平板脉动气膜冷却特性的数值研究

Numerical Study on Characteristics of Pulsation Cooling Film on Flat Plate

摘要: 通过数值模拟方法研究了冷气射流角为35˚圆孔平板气膜冷却效率在不同激励形式下的冷却效果。吹风比分别为0.3、0.5、0.7、1.0，Sr数分别为0.15、0.3、0.6。脉动波形分别为正弦波与方波。结果表明：在较低吹风比M = 0.5时，采用脉动形式会降低气膜冷却效率，不同Sr数对冷却效率无明显区别；在较高吹风比M = 1.0时，低Sr数情况下能够提高气膜冷却效率，Sr数的升高会导致气膜冷却效率的降低。吹风比M的变化会影响到脉动射流的质量流量以及抬升高度，导致随着吹风比减小出现了气膜冷却效率呈现先升后降的趋势，脉动射流相较于稳定射流的冷却效率在M = 0.7时效率提升达到20%；而在采用方波形式进行脉动时，气膜孔出现了主流入侵现象，在修改方波脉动幅值后，效率仍低于正弦脉动。

Abstract: The cooling efficiency of a flat plate air film with a round hole and a cooling jet Angle of 35˚ under different excitation modes was simulated using FLUENT. The simulations were done for nominal blowing ratio ranging from 0.3 to 1.0, and the Sr number 0.15, 0.3 and 0.6. The pulsating waveforms are sinusoidal wave and square wave respectively. The results show that when the blowing ratio M = 0.5, the pulsation will reduce the film cooling efficiency, and the Sr number has little effect on the cooling efficiency. When the blowing ratio M = 1.0, the film cooling efficiency is improved when the Sr number is low, and the increase of Sr number leads to the decrease of the film cooling efficiency. The change of blowing ratio M affects the mass flow rate and lifting height of pulsating jet. As the blowing ratio decreases, the air film cooling efficiency increases first and then decreases. When M = 0.7, the cooling efficiency of pulsating jet increases by 20% compared with that of stable jet. When the square wave is used for pulsation, main stream intrusion occurred in the hole. After the ampli-tude of the square wave pulsation is modified, the efficiency is still lower than the sinusoidal pulsa-tion.