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

• US 20100101226A1
• Filed: 03/14/2008
• Published: 04/29/2010
• Est. Priority Date: 03/28/2007
• Status: Active Grant

• Current Assignee: BorgWarner Incorporated
• Original Assignee: BorgWarner Incorporated
• Inventors: Joergl, Volker, Shutty, John
• Granted Patent: US 8,601,813 B2
• Time in Patent Office: Days
• US Class Current: 60/602
• CPC Class Codes: F02B 2039/164 the temperature of the pump, of the pump drive or the pumped fluid being limited
• CPC Class Codes: F02B 2039/168 the rotational speed of pump or exhaust drive being limited
• CPC Class Codes: F02B 29/0406 Layout of the intake air cooling or coolant circuit
• CPC Class Codes: F02B 37/12 Control of the pumps
• CPC Class Codes: F02D 2041/141 using a feed-forward control element
• CPC Class Codes: F02D 2200/021 Engine temperature
• CPC Class Codes: F02D 2200/101 Engine speed
• CPC Class Codes: F02D 41/0007 for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• 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 41/1401 characterised by the control or regulation method F02D41/1473, F02D41/1477 take precedence
• 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 26/22 with coolers in the recirculation passage
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

One embodiment of the invention may include a method of controlling exhaust gas recirculation (EGR) in a turbocharged compression-ignition engine system including a high pressure (HP) EGR path and a low pressure (LP) EGR path. The method may include 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. The determining of the target HP/LP EGR ratio may include using at least engine speed and load as input to a base model to output a base EGR value, using at least one other engine system parameter as input to at least one adjustment model to output at least one EGR adjustment value, and adjusting the base EGR value with the at least one EGR adjustment value to generate at least one adjusted EGR value.

Claims

1. A method of controlling exhaust gas recirculation (EGR) in a turbocharged compression-ignition engine system including a high pressure (HP) EGR path and a low pressure (LP) EGR path, 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, and including;

using at least engine speed and load as input to a base model to output a base EGR value;

using at least one other engine system parameter as input to at least one adjustment model to output at least one EGR adjustment value; and

adjusting the base EGR value with the at least one EGR adjustment value to generate an adjusted EGR value.

2. The method of claim 1, wherein the at least one adjustment model includes a transient load adjustment model for adjusting the base EGR value to improve a rate at which combustion gases can be delivered to an engine.

3. The method of claim 2, wherein the transient load adjustment model includes:

determining a target turbocharger boost pressure value;

comparing the target turbocharger boost pressure with an actual turbocharger boost pressure value; and

determining the at least one EGR adjustment value based on the variance between the target and actual boost pressure values.

4. The method of claim 2, wherein the transient load adjustment model includes:

determining a target induction flow value;

comparing the target induction flow value with an actual induction flow value; and

determining the at least one EGR adjustment value based on the variance between the target and actual induction flow values.

5. The method of claim 1, wherein the at least one adjustment model includes an induction temperature adjustment model for modifying induction temperatures.

6. The method of claim 5, wherein the induction temperature adjustment model includes:

determining a target induction temperature value;

comparing the target induction temperature value with an actual induction temperature value; and

determining the at least one EGR adjustment value based on the variance between the target and actual induction temperature values.

7. The method of claim 1, wherein the at least one adjustment model includes a turbocharger protection adjustment model for protecting a turbocharger against at least one of overspeed or excessive temperatures.

8. The method of claim 7, wherein the turbocharger protection adjustment model includes:

comparing a maximum turbocharger speed signal and an actual turbocharger speed signal to yield a differential speed signal; and

processing the differential speed signal with at least one other engine system parameter besides turbocharger speed to generate the at least one EGR adjustment value.

9. The method of claim 7, wherein the turbocharger protection adjustment model includes:

comparing a maximum turbocharger compressor tip temperature signal and an actual turbocharger compressor tip temperature signal to yield a differential temperature signal; and

processing the differential temperature signal with at least one other engine system parameter besides turbocharger compressor tip temperature to generate the at least one EGR adjustment value.

10. The method of claim 1, wherein the other engine system criteria include turbocharger protection, fuel economy, and engine performance, and wherein EGR is adjusted to prioritize among the criteria in the following order of decreasing priority:

turbocharger protection;

exhaust emissions;

fuel economy; and

engine performance.

11. The method of claim 1, wherein one or more of the adjustment models is disabled under predetermined system operating conditions.

12. The method of claim 11, wherein an induction temperature adjustment model is disabled when an engine is running under normal operating temperatures.

13. The method of claim 1, wherein one or more of the adjustment models overrides one or more of the other adjustment models.

14. The method of claim 13, wherein a transient load adjustment model is disabled if a turbocharger protection adjustment value exceeds a predetermined magnitude.

15. The method of claim 1, further comprising:

comparing the adjusted EGR value to at least one of an upper or lower EGR limit to prevent at least one of excessive or insufficient EGR.

16. The method of claim 1, wherein the adjusted EGR value is an adjusted LP EGR value.

17. The method of claim 16, further comprising:

calculating an HP EGR value using the adjusted LP EGR value; and

delaying downstream communication of the HP EGR value to account for EGR time lag between HP and LP EGR.

18. The method of claim 17, further comprising:

applying the target total EGR fraction to the HP EGR value and the adjusted LP EGR value to generate HP and LP EGR setpoints.

21. A computer usable medium embodying instructions executable by a processor to enable the method of claim 1.

23. A product including apparatus for implementing the method of claim 1.

19. A method of controlling exhaust gas recirculation (EGR) in a turbocharged compression-ignition engine system including a high pressure (HP) EGR path and a low pressure (LP) EGR path, the method comprising:

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 by using at least engine speed and load in at least one model to output an LP EGR value and an HP EGR value;

applying the target total EGR fraction to the LP and HP EGR values to establish LP and HP EGR setpoints; and

delaying downstream communication of the HP EGR value to account for lag time between LP and HP EGR.

20. The method of claim 19, wherein the delaying step includes delaying application of the target total EGR fraction to the HP EGR value.

22. A computer usable medium embodying instructions executable by a processor to enable the method of claim 19.

24. A product including apparatus for implementing the method of claim 19.