Abstract
Spray pattern and mean fuel droplet size of swirl injector were investigated using Laser Light Sheet Photography and PDPA respectively. And, for the formation of stratified mixture with adequate strength near spark plug at injection mode in compression stroke, spray distribution after impingement on flat piston or bowl piston in motoring engine was visualized in case of three different injector positions. Also, in-cylinder bulk air flow structure was measured in a transparent engine using PIV. Therefore, strengthening counter-rotating tumble velocity component and making piston top shape into bowl structure were found out to be effective to conserve bulk motion toward spark plug in compression stroke.