Fast Gas Analyzer Observations of Stochastic Preignition Events 2019-01-0254

The goal of this study was to generate exhaust fast gas data that could be used to identify phenomena that occur before, during, and after stochastic preignition (SPI), also called low-speed preignition (LSPI), events. Crank angle resolved measurement of exhaust hydrocarbons, NO, CO, and CO₂ was performed under engine conditions prone to these events. Fuels and engine operating strategies were varied in an attempt to understand similarities and differences in SPI-related behavior that may occur between them. Several different uncommon (typically occurring in less than 1% of engine cycles) features of the fast gas data were identified, and the correlations between them and SPI events were explored.

Although the thresholds used to define and identify these observations were arbitrary, they provided a practical means of identifying behavior in the fast gas data and correlating it to SPI occurrence. For the engine and experimental conditions used in this study, no observation was identified that was a definitive leading indicator of SPI occurrence. For some test conditions, clear differences in the behavior before and after SPI were observed, suggesting that SPI caused some of the phenomena that were seen. However, for other test conditions no clear difference between the behavior before and after SPI was seen. This suggests that there are likely multiple mechanisms by which SPI occurs and affects subsequent engine cycles.