高主流湍流度下密度比对涡轮导叶全气膜冷却特性的影响

Effects of Density Ratio on Full Film Cooling Characteristics of Turbine Guide Vane with High Mainstream Turbulence

关键词:  主流湍流度  密度比  涡轮导叶  气膜冷却效率  换热系数  液晶

Key words:  Mainstream turbulence intensity  Density ratio  Turbine guide vane  Film cooling effectiveness  Heat transfer coefficient  Liquid crystal

摘要:

为了研究高主流湍流度下二次流密度比对涡轮导叶全气膜冷却特性的影响，使用热色液晶测量了在主流湍流度为15%，二次流密度比为1.0和1.5下三维涡轮导叶的气膜冷却效率和换热系数。二次流与主流质量流量比为7.0%和12.5%。结果表明：二次流密度比增大可以降低冷气射流的动量，小流量比工况下，在叶片前缘和压力面前半段，动量较低的二次流在高主流湍流度的影响下更易耗散，增大二次流密度比使冷却效率明显降低；大流量比工况下，二次流动量降低使气膜孔后区域冷气贴附性增强，气膜冷却效率和冷气覆盖效果均得到提升。小流量比工况下，二次流密度比增大对叶片表面换热的影响较小；大流量比工况下，二次流密度比增大使吸力面中弦区域和压力面后半段的平均换热系数比分别降低15%和25%。

Abstract:

In order to study the effects of the secondary flow density ratio on the full film cooling characteristics of turbine guide vane with high mainstream turbulence, the film cooling effectiveness and heat transfer coefficient of a three-dimensional turbine guide vane model were measured using transient liquid crystal technique. The mainstream turbulence is 15% and the secondary flow density ratios are 1.0 and 1.5. The secondary flow mass flow rate ratios are 7.0% and 12.5%. The results show that the high density ratio decreases the momentum of film jets: in low mass flow rate ratio condition, the coolant with lower momentum on the leading edge and the first half of pressure side is easier to dissipate, which decreases the film cooling effectiveness; in high mass flow rate ratio condition, the decrease of secondary flow momentum enhances the attachment of coolant in the downstream of film holes, which increases the film cooling effectiveness and film coverage. In low mass flow rate ratio condition, the effect of the high secondary flow density ratio on the heat transfer of vane is insignificant; in high mass flow rate ratio condition, the increase of secondary flow density ratio decreases the average heat transfer coefficient ratio in the middle chord region of suction side and the second half of pressure side by 15% and 25%, respectively.