Numerical Simulation and Evaluation of Velocity Fluctuations During Rotating Stall of a Centrifugal Pump

Lang

Jiang

et al. 2014

Entropy

Rotating stalls are generally the first instability met in turbomachinery, before surges. This 3D phenomenon is characterized by one or more stalled flow cells which rotate at a fraction of the impeller speed. The goal of the present work is to shed some light on the entropy generation in a centrifugal fan under rotating stall conditions. A numerical simulation of entropy generation is carried out with the ANSYS Fluent software which solves the Navier-Stokes equations and user defined function (UDF). The entropy generation characteristics in the centrifugal fan for five typical conditions are presented and discussed, involving the design condition, conditions on occurrence and development of stall inception, the rotating stall conditions with two throttle coefficients. The results show that the entropy generation increases after the occurrence of stall inception. The high entropy generation areas move along the circumferential and axial directions, and finally merge into one stall cell. The entropy generation rate during circumferential propagation of the stall cell is also discussed, showing that the entropy generation history is similar to sine curves in impeller and volute, and the volute tongue has a great influence on entropy generation in the centrifugal fan.

Section: Introductionmentioning

confidence: 99%

Simulation of Entropy Generation under Stall Conditions in a Centrifugal Fan

Lang

Jiang

et al. 2014

Entropy

“…At off-design conditions, separate flow would develop on blade suction side leading to partial impeller channels being blocked [9]. At low flow rates, especially, the separate flow structure may transfer from one blade channel to the adjacent channel forming rotating stall phenomenon [10]. In centrifugal pump, flow out of impeller interacts with volute tongue periodically due to the limited blade number [11].…”

Section: Introductionmentioning

confidence: 99%

Investigation on Vibration Characteristics in a Centrifugal Pump with Special Slope Volute

Advances in Mechanical Engineering

Yang

Gao

et al. 2014

Vibration is one of the main problems which should be considered seriously in designing and operating a centrifugal pump. In this paper, a special slope volute was proposed to reduce vibration level of centrifugal pump. The goal of this paper was to analyze vibration characteristics of slope volute pump and provide a new method to reduce vibration energy in centrifugal pump. Experiments were carried out to obtain vibration signals at different flow rates of slope volute pump, which were compared with conventional spiral volute pump. Results show that vibration level is closely related to flow structure interior pump. At low flow rates, especially, vibration energy increases rapidly with the onset of rotating stall. Rotor-stator interaction mechanism changes when adopting slope volute. In slope volute pump, the peaks in power spectra correspond to different harmonics of BPF at three measuring directions; however, in spiral volute pump, the predominant components always correspond to 2 BPF . From comparison of vibration level in different frequency bands, it is found that vibration level of slope volute pump is smaller than conventional spiral volute pump. So vibration energy of centrifugal pump can be reduced effectively using slope volute.

“…Gourdain et al studied the cyclical fluctuation of the parameters such as pressure and velocity inside the compressor at a stall condition [6]. Lucius and Brenner experimentally studied the speed variation of a centrifugal pump in rotating stall stage [7]. Choi et al investigated the effects of fan speed on rotating stall inception; the results showed that, at 60% speed, tip leakage flow spillage occurred successively in the trailing blades of the misstaggered blades [8].…”

Section: Introductionmentioning

confidence: 99%

Simulation of Broadband Noise Sources of an Axial Fan under Rotating Stall Conditions

Advances in Mechanical Engineering

Wang

2014

Study on the influence of rotating stall on the aerodynamic noise of axial fan has important value to warn of the occurrence of stall through monitoring the noise variations. The present work is to analyze the aerodynamic noise before and after the phenomenon of rotating stall by solving Navier-Stokes equations, coupled with the throttle condition and the broadband noise sources model. The impeller exit rotational Mach number and rotational Reynolds number are separately 0.407 and 8.332 × 106 . The results show that the aerodynamic noise source of the fan is mainly the rotation noise under the design condition. The vortex noise accounts for the major part of fan noise after the occurrence of stall, and the maximum acoustic power level of the fan appears in the rotor domains. In the evolution process from the stall inception to the stall cell, the high noise regions of the rotor develop along the radial, circumferential, and axial directions, and the area occupied by high noise regions increases from 33% to 46% impeller channels area. On rotating stall condition, the high noise regions occupying about 46% impeller channels area propagate with the stall cell along the circumferential direction at a half of rotor speed.