反应性双射流中标量输运和化学反应特性

Characteristics of scalar transport and chemical reaction in reactive dual jets

基于OpenFOAM中pimpleFoam求解器对具有二级非平衡基元反应(A+B→R)的双平行平面射流中流动-化学反应耦合过程进行数值模拟,研究了不同射流口间距下反应物、生成物浓度标量在流场中心线上的产生、消耗和输运行为。首先将反应性单射流模拟结果与前人实验研究和数值模拟结果进行对比,验证了数值算法的精确性。结果表明:(1)两股射流在准滞止点和混合点的行为直接影响着化学反应。(2)射流相互作用尺度x*可以预测不同射流口间距下反应物和产物的湍流标量统计量。(3)在Da=0.1且Sc=0.71时,反应物和产物由对流过程主导输运。(4)反应物和产物浓度脉动之间的联合概率密度分布(joint probability distribution function,JPDF)呈“心形”,其说明反应物A和反应物B的瞬时浓度在时均值时将有利于化学反应的发生。

Based on the pimpleFoam solver in OpenFOAM,the flow-reaction coupling process of the dual parallel plane jets with a second order non-equilibrium elementary reaction(A+B→R)is numerically investigated.More specifically,the production,consumption and transportation behaviors of reactive dual jets along the centerline with different jet separation distances are considered.The simulation results of a single reactive jet are compared with the corresponding previous experimental and numerical results to verify the accuracy of the numerical algorithm adopted.The main conclusions are as follows:(1)The behavior of the two jets at the quasi-stagnation point and the mixing point directly affects the chemical reaction.(2)Jet interaction length scales can effectively predict the statistics of the reactant and product terms of jet interactions under different jet separation distances.(3)When Da=0.1 and Sc=0.71,the transport of reactants and products is dominated by the convective process.(4)The joint probability distribution function(JPDF)between the instantaneous concentrations of the reactant and product terms is“heart-shaped”,and generally speaking,the circumstances that instantaneous concentrations of reactant A and reactant B are close to the average value,are associated with high rates of chemical reactions.