Purpose
– The purpose of this paper is to elucidate the detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition.
Design/methodology/approach
– Unsteady flows in a centrifugal pump volute at non-cavitation and cavitation conditions are investigated by using a computation fluid dynamics framework combining the re-normalization group k-e turbulence model and the mass transport cavitation model.
Findings
– The flow field in pump volute is very complicated at part load condition with large pressure gradient and intensive vortex movement. Under cavitation conditions, the dominant frequency for most of the monitoring points in volute transit from the blade passing frequency to a lower frequency. Generally, the maximum amplitudes of pressure fluctuations in volute at serious cavitation condition is twice than that at non-cavitation condition because of the violent disturbances caused by cavitation shedding and explosion.
Originality/value
– The detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition are revealed and analysed.
Abstract:The influence of prewhirl regulation by inlet guide vanes (IGVs) on a centrifugal pump performance is investigated experimentally and numerically. The experimental results show that IGVs can obviously change the head and increase the efficiency of the tested centrifugal pump over a wide range of flow rates. Although the cavitation performance is degraded, the variation of the cavitation critical point is less than 0.5 m. Movement of the computed three-dimensional streamlines in suction pipe and impeller are analyzed in order to reveal the mechanism how the IGVs realize the prewhirl regulation. The calculated results show that the influence of IGVs on the cavitation performance of centrifugal pump is limited by a maximum total pressure drop of 1777 Pa, about 7.6% of the total pressure at the suction pipe inlet for a prewhirl angle of 24°.
A comprehensive analysis method is proposed to resolve the problem of simulating the complex thermoflow with two kinds of distinct characteristic lengths in a dry gas seal. A conjugated simulation of the complicated heat transfer and the gas film flow is carried out by using the commercial computational fluid dynamics (CFD) software CFX. By using the proposed method, three-dimensional velocity and pressure fields in the gas film flow and the temperature distribution within the sealing rings are investigated for three kinds of film thickness, respectively. A comparison of thermohydrodynamic characteristics of the dry gas seal is conducted between the sealed gas of air and helium. The latter one is used in a helium compressor for a high-temperature gas-cooled reactor (HTGR). From comparisons and discussions of a series of simulation results, it will be found that the comprehensive proposal is effective and simulation results are reasonable. Even under a hypothetical accidental condition, the maximum temperature rise in the dry gas seal is within the acceptable range of HTGR safety requirements.
A combined direct and inverse iterative design method was developed for the hydraulic design of centrifugal pump impellers. This method is based on the fluid continuity and motion equations and solves for the meridional velocity taking into account the effects of the blade shape on the flow. The blade shape is drawn by point-by-point integration with blade thickening and smoothing using conformal mapping. Two examples designed using the direct and inverse iterative design method are compared to results using the traditional design method with significantly different meridional velocity distributions and three-dimensional blade shapes. Numerical simulations and tests show that the highest pump efficiency is 2.2% higher with this design method than with the traditional design method. The numerical results agree well with the experiments with a smoother flow pattern than with the traditional design, especially in the volute.
(2015),"Comparative study of SGS models for simulating the flow in a centrifugal-pump impeller using single passage", Engineering Computations, Vol. 32 Iss 7 pp. 2120-2135 https://doi.org/10.1108/EC-09-2014-0193 Access to this document was granted through an Emerald subscription provided by All users group
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