Diesel engine charge air cooler bypass passage and method

1. A method for operating a diesel engine comprising the steps of:

compressing air in a compressor yielding charge air;

routing the charge air to a charge air cooler through a hot air passage;

cooling the charge air in the charge air cooler;

passing the charge air from the charge air cooler to an intake throttle through a cool air passage;

mixing the charge air with exhaust gas from an exhaust gas recirculation valve downstream of the intake throttle;

bypassing a portion of the charge air from upstream of the charge air cooler to downstream of the intake throttle through a bypass passage; and

restricting the portion of the charge air flowing through the bypass passage with an orifice.

2. The method of claim 1 , wherein the orifice is at least one of a fixed orifice and a variable orifice.

3. The method of claim 2 , wherein the variable orifice is at least one of a flapper valve and a poppet valve.

4. The method of claim 1 , wherein the step of restricting is accomplished by adjusting an effective flow area of the orifice.

5. The method of claim 1 , further comprising the steps of:

analyzing engine operating parameters in an electronic controller; and

determining an engine idle operating condition.

6. A method for operating a diesel engine comprising the steps of:

analyzing engine operating parameters in an electronic controller;

deciding on an engine operating condition in the electronic controller; controlling an intake throttle;

wherein the step of controlling said intake throttle further comprising:

closing an intake throttle when an engine idle operating condition is present; and

opening the intake throttle when an engine operating condition above idle is present;

controlling an idle speed of the engine solely by adjusting an amount of fuel injected into at least one cylinder;

bypassing air around the intake throttle and a charge air cooler through an orifice; and

controlling an exhaust gas recirculation valve;

wherein the step of controlling said exhaust gas recirculation valve further comprising:

opening an exhaust gas recirculation valve when the engine idle operating condition is present; and

closing the exhaust gas recirculation valve when an engine operating condition is changing.

7. The method of claim 6 , further comprising the steps of:

when the engine idle operating condition is present, adjusting at least one turbine actuator and setting an effective flow area for the orifice;

when the engine above-idle operating condition is present, adjusting the at least one turbine actuator for the engine operating condition above idle, and resetting the effective flow area for the orifice.

8. The method of claim 6 , further comprising the step of adjusting the orifice with the electronic controller.

9. The method of claim 8 , wherein the step of adjusting the orifice includes at least one of rotating a flapper shaft and moving a poppet.

10. A diesel engine comprising:

a first turbocharger having a first turbine and a first compressor;

a charge air cooler in fluid communication with an outlet of the compressor through a hot air passage;

an intake throttle in fluid communication with an outlet of the charge air cooler through a cool air passage;

a junction disposed downstream in fluid communication with the intake throttle;

an intake system disposed in fluid communication with the junction;

a bypass passage containing a flow restrictor disposed between the hot air passage and the junction; and

an exhaust gas recirculation system having an outlet disposed in fluid communication with the junction.

11. The diesel engine of claim 10 , wherein the bypass passage connects with the intake system at the junction, and wherein the bypass passage is directed toward an outlet of the exhaust gas recirculation system.

12. The diesel engine of claim 10 , further comprising an engine controller, wherein the engine controller is operably disposed to control the intake throttle and an exhaust gas recirculation valve.

13. The diesel engine of claim 10 , wherein flow restrictor is a fixed orifice.

14. The diesel engine of claim 4 , wherein the fixed orifice flows an adequate airflow for operating the engine at an idle condition.

15. The diesel engine of claim 10 , wherein the flow restrictor is a variable flow orifice.

16. The diesel engine of claim 15 , wherein the variable flow orifice is at least one of a poppet valve and a butterfly valve.

17. The diesel engine of claim 16 , further comprising a turbine bypass valve, disposed between the first turbine and a second turbine.

18. The diesel engine of claim 15 , wherein the variable flow orifice is capable of flowing an adequate airflow for operating the engine over an entire range of engine speed and engine load.

19. The diesel engine of claim 10 ,

wherein the junction has three inlets and an outlet;

wherein a first inlet is fluidly communicating with an outlet of the intake throttle;

wherein a second inlet is in fluid communication with an outlet of an exhaust gas recirculation valve;

wherein a third inlet is fluidly communicating with the bypass passage; and

wherein the outlet is in fluid communication with the intake system.