Evolution Process of Diffuser Stall in a Centrifugal Compressor With Vaned Diffuser
Evolution Process of Diffuser Stall in a Centrifugal Compressor With Vaned Diffuser
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DOI：
10.1115/gt2018-75462
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发表时间：
2018-06
期刊：
影响因子：
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通讯作者：
N. Fujisawa;T. Inui;Y. Ohta
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文献类型：
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作者：
N. Fujisawa;T. Inui;Y. Ohta
本文详细地描述了带叶片扩张器的离心式压气机在变工况下的流场。特别是，为了研究扩散器失速的演化过程，我们进行了实验和数值分析。在失速点，扩散器失速被启动，并在无叶片空间中的遮盖面附近旋转。此外，随着质量流量的减小，扩散器失速发展为阶段失速单元。所开发的失速单元在叶轮和扩散器通道内旋转。扩散器失速的演变过程有三种失速形式。首先，扩散器失速在绕流罩一侧附近旋转。然后，扩散器失速转移到轮毂一侧，进入叶轮通道。最后，产生了一个舞台失速。计算流体力学(CFD)分析表明，当扩散器失速向轮毂侧移动时，扩散器前缘轮毂侧附近首先产生龙卷风旋涡。下一步，由于无叶空间中的边界层分离，在轮毂侧附近形成了喉部区域堵塞。最后，扩散器通道内的堵塞扩展到叶轮通道，并发展为阶段失速。根据叶轮和扩散器通道的压力测量，当扩散器失速向轮毂侧移动时，扩散器喉部区域壳体壁上的压力波动幅度也突然增大。因此，扩散器失速的演化区域是由扩散器通道喉部附近堵塞的演化引起的。
This paper describes in detailed flow field in a centrifugal compressor with a vaned diffuser at off design point. Especially, we conducted both the experimental and numerical analysis in order to investigate the evolution process of a diffuser stall. At the stall point, the diffuser stall was initiated and rotated near the shroud side in the vaneless space. Furthermore, the diffuser stall was developed to a stage stall cell, as the mass flow was decreased. The developed stall cell was rotated within both the impeller and diffuser passages. The evolution process of the diffuser stall had three stall forms. First, the diffuser stall was rotating near the shroud side. Then, the diffuser stall shifted to the hub side and moved into the impeller passages. Finally, a stage stall was generated. From computational fluid dynamics (CFD) analysis, a tornado-type vortex was generated first, near the hub side of the diffuser leading edge, when the diffuser stall was shifted to the hub side. Next, a throat area blockage was formed near the hub side because of the boundary layer separation in the vaneless space. Finally, the blockage within the diffuser passages expanded to the impeller passages and developed into a stage stall. From the pressure measurements along the impeller and diffuser passages, the magnitude of pressure fluctuation on the casing wall of the diffuser throat area also suddenly increased when the diffuser stall shifted to the hub side. Therefore, the evolution area of the diffuser stall was caused by the evolution of the blockage near the throat area of the diffuser passage.