Methodology for the investigation of ignition near hot surfaces in a high-pressure shock tube.
Methodology for the investigation of ignition near hot surfaces in a high-pressure shock tube.
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DOI：
10.1063/1.5017275
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发表时间：
2018-05
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影响因子：
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通讯作者：
P. Niegemann;M. Fikri;I. Wlokas;M. Röder;C. Schulz
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文献类型：
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作者：
P. Niegemann;M. Fikri;I. Wlokas;M. Röder;C. Schulz
燃料/空气混合物的自燃是内燃机中的决定性过程。点火可以在压缩后的气相中均匀开始，也可以在热表面附近开始。虽然商业燃料的点火性能通常由单一量（辛烷值）描述，但已知一些燃料对两个过程具有不同的倾向。我们提出了一个新的实验概念，产生良好控制的温度不均匀性的冲击加热气体的高压激波管。使冲击加热的反应性混合物与加热的氮化硅陶瓷电热塞接触。电热塞温度可设置为1200 K，高于后反射激波气体温度（650-1050 K）。高重复率的化学发光成像被用来定位在热表面附近的点火发作。在用乙醇进行的实验中，结果表明，在大多数情况下，在冲击加热条件下，点火在电热塞附近开始不均匀，并且由于壁温高而有利。此外，几何形状，外部加热和气体动力学效应的相互作用进行了研究，通过数值模拟的冲击波在非反应流。
Autoignition of fuel/air mixtures is a determining process in internal combustion engines. Ignition can start either homogeneously in the gas phase after compression or in the vicinity of hot surfaces. While ignition properties of commercial fuels are conventionally described by a single quantity (octane number), it is known that some fuels have a varying propensity to the two processes. We present a new experimental concept that generates well-controlled temperature inhomogeneities in the shock-heated gases of a high-pressure shock tube. A shock-heated reactive mixture is brought into contact with a heated silicon nitride ceramic glow plug. The glow-plug temperature can be set up to 1200 K, higher than the post-reflected-shock gas temperatures (650-1050 K). High-repetition-rate chemiluminescence imaging is used to localize the onset of ignition in the vicinity of the hot surface. In experiments with ethanol, the results show that in most cases under shock-heated conditions, the ignition begins inhomogeneously in the vicinity of the glow plug and is favored because of the high wall temperature. Additionally, the interaction of geometry, external heating, and gas-dynamic effects was investigated by numerical simulations of the shock wave in a non-reactive flow.