An experimental study on spray characteristics after impingement on a piston surface through an asymmetrical multi-hole injector of a direct-injection spark ignition gasoline engine

Abstract

The impinging spray development inside direct-injection spark ignition (DISI) engines directly influences the engine performance and emissions. A detailed understanding of this process is very important in designing an injection system and controlling a strategy. To examine the effects of various factors on the development of a spray impinging on the piston top surface, experiments were conducted under various injection pressures, ambient pressures, and piston top surface shapes inside an optical constant-volume chamber employing a high-speed shadow photography technique. Also, the effects of the injection pressure, ambient pressure, and piston top surface shape on the impinging spray concentration, impinging spray tip penetration, impinging spray radius, impinging spray height, and impinging spray tip speed were analysed. It is shown that atomization after the spray had impinged on the piston top surface became increasingly better as the injection pressure increased. The concentration of the spray plumes before and after the spray had impinged on the piston top surface became increasingly richer as the ambient pressure increased. The impinging spray tip penetration and radius increased with increasing injection pressure, but the impinging spray tip penetration and radius decreased with increasing ambient pressure. This investigation is favourable to providing further basic data for the impinging spray history and the mixture preparation of DISI engines.