Conditional statistics in a planar liquid jet with a second-order chemical reaction
Conditional statistics in a planar liquid jet with a second-order chemical reaction
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具有二阶化学反应的平面液体射流的条件统计
DOI：
10.1016/j.ijheatmasstransfer.2014.12.008
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发表时间：
2015
影响因子：
5.2
通讯作者：
and Takashi Kubo
中科院分区：
文献类型：
--
作者：
Tomoaki Watanabe;Yasuhiko Sakai;Kouji Nagata;Osamu Terashima;and Takashi Kubo
实验研究了具有二级等温化学反应A+ B→ R的平面液体射流中的条件统计量。反应物A和B分别包含在射流和环境流中，并在非预混条件下供应到测试段中。采用I型热膜探针和光纤探针，基于光吸收光谱法，同时测量了反应性组分的流向速度、混合分数和浓度。条件平均浓度和条件平均反应速率的横向分布表明，射流出口附近的条件平均浓度和条件平均反应速率随横向位置的变化而变化，而在下游区域则与横向位置无关。在射流中心线上，当产物R的条件平均浓度有峰值时，条件平均反应速率有峰值。条件平均反应速率与条件浓度波动的协方差之间的比较表明，条件浓度波动的协方差是如此之小，条件平均反应速率的一阶矩封闭模型是有效的。条件平均流向速度几乎是线性的混合分数为小的混合分数波动。条件标量耗散率由条件矩闭合方程的预算计算。结果表明，在上游区域，条件标量耗散率为单峰，而在下游区域，条件标量耗散率在大、小混合分数值时为双峰。传统的平均标量耗散率是由混合分数的概率密度函数和条件标量耗散率计算的。射流中心线上的传统平均标量耗散率沿下游方向以（x <$）-2.9（其中x <$是到虚拟原点的距离）减小，这几乎与标度参数所预期的结果相同。
Conditional statistics, conditioned on mixture fraction, are experimentally investigated in a planar liquid jet with a second-order isothermal chemical reaction A+ B→ R. Reactants A and B are contained in the jet and ambient flows, respectively, and are supplied into the test section under the non-premixed condition. Streamwise velocity, mixture fraction and concentrations of all reactive species are simultaneously measured by using an I-type hot-film probe and an optical fibre probe based on light absorption spectrometry. The cross-streamwise profiles of conditional mean concentrations and conditional mean reaction rate show that the conditional mean concentrations and the conditional mean reaction rate near the jet exit change with the cross-streamwise position, whereas they are independent of the cross-streamwise position in the downstream regions. On the jet centreline, the conditional mean reaction rate has a peak value on the condition that the conditional mean concentration of product R has a peak value. A comparison between the conditional mean reaction rate and the covariance of conditional concentration fluctuations shows that the covariance of conditional concentration fluctuations is so small that a first moment closure model for the conditional mean reaction rate is valid. The conditional mean streamwise velocity is almost linear to the mixture fraction for small mixture fraction fluctuations. The conditional scalar dissipation rate is calculated from the budget of the conditional moment closure equation. The results show that the conditional scalar dissipation rate has a single peak value in the upstream region, whereas in the downstream region, it has two peaks for the large and small mixture fraction values. The conventional mean scalar dissipation rate is calculated from the probability density function of the mixture fraction and the conditional scalar dissipation rate. The conventional mean scalar dissipation rate on the jet centreline decreases in the downstream direction as (x∗)-2.9 (where x∗ is the distance from the virtual origin), which is almost the same as that expected from scaling arguments.