A study on the rotating stall in vaneless diffusers of centrifugal fans. (4th report. Effect of impellers).

Tsurusaki, Hiromu; ICHIHARA, Toshiaki

doi:10.1299/kikaib.54.1661

Cited by 4 publications

(5 citation statements)

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“…In this Figure, the velocity fluctuation vectors reveal two eddies (labelled G1 and G2) rotating in opposite directions and with centers near the outer circumference of the diffuser. This type of flow pattern is the same as those described in earlier reports by Tsurusaki et al (1986) as being characterized by neighboring eddies located near the diffuser outer circumference and rotating in opposite directions. Fig.…”

Section: How Rotating Stall Occurssupporting

confidence: 85%

“…However, Nagashima et al (1989) proposed that rotating stall is caused by the disturbance that develops in the reversed flow regions on the shroud wall and hub wall near the diffuser inlet as the flow rate approaches the critical value for occurrence of rotating stall. Furthermore, Tsurusaki et al (1986) investigated that the small, local periodic oscillation in the reversed flow regions on the shroud wall and hub wall occurs when the flow on the large flow side is approximately 8% higher than the flow at which rotating stall occurs.…”

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confidence: 99%

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Transient Process of Rotating Stall in Radial Vaneless Diffusers

Watanabe

Konomi

Ariga

1994

Volume 1: Turbomachinery

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This paper describes the process of rotating stall inception in a radial vaneless diffuser. Unsteady flow and rotating stall were investigated by measuring the wall static pressures and velocity distributions using X hot-wire probe. From the measurements of the velocity fluctuation, it is confirmed that the periodical disturbance in the reverse flow region as the prestall symptom occurs prior to the onset of stall and then the growth of that periodical disturbance leads to the rotating stall with fully developed non axisymmetric reversed flow. On the process of the rotating stall inception, reverse flow regions in the diffuser grow from the diffuser exit toward the inlet along the shroud and hub wall, and the rotating stall occurs when the reverse flow region on the shroud wall reaches to the impeller exit. In this paper, the effects of the diffuser exit blockage on the process of stall inception were also described. The flow rate of stall onset is moved to the lower side by the restriction of the diffuser exit width, however, this restriction does not affect the distribution of the reverse flow regions. That restriction suppresses the prestall disturbance in the reverse flow regions and then stabilize the flow in the diffuser.

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Section: How Rotating Stall Occurssupporting

confidence: 85%

mentioning

confidence: 99%

Transient Process of Rotating Stall in Radial Vaneless Diffusers

Watanabe

Konomi

Ariga

1994

Volume 1: Turbomachinery

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“…A swirling vortex is necessary in the vortex tube of the spot cooling system (Kurosaka [2]). Rotating stall often occurs in a radial vaneless diffuser (Tsurusaki [3]), and spiral vortex (Nishi et al [4], Cassidy and Falvey [5]) often occurs in a draft tube of a water turbine, and these phenomena limit the stable operation range of the machinery. Extensive research has been conducted on these harmful unsteady flows.…”

Section: Introductionmentioning

confidence: 99%

Unsteady Flows Arising in a Mixed-Flow Vaneless Diffuser System

Tsurusaki¹

2008

International Journal of Fluid Machinery and Systems

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The main objective of this study was to clarify the origin of the unsteady flows arising in a mixed-flow vaneless diffuser system and also the effects of physical components of the system. The testing equipment consists of a straight tube, a swirl generator, and a mixed-flow vaneless diffuser. Pressure fluctuations of the flow through the tube and diffuser were measured by using a semiconductor-type pressure transducer and analyzed by an FFT analyzer. In the experiment, the velocity ratio (axial velocity/peripheral velocity) of the internal flow, and the geometric parameters of the diffuser were varied. Two kinds of unsteady flows were measured according to the combination of the components, and the origin of each unsteady flow was clarified. The fundamental frequencies of unsteady flows arose were examined by two-dimensional small perturbation analysis.

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“…Flow instabilities downstream of the guide vanes have been reported to be two-dimensional inviscid flows [3]. However, research on instabilities in vaneless diffusers [7] has shown that an effective method of suppressing instabilities is to introduce an angle of inclination λ in order to create a three-dimensional flow in the flow passage. This section investigates the influence of the angle of inclination λ on the characteristics of instabilities, with the goal of optimizing the device cross-sectional shape.…”

Section: Effectiveness Of the Inclinationmentioning

confidence: 99%

“…However, few studies have been conducted regarding the onset condition and cell number corresponding to the oscillating mode of the flow instabilities. On the other hand, analogous flow instabilities downstream of the diffuser have been determined through several experimental and numerical studies [4]- [7].…”

Section: Introductionmentioning

confidence: 99%

Control of Flow Instabilities Downstream of Radial Inlet Guide Vanes

Nishibe

Sato

Tsujimoto

et al. 2011

JFST

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An attempt is made to clarify the flow instabilities downstream of inlet guide vanes by conducting experiments and performing a numerical simulation. The onset condition including the cell number and oscillating characteristics of the unsteady flow is discussed based on the measured pressure fluctuation. The propagating angular velocity ratio of the instability for various values of r 3 /r 2 (ratio of the radius of the trailing edge of the vanes to the radius of the outlet of the device) is presented as a function of vane angle β 2. The phenomenon taking place downstream of the inlet guide vanes is demonstrated to be of a different type from the rotating stall of the blades, where the amplitude of the flow oscillation depends on the number of cells and the chord length. In addition, applying the slope angle on the lower disc is found to be effective for controlling the flow instabilities.

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A study on the rotating stall in vaneless diffusers of centrifugal fans. (4th report. Effect of impellers).

Cited by 4 publications

References 0 publications

Transient Process of Rotating Stall in Radial Vaneless Diffusers

Transient Process of Rotating Stall in Radial Vaneless Diffusers

Unsteady Flows Arising in a Mixed-Flow Vaneless Diffuser System

Control of Flow Instabilities Downstream of Radial Inlet Guide Vanes

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