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Open AccessArticle

A Numerical Study on the Flow Mechanism of Performance Improvement of a Wide-Angle Diffuser by Inserting a Short Splitter Vane

1
State Key Laboratory of Hydro Science and Engineering, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
2
Senior Academy, Kyushu Institute of Technology, Tobata, Kitakyushu 804-8550, Japan
*
Authors to whom correspondence should be addressed.
Processes 2020, 8(2), 143; https://doi.org/10.3390/pr8020143 (registering DOI)
Received: 25 December 2019 / Revised: 16 January 2020 / Accepted: 19 January 2020 / Published: 22 January 2020
(This article belongs to the Special Issue CFD Applications in Energy Engineering Research and Simulation)
Usage of a wide-angle diffuser may result in unfavorable separated flow and a significant diffuser loss. To improve the performance of the diffusers, inserting short splitter vanes is known as a useful method that has been demonstrated experimentally. Regarding the role of the vane in the diffuser flow, Senoo & Nishi (1977) qualitatively explained that the lift force acting on the vane should be a key factor. However, its quantitative verification remains since then. To challenge this issue, numerical simulations of incompressible flow in a wide angle of 28° two-dimensional diffuser with and without a short splitter vane were conducted in the present study. An improvement of pressure-recovery by the vane and oscillatory flows in the diffuser are reasonably reproduced from comparison with the experimental results made by Cochran & Kline (1958). It is also found that the lift force acting on the vane varies periodically in an opposite phase with the detachment point moved back and forth on a diverging wall, since one vane is not sufficient to fully suppress the flow separation that occurred on the wall and the incoming main-flow shifts toward the other diverging wall in the diffuser. Thus, as a role of splitter vane in the diffuser, “the lift force of the vane is a key factor” may be quantitatively verified from the present numerical simulation. Further, it is confirmed by the local loss analysis that the turbulent kinetic energy production observed in mixing layers contributes most of the loss in the diffuser. Consequently, the present numerical technique may be usable to investigate the flow character in a diffuser with splitter vanes at a design stage. View Full-Text
Keywords: wide-angle diffuser; splitter vane; flow simulation; loss analysis; flow mechanism wide-angle diffuser; splitter vane; flow simulation; loss analysis; flow mechanism
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Meng, X.; Zuo, Z.; Nishi, M.; Liu, S. A Numerical Study on the Flow Mechanism of Performance Improvement of a Wide-Angle Diffuser by Inserting a Short Splitter Vane. Processes 2020, 8, 143.

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