Turbulent jet ignition (TJI) shows great potentials of achieving lean combustion. In this work, a turbulent jet ignitor was designed and made, and the engine performance, combustion characteristics, pollutant emissions and knock characteristics were detailed studied in a single-cylinder engine. The results show that the lean burn limit is greatly extended through TJI combustion, and the indicated specific fuel consumption is apparently lower than that of spark ignition (SI) combustion under part load conditions. In TJI combustion, the flame jet leads to a fast burning rate at the beginning of the combustion; and with the fuel-air mixture becomes leaner, the burning rate gradually decreases while the spark timing needs to be advanced to keep appropriate combustion phase. The NOx emission in lean burn condition is extremely low, which decreases by 95%-99% under part load conditions compared with SI combustion. Furthermore, pressure oscillations were both observed in TJI and SI combustions, in which the pressure oscillation of TJI is caused by the fast burning rate after the flame ejection, while that of SI is caused by the end-side auto-ignition. The spectrum analysis on knock frequency shows that the pressure oscillation modes of TJI and SI are different in the combustion chamber.
Keywords turbulent jet ignition; lean burn; engine performance; knock