped through the intake system 108, to the intake manifold 104, and finally to the cylinders of the engine 102.

[0017] The system 100 additionally includes a charge air cooler 128 disposed downstream of the compressor 126 in the intake system 108. The charge air cooler 128 may be an air-to-air heat exchanger, an air-to-liquid heat exchanger, or a combination of both to facilitate the transfer of thermal energy to or from the compressed air directed into the engine 102.

[0018] In certain embodiments, a wastegate (not shown) may be provided at the turbine 122 to provide an exhaust flow path that bypasses the turbine 122 in response to certain operating conditions. It is contemplated that in certain embodiments, the turbocharger 120 may not be present. It is further contemplated that in an embodiment including the turbocharger 120, the turbocharger 120 may be a variable geometry turbocharger (VGTs), a fixed geometry

turbocharger, twin-turbochargers, and/or series or parallel configurations of multiple

turbochargers. [0019] System 100 may further include various sensors associated with the engine 1 02, the intake system 108, and the exhaust system 1 10 that provide outputs to the controller 1 30 that are processed by the controller 130 to determine control operations of the system 100. As used herein, a sensor may be a physical sensor that directly measures an operating condition or output of the system 100, a virtual sensor in which the operating condition or output is determined from one or more other sensors and operating parameters of the system 100, or a combination thereof. Not all sensors typically associated with the system 100 are shown, and the illustrated sensors are provided for purposes of illustration and not limitation.

[0020] The sensors in the system 100 may include an intake manifold pressure sensor 132 (e.g., a manifold absolute pressure (MAP) sensor) and an exhaust manifold pressure sensor 136 that provides an output to the controller 130 to indicate or to determine therefrom a manifold pressure of the intake manifold 104 and exhaust manifold 106, respectively. The exhaust manifold pressure sensor may be a high data rate (HDR) sensor capable of determining the exhaust manifold pressure with an HDR measurement or in crank angle domain. In certain

embodiments, the system 100 may further include a mass air flow (MAF) sensor (not shown) used in combination with the intake manifold pressure sensor 132 to measure the mass air flow of the charge flow and to test the efficiency of operation of the EGR control valve 1 14.

[0021] The sensors in the system 100 may additionally include an engine torque sensor 134 or virtual sensor that provides an output to the controller 130 to indicate or determine therefrom an engine torque, such as the torque at an output shaft of the engine. The sensors in the system 100 may further include an exhaust manifold temperature sensor 138 that provides an output to the controller 130 to indicate or determine therefrom a temperature of the exhaust gas flowing through the exhaust manifold 106.

[0022] The system 100 may additionally include actuator position sensors. For example, a valve actuator position sensor 140 may be included that provides an output to the controller 1 30 to measure or to determine therefrom an actuator position of the EGR control valve 1 14. In certain embodiments, another actuator position sensor may be included in system 100 for providing an output to the controller 1 30 to measure or to determine therefrom an actuator position of the turbocharger 120 and/or the intake throttle 142. Additional and/or alternative sensors, or transducers, may be provided, but are not required, to measure and/or to calculate certain conditions of the system 100 to determine the intake manifold pressure, the exhaust manifold pressure, the engine torque output, the exhaust manifold temperature, the EGR control valve position, the turbocharger actuator position, and/or other operating conditions and/or position values of the system 100.

[0023] The controller 130 may be structured to functionally execute operations for managing the EGR flow. In certain embodiments, the controller 130 may be linked to the engine 102, the EGR system 1 12, and the turbocharger 120. In certain other embodiments, the controller 130 may be linked to vehicle components and/or sensors through an engine control module (ECM), or engine control unit (ECU). In certain embodiments, the controller 130 and/or ECM may form a portion of a processing subsystem including one or more computing devices having memory, processing, and communication hardware. The controller 130 and/or ECM may be a single device or a distributed device, and the functions of the controller 130 and ECM may be performed by hardware or software in a combined controller or separate controllers. In certain embodiments, the inputs to the controller 130 may be received by the ECM.

