This is for gasoline PCCi engine running with gasoline alone without diesel injection at TDC.
Hello,
normally, when PCCI/CAI/HCCI combustion is achieved one observes rather a high stability of cycle to cycle fluctuatution. Specially when compared to standard SI, petrol engines in auto-or controlled auto ignition modes present a high stability as the igntion process does no longer rely on spark and flame propagation (both very sensitive to cycle variations and not self regulating) but depends on the right distribution of radicals and respect of thermo-chemical conditions which tend to be self regulating. Nevertheless, as the conditions in which residual or recirculated exhaust gases are capital on ignition, variations even slight in temperature, pressure, injection timing, etc. can cause large variations in combustion behaviour. All this parameters must be monitored to eliminate variations in order to better control combustion efficiency and regularity
hope it is of use for you
In general, cycle to cycle variations for HCCI/PCCI engines are high when the engine is operated at limit of ignitability. This means that for each speed/load operating point with a given fuel there is a certain acceptable region of combinations of inlet temperature, compression ratio, air/fuel ratio and EGR that provides stable combustion. If you are near the edge of this stability region you can run into either excessive cycle to cycle variation or knock.
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