Fluid Dynamics of Turbine Rim Seal Structures: A Physical Interpretation Using URANS
Fluid Dynamics of Turbine Rim Seal Structures: A Physical Interpretation Using URANS
复制标题
涡轮机边缘密封结构的流体动力学：使用 URANS 进行物理解释
DOI：
10.1115/1.4055752
复制
发表时间：
2023
期刊：
影响因子：
--
通讯作者：
De Cosmo G
中科院分区：
文献类型：
--
作者：
De Cosmo G
非定常雷诺平均Navier-Stokes模型（URANS）是计算流体动力学（CFD）的一种有价值且经济有效的工具，包括涡轮主流-空腔相互作用的研究。尽管与高阶CFD方法在精度上存在差距，但URANS是少数几种适合于在各种条件下预测入口/出口的工业模拟策略之一。本文对1.5级涡轮机上游双径向密封的流场进行了数值研究。测试了各种配置，包括非吹扫和吹扫条件。通过一组敏感性分析确保了该方法的严格性，从而可以描绘出在边缘密封模拟中使用URANS的最佳实践：这包括对扇区大小、空腔域大小和叶片数量的影响进行评估。时间平均和时间分辨的流动预测捕捉相干结构的边缘间隙。提出了这些结构的三维（3D）形态和不同的入口/出口机制之间的关联。径向活动增强的区域被识别为与叶片前缘相对应。对轮缘间隙内的非定常压力信号进行了频率分析，计算出了结构数量和速度。结构是同步的磁盘旋转的非净化的情况下，但旋转速度较慢时，净化介绍。叶片和导叶的相对数量直接影响结构数量和速度。没有叶片的配置的特征在于最慢的结构。在三种不同的环空流动流量系数下进行了计算。在较低的流量系数下，径向活动和结构速度会降低，这从根本上与降低的压力不对称性和穿过边缘密封的涡流梯度有关。
Unsteady Reynolds-averaged Navier–Stokes modeling (URANS) is a valuable and cost-effective tool for computational fluid dynamics (CFD), including the investigation of mainstream–cavity interaction in turbines. Despite the gap in accuracy with higher order CFD methodologies, URANS is among the few simulation strategies of industrial interest suitable for predicting ingress/egress over a wide range of conditions. This paper presents a numerical study of the flow-field in the upstream double-radial seal of a 1.5 stage turbine. Various configurations are tested, including nonpurged and purged conditions. Rigor of the approach is ensured by a set of sensitivity analyses, allowing the delineation of a best practice on the use of URANS in rim seal simulations: this includes an assessment of the effects of sector size, cavity domain size, and blade count. Time-averaged and time-resolved flow predictions capture coherent structures in the rim gap. An association between the three-dimensional (3D) morphology of these structures and different ingress/egress mechanisms is proposed. Regions of enhanced radial activity are identified to correspond with the blade leading edges. A frequency analysis of unsteady pressure signals probed in the rim gap leads to a calculation of the structure number and speed. The structures are synchronous with the disk rotation for nonpurged cases but rotate at slower speed when purge is introduced. The relative number of blades and vanes directly influences the structure count and velocity. The configuration with no blades is characterized by the slowest structures. The calculations have been conducted at three different flow coefficients for the annulus flow. There is a reduction in radial activity and structure speed at lower flow coefficient, fundamentally related to the reduced pressure asymmetry and gradient of swirl across the rim seal.