Abstract
The Livengood-Wu integral has been applied widely as the simplest but most practical model to predict knocking or end-gas autoignition. The scientific nature of this empirical model was investigated by one of the authors. The integral value of 1/τ can be considered accumulated heat, meaning that 1/τ can be a conservable and transportable quantity, and its local integral can predict local autoignition in a heterogeneous air-fuel mixture or a diesel spray. Also, a set of several equations was developed to reproduce the temperature-, pressure-, and equivalence ratio-dependences of ignition delay time for a gasoline surrogate fuel produced using a detailed reaction mechanism. In the present report, ignition delay time equations have been developed for normal hexadecane. The Livengood-Wu integral with the equations has been applied to predict HCCI produced using a detailed reaction mechanism. When a period after distinct cool-flame reaction to ignition in an in-cylinder ignition process is prolonged, ignition timing predicted using the Livengood-Wu integral is retarded away from that produced using the detailed reaction mechanism, because the latter half of the integral is done in a distinct negative temperature coefficient region. The ignition delay time equation can be modified to weaken the negative temperature coefficient region and decrease the retard of predicted timing.
