旋转诱导下向心涡轮盘腔流动和封严特性研究

Flow and Sealing Characteristics of Radial Turbine Disk Cavity Induced by Rotation

针对向心涡轮盘腔旋转诱导入侵机制尚不明晰,以及轴流涡轮封严模型适用性有待考量的问题,采用数值模拟方法开展旋转诱导下向心涡轮盘腔流动和封严特性研究。分析了盘腔轴向间隙、径向间隙以及封严流量等参数对盘腔内部流动结构及转子轴向推力的影响规律,研究封严效率变化趋势并进行最小封严流量模型推导。研究表明:随着径向间隙减小以及封严流量增大,盘腔出口处的涡系外移且尺度减小;在减小轴向间隙或增大封严流量时,盘腔内流动结构从Batchelor流型向Stewartson流型演变;转子轴向推力合力主要受盘腔轴向间隙和封严流量影响;旋转诱导下的Orifice Model具有很好的适用性;本文推导出的最小封严流量模型表明其最小封严流量显著小于轴流涡轮。

The research was conducted to study the mechanism of rotationally induced ingress in radial turbine cavity and the feasibility of axial turbine sealing model.The 3-D numerical simulations were carried out to investigate the flow and sealing characteristics of radial turbine disk cavity under rotational induction.The effects of the axial clearance,radial clearance,and the sealing flow on the internal flow structure and rotor axial thrust were analyzed.Then the variation of the sealing efficiency was studied as well as the minimum sealing flow model was presented.The results show that the vortex at the outlet of the disk cavity is out-shift and its size decreases with the decrease of the radial clearance and the increase of sealing flow.When the axial clearance decreases or the sealing flow increases,the flow structure in the disc cavity changes from Batchelor flow to Stewartson flow.Besides,the rotor axial combined thrust is determined by the sealing flow and the axial clearance of the disk cavity.Orifice Model is of ideal applicability for the radial turbine under rotational induction.In addition,the minimum sealing flow model derived in this paper indicates that the minimum sealing flow of radial turbine is significantly smaller than that of axial turbine.