HIGH LOAD OPERATION IN A HOMOGENEOUS CHARGE COMPRESSION IGNITION ENGINE

• US 20080178848A1
• Filed: 01/29/2007
• Published: 07/31/2008
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Rodman, Anthony, Hardy, William L., Hergart, Carl-Anders, Liechty, Michael P., Duffy, Kevin P., Kieser, Andrew J.
• Granted Patent: US 7,469,181 B2
• Time in Patent Office: Days
• US Class Current: 123/481
• CPC Class Codes: F02B 1/12 with compression ignition with fuel-air charge ignited by compression ignition of an additional fuel F02B7/00
• 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: F02D 35/028 by determining the combustion timing or phasing
• CPC Class Codes: F02D 41/0065 Specific aspects of external EGR control constructional details of EGR system F02M26/00
• CPC Class Codes: F02D 41/0085 Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio
• CPC Class Codes: F02D 41/2422 Selective use of one or more tables
• CPC Class Codes: F02D 41/3035 a mode being the premixed charge compression-ignition mode
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A homogeneous charge compression ignition engine is set up by first identifying combinations of compression ratio and exhaust gas percentages for each speed and load across the engines operating range. These identified ratios and exhaust gas percentages can then be converted into geometric compression ratio controller settings and exhaust gas recirculation rate controller settings that are mapped against speed and load, and made available to the electronic engine controller. This provides the engine controller with a look up table of what compression ratio and exhaust gas rates should be at each speed and load. The engine controller also balances at least one of combustion phasing and energy release among a plurality of cylinders in order to enable higher load operation.

Claims

1. A method of operating an engine, comprising the steps of:

compressing a mixture of fuel, exhaust gas and air in a combustion chamber to an autoignition condition of the fuel;

setting an exhaust gas recirculation rate sufficient to achieve a NOx level;

setting geometric compression ratio corresponding to a combustion phasing, given the exhaust gas recirculation rate setting; and

making different gas exchange valve timing control settings among a plurality of combustion chambers.

2. The method of claim 1 wherein the exhaust gas recirculation rate setting at each engine load is less than a smoke limit, but sufficient to satisfy a combustion pressure rise rate limit.

3. The method of claim 2 including a step of sensing exhaust gas in the exhaust gas recirculation system down stream from an exhaust gas recirculation controller;

and

adjusting the exhaust gas controller based upon the exhaust gas recirculation rate setting and the sensed exhaust gas.

4. The method of claim 1 including a step of sensing geometric compression ratio;

and

adjusting a geometric compression ratio controller based upon the exhaust gas recirculation rate setting and the sensed geometric compression ratio.

5. The method of claim 4 wherein the exhaust gas recirculation rate setting at each engine load is less than a smoke limit, but sufficient to satisfy a combustion pressure rise rate limit.

6. The method of claim 5 including a step of sensing exhaust gas in the exhaust gas recirculation system down stream from an exhaust gas recirculation controller;

and

adjusting the exhaust gas controller based upon the exhaust gas recirculation rate setting and the sensed exhaust gas.

7. The method of claim 1 wherein the making step includes a step of balancing combustion phasing among the plurality of combustion chambers.

8. The method of claim 1 including a step of linking a control map of exhaust gas recirculation rate settings for each combination of speed and load to an electronic engine controller.

9. The method of claim 1 including a step of linking a control map of geometric compression ratio settings for each combination of speed and load to an electronic engine controller.

10. The method of claim 9 including a step of linking a control map of exhaust gas recirculation rate settings for each combination of speed and load to an electronic engine controller.

11. The method of claim 10 wherein the making step includes a step of balancing combustion phasing among the plurality of combustion chambers.

12. A homogeneous charge compression ignition engine comprising:

an engine housing having at least one combustion chamber disposed therein;

an exhaust gas recirculation rate control system with a range of settings sufficient to achieve a NOx level at each engine operating condition;

a geometric compression ratio control system with a range of settings;

a gas exchange valve timing controller associated with each combustion chamber; and

an electronic engine controller linked to a map of exhaust gas recirculation rate controller settings for each speed and load across an operating range; and

the electronic engine controller being linked to a map of geometric compression ratio controller settings for each speed and load across the operating range.

13. The engine of claim 12 wherein the exhaust gas recirculation rate control system includes an exhaust gas sensor downstream from exhaust gas recirculation rate controller.

14. The engine of claim 13 wherein the electronic engine controller is configured to adjust the exhaust gas recirculation rate controller based upon the exhaust gas recirculation rate controller settings map and the exhaust gas sensor.

15. The engine of claim 14 wherein the electronic engine controller is configured to balance combustion phasing among a plurality of combustion chambers via the gas exchange valve timing controllers.

16. The engine of claim 15 wherein the electronic engine controller is configured to balance combustion heat release among a plurality of combustion chamber via separate fuel injectors associated with each combustion chamber.

17. A method of setting up a homogenous charge compression ignition engine, comprising the steps of:

identifying a combination of compression ratio and exhaust gas percentage that satisfy a pressure rise rate limit and a peak cylinder pressure limit;

performing the identifying step across an engine operating range at a plurality of combinations of speed and load; and

mapping the identified combinations of compression ratio and exhaust gas percentage to combinations of speed and load; and

storing the mapping on a medium linked to an electronic engine controller.

18. The method of claim 17 including a step of configuring the electronic engine controller to balance combustion phasing among a plurality of engine cylinders via control of individual gas exchange valve timing controls of individual combustion chambers.

19. The method of claim 17 including a step of configuring the electronic engine controller to balance combustion heat release among a plurality of engine cylinders via control of individual fuel injectors of individual combustion chambers.

20. The method of claim 19 including a step of configuring the electronic engine controller to close loop control exhaust gas percentage via an exhaust sensor downstream from an exhaust gas recirculation controller.