CONTROLLING EXHAUST GAS RECIRCULATION IN A TURBOCHARGED COMPRESSION-IGNITION ENGINE SYSTEM

• US 20090132153A1
• Filed: 12/20/2006
• Published: 05/21/2009
• Est. Priority Date: 12/20/2005
• Status: Active Grant

• Current Assignee: BorgWarner Incorporated
• Original Assignee: BorgWarner Incorporated
• Inventors: Mueller, Volker, Joergl, Volker, Shutty, John
• Granted Patent: US 10,132,230 B2
• Time in Patent Office: Days
• US Class Current: 701/108
• CPC Class Codes: F01N 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02B 37/24 by using pumps or turbines with adjustable guide vanes
• CPC Class Codes: F02D 41/0072 Estimating, calculating or determining the EGR rate, amount or flow sensors in EGR systems F02M26/45
• CPC Class Codes: F02D 9/04 concerning exhaust conduits throttle valves, or arrangements thereof in conduits F02D9/08
• CPC Class Codes: F02M 26/05 High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• CPC Class Codes: F02M 26/06 Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor
• CPC Class Codes: F02M 26/10 having means to increase the pressure difference between the exhaust and intake system, e.g. venturis, variable geometry turbines, check valves using pressure pulsations or throttles in the air intake or exhaust system
• CPC Class Codes: F02M 26/15 in relation to engine exhaust purifying apparatus
• CPC Class Codes: F02M 26/16 with EGR valves located at or near the connection to the exhaust system
• CPC Class Codes: F02M 26/24 with two or more coolers
• CPC Class Codes: F02M 26/38 with two or more EGR valves disposed in parallel
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method of controlling exhaust gas recirculation (EGR) in a turbocharged compression-ignition engine system including an engine, an induction subsystem in upstream communication with the engine, an exhaust subsystem in downstream communication with the engine, a high pressure EGR path between the exhaust and induction subsystems upstream of a turbocharger turbine and downstream of a turbocharger compressor, and a low pressure EGR path between the exhaust and induction subsystems downstream of the turbocharger turbine and upstream of the turbocharger compressor. A target total EGR fraction for compliance with exhaust emissions criteria is determined, then a target HP/LP EGR ratio is determined to optimize other engine system criteria within the constraints of the determined target total EGR fraction.

Claims

1. A method of controlling exhaust gas recirculation (EGR) in a turbocharged compression-ignition engine system including an engine, an induction subsystem in upstream communication with the engine, an exhaust subsystem in downstream communication with the engine and including an exhaust throttle valve, a high pressure EGR path between the exhaust and induction subsystems upstream of a turbocharger turbine and downstream of a turbocharger compressor and including an HP EGR valve, and a low pressure EGR path between the exhaust and induction subsystems downstream of the turbocharger turbine and upstream of the turbocharger compressor and including an LP EGR valve, the method comprising:

drawing fresh air into the induction subsystem;

inducting induction gases into the engine through the induction subsystem;

exhausting exhaust gases from the engine through the exhaust subsystem;

recirculating exhaust gases from the exhaust subsystem through at least one of the high or low pressure EGR paths to the induction subsystem;

sensing one or more proxy parameters indicative of total EGR fraction;

estimating total EGR fraction responsive to the sensed proxy parameter(s) as input to at least one engine system model, and not using EGR flow sensors;

determining a target total EGR fraction for compliance with exhaust emissions criteria;

determining a target HP/LP EGR ratio to optimize fuel economy criteria within the constraints of the determined target total EGR fraction;

generating HP EGR and LP EGR setpoints in accordance with the determined target HP/LP EGR ratio;

determining target HP and LP EGR valve and exhaust throttle valve opening percentages corresponding to the HP and LP EGR setpoints;

adjusting at least one of the HP and LP EGR fractions by processing the estimated total EGR fraction as process variable input and the target total EGR fraction as setpoint input, wherein at least one of the setpoints or opening percentages are adjusted; and

applying the HP EGR and LP EGR valve and exhaust throttle valve opening percentages to the HP EGR and LP EGR valves and exhaust throttle valve.

2. The method of claim 1 wherein the proxy parameter(s) include at least one of air mass flow, O₂, or engine system temperatures.

3. The method of claim 1 wherein the total EGR fraction estimating step may include using the engine system model(s) to formulaically or empirically correlate the proxy parameter(s) to the total EGR fraction.

