Effects on Cycle-to-Cycle Variations and Knocking Combustion of Turbulent Jet Ignition (TJI) with a Small Volume Pre-Chamber 2020-01-1119

Turbulent jet ignition (TJI) has the advantages of improving burning rates and expanding lean burn limitations of gasoline engines. Based on a single cylinder engine, combustion process with different ignition methods, including single spark ignition, twin spark ignition, one-hole TJI and seven-hole TJI, are studied in this work. Experiments are carried out under conditions with different air/fuel equivalence ratios and different engine loads. Results show that the cycle-to-cycle variations of TJI combustion, which is evaluated by coefficient of variations (CoV) of IMEP and CoV of peak pressure, are obviously reduced due to the fast burning rate induced by the jet flame, and one-hole TJI combustion has the best combustion stability, especially for reducing the CoV of peak pressure. Furthermore, under full-load conditions, pressure oscillations are observed in TJI combustion, and the intensity distribution is different from that in SI combustion, which means that the roots causing the pressure oscillations of TJI and SI are different. Pressure oscillations in TJI combustion are caused by the local fast burning rate of the hot jets, while the pressure oscillations of SI are caused by end-gas auto-ignition, which randomly happens during combustion. Under TJI knock condition, excellent combustion stability and great auto-ignition consistency can still be achieved. Considering these features of TJI combustion, a new combustion concept, jet induced compression ignition (JICI), and a different ignition method, spark combined jet ignition (SCJI), are proposed in order to organize combustion with high efficiency, stability and controllability.