阶梯形凹槽对涡轮叶顶泄漏流的影响

Effect of stepped squealer tip on flow of leakage through turbine blade tip

叶顶间隙泄漏流动是影响涡轮损失的重要因素,在转子叶片叶尖采用被动控制结构是减少泄漏流流量,降低泄漏损失的有效手段.其中,凹槽形叶顶是一种几何构型简单、且有效抑制泄漏损失的涡轮叶顶修形结构.针对持续提高凹槽叶顶的泄漏流控制的需求,本文综合分析凹槽叶顶泄漏流涡系结构和泄漏流控制机理,对常规凹槽结构进行修改,提出新型阶梯形凹槽叶顶结构,详细讨论了不同形式的凹槽对间隙泄漏流动控制的影响.研究结果表明:修形的叶顶凹槽可以有效降低泄漏流流量,减少泄漏损失.随着凹槽深度增加,凹槽内涡结构强度增加,叶顶泄漏流流量降低.沿泄漏流流动方向,对于相同深度的凹槽,凹槽底部为后台阶形式的凹槽对泄漏流的抑制作用要优于前台阶流动,而前台阶形式的叶顶凹槽则不利于泄漏流流动的控制.

Flow of leakage through the clearance of a turbine blade tip is an important factor that affects turbine loss.Setting up proper geometrical structures for the blade tip is an effective method for realizing passive control of leakage flow and suppressing loss due to leakage.Among these structures,squealer tip is a simple and widely studied control structure|and with focus on elucidating its vortex system structure and suppression mechanism,this study proposes a new stepped squealer blade tip structure by modifying that of a conventional one in order to further improve its control effect on the flow of leakage.Influences of different squealer tips on the control of the flow of leakage are discussed in detail.Results show that the modified squealer tip can effectively alter the flow of leakage and suppress loss due to leakage.With increase in the depth of the squealer tip,the strength of vortex structures in the groove increases and the flow of leakage through the tip decreases.With respect to the same depth of squealer tip,the back-stepped squealer tip exhibits better suppression effect on the flow of leakage than the front-stepped squealer tip along the direction of the flow of leakage.The front-stepped squealer tip is not effective for controlling the flow of leakage.