隔板位置对凹槽叶顶传热和冷却性能的影响
Effect of Rib Location on the Heat Transfer and Cooling Characteristics of Squealer Tip

采用数值求解RANS方程(Reynolds averaged Navier？？Stokes equations)的方法,对3种带隔板的凹槽叶顶间隙内的流动、传热以及冷却特性进行了研究,隔板分别位于凹槽25％、50％和75％弦长处,3种结构分别称为rib25、rib50、rib75,并与无隔板时的常规凹槽叶顶间隙内的总压损失、传热和冷却特性进行了对比。结果表明:随着叶顶间隙的增大,叶顶表面传热系数逐渐增大;rib75结构的气动损失最小,在无气膜冷却条件下,rib75结构的叶顶比纯凹槽叶顶的总压损失低0.16％,对于叶顶带中弧线气膜冷却工况,rib75结构叶顶的总压损失比带常规凹槽叶顶的叶栅低0.15％;随着隔板向前缘方向移动,凹槽底部前缘吸力面侧的高传热区明显减小,在常规凹槽、rib25、rib50、rib75这4种叶顶结构中,rib25结构的叶顶平均传热系数与常规凹槽叶顶相近;加入叶顶中弧线气膜孔后,带隔板的叶顶可使冷气流更易聚集在凹槽底部区域,冷却效果显著提高,其中rib25结构具有最佳的冷却效果,比常规凹槽叶顶的平均冷却系数约高21.5％。
A numerical solution based on RANS (Reynolds averaged Navier？？Stokes) equations was adopted to investigate the flow, heat transfer and film cooling characteristics in three modified squealer tip gaps where the ribs are configured at 25％, 50％ and 75％ axial chord in the squealer cavity, called rib25, rib50 and rib75, respectively. The total pressure loss, heat transfer and film cooling effects in the three tip configurations (rib25, rib50 and rib75) were also compared with that in the conventional squealer tip. The results showed that the heat transfer coefficient increases with the size of tip gap. The rib75 configuration has the lowest total pressure loss among four tip configurations (conventional squealer tip, rib25, rib50 and rib75). Without film cooling, the total pressure loss in rib75 configuration is 0.16％ lower than that of the conventional squealer tip. With the tip camber line film cooling, the total pressure loss in rib75 configuration is lower than that of the conventional squealer tip by 0.15％. As the rib moves to the leading edge direction, the strong heat transfer area near the suction side can be effectively reduced in the no film cooling condition. Among four tip configurations (conventional squealer tip, rib25, rib50 and rib75), the area？？averaged heat transfer coefficient on rib25 tip is close to that on conventional squealer tip. As the rib is installed in the cavity, coolants are easier to be accumulated in the squealer cavity than in the conventional squealer tip, which significantly improves the film cooling effect on the squealer cavity floor. Among four squealer tips, rib25 has the best cooling effect on blade tip. The area？？averaged film cooling coefficient on rib25 tip is higher than that of the conventional squealer tip by 21.5％