正弦脉动激励对气膜冷却特性的影响

Effect of sinusoidal pulsating excitation on film cooling characteristics

为了探究正弦脉动激励对气膜冷却特性的影响,采用大涡模拟方法,针对具有正弦脉动特征的气膜冷却射流与平板主流的相干机制展开研究,在平均吹风比为0.5和1.5的条件下重点研究脉动频率和幅值对气膜冷却流动传热的影响。研究结果表明:在高吹风比工况下,冷气脉动有助于提高气膜冷却性能,而在低吹风比工况下,作用效果完全相反;增大脉动幅值强化了肾形涡对的卷吸作用,而脉动频率变化的影响则不明显;在正弦脉动下,没有出现方波脉动那样大尺度的起动涡结构;与连续性射流相比,脉动射流可以显著提升气膜孔下游的湍流动能,但随着流向距离增加,脉动射流的影响变弱;功率谱密度分析结果表明,冷气脉动对小尺度涡旋能量的影响较明显。

In order to study the effects of sinusoidal pulsation excitation on film cooling characteristics,large eddy simulation method was used to study the interaction mechanism between the film cooling jet with sinusoidal pulsation and the plate mainstream.Under the condition that the time-average blowing ratio of 0.5 and 1.5,the effects of pulsation frequency and amplitude on film cooling flow and heat transfer were investigated.The results show that under the condition of high blowing ratio,pulsating jet helps to improve the film cooling performance,while under the condition of low blowing ratio,the effect is completely opposite.The increase of pulsation amplitude strengthens the entrainment of the kidney vortex pair,while the effect of pulsation frequency is not obvious.During the sinusoidal pulsation,there is no large-scale starting vortex structure such as square wave pulsation.Compared with the continuous jet,the pulsating jet can significantly increase the turbulent kinetic energy downstream of the film hole,but with the increase of the flow distance,the effect of the pulsating jet becomes weaker.The results of power spectral density analysis show that the cold air pulsation has an obvious effect on the small-scale vortex energy.