Investigation on axial effect of slot casing treatment in a transonic compressor

• Published in: Applied thermal engineering Vol. 126; pp. 53 - 69
• Main Authors: Zhou, Xiaoyong, Zhao, Qingjun, Cui, Weiwei, Xu, Jianzhong
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 05.11.2017; Elsevier BV
• Subjects: Axial skewed slot; Bleeding; Boundary layer; Casing treatment; Compressors; Computational fluid dynamics; Computer simulation; Downstream effects; Effects; Flow separation; Simulation; Stalling; Tip leakage vortex; Transonic compressor; Transonic compressor; Axial skewed slot; Casing treatment; Tip leakage vortex
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2017.07.165

•The relative importance of the mechanisms of slot casing treatment is obtained.•The bleeding and injecting effect is the most important mechanism for the slots.•Effective slots should cover the tip leakage vortex and boundary separation zone. This paper reports the effect of the axial position of the slot casing treatment on the performance of transonic compressor NASA Rotor 67 by unsteady numerical simulation. The interaction of the recirculation in the slots and flow near the blade tip is analyzed to understand the flow mechanisms. The relative importance of the mechanisms of stall margin improvement due to the slot casing treatment is evaluated with the relative weight method. The results show that the bleeding and injecting effect caused by the recirculation is the most important factor that affects the blockage in the blade tip region, which determines the stall margin improvement. When the slots cover the initial position of the tip leakage vortex (TLV) and the boundary layer separation zone downstream the shock, the recirculation is stronger due to the larger pressure difference between the front and rear part of the slots. Consequently, the slot casing treatment can reduce the blockage near the casing more effectively, which results in a larger stall margin improvement. Shifting the slots upstream or downstream will reduce the driving force for the recirculation and the effect extent on the low energy fluid of the slots, which decreases the stall margin improvement.