Abstract
To better reveal the mechanism of the rotor-stator interference between the impeller and the guide vane and the evolution process of the stall vortex under the part-load conditions, numerical simulation is carried out based on the DDES turbulence model, which can better capture vortex structure. And the pressure pulsation and the radial velocity distribution of the centrifugal pump are studied. The vortex structure and pressure fluctuation of pump internal flow field under part-load condition of Q = 0.4 Qdes are mainly analyzed. The analysis results show that the stall vortex is formed at the inlet of the impeller and evolves to the outlet of the impeller, the front cover to the rear cover according to the fluid flow direction, and then disappears. Besides, under the part-load condition, the vorticity of the impeller outlet is always obviously less than that of the impeller inlet as the flow rate increases. Due to the asymmetric action of the volute, the radial velocity distribution law of flow channel C1 is different from other flow channels at different blade heights. By analyzing the radial velocity, the phenomenon that the jet-wake flow impacts the guide vane with the rotation of the impeller is the main reason for the rotor-stator interference. And large radial velocity gradients appear at the front and rear cover plates, which will cause high energy loss and reduce pump efficiency. Besides, the conclusion can be drawn that the region with the strongest rotor-stator interference is the inlet region of the guide vane suction surface. It also occurs near the volute tongue but is lower due to the effect of the guide vane. This research may serve as a reference for the safe operation of centrifugal pumps under part-load conditions.
Highlights
Nowadays, with the development of science and technology, the pump, especially the centrifugal pump, has been an indispensable power machine everywhere we can see, applied widely in agriculture, aerospace, water conservancy engineering, nuclear industries, and medical treatment [1,2,3]
The dominant work of this paper is to carry out the DDES analysis of flow field at the off-design condition of a centrifugal pump and reveal the mechanism of rotor-stator interaction (RSI) and the formation mechanism of stall vortex, which can provide some reference for reduction of pressure pulsation and improvement of internal flow field and efficiency
E boundary layer at the inlet of the impeller blade breaks away when the centrifugal pump runs under the condition of part-load, leading to the formation of a vortex. e smaller the flow rate is, the larger the vortex is, resulting in the blockage of the impeller inlet, which leads to unnecessary energy loss and a reduction in the efficiency of the centrifugal pump
Summary
With the development of science and technology, the pump, especially the centrifugal pump, has been an indispensable power machine everywhere we can see, applied widely in agriculture, aerospace, water conservancy engineering, nuclear industries, and medical treatment [1,2,3]. To better capture the vortex structure and obtain more superior flow field information, many scholars have introduced the DDES turbulence model into the numerical simulation analysis of rotating machinery, which is the relatively accurate turbulence model at present [20,21,22]. At present, this method is applied more in compressors and less in pumps [23,24,25,26]. The dominant work of this paper is to carry out the DDES analysis of flow field at the off-design condition of a centrifugal pump and reveal the mechanism of RSI and the formation mechanism of stall vortex, which can provide some reference for reduction of pressure pulsation and improvement of internal flow field and efficiency
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