Combustion Phasing Variation Reduction for Late-Phasing HCCI Through Cycle-to-Cycle Pilot Injection Timing Control

Late-phasing homogeneous charge compression ignition (HCCI) operating conditions have the potential to expand the useful operating range of HCCI. However, these conditions exhibit significant variation in combustion timing and work output from one cycle to the next. Cyclic variations in the combustion timing of HCCI combustion at late-phasing operating conditions can be removed through the use of cycle-to-cycle control of pilot fuel injection timing. A nonlinear, discrete-time model of the recompression HCCI process captures the oscillations in late-phasing HCCI; when this model is linearized, it represents these dynamics as a pole on the negative real-axis. A simple lag compensator eliminates the oscillations in combustion phasing and drastically improves the operability of late-phasing HCCI. in both simulation and experiment.