| The outlet guide vane is an important energy recovering component of an axial flow pump. By recovering outlet velocity circulation, it converts the kinetic energy to pressure energy, thus reducing the hydraulic loss of the passageway, improving hydraulic efficiency of the pump and pump unit and benefiting the stable operation of the pump station. Therefore, the studies on the optimization design of the guide vane have both theoretical and practical significance.This article adopts the method of CFD to study the effect of different swept angles of the outlet guide vane on the performance of axial-flow pump. The guide vane design at six different swept angles is carried out in order to reduce flow separation from the inlet, outlet and backside of the guide vane and improve its circulation recovery ability. The six different outlet guide vanes are obtained through rotating 3D coordinate values of guide vane airfoil sections to varying degrees clockwise or counterclockwise. The K-ε turbulence model is used to carry out the steady and unsteady numerical simulation calculation and comparative analysis of 6 schemes under 8 working conditions. Meanwhile, in order to further study the effect of the+16° guide vane on the internal pressure fluctuation of the axial pump,20 monitoring points are arranged in four sections, namely, the surface of the inlet of the impeller, the surface between the impeller and guide blade, the surface of the guide vane and the surface of the outlet of the guide vane. First of all, all monitoring points under the optimal condition were monitored, and then the monitoring points in the middle of each section under three different working conditions are monitored, thus the time-domain characteristics of the pressure fluctuation of every monitoring point are obtained and they can convert to the frequency-domain characteristics by FFT.The comparative analysis shows that the efficiency of forward swept guide vane is higher than that of backward swept guide vane, that the axial flow pump efficiency of the+16° guide vane is the highest, and that the reliability of the numerical simulation is verified through model test. They analysis of the numerically simulated internal flow field of the+16° guide vane shows that forward swept guide vane can better reduce the flow separation than the 0° guide vane, especially near the hub of the outlet of the guide vane and better recycle the velocity circulation. The unsteady analysis of the pressure fluctuation shows that the pressure fluctuation frequency of the monitoring points is mainly controlled by the impeller rotation frequency, that pressure fluctuation amplitude of from hub to shroud increases gradually at the position before the impeller, that it first decreases and then increases at the position of between the impeller and guide vane and at the position of the surface of guide vane, that it increases first and then decreases at the position of the outlet of guide vane, that as a whole, the pressure fluctuation amplitude at all the monitoring points in the+16° gaide vane were smaller than the 0° guide vane, in which the amplitude at the position of the surface of guide vane and the outlet of guide vane are 40% smaller on the average, that the pressure fluctuation frequency of almost all the monitoring points of the 0° guide vane is mainly controlled by the impeller rotation frequency except that the monitoring point at the outlet of the guide vane is controlled by the pump rotation frequency, that the pressure fluctuation frequency of almost all the monitoring points of the+16° guide vane are mainly controlled by the impeller rotation frequency, and that under small flow working condition, the pressure fluctuation frequency of the monitoring points at the position of the surface of the guide vane and at position of guide vane outlet is mainly controlled by the axial flow pump rotation frequency. The 0° guide vane is affected more by eddy current secondary wave than the+16° guide vane.Therefore, the forward swept guide vane has better performance than backward swept guide vane, and the+16° guide vane has best performance. The+16° guide vane can improve the performance of the pump and the water flow regime near the hub of the outlet of the guide vane, recycle velocity circulation, reduce the water pressure pulsation in the pump, especially under the optimal working condition and mass flow working condition. |
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