[0024] Any of the operations of example procedures described herein may be performed at least partially by the controller 130. In certain embodiments, the controller 130 includes stored data values, constants, and functions, as well as operating instructions stored on a non-transient computer readable medium. In certain embodiments, the controller 130 includes one or more modules structured to functionally execute the operations of the controller 130. The description herein including modules emphasizes the structural independence of the aspects of the controller 130, and illustrates one grouping of operations and responsibilities of the controller 130. Other groupings that execute similar overall operations are understood within the scope of the present application. Modules may be implemented in hardware and/or instructions stored on a non- transient computer readable medium, and modules may be distributed across various hardware or instructions stored on a non-transient computer readable medium. More specific descriptions of certain embodiments of the controller 130 and operations processed therein are included in the sections referencing FIGS. 2-3. Operations illustrated are understood to be exemplary only, and operations may be combined or divided, and added or removed, as well as re-ordered in whole or in part.

[0025] Certain operations described herein include operations to interpret one or more parameters. Interpreting, as utilized herein, includes receiving values by any method known in the art, including at least receiving values from a datalink or network communication, receiving an electronic signal (e.g., a voltage, frequency, current, or pulse-width modulation (PWM) signal) indicative of the value, receiving a software parameter indicative of the value, reading the value from a memory location on a computer readable medium, receiving the value as a run-time parameter by any means known in the art, and/or by receiving a value by which the interpreted parameter can be calculated, and/or by referencing a default value that is interpreted to be the parameter value.

[0026] One example embodiment 200 of the controller 130 is shown in FIG. 2. The controller 130 may be structured to receive and interpret an exhaust manifold pressure input 202, an intake manifold pressure input 204, an exhaust manifold temperature input 206, an engine torque input 208, and an EGR control valve position input 210. In certain embodiments, the controller 130 may be further structured to receive and interpret additional and/or alternative inputs than those referenced in FIG. 2.

[0027] The embodiment 200 of the controller 130 includes an effective flow area determination module 220, a pressure differential compensation module 230, an EGR flow rate determination module 240, an EGR fraction determination module 250, and an EGR flow control module 260. Other controller 130 arrangements that functionally execute the operations of the controller 130 are contemplated in the present application. In certain embodiments, the pressure differential compensation module 230 may be omitted.

[0028] The effective flow area determination module 220 may be structured to receive and interpret the exhaust manifold pressure input 202, the intake manifold pressure input 204, and the EGR control valve position input 210. The effective flow area determination module 220 may be further structured to determine and output a manifold pressure differential 224 by determining the difference between the exhaust manifold pressure input 202 and the intake manifold pressure input 204. The effective flow area determination module 220 may additionally be structured to determine and output an effective flow area 222 in response to the manifold pressure differential 224 and the EGR control valve position input 210.

[0029] The pressure differential compensation module 230 may be structured to receive and interpret the manifold pressure differential 224 determined at the effective flow area

determination module 220 and the engine torque input 208. The inventors have discovered that prior EGR flow models have an EGR flow rate determination error that is correlated to the engine torque and the manifold differential pressure, indicating that the error could be caused by exhaust manifold pressure pulsation that is not captured in the average exhaust manifold pressure data used in prior art EGR flow models. The pressure differential compensation module 230 may be further structured to determine and output a compensation term 232 based on a function of the engine torque input 208, exhaust manifold pressure, or the manifold pressure differential 224 caused by insufficient exhaust manifold pressure sampling. In certain embodiments the compensation term 232 compensates the manifold pressure differential 224 for exhaust manifold pressure pulsations and a low sampling rate for the exhaust manifold pressure.

[0030] The EGR flow rate determination module 240 may be structured to receive and interpret the effective flow area 222, the manifold pressure differential 224 from the effective flow area determination module 220, and the compensation term 232 from the pressure differential compensation module 230. The EGR flow rate determination module 240 may be additionally structured to receive and interpret the exhaust manifold pressure input 202, the intake manifold pressure input 204, and the exhaust manifold temperature input 206. The EGR flow rate determination module 240 may be further structured to determine an EGR flow rate 242 based on the effective flow area 222, the manifold pressure differential 224, the exhaust manifold pressure input 202, the intake manifold pressure input 204, and the exhaust manifold temperature input 206. In certain embodiments, the EGR flow rate determination module 240 may be structured to determine the EGR flow rate 242 further based on an adjusted pressure differential determined in response to the compensation term 232.

