涡发生器高度对气膜冷却性能影响的实验研究

摘要

A test rig is constructed to investigate the effects of vortex generator height on film cooling property.The thermocouples and the technology of Particle Image Velocimetry (PIV) are used to measure the wall temperature and visualize the flow distribution.The experiment is carried out in a single-jet structure with an inclination angle of 20 degrees.The scale of turbulence and the blowing ratio are set to be 0.4％ and 1.5 respectively.The film cooling effectiveness and the flow structure in the vortex generators of five different heights are measured.It indicates that the film cooling performance can be significantly improved by the vortex generator,and the performance of the vortex generator is obviously affected by the height.With the increasing height of the vortex generator,the performance of the vortex generator is first enhanced and then deteriorated.At the optimal height,the average film cooling effectiveness of the plate equipped with vortex generator is increased by 81％ compared with the case without vortex generator.Analyzing the PIV flow,the enhancement of film cooling is found owing to the formation of anti-kidney pair of vortices.However,in the shortest height model the anti-kidney vortices generated is too weak to effectively transport the jet toward the wall,while in the highest height model the vortex generator penetrates into the hot gas entrained into the strong anti-kidney vortices to decline the cooling effectiveness.%为了研究涡发生器高度对气膜冷却性能影响的规律,搭建了气膜冷却实验台,利用热电偶测温获得气膜有效度,采用粒子成像测速(PIV)技术拍摄了流场结构.实验中采用20°单孔射流结构,在主流湍流度为0.4％、吹风比M=1.5的条件下,完成了5种不同高度涡发生器的气膜冷却效果以及流场结构的测量.气膜有效度的测量结果表明,涡发生器能显著提高气膜冷却性能,其高度对气膜冷却性能的影响显著,该影响随着高度的增加先增大后减小,最优高度下平均气膜有效度相对不带涡发生器情况提高了81％.结合PIV流场结果分析可知:反肾形涡对将冷气卷向壁面是涡发生器提高气膜冷却性能的根本原因,但涡发生器高度过低时产生的反肾形涡对强度较弱,不能有效地将射流牵引至壁面;当涡发生器高度过高时则会穿透射流,将部分主流卷入到反肾形涡对中,从而削弱冷却效果.