Exhaust gas recirculation system

• US 6,216,458 B1
• Filed: 06/09/1999
• Issued: 04/17/2001
• Est. Priority Date: 03/31/1997
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Davis, Todd A., Alger, Matthew J., Bailey, Brett M., Lawrence, Keith E., Coleman, Gerald N., Liang, Cho Y., Feucht, Dennis D.
• Primary Examiner(s): KOCZO JR, MICHAEL
• Application Number:
  US09/328,943
• Time in Patent Office: 678 Days
• Field of Search: 606/052, 123/568.12
• US Class Current: 60/605.2
• CPC Class Codes: F01N 3/02 for cooling, or for removing solid constituents of, exhaust by means of electric or electrostatic separators F01N3/01 ; mixing air with exhaust in tailpipes F01N13/082, F01N13/20
• CPC Class Codes: F02B 29/0425 Air cooled heat exchangers
• 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 33/44 Passages conducting the charge from the pump to the engine inlet, e.g. reservoirs
• 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 37/16 by bypassing charging air
• CPC Class Codes: F02B 37/164 the bypassed air being used in an auxiliary apparatus, e.g. in an air turbine
• CPC Class Codes: F02D 21/08 the other gas being the exhaust gas of engine
• 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 26/10 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 26/19 Means for improving the mixing of air and recirculated exhaust gases, e.g. venturis or multiple openings to the intake system
• CPC Class Codes: F02M 26/25 with coolers having bypasses
• CPC Class Codes: F02M 26/27 with air-cooled heat exchangers
• CPC Class Codes: F02M 26/34 with compressors, turbines or the like in the recirculation passage
• 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 26/43 in which exhaust from only one cylinder or only a group of cylinders is directed to the intake of the engine
• CPC Class Codes: F02M 26/47 the characteristics being temperatures, pressures or flow rates
• CPC Class Codes: F02M 26/62 in response to fuel pressure
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

An exhaust gas recirculation (EGR) system for a turbo-charged internal combustion engine is provided. The EGR system includes a recirculation conduit for recirculating a volume of exhaust gas from the exhaust manifold to the intake manifold; a cooling air conduit for transporting a flow of cooling air; and a gas-to-air heat exchanger disposed in operative association with the recirculation conduit and the cooling air conduit and adapted for cooling the volume of recirculated exhaust gas in the recirculation conduit. The cooling air passing through the gas-to air heat exchanger can be diverted from the pressurized intake air, cooled (ATAAC) air, or even fresh ambient air obtained from a source external to said engine and which optionally may be forcibly directed through the heat exchanger via a blower. The disclosed embodiments disclose EGR systems where the exhaust gases are driven from the exhaust manifold to the intake manifold through different techniques including peak clipping EGR systems, venturi based EGR systems, pumped EGR systems or piston pumped EGR systems.

Claims

1. An exhaust gas recirculation system for a compression ignition engine having an intake circuit, an intake manifold, an exhaust circuit and an exhaust manifold, said intake circuit including an intake air pressurizing device, said exhaust gas recirculation system comprising:

an exhaust gas recirculation conduit for diverting a flow of recirculated exhaust gas to said intake circuit;

a cooling air conduit for transporting a flow of cooling air used to cool said recirculated exhaust gas, said cooling air conduit is in fluid communication with said exhaust circuit; and

an air to EGR heat exchanger disposed in operative association with said exhaust gas recirculation conduit and said cooling air conduit and adapted for cooling said exhaust gas in said exhaust gas recirculation conduit.

2. The exhaust gas recirculation system of claim 1 wherein said cooling air is pressurized intake air diverted from the intake circuit downstream of said intake air pressurizing device.

3. The exhaust gas recirculation system of claim 1 wherein said intake circuit includes an air-to-air after-cooler and said cooling air is cooled intake air diverted from the intake circuit downstream of said air-to-air after-cooler.

4. The exhaust gas recirculation system of claim 1 further comprising a blower adapted for forcibly transporting said air through said cooling air conduit.

5. The exhaust gas recirculation system of claim 1 wherein said exhaust gas recirculation conduit is disposed in fluid communication with one or more cylinders for driving a flow of exhaust gas from said cylinders to said intake manifold using the pumping action of said cylinders.

