点火准则和稀释气体对乙烯点火延时的影响

利用矩形截面激波管研究点火准则和稀释气体对乙烯点火延时的影响。采用压电传感器记录测点压力时间历程，采用光谱仪和光电倍增管记录自发光强时间历程，以压力、总自发光强与·OH和·CH自由基特定能级发射光强等信号判定是否发生自点火，给出自点火过程的时间起始点和终止点，得到了不同点火准则和稀释气体对应的乙烯/氧气/氮气和乙烯/氧气/氩气点火延时。结果表明：相同工况的乙烯点火延时测量数据相对误差约为15%，数据验证了本文实验和测量方法可靠性。针对当量比为1.0、压力为0.2 MPa，得到了温度范围为905～1 489 K，稀释气体的摩尔分数为75%氮气和75%氩气时的乙烯点火延时，给出点火延时和温度拟合的Arrhenius型表达式。不同点火准则会影响所测点火延时数据，但多次测量结果确定的点火延时和温度变化规律近似相同。不同稀释气体对激波管自点火流场的影响表现为和流场均匀性以及混合物比热相关。相同工况的乙烯/氧气/氮气点火延时大于乙烯/氧气/氩气点火延时。高温区和低温区的乙烯/氧气/氩气点火延时与温度的拟合关系不同，转折温度约为1 121 K。

Influence of ignition criterion and dilution gas on ignition delay of ethylene

Ignition delay of ethylene (C₂H₄) are measured under different temperatures in a rectangle shock tube to recognize the effects from diluent gases (nitrogen or argon) and criteria which is identified by pressure, bulk and radical chemiluminescences of OH and CH at specified wavelengths. Pressures were recorded by piezoelectric sensors (PCBs), and bulk chemiluminescence was detected by a photomultiplier (PMT) and an optical fiber. The chemiluminescences of OH and CH radicals were grated by spectrometer first, and then recorded by the PMT. The ignition delay is determined from the pressure and intensity histories of bulk and radical chemiluminescences at the points which share the same distances from the close end. Ignition delay database was built for mixture of C₂H₄/O₂/N₂ and C₂H₄/O₂/Ar. Measurement and methodology are verified by the repeated experimental data under the same conditions. In the case of stoichimetric equivalence and pressure at 0.2 MPa, ignition delays were obtained and fitted with temperature as Arrhenius formula for mixtures of C₂H₄/O₂/N₂ and C₂H₄/O₂/Ar at temperature ranging from 905 K to 1 489 K. Results show that the relative error of ignition delays is about 15%. Based on pressure, bulk and radical chemiluminescences, the relationships between the ignition delay and temperature remain the same although the ignition delay from single measurement is a bit different. Basically, the ignition delay of C₂H₄/O₂/N₂ is greater than that of C₂H₄/O₂/Ar. The fitting relationship between ignition delay and temperature of C₂H₄/O₂ /Ar in high temperature zone and low temperature zone is different, and the turning temperature is about 1 121 K.