Fueling strategy for controlled-autoignition engines
Methods and systems for controlling combustion performance of an engine during recompression HCCI combustion are provided. The method includes regulating a valve actuation timing and a fuel injection timing to cause a combustion phasing of at least one cylinder of the engine to approach a target combustion phasing, and estimating current combustion state information based on the combustion phasing. The current combustion state information includes at least one of a temperature, a pressure, and a pre-combustion charge composition associated with the at least one cylinder. The method further includes determining a target fuel injection amount, and determining whether the target fuel injection amount would require actuator settings that violate predetermined constraints in order to cause the combustion phasing to approach the target combustion phasing. A fuel injection amount is adjusted when the target fuel injection amount would require actuator settings that violate the predetermined constraints.
1. A method for controlling combustion performance of an engine during recompression homogeneous charge compression ignition (“HCCI”), the method comprising:
regulating a valve actuation timing and a fuel injection timing to cause a combustion phasing of at least one cylinder of the engine to approach a target combustion phasing;
estimating current combustion state information based, at least in part, on the combustion phasing of the at least one cylinder, the current combustion state information including at least one of a temperature associated with the at least one cylinder, a pressure associated with the at least one cylinder, and a pre-combustion charge composition associated with the at least one cylinder;
determining a target fuel injection amount;
determining, based on the estimated current combustion state information, whether the actuator settings required to cause the combustion phasing of the at least one cylinder of the engine to approach the target combustion phasing would violate predetermined constraints if the target fuel injection amount is injected,
wherein the actuator settings required to cause the combustion phasing of the at least one cylinder of the engine to approach the target combustion phasing includes an adjustment to the valve actuation timing and an adjustment of the fuel injection timing; and
determining an adjusted fuel injection amount when the target fuel injection amount would require actuator settings that violate the predetermined constraints.
2. The method of claim 1 , wherein determining whether the required require actuator settings would violate the predetermined constraints includes determining a maximum fuel injection amount and a minimum fuel injection amount based on the estimated current combustion state information that would not require actuator settings that violate the predetermined constraints.
3. The method of claim 2 , wherein determining the adjusted fuel injection amount includes adjusting the fuel injection amount to equal the maximum fuel injection amount when the target fuel injection amount exceeds the maximum fuel injection amount.
4. The method of claim 2 , wherein determining the adjusted fuel injection amount includes adjusting the fuel injection amount to equal the minimum fuel injection amount when the target fuel injection amount is less than the minimum fuel injection amount.
5. The method of claim 1 , further comprising injecting the adjusted fuel injection amount when the target fuel injection amount would require actuator settings that violate the predetermined constraints.
6. The method of claim 5 , further comprising injecting the target fuel injection amount when the target fuel injection amount would require actuator settings that satisfy the predetermined constraints.
7. The method of claim 6 , wherein the injected fuel amount is regulated with a closed-loop fuel governor controller independent of the valve actuation timing and the fuel injection timing.
8. The method of claim 1 , wherein the valve actuation timing and the fuel injection timing are simultaneously regulated with a closed-loop combustion phasing controller.
9. The method of claim 1 , wherein the predetermined constraints include at least one of actuator component constraints, actuator control authority constraints, and combustion performance constraints.
10. The method of claim 9 , wherein the actuator component constraints include at least one of range and rate limitations of actuators controlling the valve actuation timing and the fuel injection timing.
11. The method of claim 9 , wherein the actuator control authority constraints include at least one of a relative magnitude of authority and a bandwidth of actuators controlling the valve actuation timing and the fuel injection timing.
12. The method of claim 9 , wherein the combustion performance constraints include at least one of limited pressure rise rates, air-to-fuel ratios, and maximum allowable emissions.
13. The method of claim 1 , wherein the target fuel injection amount is determined based, at least in part, on a commanded torque.