Methodology for extending the high load limit of HCCI operation by adjusting injection timing and spark timing
A method for operating an internal combustion engine including extended operation in a homogeneous charge compression ignition mode at high loads includes operating the engine in the homogeneous charge compression ignition mode including spark-assisted ignition, monitoring an engine load, monitoring an engine speed, determining the engine to be in a high ringing range based upon the engine load and the engine speed, and when the engine load is in the high ringing range, operating the engine in a reduced ringing mode. The reduced ringing mode includes modulating a fuel injection timing according to a calibrated maximum combustion chamber cooling fuel injection timing, determining a preferred combustion phasing value, and modulating a spark timing based upon the modulated fuel injection timing and the preferred combustion phasing value.
1. Method for controlling an internal combustion engine capable of operating in a homogeneous charge compression ignition mode, including extended operation in the homogeneous charge compression ignition mode at high loads by reducing occurrence of ringing within the engine, said method comprising:
operating the engine in the homogeneous charge compression ignition mode including spark-assisted ignition;
monitoring an engine load;
monitoring an engine speed;
determining when the engine is in a high ringing range based upon the engine load and the engine speed; and
when the engine load is in the high ringing range, operating the engine in a reduced ringing mode, comprising
modulating a fuel injection timing during an intake stroke according to a calibrated maximum combustion chamber cooling fuel injection timing, said modulated fuel injection timing selected to maximize heat transfer to the injected fuel reducing energy within the combustion chamber available for homogeneous charge compression ignition,
determining a preferred combustion phasing value, and
modulating a spark timing to maintain the preferred combustion phasing value, the modulated spark timing based upon the modulated fuel injection timing and the preferred combustion phasing value.
2. The method of claim 1 , wherein operating the engine in the reduced ringing mode further comprises:
determining a predicted increase in an air fuel charge density based upon the modulated fuel injection timing during the intake stroke; and
increasing an exhaust gas recirculation percentage based upon the predicted increase in the air fuel charge density.
3. The method of claim 1 , wherein operating the engine in the reduced ringing mode further comprises:
predicting an auto-ignition timing based upon the engine load and the engine speed; and
utilizing a spark timing before the predicted auto-ignition timing, wherein the spark timing is selected to combust a portion of a air fuel charge before the predicted auto-ignition timing.
4. The method of claim 1 , wherein operating the engine in the reduced ringing mode further comprises:
modulating for each cylinder of the engine a cylinder specific fuel injection timing during an intake stroke according to a cylinder specific calibrated maximum combustion chamber cooling fuel injection timing; and
modulating for each cylinder of the engine a cylinder specific spark timing based upon the cylinder specific fuel injection timing during the intake stroke and the preferred combustion phasing value.
5. The method of claim 1 , wherein the calibrated maximum combustion chamber cooling fuel injection timing comprises:
when the engine load is in a medium range, a timing selected in relation to an opening of an intake valve; and
when the engine load is a high range, a timing selected in relation to an intake valve peak opening.
6. The method of claim 1 , further comprising:
monitoring a predicted timing of auto-ignition; and
wherein modulating the spark timing is further based upon moving the spark timing being before the predicted timing of auto-ignition.
7. Method for controlling an internal combustion engine operable in a homogeneous charge compression ignition mode, including operation in a high ringing range, the method comprising:
monitoring an engine speed;
monitoring an engine load;
monitoring a preferred combustion phasing value;
determining a pre-assigned negative valve overlap based upon the engine speed and the engine load;
determining a maximum combustion chamber cooling fuel injection timing based upon the engine load, the fuel injection timing modulated during an intake stroke and the fuel injection timing selected to maximize heat transfer to the injected fuel reducing energy within the combustion chamber available for homogeneous charge compression ignition;
determining a desired exhaust gas recirculation percentage based upon the maximum combustion chamber cooling fuel injection timing;
determining a desired spark timing to maintain the preferred combustion phasing value, the modulated spark timing based upon balancing the preferred combustion phasing value and the maximum combustion chamber cooling fuel injection timing; and
operating the engine based upon the desired spark timing.
8. The method of claim 7 , wherein the preferred combustion phasing value is based upon maximizing a predicted combustion efficiency at the engine speed and the engine load.
9. Internal combustion engine system, comprising:
an internal combustion engine, configured for selective operation in a homogeneous charge compression ignition combustion mode;
a control module configured to monitor engine operating states and control engine operation; and
an engine control subsystem configured to control engine operation based upon the monitored engine operating states, comprising
operating the engine in the homogeneous charge compression ignition mode including spark-assisted ignition,
monitoring an engine load,
monitoring an engine speed,
determining the engine to be in a high ringing range based upon the engine load and the engine speed, and
when the engine load is in the high ringing range, operating the engine in a reduced ringing mode comprising
modulating a fuel injection timing during an intake stroke according to a calibrated maximum combustion chamber cooling fuel injection timing, said modulated fuel injection timing selected to maximize heat transfer to the injected fuel reducing energy within the combustion chamber available for homogeneous charge compression ignition;
determining a preferred combustion phasing value, and
modulating a spark timing to maintain the preferred combustion phasing value, the modulated spark timing based upon the modulated fuel injection timing and the preferred combustion phasing value.
10. The system of claim 9 , wherein operating the engine in the reduced ringing mode further comprises:
determining a predicted increase in air fuel charge density based upon the modulated fuel injection timing during the intake stroke; and
increasing an exhaust gas recirculation percentage based upon the predicted increase in air fuel charge density.
11. The system of claim 9 , wherein operating the engine in the reduced ringing mode further comprises:
predicting an auto-ignition timing based upon the engine load and the engine speed; and
utilizing a spark timing before said predicted auto-ignition timing, wherein the spark timing is selected to combust a portion of a air fuel charge before the predicted auto-ignition timing.
12. The system of claim 9 , wherein operating the engine in the reduced ringing mode further comprises:
modulating for each cylinder of the engine a cylinder specific fuel injection timing during an intake stroke according to a cylinder specific calibrated maximum combustion chamber cooling fuel injection timing; and
modulating for each cylinder of the engine a cylinder specific spark timing based upon cylinder specific fuel injection timing and the preferred combustion phasing value.
13. The system of claim 9 , wherein the calibrated maximum combustion chamber cooling fuel injection timing comprises:
when the engine load is in a medium range, a timing selected in relation to an opening of an intake valve; and
when the engine load is a high range, a timing selected in relation to an intake valve peak opening.
14. The system of claim 9 , wherein the engine control subsystem configured to control engine operation based upon the monitored engine operating states further comprises:
monitoring a predicted timing of auto-ignition; and
wherein modulating the spark timing is further based upon moving the spark timing being before the predicted timing of auto-ignition.