利用PLIEF技术研究超高压燃油喷雾雾化和混合过程

Fuel Atomization and Mixing Under Ultra-High Injection Pressure by Using Planar Laser Induced Exciplex Fluorescence Technique

采用复合激光诱导荧光(PLIEF)技术,对燃烧室内自由发展阶段超高压喷雾的贯穿距离、锥角及气液相浓度分布情况进行了研究.实验中喷油压力从160 MPa升高到220 MPa,环境气体密度由3.7 kg/m3变化到7.4 kg/m3.研究发现,随着喷油压力升高,气相喷雾不均匀度在喷油定时T=42°CA BTDC时减小了36.7%,而在喷油定时T=-6°CA BTDC时仅减小28.4%.同时,气、液相喷雾锥角显著增大,贯穿距离小幅度减小.根据实验数据,提出了一个喷雾贯穿距离修正公式.研究还发现,当L/d0≥90时,喷雾已得到充分发展,比传统压力研究结果小很多.

The effect of injection pressure on liquid and vapor sprays characteristics under the conditions of ultra-high injection pressure were studied by using planar laser induced exciplex fluorescence （PLIEF） technique in an optical engine. The injection pressure was changed from 160 MPa to 220 MPa, the ambient gas density was changed from 3.7 kg/m^3 to 7.4 kg/m^3. Experiment results revealed that the vapor phase inhomngeneity decreased by 36.7% as injection pressure increased from 160 MPa to 220 MPa at the injection timing of 42° CA BTDC, and only 28.4 % at the injection timing of - 6° CA BTDC. The liquid and vapor phase sprays angles increased remarkably, on the contrary, the liquid and vapor phases spray penetration decreased. Based on the experiment data, a revised spray penetration formula was put forward. It was also found that both liquid and vapor phase sprays have been full developed when LI d0≥ 90 which is much less than that observed at lower injection pressure.