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25 เมษายน 2566 , 14:08:29
Flow and Noise Characteristics of Centrifugal Fan under Different Stall Conditions
An implicit, time-accurate 3D Reynolds-averaged Navier-Stokes (RANS) solver is used to simulate the rotating stall phenomenon in a centrifugal fan. The goal of the present work is to shed light on the flow field and particularly the aerodynamic noise at different stall conditions. Aerodynamic characteristics, frequency domain characteristics, and the contours of sound power level under two different stall conditions are discussed in this paper. The results show that, with the decrease of valve opening, the amplitude of full pressure and flow fluctuations tends to be larger and the stall frequency remains the same. The flow field analysis indicates that the area occupied by stall cells expands with the decrease of flow rate. The noise calculation based on the simulation underlines the role of vortex noise after the occurrence of rotating stall, showing that the high noise area rotates along with the stall cell in the circumferential direction.Get more news about Vortex Centrifugal Fan,you can vist our website!
1. Introduction
As the power source of the air and gas system in the thermal power plant, the operation status of the centrifugal fan is directly related to the safe and economic operation of the power plant. Rotating stall in the centrifugal fan is a local instabilities phenomenon in which one or more cells propagate along the blade row in the circumferential direction. The nonuniform flow, the so-called stall cell, rotates as a fraction of the shaft speed, typically between 20% and 70%. This running mode is responsible for strong vibrations which could damage the blades [1]. Meanwhile, it will increase the aerodynamic noise.
In order to reveal the generation mechanism of rotating stall, lots of models and theories have been proposed since the 1960s. Especially, experimental methods were widely used to illustrate the characteristics of internal flow field during stall. Lennemann and Howard discussed the causes of stall cells in low flow rate condition through the hydrogen bubble flow visualization method [2]. Lucius and Brenner experimentally studied the speed variation of a centrifugal pump in rotating stall stage [3]. For the centrifugal turbomachine, multiple factors can affect the characteristics of stall. Vaneless diffuser, for example, has significant influence on stall. Hasmatuchi et al. experimentally investigated the effect of blowing technology on the flow field of a centrifugal pump under rotating stall [4]. Rodgers conducted an experimental research on rotating stall in a centrifugal compressor with a vaneless diffuser and found that the stall margin can be improved through adjusting the expansion pressure factor [5]. Abidogun carried out an experiment to investigate the influence of vaneless diffuser on the stall characteristics. The results showed that increasing the length of diffuser can improve the rotating speed of stall, and the change of width showed no effect on stall [6].
2. Centrifugal Fan Description
The configuration of centrifugal fan studied in this work is shown in Figure 1. It is composed of current collector, impeller with 12 airfoil blades, and the volute. The inlet and outlet diameter of the impeller are 568 mm and 800 mm, respectively. The inlet and outlet width of impeller are 271 mm and 200 mm, respectively. The nominal rotation speed is 1450 rpm. The volute tongue gap is 1% of the impeller outlet diameter. The width of the rectangular volute is 520 mm, and a simple antivortex ring is set inside the volute to reduce the generation of vortex. At the design operating point, the volume flow is 6.32 m3/s and the full pressure is 1870 Pa. |
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