锯齿电极等离子体激励器对气膜冷却效率影响的数值研究

Numerical Simulation of Effects of Saw Tooth Plasma Actuator on Film Cooling Efficiency

为获得锯齿电极等离子体激励器提高气膜冷却效率的机理,对有/无锯齿电极等离子体激励器作用下的平板气膜冷却流场进行了数值研究,并采用唯象模型模拟锯齿电极等离子体激励器对流场所施加的电场力。结果表明,冷却射流在锯齿电极等离子体激励器的下拉诱导作用下对主流的穿透率降低,射流中心轨迹高度的下降幅度沿流向发展逐渐增大;锯齿电极等离子体激励器气动激励作用下气膜孔下游的肾形涡的强度与尺度均减小,同时肾形涡的两侧产生与其旋转方向相反的小尺度的反肾形涡,进一步抑制了肾形涡的发展;锯齿电极等离子体激励器产生的展向扩散效应提高了冷却射流的展向扩张能力,从而提高了气膜冷却效率,与无等离子体气动激励相比,锯齿电极等离子体激励器作用下平板中心线与展向平均气膜冷却效率分别提高了50%与200%。

In this article, to reveal the mechanism of saw tooth plasma actuator on enhancing flat plate film cooling efficiency, the film cooling flow fields with and without plasma actuation are numerically investigated. A phenomenological plasma model was used to provide the electric field generated by the saw tooth plasma actua- tor, resulting in a plasma force vector. Results show that with the downward plasma force, the penetration depth of the cold jet into the crossflow greatly reduces, and the reduction of the jet trajectory height gradually increases while approaching downstream, thus the strength and the size of the kidney shaped vortex are decreased. More- over, the saw tooth plasma actuator induces small scale anti-kidney shaped vortices, which have opposite rotat- ing direction with the kidney shaped vortex, so the strength of the kidney shaped vortex is further weakened. The spanwise-spreading effects of the saw tooth plasma actuator promote the spanwise spreading rate of the cold jet, thus the film cooling efficiency is enhanced. When the saw tooth plasma actuation is applied, the centerline and the spanwise-averaged film cooling efficiency are improved by 50% and 200% at most, respectively.