[0031] The EGR fraction determination module 250 may be structured to receive and interpret the EGR flow rate 242 determined at the EGR flow rate determination module 240. The EGR fraction determination module 250 may be further structured to determine and output an EGR flow fraction 252 (i.e., a fraction of EGR flow in the charge flow) based on the EGR flow rate 242.

[0032] The EGR flow control module 260 may be structured to receive and interpret the EGR flow fraction 252, determined at the EGR fraction determination module 250, to determine an EGR flow control command 262 based on the EGR flow fraction 252. The EGR flow control command 262 may be provided to a component of the system 100 to change the position of an actuator to adjust the EGR flow through the EGR system 1 12 to provide a desired EGR fraction in the charge flow. In certain embodiments, the EGR flow control command may be provided to an actuator of the EGR control valve 1 14, an actuator of the intake throttle valve 142, and/or an actuator of the turbocharger 120. In one such example, the EGR flow control command 262 may modulate an actuator of the intake throttle valve 142 to control the charge flow to designated EGR cylinders to produce more or less exhaust flow, whichever is indicated by the EGR flow control command 262. In another example, an actuator of the EGR control valve 1 14 may be adjusted to provide the desired increase or decrease in EGR flow based on the EGR flow control command 262. In still another example, an actuator of the turbocharger 120 may adjust the boost output of the turbocharger 120 (i.e., act as a pressure relief valve) based on the EGR flow control command 262.

[0033] FIG. 3 provides an example procedure for determining an EGR flow rate, while the graphs illustrated in FIGS. 4-10 illustrate test results of application of the equations used in the example procedure illustrated in FIG. 3, which are described in further detail below.

[0034] With reference to FIG. 3, the schematic flow diagram and related description which follows provides an illustrative embodiment of performing procedures for determining an EGR flow rate using an EGR model to estimate EGR flow rate based on exhaust manifold and intake manifold measurements, such that use of orifice or venture measurement techniques may be avoided. Operations illustrated are understood to be exemplary only, and operations may be combined or divided, and added or removed, as well as re-ordered in whole or part, unless stated explicitly to the contrary herein. Certain operations illustrated may be implemented by a computer, such as the controller 130, executing a computer program product on a computer readable medium, where the computer program product comprises instructions causing the computer to execute one or more of the operations, or to issue commands to other devices to execute one or more of the operations.

[0035] The procedure 300 may be put into operation by programming the controller 130 for use in, for example, the system 100. The procedure 300 begins at operation 302, in which a control routine for providing various inputs to the controller 130 to determine the EGR flow rate.

Operation 302 may begin by interpreting a key-on event, completion of a cycle, restarting procedure 300, and/or by initiation by the operator or a technician.

[0036] Procedure 300 continues from operation 302 to operation 304 to determine a pressure differential between the exhaust manifold pressure and the intake manifold pressure utilizing the equation: Δ = Pern - Pirn Equation 1 where Δρ is the pressure differential, p_em is the exhaust manifold pressure, and p_irn is the intake manifold pressure.

[0037] From operation 304, procedure 300 continues to operation 306 to determine an effective flow area as a function of the position of the EGR control valve 1 14 and the pressure differential determined at operation 304. A traditional approach of modeling EGR flow typically considers an EGR loop (e.g., the EGR cooler 1 16, the EGR control valve 1 14, etc. as illustrated in the EGR system 1 12 of FIG. 1 ) as an orifice, then utilizes an orifice model to predict EGR flow based on the pressure differential determined at operation 304, the exhaust manifold pressure, the exhaust manifold temperature, and the EGR control valve position utilizing the known equation:

