突扩膨胀射流冲击换热与流动的数值模拟

采用大涡模拟模型对突扩膨胀射流冲击平板的传热特性及喷嘴内部流场进行数值模拟,得到不同进口Re数,不同膨胀比情况下喷嘴内部流场和射流冲击平板时的换热效果,分析了不同进口Re数、膨胀比E、冲击高度H/d对换热和流动的影响.研究表明,与直喷嘴进行对比,由于膨胀喷嘴射流与周围介质的掺混、渗透作用使射流的流速大大降低,最大速度偏离几何中心,使得换热效果减弱,对加热平板的冷却具有不对称性,但使得整个换热板的平均冷却效果更加均匀.

Numerical simulation of the impinging heat transfer characteristics and flow field of a sudden expansion jet

The heat transfer characteristics and flow field of a sudden expansion jet impinging onto a flat plate was simulated by Large-Eddy Simulation(LES) model.The temperature distributions in the heating plate as well as the flow fields inside the expansion jet nozzle were acquired and analyzed under different inlet Reynolds numbers,expansion ratios and distances from the inlet to the plate.The results show that the speed of expansion jets reduced greatly compared with inline nozzles because the expansion jet mixed with the surrounding medium and penetrated,while the maximum speed deviated from the geometric center and the heat transfer effect was weakened.However,the average cooling effect of the whole heat transfer becomes much more uniform,although the plate is cooled asymmetrically.