低温低密度下喷油压力对柴油喷雾火焰特性影响

Effect of injection pressure on the flame characteristics of diesel spray under low-temperature and low-density conditions

针对柴油机低温低密度工况着火困难问题,本文在723K、14kg/m3环境的定容燃烧弹上,对40、80、120和160MPa4组喷油压力试验。高速摄影直拍获取火焰图像,进行蓝、热焰分离和双色法分析。研究发现:低温低密度下,随喷油压力增加,火焰脱体长度增加,温度下降。喷油压力过高,气流“吹熄”和蒸发作用增强,不利于燃油稳定燃烧。

Igniting diesel engines under low-temperature and low-density conditions is difficult.Experiments under the injection pressures of 40, 80,120,and 160 MPa were performed at 723 K and 14 kg/m 3 in a constant volume vessel to solve the problem of difficult diesel engine ignition. Flame images were captured through a high-speed direct imaging technique. Blue flame was distinguished from hot flame,and two-color analysis was implemented.Results showed that flame take-off length increased with the increase in injection pressure,whereas flame temperature decreased. Therefore,the blow-off effect and the evaporation cooling effect intensified with the increase in injection pressure,and high injection pressure was not conducive for stable flame combustion under low- temperature and low-density conditions.