™-EGR = k * Equation 2

where rh_EGR is the EGR flow rate, k is a calibration constant, and A is the effective flow area,

EGR

and where k * A =— ^ ^ and EGR_pos is the position of the EGR control valve. FIG. 4 illustrates test results 400 of an EGR virtual sensor based on the traditional orifice model, which resulted in a standard deviation of over 23%. FIGS. 5 and 6 illustrate that the effective flow area of the traditional model of Equation 2 is a function not only of EGR valve position but also a function of the pressure differential, the pressure differential being greater the closer the position of the EGR valve is to the closed position (i.e., 0% open). The test results 500 illustrated in FIG. 5 and test results 600 illustrated in FIG. 6 each illustrate the relation between the orifice effective flow area, engine pressure differential, and the EGR control valve position.

[0038] Based on the relation between EGR valve position, the effective flow area, and engine differential pressure, a new model of the effective flow area determines the orifice effective flow area as a function of EGR control valve position and the engine pressure differential utilizing the equation: k * A = a * arctan(fr * EGR_pos + c) * arctan(d * Δρ + ) + g Equation 3 where a, b, c, d, f , g are calibration parameters.

[0039] Using the effective flow area determined according to Equation 3, an EGR flow rate may be calculated utilizing the following EGR flow model equation:

Equation 4

[0040] FIG. 7 illustrates test results 700 of an EGR virtual sensor based on the improved EGR model of Equation 4 compared to measured EGR flow rates, which resulted in a standard deviation of around 12.5%. It should be noted that the EGR flow rate that may be calculated from the improved EGR model of Equation 4 may be sufficient in certain applications, such that in certain embodiments operation 308 may be omitted.

[0041] Procedure 300 continues from operation 306 to operation 308 to compensate for low sampling of exhaust manifold pressure measurements, which does not account for exhaust manifold pressure pulsations under certain engine operating conditions, such as at higher engine torques and lower engine pressure differentials. A portion of the error in the EGR flow rates determined according to Equation 4 is believed to be correlated to engine torque and the engine pressure differential. As a result, the EGR flow rate determination error in Equation 4 may be caused by the exhaust manifold pressure pulsations not captured in the mean exhaust manifold pressure data used in determining the EGR flow rates according Equation 4. For example, due to the nonlinearity in Equation 4 with respect to the pressure differential (i.e., the square root of Δρ), a larger exhaust manifold pressure pulsation, which generally occurs at higher engine torque, and a smaller engine pressure differential can result in an increased error generated by averaging exhaust manifold pressure pulsations. To reduce the error caused by the exhaust manifold pressure pulsations, a compensation term has been developed to compensate the offset caused by an insufficient exhaust manifold pressure sampling rate. One example of a compensation term may be determined as a function of the engine torque and the pressure differential. FIG. 8 illustrates test results 800 of a further improved EGR model with an exhaust manifold pressure pulsation compensation term resulting in a standard deviation of around 10.5% utilizing the following equation: m_EGR = / Ι(Δ_Ρ - ^¾)Τ^ Equation 5

where Eng_Tq is the engine torque and h is a calibration parameter.

[0042] In certain embodiments, the EGR flow measurement determination may be improved by using a high data rate (HDR) pressure measurement to capture pressure pulsation in the crank angle domain. A comparison of EGR flow measured by a test cell and EGR flow estimation without HDR pressure measurements is shown in a first embodiment 900 in Fig. 9. In a second embodiment 1000, EGR flow rates determined with HDR measurement are illustrated in FIG. 10. As can be seen in the illustrations, the first embodiment 900 without the HDR measurement resulted in a standard deviation of just over 13%, while the second embodiment 1000 with the HDR measurement resulted in an improved standard deviation of 9.36%.

[0043] Procedure 300 continues from operation 308 to operation 310 to determine the EGR flow rate utilizing one of the EGR models of Equations 4 and 5. In certain embodiments, the compensation term and/or HDR exhaust manifold and/or intake manifold pressure measurements may be used to compensate for the nonlinearity offset caused by the exhaust manifold pressure pulsations to determine the EGR flow rate.

