关键词: 车辆工程, GDI汽油机, 多次喷射, 喷雾特性, 燃烧特性

Abstract: A three-dimensional simulation model of the GDI gasoline engine was established, and the spray and combustion models were verified through the constant volume bomb test and the engine bench test. The spray and combustion process adopting single, two-stage and three-stage injection strategies was simulated under 2000r/min full load conditions. The results show that the split injection strategy is beneficial for fuel evaporation; compared with the single injection strategy, the two-stage injection and three-stage injection strategy increase fuel evaporation by 15.6% and 19.5%, respectively. The single injection strategy forms homogeneous mixture at ignition time, while the two-stage injection and three-stage injection strategies form thick stratified mixture near spark plug and thin stratified mixture in other regions at ignition time. Compared with the single injection strategy, the peak value of cylinder pressure of the two-stage injection strategy has been greatly improved. The peak value of cylinder pressure of the three-stage injection strategy is further increased, which is 0.73 MPa higher than that of the single injection strategy. The two-stage injection strategy has a shorter flame development period and a longer combustion period. The three-stage injection strategy has a shorter flame development period and rapid combustion period, which means better combustion characteristics can be gained by employing three-stage injection strategy. Compared with the single injection strategy, both two-stage injection strategy and three-stage injection strategy can improve the indicated thermal efficiency, which increases by 0.4% and 5.9% respectively.

Key words: vehicle engineering, GDI engine, split injection, spray characteristics, combustion characteristics