In-cylinder mixture distribution of direct injection LPG using laser-induced fluorescence

Mixture distribution in the cylinder of a LPG engine was quantitatively measured by using PLIF in direct injection mode. The results show that the injection in the compression stroke forms a stratified mixture with high concentration near the spark plug at the ignition timing. Injection at 60° CA BTDC has better effect in stratification than injection at 90° CA BTDC. Injection at 290° CA BTDC only forms the homogenous mixture. High concentration aera formed by injection at 60° CA BTDC is largely influenced by swirl and is difficult to diffuse. There is no distinct rich area when the injection starts at 90° CA BTDC and relative homogenous mixture appears after 30° CA BTDC. In the calculation area around the spark plug's pole, mixture formed by injection at 60° CA BTDC shows lower cycle variations than the cases that injection starts at 90° CA BTDC or 290° CA BTDC.