Exhaust gas recirculation system with control of EGR gas temperature

• US 20060137665A1
• Filed: 11/29/2005
• Published: 06/29/2006
• Est. Priority Date: 11/29/2004
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Huang, Yiqun, Khair, Magdi K., Sharp, Christopher A., Webb, Cynthia C.
• Granted Patent: US 7,195,006 B2
• Time in Patent Office: Days
• US Class Current: 123/568.120
• CPC Class Codes: F01N 3/28 Construction of catalytic reactors
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• 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: 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 26/24 with two or more coolers
• CPC Class Codes: F02M 26/25 with coolers having bypasses
• CPC Class Codes: F02M 26/35 with means for cleaning or treating the recirculated gases, e.g. catalysts, condensate traps, particle filters or heaters
• CPC Class Codes: F02M 26/38 with two or more EGR valves disposed in parallel

Abstract

A method and system for controlling the temperature of recirculated exhaust gas in an exhaust gas recirculation (EGR) system, such as those used in connection with diesel engines. An EGR loop (which may be either a high pressure loop or a low pressure loop) has a dual-leg segment with an EGR cooler on one leg and an EGR heater on the other leg. By means of a valve, the EGR gas may be diverted to either one leg or the other, thereby providing either cooled or heated EGR gas to the engine.

Claims

1. A high-pressure loop exhaust gas recirculation (EGR) system for recirculating exhaust from an engine, the engine having an air intake line, a turbocharger, and a primary exhaust line, comprising:

an EGR loop for carrying EGR gas, the loop branching from the primary exhaust line upstream the turbine of the turbocharger and entering the engine air intake line downstream the compressor of the turbocharger;

a dual-leg segment of the EGR loop, a first leg having an EGR cooler and a second leg having an EGR heater; and

a diverter valve at the input to the dual-leg segment, the diverter valve operable to control the amount of EGR flow through the first leg relative to the second leg;

wherein, downstream the cooler and the heater, the first leg and the second leg are rejoined to a single flow in the EGR loop.

2. The system of claim 1, further comprising an EGR control valve at the point where the first leg and the second leg are rejoined.

3. The system of claim 1, further comprising a thermal insulator associated with the second leg.

4. The system of claim 1, wherein the engine is a diesel engine.

5. The system of claim 1, wherein the heater is a catalyst.

6. A low pressure loop exhaust gas recirculation (EGR) system for recirculating exhaust from an engine, the engine having an air intake line, a turbocharger, and a primary exhaust line, comprising:

an EGR loop for carrying EGR gas, the loop branching from the primary exhaust line downstream the turbine of the turbocharger and entering the engine air intake line upstream the compressor of the turbocharger;

a dual-leg segment of the EGR loop, a first leg having an EGR cooler and a second leg having an EGR heater; and

a diverter valve at the input to the dual-leg segment, the diverter valve operable to control the amount of EGR flow through the first leg relative to the second leg;

wherein, downstream the cooler and the heater, the first leg and the second leg are rejoined to a single flow in the EGR loop.

7. The system of claim 6, further comprising an EGR control valve at the point where the first leg and the second leg are rejoined.

8. The system of claim 6, further comprising a thermal insulator associated with the second leg.

9. The system of claim 6, wherein the engine is a diesel engine.

10. The system of claim 6, wherein the heater is a catalyst.

11. A method of controlling the temperature of recirculated exhaust gas in an exhaust gas recirculation (EGR) system of an engine having an air intake line, a turbocharger, and a primary exhaust line, the method comprising:

recirculating exhaust gas via an EGR loop, the loop branching from the primary exhaust line and entering the engine air intake line;

wherein the loop has a dual-leg segment, with a first leg having an EGR cooler and a second leg having a EGR heater; and

using a diverter valve at the input to the dual-leg segment to control the amount of EGR flow through the first leg relative to the second leg.

12. The method of claim 11, wherein the EGR system is a high pressure loop system.

13. The method of claim 11, wherein the EGR system is a low pressure loop system.

14. The method of claim 11, further comprising using an EGR control valve at the point where the first leg and the second leg are rejoined to further control the flow of EGR.

15. The method of claim 11, further comprising using a thermal insulator associated with the second leg to reduce EGR heat loss.

16. The method of claim 11, wherein the engine is a diesel engine.

17. The method of claim 11, wherein the EGR heater is a catalyst.

18. The method of claim 11, wherein the engine has an aftertreatment device on the primary exhaust line, and further comprising increasing the relative flow through the first leg in response to operating conditions associated with the aftertreatment device.

19. The method of claim 11, further comprising increasing the relative flow through the second leg in response to engine load conditions.

20. The method of claim 11, wherein the diverter valve is controlled by signals from an engine control unit.

21. The method of claim 11, further comprising increasing the relative flow through the second leg during cold start conditions of the engine.