Method and system of transient control for homogeneous charge compression ignition (HCCI) engines

• US 20100031924A1
• Filed: 08/07/2008
• Published: 02/11/2010
• Est. Priority Date: 08/07/2008
• Status: Active Grant

• Current Assignee: United States Environmental Protection Agency
• Original Assignee: United States Environmental Protection Agency
• Inventors: Sun, Ruonan, Tang, Xiaoguo
• Granted Patent: US 8,055,432 B2
• Time in Patent Office: Days
• US Class Current: 123/435
• 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: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 35/024 using an estimation
• CPC Class Codes: F02D 35/027 using knock sensors
• CPC Class Codes: F02D 41/009 using means for generating position or synchronisation signals
• CPC Class Codes: F02D 41/1402 Adaptive control
• CPC Class Codes: F02D 41/3035 a mode being the premixed charge compression-ignition mode
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A HCCI engine with a model reference adaptive feedback control system maintains stable HCCI combustion during speed/load transitions by: (1) estimating the maximum rate of pressure rise (MRPR), for each cycle, from an extra-cylinder sensor metric, such as a crankshaft dynamics or knock sensor metric, via statistical vector-to-vector correlation; (2) periodically self-tuning the vector-to-vector correlation; (3) applying knowledge base models to guide cycle-to-cycle adjustments of fuel quantity and other engine parameters, to maintain a target MRPR value.

Claims

1. A method of operating a multicylinder homogeneous charge compression ignition (HCCI) internal combustion engine, comprising:

taking into each of a plurality of combustion chambers a quantity of fuel and a quantity of charge-air,

calculating a cylinder-specific crankshaft dynamics metric,

determining the approximate maximum rate of pressure rise in the combustion chamber of each cylinder, for each combustion event, from the crankshaft dynamics metric, and

adjusting fuel quantity along with one or more engine state parameters, responsive to the determined maximum rate of pressure rise, in order to adjust the maximum rate of pressure rise for subsequent combustion events.

2. The method of claim 1, further comprising calculating the cylinder-specific crankshaft dynamics metric from the difference between (1) crankshaft rotational velocity in a first crank angle window, corresponding to the combustion event in the specific cylinder, and (2) crankshaft rotational velocity in a second crank angle window, corresponding to the inertia-dominated phase of crankshaft rotation.

3. The method of claim 2, further comprising determining crankshaft rotational velocity by counting CPU ticks during each of the first and second crank angle windows, using an engine control module counter and signals from a crankshaft position sensor.

4. The method of claim 1, further comprising:

modulating fuel quantity by a small, known increment above and below a nominal fuel quantity, to produce a rolling alternation across sequentially firing cylinders of a relatively fuel-rich and a relatively fuel-lean cylinder, and

calculating the cylinder-specific crankshaft dynamics metric from the difference between (1) crankshaft rotational velocity in a first crank angle window, corresponding to the combustion event in a fuel-rich cylinder and (2) crankshaft rotational velocity in a second crank angle window, corresponding to the combustion event in the successively firing fuel-lean cylinder.

5. The method of claim 4, further comprising determining crankshaft velocity by counting CPU ticks during each of the first and second crank angle windows, using an engine control module counter and signals from a crankshaft position sensor.

6. The method of claim 1, further comprising:

modulating fuel quantity by a small, known increment above and below a nominal fuel quantity, to produce a rolling alternation across sequentially firing cylinders of a relatively fuel-rich and a relatively fuel-lean cylinder, where each successively firing pair of fuel-rich and fuel-lean cylinders is separated by a fuel-nominal cylinder, and

calculating the cylinder-specific crankshaft dynamics metric from the difference between (1) crankshaft rotational velocity in a first crank angle window, corresponding to the combustion event in a fuel-rich cylinder and (2) crankshaft rotational velocity in a second crank angle window, corresponding to the combustion event in the successively firing fuel-lean cylinder.

7. The method of claim 6, further comprising determining crankshaft velocity by counting CPU ticks during each of the first and second crank angle windows, using an engine control module counter and signals from a crankshaft position sensor.

8. The method of claim 1, further comprising determining the approximate maximum rate of pressure rise from the crankshaft dynamics metric via statistical vector-to-vector correlation.

9. The method of claim 8, further comprising self-tuning the statistical vector-to-vector correlation based on signals from a knock sensor.

10. The method of claim 1 further comprising adjusting the fuel quantity and one or more engine state parameters for subsequent combustion events, responsive to:

(1) a feedback signal, reflecting a difference between the determined and target values for either the maximum rate of pressure rise or the crankshaft dynamics metric, and,

(2) guidance from a knowledge base model of engine operation.