[0044] From operation 310, procedure 300 continues to operation 312 to adjust a fraction of EGR flow in a charge flow based on the EGR flow rate determined at operation 310 before proceeding to operation 314, where procedure 300 ends. In certain embodiments, adjusting the fraction of EGR flow in the charge flow includes adjusting the position of an actuator of the EGR control valve 1 14, an actuator of the throttle valve 142, and/or an actuator of the turbocharger 120.

[0045] Certain operations described herein include operations to interpret or determine one or more parameters. Interpreting and/or determining, as utilized herein, includes receiving values by any method known in the art, including at least receiving values from a datalink or network communication, receiving an electronic signal (e.g. a voltage, frequency, current, or PWM signal) indicative of the value, receiving a software parameter indicative of the value, reading the value from a memory location on a computer readable medium, receiving the value as a run-time parameter by any means known in the art, and/or by receiving a value by which the interpreted parameter can be calculated, and/or by referencing a default value that is interpreted to be the parameter value.

[0046] As is evident from the figures and text presented above, a variety of aspects,

embodiments and refinements of the present disclosure are contemplated. One aspect involves a method includes operating an internal combustion engine including an intake manifold, an exhaust manifold, and an EGR system that provides an EGR flow to mix with a fresh air flow to provide a charge flow to the internal combustion engine, the EGR system including an EGR control valve operable to control the EGR flow to the intake manifold, determining an effective flow area of the EGR system in response to a position of the EGR control valve and the pressure differential between an EMP and an IMP, determining an EGR flow rate in response to at least the effective flow area and the pressure differential between the EMP and the IMP, and adjusting a fraction of EGR flow in the charge flow in response to the EGR flow rate.

[0047] In one embodiment, the method further includes measuring a torque of the internal combustion engine and determining a compensation term as a function of the torque of the internal combustion engine and the pressure differential. Determining the EGR flow rate is further determined in response to the compensation term. In another embodiment, the compensation term compensates the pressure differential used in determining the EGR flow rate. In yet another embodiment, the method further includes determining the EMP with a HDR or crank angle triggered measurement. In still another embodiment, adjusting a fraction of EGR flow in the charge flow comprises adjusting at least one of the EGR control valve, a throttle valve of the intake manifold, and a position of an actuator of a turbocharger. In yet another embodiment, the EGR flow is further determined in response to the EMP, the IMP and the exhaust manifold temperature.

[0048] Another aspect involves a system that includes an internal combustion engine including an exhaust manifold and an intake manifold, the internal combustion engine operable to receive a charge flow to the intake manifold from an intake system and produce an exhaust gas flow to an exhaust system from the exhaust manifold, an EGR system fluidly coupling the exhaust system and the intake system, the EGR system including an EGR control valve operable to control an amount of recirculated exhaust gas in the charge flow, and a controller in electrical

communication with the internal combustion engine and the EGR system. The controller is structured to determine an EGR flow rate in response to at least an effective flow area of the EGR system and a pressure differential between an EMP and an IMP of the internal combustion engine. The effective flow area is determined in response to a position of the EGR control valve and the pressure differential between the EMP and the IMP.

[0049] In one embodiment, the controller is further structured to determine a compensation term as a function of an engine torque and the pressure differential and determine the EGR flow rate further as a function of the compensation term. In another embodiment, the compensation term compensates the pressure differential. In still another embodiment, the controller is further structured to determine a HDR or crank angle triggered EMP measurement and determine the EGR flow rate further as a function of the HDR or crank angle triggered EMP measurement.

[0050] In yet another embodiment, the system further includes a turbocharger including a turbine in the exhaust system and a compressor in the intake system. In still yet another embodiment, the EGR system is connected to the exhaust system upstream of the turbine of the turbocharger. In yet still another embodiment, the turbocharger comprises a VGT. In another embodiment, the controller is further structured to provide an EGR flow control command to an EGR flow control device to adjust an EGR flow in the charge flow in response to the determined EGR flow rate. In yet another embodiment, the controller is structured to determine the EGR flow rate in response to the EMP, the IMP, and an exhaust manifold temperature.

