The Application of an Enhanced Ignition Delay Model to HCCI Engines and Comparison to Engine Measurements 2007-01-0048
The paper describes the application of an enhanced ignition delay model, developed by Yates and co-workers, to the operation of a single cylinder HCCI engine. The ignition delay description was further expanded in this paper to incorporate the effects of air-fuel ratio changes (to cater for lean operation) and residual exhaust gas. Variable combustion (heat release) duration was added, yielding improvement on the common assumption of a fixed duration.
The model was compared to measurement performed in a variable compression ratio, single cylinder Ricardo E6 engine and the paper details the engine preparation, test procedure and results. A variety of fuels were tested and modelled and results for two fuels (n-heptane and methanol) were presented in the paper. These two fuels represent extremes of autoignition resistance (with octane numbers of 0 and 106, respectively).
Comparison between modelled and measured data yielded discrepancies in three areas: the combustion duration, ignition phasing and the existence of cool flame heat release. All three discrepancies were traced to simplifications in the engine and ignition delay model.