The Spray Behavior of Liquid LPG at Different Back Pressures During Injection in a Constant Volume Chamber

In direct injection spark ignition engines (DISI) two different injection strategies are often used. Late injection is used to obtain a stratified charge whereas a homogeneous mixture can be obtained by early injection. One of the main problems is the ignition of the mixture in both situations. The spray contour has to be at a fixed position with respect to the spark plug for the stratified situation.

The results of a research project on a direct fuel injection system for liquid petroleum gas (LPG) in a DISI engine are presented. In the first step of the project two different swirl injectors are tested in a constant volume chamber. The spray penetration and spray angle are determined from high speed images. Flash-boiling of the spray changes the spray angle significantly. Therefore, optimization of the position of the swirl injector tip relative to the spark plug is extremely difficult. In a second phase tests on a single cylinder research engine are recommended to obtain more knowledge about the influence of the direct injection of liquid LPG on the combustion process.