Inventi Impact: Combustion

Inventi:eco/22029/17

Combustion and Emission Characteristics According to the Fuel Injection Ratio of an Ultra-Lean LPG\nDirect Injection Engine

The effect of the fuel injection ratio on the combustion and emission characteristics of\nstratified lean mixture combustion was investigated for a spray-guided liquefied petroleum gas\n(LPG) direct injection engine. Inter-injection spark-ignition combustion�a specially designed\ncombustion strategy for LPG fuel derived from a two-staged injection�was employed to maximize\nthe improvement in thermal efficiency when combustion stability is secured. When changing the fuel\ninjection ratio, the optimum spark advance and fuel injection timings were experimentally determined\nto maximize the thermal efficiency based on sweeping timings. The optimum fuel injection ratio with\nthe highest thermal efficiency (42.76%) and stable operation was 60%/40%, with the optimization\nof the spark advance and fuel injection timing, because of the locally rich mixture region in the\nrecirculation zone. NOx emissions were at their highest level with a fuel injection ratio of 60%/40%\nbecause of the high combustion temperature, and the levels of total hydrocarbon and CO emissions\nwith 50%/50% and 60%/40% fuel injection ratios were similar, whereas emissions at 70%/30% were\nsignificantly higher because of fuel wetting and the formation of over-lean mixture.