Combustion influence of a pre-chamber ignition system in a SI commercial engine 2018-36-0115
Environmental policies and fuel costs have driven the development of new technologies for internal combustion engines. In this sense, the use of mixtures with small portions of fuel allows lower fuel consumption and pollutants emissions, emerging as a promising strategy. Despite the advantages, lean burn requires a larger energy source to provide satisfactory flame propagation speed and consequently a stable combustion. The use of pre-chamber ignition systems (PCIS) has been used in SI engines to assist the start of combustion of lean mixtures, in which a supplementary fuel system can stratify the amount of either liquid or gaseous fuels supplied to the pre-chamber. In this context, this paper aims to evaluate combustion characteristics of a commercial engine with the use of stratified PCIS operating with impoverished mixtures of ethanol-air in main-chamber and hydrogen assistance in pre-chamber. For this analysis bench dynamometer tests were performed evaluating cylinder pressure, exhaust gas temperature, fuel conversion efficiency, cycle thermal efficiency, coefficient of variation of the indicated mean effective pressure, apparent heat release rate, flame development angle and burn duration. As expected, the high amount of energy supplied by the PCIS favored combustion characteristics and exhaust gas temperatures that points to favorable conditions to reduce emissions and fuel consumption. Improvement on combustion stability can also enable the extension of lean limit, making the system even more attractive.