冠齿脉冲射流冲击平直靶板对流换热实验

采用红外热像测试技术对占空比（DC）恒定为0.5的冠齿脉冲射流冲击平直靶面，在不同雷诺数（5 000～20 000）、无量纲冲击间距（2～8）和工作频率（10～25 Hz）下进行了对流换热实验研究。结果表明：在小射流冲击间距下，冠齿脉冲射流冲击局部努塞尔数云图在射流驻点附近呈现较为明显波瓣状分布；冠齿喷管在脉冲射流冲击中依然体现出强化对流换热的作用机制，雷诺数和工作频率分别为10 000和15 Hz工况下，射流冲击驻点附近的表面传热系数相对圆形脉冲射流提高幅度在20%～30%之间；在冠齿脉冲射流中，脉冲主动激励和冠齿被动诱导激励之间存在着内在的相干机制，导致其对流换热特性与冠齿连续射流和圆形脉冲射流有较大的差异。

Experiment on convective heat transfer of pulsed chevron jet impingement on flat plate

An experimental investigation was performed to study the convective heat transfer characteristics of pulsed chevron jet impingement on a flat plate, by using infrared imaging technique. The pulsed jet was fixed at a specific duty cycle （DC） of 0.5, the experiments were conducted under Reynolds number of 5000?20000, Dimensionless impingement spacing of 2?8 and working frequency of 10?25 Hz. Results indicated that the local Nusselt number distribution in the vicinity of jet stagnation presented a lobed pattern resembling the shape of the configuration. The pulsed chevron jet was confirmed to be capable of enhancing the jet impingement heat transfer related to the pulsed round jet. Under Reynolds number of 10000 and working frequency of 15 Hz, the convective heat transfer in the vicinity of jet stagnation could be increased by 20%?30% with the use of pulsed chevron jet, when compared with the pulsed round jet. In general, the heat transfer characteristics in the pulsed chevron jet impingement were found somewhat distinct from that in the steady chevron jet impingement as well as the pulsed round jet impingement, due to the inherent interaction of active excitation by the pulsation and passive excitation induced by chevron nozzle.