[0051] Still another aspect involves an apparatus that includes an electronic controller in operative communication with a plurality of sensors operable to provide signals indicating conditions of a system, the system including an internal combustion engine that includes an exhaust manifold and an intake manifold, an EGR system fluidly coupling the exhaust system and the intake system. The internal combustion engine is operable to receive a charge flow to the intake manifold from an intake system and produce an exhaust gas flow to an exhaust system from the exhaust manifold. The EGR system includes an EGR control valve operable to control an amount of recirculated exhaust gas in the charge flow.

[0052] The electronic controller includes an effective flow area determination module structured to determine an effective flow area of the EGR system in response to a position of the EGR control valve and a pressure differential between an EMP and an IMP of the internal combustion engine. The electronic controller additionally includes an EGR flow rate determination module structured to determine an EGR flow rate in response to at least the effective flow area and the pressure differential. The electronic controller further includes an EGR fraction determination module structured to determine a fraction of EGR flow in the charge flow in response to the EGR flow rate.

[0053] In one embodiment, the electronic controller still further includes an EGR flow control module structured to provide an EGR flow control command to one or more EGR flow control devices in response to the EGR flow fraction. In another embodiment, the one or more EGR flow control devices includes the EGR control valve. In still another embodiment, the system further includes a VGT, and wherein the one or more EGR flow control devices includes an actuator of the VGT. In yet another embodiment, the electronic controller further includes a pressure differential compensation module structured to compensate the pressure differential as a function of a torque of the internal combustion engine and the pressure differential and the EGR flow rate determination module is further structured to determine an EGR flow rate in response to the compensated pressure differential.

[0054] In still yet another embodiment, the compensated pressure differential is determined as a function of the difference between the pressure differential and a ratio of a product of the engine torque and a constant to the pressure differential. In yet still another embodiment, the EGR flow rate determination module is further structured to determine the EGR flow rate based on a high data rate EMP measurement. In another embodiment, the EGR flow rate determination module is further structured to determine the EGR flow rate in response to the EMP, the IMP, and an exhaust manifold temperature.

[0055] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described. Those skilled in the art will appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

[0056] In reading the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary.

Claims

WHAT IS CLAIMED IS :

1 . A method, comprising:

operating an internal combustion engine including an intake manifold, an exhaust manifold, and an exhaust gas recirculation (EGR) system that provides an EGR flow to mix with a fresh air flow to provide a charge flow to the internal combustion engine, the EGR system including an EGR control valve operable to control the EGR flow to the intake manifold;

determining an effective flow area of the EGR system in response to a position of the EGR control valve and the pressure differential between an exhaust manifold pressure (EMP) and an intake manifold pressure (IMP);

determining an EGR flow rate in response to at least the effective flow area and the pressure differential between the EMP and the IMP; and

adjusting a fraction of EGR flow in the charge flow in response to the EGR flow rate.

2. The method of claim 1 , further comprising:

measuring a torque of the internal combustion engine; and

determining a compensation term as a function of the torque of the internal combustion engine and the pressure differential,

wherein determining the EGR flow rate is further in response to the compensation term.

3. The method of claim 2, wherein the compensation term compensates the pressure differential used in determining the EGR flow rate.

4. The method of claim 1 , further comprising determining the EMP with a high data rate or crank angle triggered measurement.

5. The method of claim 1 , wherein adjusting a fraction of EGR flow in the charge flow comprises adjusting at least one of the EGR control valve, a throttle valve of the intake manifold, and a position of an actuator of a turbocharger.

6. The method of claim 1 , wherein the EGR flow rate is further determined in response to the EMP, the IMP, and an exhaust manifold temperature.

