Abstract
In an attempt to improve the thermal efficiency and fuel consumption in a direct injection spark ignition engine, it is proposed that high-pressure delayed injection can be a good candidate for a way to avoid knock. The more knock resistant combustion with late injection around top dead center can be realized by finer spray dispersion from higher injection pressure with a centrally mounted injector. The experimental investigation on the mixture preparation with the injection strategy and knock propensity suggest that it is preferable to delay injection timing as far up to the end of compression stroke to obtain the best possible thermal efficiency in an operating condition. Simultaneous analysis by computation with a simple knock model also supports the experimental results and suggests that the effects can be further exploited through accelerated fuel evaporation and mixture formation.
