空气和甲烷／空气氛围中喷油压力对柴油燃烧特性的影响

摘要

Experiments about the ignition and combustion processes and soot formation characteristic of diesel fuel in air atmosphere (AA) and premixed methane/air mixture atmosphere (MAA) respectively,were conducted in an optical constant volume combustion chamber at different injection pressures.It is shown that,the test results in AA and MAA have the same change trends:with the increase of injection pressure from 40 to 160 MPa,the ignition delay is short ened from 2.6 ms(AA)and 2.8 ms(MAA)to 2.0 ms and 2.1 ms respectively;and the combustion duration is shortened from 5.2 ms (AA) and 4.9 ms (MAA) to 3.3 ms and 3.2 ms.At high injection pressure,the flame lift-off length becomes longer;the combustion pressure rise rates increase;the moment at which the heat release rate begins to rise is advanced and the peak value also increases;spatially integrated natural luminosity (SINL) and time integrated natu ral luminosity (TINL) are both reduced significantly.However,owing to the addition of methane in MAA,the flame lift-off length becomes longer;the ignition delay is prolonged by 0.18 ms on average;the combustion duration is shortened by 0.15 ms;the moments that both the combustion pressure and the heat release rate begin to rise are de layed;and the peak values of heat release rate in MAA are increased.The SINL and TINL in MAA are both lower than those in AA.%利用高速摄像的方法,在定容燃烧弹内对比了柴油在空气(AA)和在甲烷／空气(MAA)氛围中的燃烧过程和碳烟生成特性.结果表明:两种氛围中喷油压力对柴油着火和燃烧影响规律一致;当喷油压力从40 MPa升高到160 MPa时,柴油在空气和甲烷／空气氛围中滞燃期分别由2.6 ms和2.8 ms缩短至2.0 ms和2.1 ms,燃烧持续期分别由5.2 ms和4.9 ms缩短至3.3 ms和3.2 ms;火焰浮起长度增加,燃烧压力更快达到峰值,放热率曲线上升始点提前,放热率峰值增大;空间综合自然发光度(SINL)和时间积分自然发光度(TINL)均大幅度降低.但在甲烷／空气氛围中与在空气中相比,柴油滞燃期平均延长0.18 ms,燃烧持续期平均缩短0.15 ms;火焰浮起长度增加,燃烧压力和放热率升高始点均推迟,放热率峰值升高;SINL和TINL均有所降低.