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Nonideal effects behind reflected shock waves in a high-pressure shock tube

机译：高压激波管中反射激波背后的非理想影响

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Shock tubes often experience temperature and pressure nonuniformities behind the reflected shock wave that cannot be neglected in chemical kinetics experiments. Because of increased viscous effects, smaller tube diameters, and nonideal shock formation, the reflected-shock nonidealities tend to be greater in higher-pressure shock tubes, Since the increase in test temperature (DeltaT(5)) is the most significant parameter for chemical kinetics, Experiments were performed to characterize DeltaT(5) in the Stanford High Pressure Shock Tube using infrared emission from a known amount of CO in argon. From the measured change in vibrationally equilibrated CO emission with time, the corresponding dT(5)/dt (or DeltaT(5) for a known time interval) of the mixture was inferred assuming an isentropic relationship between post-shock temperature and pressure changes. For a range of representative conditions in argon (23-530 atm, 1275-1900 K), the test temperature 2 cm from the endwall increased 3-8 It after 100 mus and 15-40 K after 500 mus, depending on the initial conditions. Separate pressure measurements using a shielded piezoelectric transducer confirmed the isentropic assumption. An analytical model of the reflected-shock gas dynamics was also developed, and the calculated DeltaT(5)'s agree well with those obtained from experiment. The analytical model was used to estimate the effects of temperature and pressure nonuniformities on typical chemical kinetics measurements, When the kinetics are fast (< 300 s), the temperature increase is typically negligible, although some correction is suggested for kinetics experiments lasting longer than 500 mus The temperature increase. however, has a negligible impact on the measured laser absorption profiles of OH (306 nm) and CH3 (216 nm), validating the use of a constant absorption coefficient. Infrared emission experiments are more sensitive to temperature and density changes, so T-5 nonuniformities should be taken into account when interpreting ir-emission data. [References: 53]
机译：激波管经常在反射的激波后面经历温度和压力的不均匀性，这在化学动力学实验中是不能忽略的。由于增加的粘性效应，较小的管径和非理想的冲击形成，在较高压力的冲击管中，反射冲击的非理想性往往更大，因为测试温度的升高（DeltaT（5））是化学反应的最重要参数在斯坦福高压激波管中，使用来自氩气中已知量的一氧化碳的红外发射来表征DeltaT（5）。根据测得的振动平衡CO排放随时间的变化，假设震后温度和压力变化之间存在等熵关系，则可以推断出混合物的相应dT（5）/ dt（或已知时间间隔的DeltaT（5））。对于氩气中的一系列典型条件（23-530 atm，1275-1900 K），距端壁2 cm的测试温度在100 mus后升高3-8 It，在500 mus后升高15-40 K，这取决于初始条件。使用屏蔽压电传感器的单独压力测量结果证实了等熵假设。还建立了反射冲击气体动力学的分析模型，计算出的DeltaT（5）与从实验中获得的结果非常吻合。使用分析模型来估计温度和压力不均匀性对典型化学动力学测量的影响。当动力学快速（<300μs）时，温度升高通常可以忽略不计，尽管建议对动力学实验进行一些校正以持续超过500亩温度升高。但是，对OH（306 nm）和CH3（216 nm）的激光吸收曲线的测量影响可忽略不计，这证实了使用恒定的吸收系数。红外发射实验对温度和密度变化更敏感，因此在解释发射数据时应考虑T-5的不均匀性。 [参考：53]

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