Defining Knock Characteristics and Autoignition Conditions of LPG with a Possible Correlation for the Control Strategy in a SI Engine

An investigation of some engine knock characteristics of commercial LPG with 83…87% propane and 9…15% alkenes has been carried out on a spark ignition engine for heavy-duty vehicles. The best possibilities for defining the knock characteristics by the cylinder pressure record analysis were examined first. Some particularities of LPG autoignition in an engine were also put forth, considering the critical pressure and end-gas temperature, and the heat release rates due the critical reactions prior to autoignition; these particularities were compared with previous findings for pure propane. The problem of a possible correlation between knock intensity and the parameters used by an algorithm for combustion control was also approached.