油气混合参数对柴油机低温燃烧过程的影响

Effects of fuel injection and intake parameters on low temperature combustion

应用三维CFD模拟研究了喷油和进气参数包括喷油压力、喷孔直径和进气压力对柴油机低氧浓度低温燃烧(LTC)过程的影响。结果表明:随着喷油压力增加或喷孔直径的减小,各氧浓度下缸内燃烧压力和温度峰值都增大;相同氧浓度条件下预混燃烧的强度增大,出现明显预混燃烧的氧浓度增大;相同氧浓度条件下的soot排放降低;缸内局部温度最大值增大,NOx排放增大。进气压力增大,缸内压力上升更快,但缸内平均温度略有降低,相同氧浓度下着火时刻提前,滞燃期缩短;燃烧过程中局部缺氧的状况得到改善,相同氧浓度条件下燃油的燃烧更加完全,放出的总热量更多,燃烧效率明显提高;soot峰值和最终排放值都减小,NOx生成量进一步降低。

The effects of fuel injection and intake parameters on low temperature combustion are investigated using CFD modeling in the present study. With the increase of injection pressure or decrease of nozzle hole diameter： the maximum in-cylinder pressure and temperature increase. Heat release from premixed combustion increases at the same oxygen concentration and oxygen concentration that obvious premixed combustion appears increases. As to emissions, soot emission decreases because of the improvement of mixing of fuel and air and NO~ emission increases because the increase of local temperature in the cylinder. With the increase of intake pressure： the maximum cylinder pressure increases but the maximum cylinder temperature decreases. The ignition timing advances at the same oxygen concentration. The combustion efficiency increases. As to emissions, both soot and NOx emissions decrease.