The Influence Of The Inlet Guide Vane On The Performance Of Axial Flow Pump

Large-scale axial flow pumps usually adopt adjustable vane to regulate the operating conditions. The application of the dynamic adjusting mechanism of the impeller blade to the vertical pumps is comparatively mature. But direct application of this mechanism to the horizontal pumps in low-head pump stations will lead to problems. Because the pump rotational speed of the horizontal pumps is low, the gearboxes are often needed to decelerate. And the gearbox lies between the pump and dynamo, which results in the the difficulty of the placement of the dynamic adjusting mechanism of the impeller blade. Therefore, the normal practice is to plant the adjusting mechanism into the straight guide vane in front of the impeller blade, thus, the directly adjusting the inlet guide vane to regulate the operating conditions is worthy of being considered. Compared with the dynamic adjusting mechanism of the impeller blade, the mechanism planted in the inlet guide vane which is always stationary is simplified and production cost can be reduced. In order to futher test and verify the feasibility and the strenths and weaknesses of the inlet guide vanes regulating the pump operating conditions, the comparison of the axial flow pump performance with and without the inlet guide vane becomes very significant.Based on the analysis of the inlet guide vanes regulating the operating conditions, the Reynolds-averaged N-S equations and the standard k-ε turbulent flow model are adopted in this paper to numerically calculate the three-dimensioal flow fields and analyze the feasibility as well as the concrete regulation effects of the inlet guide vanes regulating operating conditions. The main contents include (1) the influence of adjusting the impeller blade to certain different angles on the axial flow pump performance;(2) the influence of adjusting the inlet guide vane to certain different angles on the energy characteristics and the suction head characteristics when the impeller blade is set to a fixed angle;(3) the analysis of the energy loss of the inlet guide vane;(4) the analysis of the influence of the number of blades used in the inlet guide vane on the regulation effects.The research shows that adjusting the inlet guide vane to certain angles can effectively change the axial flow pump characeristics, thus to realize the purpose of regulating the operating conditions. The distribution of the pump operation condition range with high efficiency on the universal characteristics is quite different from that under the adjusting the impeller blade. When the impeller blade is adjusted, the long axis of the oval of the the pump operation condition range with high efficiency almost parallels with the capacity axis, and therefore this adjusting applies to the situation with narraow scope of head and wide range of flow control; on the contrary, when the inlet guide vane is adjusted, the the long axis of the oval of the the pump operation condition range with high efficiency approximately parallels with the diagonal of the Q-H axis, therefore, it applies to the situation with wide scope of head. When the inlet guide vane amplifies its angle adjustment, its water loss increases. The guide vane fits the positive angle; It can improve the saddle area on the universal characteristics, thus to make the high-head operating conditions more steady; it increases the net positive suction head required, as a result, the design operating point should increase0.5meters. Its water loss will reduce the overall pump efficiency to some degree, but not so much as that of the dynamic adjusting mechanism of the impeller blade. In a word, the adoption of the adjustable inlet guide vane to regulate the operating conditions is of great value in practice.