Stall inception and control in a transonic fan, part A: Rotating stall inception

Khaleghi, Hossein

doi:10.1016/j.ast.2014.12.004

Cited by 37 publications

(14 citation statements)

References 32 publications

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“…20 for spike-initiated rotating stall. It is shown in Khaleghi 21 that the current rotor (NASA Rotor 67) has the same stalling mechanism. The relative velocity vectors in Figure 5(a) and (b) show that the slots do not reduce the relative flow angles at the leading-edge plane.…”

Section: Resultsmentioning

confidence: 99%

Effect of axial skewed slot casing treatment in a transonic fan

Khaleghi

2016

Proceedings of the Institution of Mechanical Engineers, Part G:

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This paper reports on a time-accurate numerical investigation of axial-skewed slot casing treatment in a high-speed axial fan. Twenty-two axial and radial skewed slots are placed over the casing of the rotor and choke to stall unsteady computations are conducted. Results show that endwall fluid is absorbed by the slots from the downstream part of the blade passage and is injected to the upstream part with a swirl contrary to the blade rotation. This gives the injected fluid a great circumferential velocity component in the relative frame of reference. The shock is, hence, pushed toward the trailing-edge plane and the pressure difference between the pressure and suction surfaces is reduced. Consequently, the occurrence of the leading-edge vortex spillage, which is believed to be the key to stall initiation for the current rotor, is postponed to lower mass flow rates.

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Section: Resultsmentioning

confidence: 99%

Effect of axial skewed slot casing treatment in a transonic fan

Khaleghi

2016

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…Though some discrepancies exist, they are in the same order of magnitudes as in other studies. 28,29 Based on this comparison, the numerical method adopted in the present paper is considered reliable to predict the compressor performance.…”

Section: Model Compressor and Numerical Proceduresmentioning

confidence: 99%

Effect of tip clearance dimension on unsteadiness in a low-reaction aspirated transonic compressor rotor

Zhu

Cai

Wang

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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A three-dimensional, multi-passage unsteady numerical study was conducted to enhance the understanding of unsteady flow phenomena in the tip region of highly loaded compressors. The first-stage rotor of a three-stage transonic low-reaction compressor was chosen as the computational model. Three different tip clearance sizes were calculated to demonstrate the effect of the tip clearance dimension on the unsteadiness in the rotor tip region. It was found that the unsteadiness existed at the vicinity of the stall point when the tip clearance size was larger than the design value. The unsteadiness in the tip region appeared as a “multi-passage structure” in the nine-passage unsteady simulation and it propagated along the circumferential direction. Tip leakage vortex breakdown was the source of unsteady flow behavior. Besides, special attention was paid to the difference between the conventional transonic rotor and the low-reaction rotor. The scale of the flow separation downstream of the shock wave was controllable for the low-reaction rotor even at near-stall conditions. The boundary layer would reattach to the blade surface due to local axial acceleration. Finally, attempts were made to study the stall mechanism of the low-reaction rotor.

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“…When the microplates are introduced, such a complex grid topology is designed for both the original and controlled fans, in order to ensure that the same high-quality O-type grids are generated at the locations of microplates. In previous RANS investigations, the total number of grid points for one blade passage is mainly varied from 2.210 5 to 6.110 5 (Zhu et al, 2005;Corsini et al, 2009 andKim et al, 2011 andKhaleghi, 2015a and2015b). For the present investigation, finer grid test is not conducted considering the total number of mesh cells is already one order of magnitude larger than those applied in the previous numerical investigations.…”

Section: Fig 4 Computational Domain For the Axial Flow Fanmentioning

confidence: 99%

“…The CFD simulations were performed using the commercial software ANSYS CFX and shear stress transport (SST) turbulence model (Menter 1994). CFX software and SST turbulence model were also adopted by Khaleghi (2015aKhaleghi ( , 2015b to investigate the stall inception and control in a transonic fan. Louw et al (2014) numerically investigated the flow fields in an axial flow fan at low flow rates.…”

Section: Introductionmentioning

confidence: 99%

A Computational Study on the Performance Improvement of Low-Speed Axial Flow Fans with Microplates

Luo

Huang

Sun

et al. 2017

JAFM

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This paper proposes the use of microplates as a new flow control device to suppress boundary layer separation on blades and thus improve the aerodynamic performance of a low-speed axial flow fan. A computational study is performed by means of computational fluid dynamics (CFD) simulations. Numerical investigations are carried out based on Reynolds-averaged Navier-Stokes (RANS) method. The shear stress transport (SST) turbulence model and high-quality computational grids are adopted for CFD simulations. An exhaustive comparison of the fans with and without control has been conducted in terms of characteristic curves, streamlines and pressure distributions. The purpose of this work is to better understand the underlying flow control mechanisms of microplates. It is found that the total efficiency is slightly lowered when the controlled fan operates at the design flow rate. However, as the flow rate changes, the total efficiency of the controlled fan varies more gently than the original fan without control. Traced streamlines show that flow separation on blade surfaces is effectively controlled and radial flow migration on the suction surface is evidently diminished. Numerical results indicate that microplates significantly alleviate fan stall and have considerable beneficial effects on fan performance.

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Stall inception and control in a transonic fan, part A: Rotating stall inception

Cited by 37 publications

References 32 publications

Effect of axial skewed slot casing treatment in a transonic fan

Effect of axial skewed slot casing treatment in a transonic fan

Effect of tip clearance dimension on unsteadiness in a low-reaction aspirated transonic compressor rotor

A Computational Study on the Performance Improvement of Low-Speed Axial Flow Fans with Microplates

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