4. The method of claim 3 wherein the engine system model(s) include at least one of lookup tables or maps that cross reference EGR fraction values with proxy parameter values.

5. The method of claim 4 wherein the engine system model(s) are based on engine speed and intake manifold pressure and temperature.

6. The method of claim 1 wherein the step of determining the target HP/LP EGR ratio includes overriding the fuel economy criteria in favor of other engine system criteria, within the constraints of the determined target total EGR fraction

7. The method of claim 6 wherein the other engine system criteria includes engine system performance.

8. The method of claim 7, wherein the other engine system criteria further includes at least one of engine system protection or maintenance specifications.

9. The method of claim 1 further comprising closed-loop controlling of the turbocharger.

10. The method of claim 1 wherein the LP EGR valve includes an intake throttle valve, wherein the valves are operated by a common actuator.

11. The method of claim 1 wherein the HP EGR valve includes an exhaust throttle valve, wherein the valves are operated by a common actuator.

12. The method of claim 1 wherein the step of determining a target HP/LP EGR ratio includes using a turbocharger efficiency model.

13. The method of claim 1 further comprising adjusting the LP EGR setpoint with closed-loop control.

14. The method of claim 1 wherein the step of determining target HP and LP EGR opening percentages includes using open-loop models with engine load, engine speed, and turbocharger boost pressure as inputs.

15. The method of claim 14 wherein the opening percentages are applied such that the exhaust throttle valve is substantially closed at about 0% EGR and gradually opens to a substantially 100% open position at about 20% EGR, whereas the LP EGR valve stays substantially closed from about 0% EGR to about 20% EGR and, thereafter, the exhaust throttle valve stays substantially 100% open until total EGR reaches about 70%, and the LP EGR valve gradually opens to substantially 100% open at about 70% EGR, whereafter the LP EGR valve remains substantially 100% open, while the exhaust throttle valve gradually closes until it is substantially closed at about 100% EGR.

16. The method of claim 1 further comprising adjusting the HP EGR setpoint with closed-loop control.

17. The method of claim 1 further comprising adjusting the HP and LP EGR setpoints with closed-loop control according to the proportion of the HP and LP setpoints.

18. The method of claim 1 further comprising adjusting one or the other of the HP and LP EGR setpoints with closed-loop control, depending on engine operating conditions at any given moment.

19. A method of controlling exhaust gas recirculation (EGR) in a turbocharged compression-ignition engine system including an engine, an induction subsystem in upstream communication with the engine, an exhaust subsystem in downstream communication with the engine, a high pressure EGR path between the exhaust and induction subsystems upstream of a turbocharger turbine and downstream of a turbocharger compressor and including an HP EGR valve, and a low pressure EGR path between the exhaust and induction subsystems downstream of the turbocharger turbine and upstream of the turbocharger compressor and including an LP EGR valve, the method comprising:

sensing a proxy parameter indicative of total EGR fraction;

estimating total EGR fraction responsive to the sensed proxy parameter as input to at least one engine system model, and not using EGR flow sensors;

determining a target total EGR fraction for compliance with exhaust emissions criteria;

determining a target HP/LP EGR ratio to optimize other engine system criteria within the constraints of the determined target total EGR fraction;

generating HP EGR and LP EGR setpoints in accordance with the determined target HP/LP EGR ratio;

determining target HP and LP EGR valve opening percentages corresponding to the HP and LP EGR setpoints;

adjusting at least one of the HP or LP EGR fractions using closed-loop control, wherein at least one of the HP or LP EGR setpoints or opening percentages is adjusted; and

applying the HP EGR and LP EGR valve opening percentages to the HP EGR and LP EGR valves.

20. A method of controlling exhaust gas recirculation (EGR) in a turbocharged compression-ignition engine system including an engine, an induction subsystem in upstream communication with the engine, an exhaust subsystem in downstream communication with the engine, a high pressure EGR path between the exhaust and induction subsystems upstream of a turbocharger turbine and downstream of a turbocharger compressor, and a low pressure EGR path between the exhaust and induction subsystems downstream of the turbocharger turbine and upstream of the turbocharger compressor, the method comprising:

determining a target total EGR fraction for compliance with exhaust emissions criteria; and

determining a target HP/LP EGR ratio to optimize other engine system criteria within the constraints of the determined target total EGR fraction.