Analysis of Mixture Formation of Direct Injection Gasoline Engine

Direct injection gasoline engines require extremely advanced control of air-fuel mixture in order to achieve good stratified combustion. The method of examining quality of mixture formation in combustion chambers is essential for the achievement. In this research, air-fuel mixture in combustion chamber of the TOYOTA D-4 engine was analyzed in space and time by visualization as well as Air/Fuel ratio measurement by multi-point and high response techniques. Thus the effects that injection timing, swirl and fuel pressure exerted to mixture formation were elucidated. For realizing good stratified combustion, the following were identified as necessary:

1. 1.
   to select the optimized timing interval between injection and ignition at which the Air/Fuel ratio near the ignition plug at ignition can be maintained at 10 to 20
2. 2.
   to control swirl intensity accurately corresponding to engine operating conditions, in order to guide air fuel mixture to ignition plug without dispersing the mixture
3. 3.
   to allow spray to follow swirl flow by 15 μm droplet size with 12 MPa fuel pressure