航空煤油裂解气的高温自点火延迟特性

航空煤油是一种典型的吸热性碳氢燃料,燃料在进入燃烧室之前通过热裂解产生裂解产物而吸热,可在高速飞行器的热防护中起着重要作用。航空煤油及其裂解气的自点火延迟特性是冲压发动机设计的主要参数之一,也是验证燃烧反应机理的重要数据。本研究在化学激波管中,利用反射激波对航空煤油及其裂解气进行自点火,获得了点火温度在900~1820 K,压力为1.01×10^5Pa,当量比为1.0条件下RP-3航空煤油、裂解气及主要裂解成分氢气、甲烷、乙烯和乙烷的自点火延迟时间。点火延迟时间定义为反射激波到达测量点时引起的压力信号起跳到CH^*自由基信号大量出现时的时间间隔。实验结果表明,点火延迟时间随温度的升高明显缩短;在相同工况下,甲烷点火延迟时间最长,氢气最短,裂解气的点火延迟时间比航空煤油略长;裂解气活化能接近于航空煤油的活化能,都在180 kJ·mol^-1左右,单组分中的氢气点火活化能最低,为127.8 kJ·mol^-1。实验结果与相应的燃烧动力学机理模拟结果进行了对比,机理能很好预测温度对点火延迟时间的影响规律。对机理进行了敏感度分析,得到了影响燃料点火的主要基元反应。

High Temperature Auto-ignition Delay Characteristics of Pyrolysis Gas of Aviation Kerosene

Aviation kerosene is a typical endothermic hydrocarbon fuel,and its pyrolysis gas absorbs heat before entering com-bustion chamber,which plays an important role in the heat protection of high-speed aircraft.Auto-ignition delay time of hydrocarbon fuel and its pyrolysis gas is one of main parameters for ramjet design,and is important data to validate the combustion reaction mechanism.In this work,the reflected shock wave was used to ignite fuels.Aviation kerosene and its pyrolysis gas in a chemical shock wave tube was studied.Ignition delay time was defined as the time interval between the arrival of reflected wave indicated by the jump of pressure signal and the onset of CH*emission signal.Auto-ignition delay times of RP-3 kerosene,pyrolysis gas,hydrogen,methane,ethylene and ethane were measured in the temperature range of 900-1820 K,at pressure of 1.01×10^5 Pa and equivalence ratio of 1.0.Experimental results demonstrate that ignition delay time decreases with the increase of tem-perature.In the same condition,ignition delay time of methane is the longest and that of hydrogen is the shortest,and the ignition delay of pyrolysis gas is slightly longer than that of aviation kerosene.The activation energy of pyrolysis gas is very close to that of aviation kerosene,around 180 kJ·mol^-1.The lowest ignition activation energy of all single component is hydrogen,which is 127.8 kJ·mol^-1.The experimental results were compared with the simulation results of combustion kinetic mechanism,which can predict the influence of temperature on ignition delay time.Furthermore,sensitivity analysis of the mechanism was carried out,and the main elementary reactions affecting fuel ignition were obtained.