The effect of diluent gases on ignition delay times in the shock tube and in the rapid compression machine
The effect of diluent gases on ignition delay times in the shock tube and in the rapid compression machine
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DOI：
10.1016/j.combustflame.2007.06.010
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发表时间：
2007-10
影响因子：
4.4
通讯作者：
J. Würmel;E. Silke;H. Curran;M. Ó. Conaire;J. Simmie
中科院分区：
文献类型：
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作者：
J. Würmel;E. Silke;H. Curran;M. Ó. Conaire;J. Simmie
用于制备试验燃料/氧气混合物的稀释气体是惰性的，不参与化学反应。然而，它确实有影响的测量点火延迟时间在快速压缩机和激波管氩气减速点火在RCM中，但加速它在激波管在某些条件下。这种相反的效果是由于这些实验装置所涉及的时间尺度。RCM中的典型点火延迟时间在1-200 ms范围内，而激波管中的点火延迟时间要短得多（10-1000 μs）。比较RCM实验和模拟氦，氩，氙，氮已经显示出极端的热损失在后压缩期间，特别是氦。2，3-二甲基戊烷的自燃测量突出了点火延迟时间对所用稀释剂类型的直接依赖性，其中用氩气记录了较长的点火延迟时间。这种增加的点火延迟时间是由于氩气在后压缩期间的极端冷却。这一观察结果通过氦和氩的对比实验得到了加强，其中氦的稀释效果甚至更强，这是由于其更高的导热性。在激波管中，稀释剂效应与RCM中相反。对于异辛烷的稀释混合物，根据两种稀释气体的相对热容，计算预测，含有氩气的混合物将比含有氮气的混合物更快地点燃。总的来说，我们得出的结论是，在实验装置中的稀释气体的选择必须小心，点火延迟时间可以强烈地依赖于所使用的稀释气体的类型。
The diluent gas used in the preparation of test fuel/oxygen mixtures is inert and does not take part in the chemical reaction. However, it does have an effect on the measured ignition delay time both in rapid compression machines and in shock tubes—argon decelerates ignition in the RCM, but accelerates it in the shock tube under some conditions. This opposite effect is due to the times scales involved in these experimental devices. Typical ignition delay times in the RCM are in the region of 1–200 ms, while those in the shock tube are much shorter (10–1000 μs). Comparative RCM experiments and simulations for helium, argon, xenon, and nitrogen have shown extreme heat loss in the postcompression period, particularly for helium. Autoignition measurements of 2,3-dimethylpentane have highlighted a direct dependency of ignition delay time on the type of diluent used, where longer ignition delay time were recorded with argon. This increased ignition delay time is due to the extreme cooling of argon in the postcompression period. This observation was strengthened by comparative experiments with helium and argon, where the diluent effect was even stronger for helium, caused by its higher thermal conductivity. In the shock tube, the diluent effect is opposite to that in the RCM. For dilute mixtures of isooctane, calculations have predicted that mixtures with argon will ignite faster than those with nitrogen, based on the relative heat capacities of the two diluent gases. Overall, we conclude that the choice of diluent gases in experimental devices must be made with care, as ignition delay times can depend strongly on the type of diluent gas used.