Flow Structure and Unsteady Behavior of Hub-Corner Separation in a Stator Cascade of a Multi-Stage Transonic Axial Compressor
Flow Structure and Unsteady Behavior of Hub-Corner Separation in a Stator Cascade of a Multi-Stage Transonic Axial Compressor
复制标题
DOI：
10.1115/gt2018-76480
复制
发表时间：
2018-06
期刊：
影响因子：
--
通讯作者：
S. Saito;Kazutoyo Yamada;M. Furukawa;Keisuke Watanabe;A. Matsuoka;N. Niwa
中科院分区：
文献类型：
--
作者：
S. Saito;Kazutoyo Yamada;M. Furukawa;Keisuke Watanabe;A. Matsuoka;N. Niwa
本文描述了一台两级跨音速轴流压气机的非定常流动现象，特别是第一级静叶的流场。高负荷静叶片容易在轮毂上产生流动分离，即轮毂-角部分离。采用大规模分离涡模拟方法（DES）对第一级静叶进行了全环量和全级的4.5亿个计算单元的模拟，详细研究了第一级静叶毂角分离的流动机理。数据挖掘技术为压气机内部复杂流场的详细分析提供了支持。本文所采用的数据挖掘技术包括基于临界点理论的涡识别和极限流线型的拓扑分析。模拟结果表明，毂角分离区的流场主要为龙卷风型分离涡。在时均流场中，叶毂角分离涡是由叶毂壁面上的主流、前间隙泄漏流和穿过叶栅通道流向静叶吸力面的二次流相互作用而产生的。中心角分离涡在中弦附近发生涡破裂，中心角分离引起的高损失区急剧扩大。在静叶通道的后部，高损失区域被毂角分离涡的诱导速度径向向外迁移。静叶内的流场受到上下游转子的影响，这使得人们很难理解非定常效应。应用锁相系综平均技术对非定常流场进行了分析。从锁相流场可以看出，上游转子的尾迹干扰比下游转子的激波干扰对静叶流场的影响更大。在非定常流场中，叶片吸力面也会出现局部分离，但会被上游转子的尾迹周期性地扫走。轮毂壁面分离涡与叶片吸力面分离涡汇合，形成一个弓形涡。
This paper describes unsteady flow phenomena of a two-stage transonic axial compressor, especially the flow field in the first stator. The stator blade with highly loaded is likely to cause a flow separation on the hub, so-called hub-corner separation. The flow mechanism of the hub-corner separation in the first stator is investigated in detail using a large-scale detached eddy simulation (DES) conducted for its full-annulus and full-stage with approximately 4.5 hundred million computational cells. The detailed analysis of complicated flow fields in the compressor is supported by data mining techniques. The data mining techniques applied in the present study include vortex identification based on the critical point theory and topological analysis of the limiting streamline pattern. The simulation results show that the flow field in the hub-corner separation is dominated by a tornado-type separation vortex. In the time averaged flow field, the hub-corner separation vortex rolls up from the hub wall, which is generated by the interaction between the mainstream flow, the leakage flow from the front partial clearance and the secondary flow across the blade passage toward the stator blade suction side. The hub-corner separation vortex suffers a vortex breakdown near the mid chord, where the high loss region due to the hub-corner separation expands drastically. In the rear part of the stator passage, a high loss region is migrated radially outward by the induced velocity of the hub-corner separation vortex. The flow field in the stator is influenced by the upstream and downstream rotors, which makes it difficult to understand the unsteady effects. The unsteady flow fields are analyzed by applying the phase-locked ensemble averaging technique. It is found from the phase-locked flow fields that the wake interaction from the upstream rotor has more influence on the stator flow field than the shock wave interaction from the downstream rotor. In the unsteady flow field, a focal-type separation also emerges on the blade suction surface, but it is periodically swept away by the wake passing of the upstream rotor. The separation vortex on the hub wall connects with the one on the blade suction surface, forming an arch-like vortex.