11. The method of claim 10, further comprising:

adjusting fuel quantity during combustion mode switching, in an engine operable in both homogeneous charge compression ignition (HCCI) and spark ignition (SI) modes, to account for differences in thermal efficiency between HCCI and SI combustion,

detecting the current combustion mode from the determined value of the maximum rate of pressure rise or crankshaft dynamics metric, and

selecting a knowledge base model of engine operation appropriate to the detected combustion mode.

12. A method of determining the maximum rate of pressure rise in one or more combustion chambers of an internal combustion engine, comprising:

determining a statistical vector-to-vector correlation between the maximum rate of pressure rise and a crankshaft dynamics metric,

calculating the crankshaft dynamics metric, and

using the statistical vector-to-vector correlation to estimate the maximum rate of pressure rise from the crankshaft dynamics metric.

13. An internal combustion engine operable in homogeneous charge compression ignition combustion mode, comprising:

an engine body with a plurality of combustion cylinders formed therein,

a combustion chamber formed in each combustion cylinder for combustion of a fuel and charge-air mixture,

a crankshaft,

a crankshaft position sensor,

a knock sensor,

an engine control module counter, configured to count CPU ticks during each of two crank angle windows, based on signals from the crankshaft position sensor, and

an engine computer, programmed to

(1) calculate a cylinder-specific crankshaft dynamics metric from the difference between CPU ticks during the two crank angle windows, for each combustion event,

(2) determine the maximum rate of pressure rise in the combustion chamber of each cylinder from the cylinder-specific crankshaft dynamics metric, through a statistical vector-to-vector correlation function stored therein,

(3) calculate a cylinder-specific knock sensor metric based on signals from the knock sensor,

(4) periodically self-tune the statistical vector-to-vector correlation function used to determine the maximum rate of pressure rise from the crankshaft dynamics metric, based on the knock sensor metric, and

(5) order adjustments in fuel quantity and one or more engine state parameters, responsive to the determined maximum rate of pressure rise, to adjust the maximum rate of pressure rise for subsequent combustion events.

14. The internal combustion engine of claim 13, wherein the engine computer is further programmed to order the adjustments in fuel quantity and the one or more engine state parameters responsive to:

(1) a feedback signal, reflecting a difference between the determined and target values for either the maximum rate of pressure rise or the crankshaft dynamics metric, and

(2) guidance from a knowledge base model also stored in the engine computer, which guidance is used by the engine computer to maintain the maximum rate of pressure rise around a target value during transient operation, and to maximize the range of fuel quantity yielding stable values for the maximum rate of pressure rise during both steady state and transient operation.

15. The internal combustion engine of claim 13, additionally operable in spark ignition combustion mode, wherein the engine computer is further programmed to

(1) detect the current combustion mode from the determined value of the maximum rate of pressure rise or the crankshaft dynamics or knock sensor metric,

(2) select a knowledge base model of engine operation appropriate to the detected combustion mode,

(3) switch between HCCI and SI combustion modes depending on load demands, and

(4) adjust fuel quantity during HCCI-SI mode switching to account for differences in thermal efficiency between HCCI and SI combustion.

16. A method of operating a multicylinder homogeneous charge compression ignition (HCCI) internal combustion engine, comprising:

taking into each of a plurality of combustion chambers a quantity of fuel and a quantity of charge-air,

calculating an integrated metric of signals received from each of one or more extra-cylinder sensors, to produce one or more extra-cylinder sensor metrics for each combustion event,

determining the approximate maximum rate of pressure rise in the combustion chamber of each cylinder, for each combustion event, from the one or more extra-cylinder sensor metrics, through one or more statistical vector-to-vector correlation functions, and

adjusting fuel quantity along with one or more engine state parameters, responsive to the determined maximum rate of pressure rise, in order to adjust the maximum rate of pressure rise for subsequent combustion events.

17. The method of claim 16, further comprising:

calculating at least two extra-cylinder sensor metrics, and

periodically self-tuning the statistical vector-to-vector correlation functions, through which the maximum rate of pressure rise is determined from the extra-cylinder sensor metrics.

18. The method of claim 16, wherein one of the extra-cylinder sensor metrics is a knock sensor metric, calculated from signals received from a knock sensor.

19. The method of claim 16, wherein one of the extra-cylinder sensor metrics is a crankshaft dynamics metric, calculated from signals received from a crank angle position sensor.

20. The method of claim 16, wherein two of the extra-cylinder sensor metrics are a crankshaft dynamics metric and a knock sensor metric.

21. The method of claim 20, further comprising using the crankshaft dynamics metric and knock sensor metric to self-tune the statistical vector-to-vector correlation functions through which the maximum rate of pressure rise is determined.