6. The exhaust gas recirculation system of claim 1 wherein said intake circuit further includes a venturi element disposed downstream of said air intake pressurizing device, and wherein said exhaust gas recirculation conduit is disposed in fluid communication with said venturi element for driving a flow of exhaust gas to said intake manifold via said venturi element.

7. The exhaust gas recirculation system of claim 1 further comprising a blower operatively disposed in said exhaust gas recirculation conduit for driving a flow of exhaust gas from said exhaust manifold to said intake manifold.

8. The exhaust gas recirculation system of claim 1 further including an exhaust gas recirculation valve disposed in said exhaust gas recirculation conduit and responsive to pressure changes in said exhaust manifold such that a flow of recirculated exhaust gas from said exhaust manifold to said intake manifold occurs at selected peak pressures within said exhaust manifold.

9. The exhaust gas recirculation system of claim 1 further including one or more flow control devices for controlling the flow of recirculated exhaust gas in said exhaust gas recirculation conduit and the flow of cooling air in said cooling air conduit.

10. The exhaust gas recirculation system of claim 9 further comprising a cooling air bypass conduit for controllably diverting a portion of said cooling air from said air to EGR heat exchanger.

11. The exhaust gas recirculation system of claim 9 further including a sensor disposed proximate to the intake manifold and adapted for measuring intake manifold conditions and controlling said flow control devices in response thereto.

12. The exhaust gas recirculation system of claim 11 wherein said sensor is a temperature sensor adapted to ascertain the temperature proximate the intake manifold and controlling said flow control devices in response thereto.

13. The exhaust gas recirculation system of claim 11 wherein said sensor is a pressure sensor adapted to ascertain the pressure proximate the intake manifold and controlling said flow control devices in response thereto.

14. The exhaust gas recirculation system of claim 9 further including a mass flow sensor disposed along said intake circuit and adapted for measuring the mass flow rate of said intake air and controlling said flow control devices in response thereto.

15. A method of recirculating exhaust gas in an internal combustion engine, said engine having an intake circuit including an intake air pressurizing device, an intake manifold, and an exhaust circuit including an exhaust manifold, the method comprising the steps of:

recirculating a volume of exhaust gas to said intake manifold via a recirculation conduit and an air to EGR heat exchanger;

directing a flow of cooling air through a cooling air conduit and said air to EGR heat exchanger to said exhaust circuit; and

cooling said recirculated exhaust gas in said air to EGR heat exchanger using said flow of cooling air.

16. The method of recirculating exhaust gas of claim 15 wherein said cooling air is pressurized intake air diverted from said intake circuit downstream of said intake air pressurizing device.

17. The method of recirculating exhaust gas of claim 15 wherein the step of directing said flow of cooling air further comprises forcibly directing said flow of cooling air through said cooling air conduit and said air to EGR heat exchanger with the aid of a blower.

18. The method of recirculating exhaust gas of claim 15 wherein the step of recirculating a volume of exhaust gas to said intake manifold further comprises the step of driving a flow of exhaust gas from one or more cylinders directly to said intake manifold via said recirculation conduit using the pumping action of said cylinders.

19. The method of recirculating exhaust gas of claim 15 wherein said intake circuit further includes a venturi element disposed downstream of said air intake pressurizing device, and the step of recirculating a volume of exhaust gas to said intake manifold further comprises driving a flow of exhaust gas to said venturi element via said pressure differential between said venturi element and said exhaust manifold created by said venturi effect.

20. The method of recirculating exhaust gas of claim 15 wherein said engine further includes an exhaust gas recirculation valve disposed in said exhaust gas recirculation conduit responsive to the pressure changes in said exhaust manifold such that a flow of recirculated exhaust gas from said exhaust manifold to said intake manifold occurs at selected peak pressures within said exhaust manifold.

21. The method of recirculating exhaust gas of claim 15 wherein the step of recirculating a volume of exhaust gas further comprises the step of driving a flow of exhaust gas from said exhaust manifold to said intake manifold with a blower operatively disposed in said exhaust gas recirculation conduit.