The Effects of Mixture Preparation and Trapped Residuals on the Performance of a Spark-Ignition Engine with Air-Shrouded Port Injectors, at Low Load and Low Speed

Abstract

This paper is concerned with the steady state combustion performance of a port-injected spark-ignition engine operating at low load and low speed. The main areas of investigation were the effects of mixture quality and trapped combustion residuals on combustion performance. The behaviour of the inlet manifold fuel film was also investigated under various engine running conditions. The effects of injection timing were quantified, both with warm and hot engine coolant. Each of the six fuel injectors on the engine was equipped with an air-shrouded injector which improved fuel-spray atomization. Tests were carried out both with and without air flowing through the shrouds. A new method is also presented which provides a measure of the size of the inlet-manifold wall film under various engine running conditions. Finally, measurements of the amount of trapped combustion residuals are presented, and their effect on combustion performance is quantified.