涡轮叶栅叶冠泄漏流动数值研究

Numerical Investigation on Shroud Leakage Flow in Turbine Cascade

关键词:  叶冠泄漏流动  小展弦比  平面叶栅  篦齿数  篦齿排列方式 

Key words:  Shroud leakage flow  Low aspect ratio  Cascade  Seal number  Seal arrangement

摘要:

以小展弦比涡轮叶栅为研究对象,利用三维数值计算的方法研究了篦齿数、篦齿排列型式、上下游压力以及径向间隙对叶冠泄漏流量的影响,并分析了泄漏流动与主流的相互作用。研究表明,叶片排上下游压比和径向间隙是影响叶冠泄漏流动的主要因素,篦齿数和篦齿排列型式对泄漏流量的大小和出口气流角均有重要影响。考虑了主流的影响之后,叶冠出口流动呈现出高度的三维性和周向不均匀性。在周向压力梯度的作用下,径向速度以正负交替的形式出现,而且周向速度和轴向速度则出现了明显的分层结构。 

Abstract:

In gas turbine,tip endwall secondary flows and related losses are significantly influenced by shroud leakage flow. Based on low aspect ratio turbine cascade, three-dimensional numerical simulation was taken to investigate the effects of seal number, seal arrangement, pressure ratio and radial tip clearance on shroud leakage flow and the interaction between shroud leakage flow and main flow. Results show that,pressure ratio across the blade row and radial tip clearance are the main factors while the seal number and seal arrangement have primary effects on the leakage mass flow rate and exit flow angle. When the interaction between main flow and shroud leakage flow is taken into account, the flow inside the shroud exit cavity presents highly complex three-dimensional and circumferential non-uniformity. Under the effects of circumferential pressure gradient, the radial component of velocity shows positive and negative alternative distribution. At the same time the circumferential and axial components of velocity appear to have the obviously layered distribution. 