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首页> 外文会议>American Society of Mechanical Engineers(ASME) Turbo Expo vol.5 pt.A; 20040614-17; Vienna(AT) >UNSTEADY SIMULATION AND INVESTIGATION OF TIP LEAKAGE FLOW BASED ON DISSIPATION FUNCTION
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UNSTEADY SIMULATION AND INVESTIGATION OF TIP LEAKAGE FLOW BASED ON DISSIPATION FUNCTION

机译：基于耗散函数的尖端泄漏流的非稳态模拟与研究

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摘要

Further improvements of flow in tip clearance demand a better understanding of its complex structure and this would not be possible if we are not able to provide an interpretative or a more realistic presentation of its main effects, i.e., viscous dissipation and mixing. To do so and to gain further insights into the details and distribution of viscous dissipation, a commercial N-S solver has been employed for simulation and investigation of the unsteady flow field inside the tip clearance of a turbine rotor in first stage. The main objective of this paper is to introduce the direct implementation of dissipation function for viscous dissipation assessment in tip leakage flow. This idea seems to be the simplest and at the same time, the most straightforward approach to simulate and calculate the viscous dissipation caused by viscous effects. It is shown that the dissipation function can be employed as a strong and convenient tool in direct identification and assessment of regions of high viscous dissipation. It has been found that in tip leakage flow, regions of high viscous effects are located near casing rather than blade tip. Near casing, leakage flow creates a source point in pressure side and a sink point in suction side on rotor blade tip projection on the casing. It is shown that the time-averaged viscous dissipation in tip leakage flow is dissimilar for rotor blades. This result, which is caused by flow unsteadiness, is a helpful hint that can be taken by blade designers to design non-uniform rotor blades, that is, to design blades with different geometries and aerodynamic loads, both circumferentially and radially, to minimize the viscous dissipation. The casing passage vortex, the end wall boundary layers, and the wakes from the upstream stator significantly enhance the unsteadiness of the flow to the tip region of rotor blades. Results indicate that there exists a strong interaction between leakage flow and annulus-wall boundary layer.
机译：针尖间隙的流动的进一步改善要求对它的复杂结构有更好的了解，如果我们不能对它的主要作用，即粘性耗散和混合提供解释性或更现实的表现，这将是不可能的。为此，为了进一步了解粘性耗散的细节和分布，已使用商用N-S求解器对第一阶段涡轮转子的叶尖间隙内的非稳态流场进行仿真和研究。本文的主要目的是介绍耗散函数的直接实现，以评估尖端泄漏流中的粘性耗散。这个想法似乎是最简单，同时也是最直接的方法，用于模拟和计算由粘性效应引起的粘性耗散。结果表明，耗散函数可以用作直接识别和评估高粘性耗散区域的强大便捷工具。已经发现，在尖端泄漏流中，高粘性效应的区域位于壳体附近而不是叶片尖端。在机壳附近，泄漏流会在机壳上的转子叶片尖端投影上在压力侧产生源点，在吸力侧产生沉点。结果表明，转子叶片的叶尖泄漏流中的时间平均粘性耗散是不同的。由流动不稳定引起的这一结果是一个有用的提示，叶片设计者可以借此来设计不均匀的转子叶片，即设计具有不同几何形状和空气动力学载荷的叶片（在周向和径向上），以最大程度地减少叶片的运动。粘性耗散。壳体通道涡流，端壁边界层和上游定子的尾流显着增加了流向转子叶片尖端区域的不稳定度。结果表明，泄漏流与环空边界层之间存在很强的相互作用。

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