柴油机高压喷雾雾场的温度测量

Measurement of Temperature in High Pressure Diesel Sprays

喷雾场的温度对燃油的蒸发，混合气的形成，着火以及火焰传播有着决定性影响。在进行数学模拟时，雾场温度是很重要但很难测量的参数，迄今尚少有直接测量结果的报道。本文用薄膜式热电偶测量了柴油机高压喷雾雾场内的温度随时间的变化。热电偶经氩离子脉冲激光器标定，其时间常数约为６０‘μｓ。燃油喷射压力为１０２ＭＰａ～１３４ＭＰａ。测量结果表明，在本实验条件下，雾场内的温度与环境气体温度相差只有８Ｋ～３０Ｋ左右，比预计值要小很多。而且，环境温度较高时，雾场内外温度差减小。这可能是由于热管效应的作用。喷油压力对雾场内外温差没有明显影响，雾场外围处比雾场中心处与环境的温差要小。近喷嘴处的温度测量值随时间单调下降，且与环境温度相差较大，表明此处燃油沉积作用比较明显。

Temperature in fuel spray field has a determinant influence on fuel evaporating,mixture formation,ignition and flame spreading and is very important for numerical simulating.However,the experimental results of direct measurement of such temperature have scarcely been reported.In this paper,the variation of temperature with time in the high pressure diesel sprays has been measured with a film type thermocouple at several different positions.The range of the fuel injection pressure is 102 MPa to 134 MPa.The responsive time constant of the thermocouple has been calibrated by the argon Laser pulse and has a value of 60 microseconds.The experimental results show that the deference of the temperature in the spray field and environment is only several degrees,which is much smaller than that was expected.The difference decreases when the ambient temperature increases.It is supposed that this phenomenon may be caused by the heat tube effect.In the range of 102 MPa to 134 MPa,the injection pressure has little influence on the temperature difference.However,the temperature difference at the outer shell of the spray is smaller than that at the spray center.At the measurement position near the nozzle,the detected temperature decreases monotonously and reaches a value much lower than that at the position far from the nozzle.It shows that the deposition of fuel on the thermocouple at this position plays an obvious role.