Diffuser Stall Inception in a High-Pressure Ratio Centrifugal Compressor with Fishtail Pipe Diffuser
動画引用元論文
Diffuser Stall Inception in a High-Pressure Ratio Centrifugal Compressor with Fishtail Pipe Diffuser
- 著 者
- Atsushi Ogino, Ryo Nakayama, Eijiro Kitamura, Nobumichi Fujisawa, Satoshi Aoyama, Yutaka Ohta
- 収 録
- Proceedings of ASME Turbo Expo 2023
- 発 行
- 2023年6月
- 要 旨
- This paper presents the stall inception of fishtail pipe diffuser investigated by both unsteady and steady numerical analyses. Fishtail pipe diffuser decelerates the air flow from impeller and induces the flow to the combustor by changing the flow direction from radial to axial. Each unsteady numerical simulation with full annulus model and steady simulation with 1 passage model was performed to investigate the stall inception of the fishtail pipe diffuser attached on the transonic centrifugal compressor stage by commercial code for the design speed, where the flow at the diffuser inlet is supersonic. The numerical simulations were well validated by experimental results. The characteristics of speed-lines and stall points by the numerical simulations matched the surge line of the experimental result. In near stall condition, the separation flow was observed on the suction side wall at the bend section of diffuser. The separation extended upstream by further increase of back pressure of diffuser. When the separation affected the boundary layer on throat wall, diffuser stall occurred. To confirm the effect of the bend, the numerical analysis of the straight shape diffuser was also performed. Straight diffuser was confirmed more stable than the diffuser with bend. From these observations, it was concluded that stall inception was the suction side boundary layer separation promoted by the secondary flow due to the bend.
Speaker
荻野 敦 / Atsushi Ogino
その他 執筆論文（共著含む）
Unsteady Flow Mechanism of Impeller Stall Inception in a High-Pressure Ratio Centrifugal Compressor with Bleed Slots
- 著 者
- Nobumichi Fujisawa, Yuta Yamamoto, Yutaka Ohta, Atsushi Ogino, Ryo Nakayama, Eijiro Kitamura
- 収 録
- ASME Journal of Turbomachinery Online journal
- 発 行
- 2024年12月
- 要 旨
- The impeller stall inception in a high-pressure ratio centrifugal compressor with bleed slots was investigated by experiments and unsteady numerical analysis. This study reported that the flow instability of the internal flow was first initiated around the leading edge of the splitter blades and finally resulted in tip leakage flow instability at the leading edge of the main blades. The impeller stall consisted of a stall cell and rotated about 70% of the impeller rotational speed. Furthermore, a pressure disturbance occurs at the splitter blade leading edge before the main blade leading edge. The blockage within the passage of the suction side at the leading edge of the splitter blade was first increased because the leading-edge separation on the suction surface of the splitter blade was enlarged. The blockage within the passage of the pressure side was increased after that of the suction side stopped increasing. Therefore, the blockage development of both pressure and suction passage at the leading edge of the splitter blade was the main cause of the stall inception. Then, a longitudinal vortex was formed near the bleed slots and blocked the mainstream near tip side. Subsequently, the reverse flow region in the inducer was developed and extended to the impeller inlet. Finally, the flow angle to the main blade increased, the spillage occurred at a leading edge of a main blade, and the rotating stall was generated. The cause of impeller instability was the separation of the suction surface of the splitter blade and the formation of a stagnation region on the pressure surface at the splitter leading edge.