7. A system, comprising:

an internal combustion engine including an exhaust manifold and an intake manifold, the internal combustion engine operable to receive a charge flow to the intake manifold from an intake system and produce an exhaust gas flow to an exhaust system from the exhaust manifold; an exhaust gas recirculation (EGR) system fluidly coupling the exhaust system and the intake system, the EGR system including an EGR control valve operable to control an amount of recirculated exhaust gas in the charge flow; and

a controller in electrical communication with the internal combustion engine and the EGR system, wherein the controller is structured to:

determine an EGR flow rate in response to at least an effective flow area of the

EGR system and a pressure differential between an exhaust manifold pressure (EMP) and an intake manifold pressure (IMP) of the internal combustion engine,

wherein the effective flow area is determined in response to a position of the EGR control valve and the pressure differential between the EMP and the IMP.

8. The system of claim 7, wherein the controller is further structured to:

determine a compensation term as a function of an engine torque and the pressure differential; and

determine the EGR flow rate further as a function of the compensation term.

9. The system of claim 8, wherein the compensation term compensates the pressure differential.

10. The system of claim 7, wherein the controller is further structured to:

determine a high data rate (HDR)or crank angle triggered EMP measurement; and determine the EGR flow rate further as a function of the HDR or crank angled triggered

EMP measurement.

1 1 . The system of claim 7, further comprising a turbocharger including a turbine in the exhaust system and a compressor in the intake system.

12. The system of claim 1 1 , wherein the EGR system is connected to the exhaust system upstream of the turbine of the turbocharger.

13. The system of claim 1 1 , wherein the turbocharger comprises a variable-geometry turbocharger.

14. The system of claim 1 1 , wherein the controller is further structured to:

provide an EGR flow control command to an EGR flow control device to adjust an EGR flow in the charge flow in response to the determined EGR flow rate.

15. The system of claim 1 1 , wherein the controller is further structured to determine the EGR flow rate in response to the EMP, the IMP, and an exhaust manifold temperature.

16. An apparatus, comprising:

an electronic controller in operative communication with a plurality of sensors operable to provide signals indicating conditions of a system, the system including an internal combustion engine that includes an exhaust manifold and an intake manifold, an exhaust gas recirculation (EGR) system fluidly coupling the exhaust system and the intake system,

wherein the internal combustion engine is operable to receive a charge flow to the intake manifold from an intake system and produce an exhaust gas flow to an exhaust system from the exhaust manifold,

wherein the EGR system includes an EGR control valve operable to control an amount of recirculated exhaust gas in the charge flow, and

wherein the electronic controller includes:

an effective flow area determination module structured to determine an effective flow area of the EGR system in response to a position of the EGR control valve and a pressure differential between an exhaust manifold pressure (EMP) and an intake manifold pressure (IMP) of the internal combustion engine; an EiGR flow rate determination module structured to determine an EGR flow rate in response to at least the effective flow area and the pressure differential between the EMP and the IMP; and

an EGR fraction determination module structured to determine a fraction of EGR flow in the charge flow in response to the EGR flow rate.

17. The apparatus of claim 16, wherein the electronic controller further includes:

an EGR flow control module structured to provide an EGR flow control command to one or more EGR flow control devices in response to the EGR flow fraction.

18. The apparatus of claim 17, wherein the one or more EGR flow control devices includes the EGR control valve.

19. The apparatus of claim 17, wherein the system further includes a variable-geometry turbocharger (VGT), and wherein the one or more EGR flow control devices includes an actuator of the VGT.

20. The apparatus of claim 16, wherein the electronic controller further includes:

a pressure differential compensation module structured to compensate the pressure differential as a function of a torque of the internal combustion engine and the pressure differential,

wherein the EGR flow rate determination module is further structured to determine an EGR flow rate in response to the compensated pressure differential.

21 . The apparatus of claim 20, wherein the compensated pressure differential is determined as a function of the difference between the pressure differential and a ratio of a product of the engine torque and a constant to the pressure differential.

22. The apparatus of claim 16, wherein the EGR flow rate determination module is further structured to determine the EGR flow rate based on a high data rate EMP measurement.

23. The apparatus of claim 16, wherein the EGR flow rate determination module is further structured to determine the EGR flow rate in response to the EMP, the IMP, and an exhaust manifold temperature.