Numerical study of controlling a lean mixture autoignition in the hybrid HCCI engine using high frequency corona discharges

Abstract

A relationship has been established between the ignition timing of the region, activated by a high frequency corona discharge, and the autoignition timing of unburned gas in the hybrid HCCI engine in a propane-air mixture. This relationship depends on the equivalence ratio ϕ: the leaner the mixture, the weaker the dependence. For a richer mixture (ϕ = 0.7), autoignition is a sequential propagation of autoignition waves in unburned gas, in a leaner mixture (ϕ = 0.5) spontaneous ignition right away of the entire volume occurs just in front. It has been shown that autoignition event can be controlled by varying the discharge initiation timing, the configuration of discharge region, and the specific energy input into the streamer channel. These parameters are varied in wide range values, but occurrence of autoignition falls into suitable range of ignition angles corresponding to the optimal operating conditions of HCCI engine. It has been revealed that the controlling the onset of autoignition in a very lean mixture is less effective than in a richer one.