The Study On The Influence Of Guide Vane Structure On The Hydraulic Performance And Pressure Pulsation Of Nuclear Main Pump

Nuclear power has been widely exploited and utilized because of its clean,stable and high efficiency.Nuclear main pump is the core equipment in the whole nuclear power plant,its high efficiency,long term safe and stable operation is the guarantee of nuclear power development.In order to improve the hydraulic efficiency of nuclear main pump,taking a centrifugal nuclear main pump as the research object,devising five different guide vanes which are namely radial guide vane,twisted guide vane,the guide vane with half height,straight blade for cutting guide blade close to volute outlet and thick cylindrical guide vane,the internal flow characteristics and pressure pulsation characteristics of the pump with different schemes are compared by numerical simulation.Firstly,the three-dimensional numerical simulation of the main pump prototype is carried out under different flow conditions,which the external characteristic curve and internal flow law of the nuclear main pump are obtained.The results showed that the flow condition of model pump under the design is the best,pressure and velocity distributions are uniform,there is no vortex and back-flow in the flow.But the matching relationship between the design parameters of the impeller outlet and the guide vane inlet is more suitable for large flow conditions;Under the condition of small flow,the whirlpool blocked the channel in the impeller and guide vanes,at the exit of the guide vane,the flow separation is serious,and there is impact back-flow in the annular water chamber.Secondly,in order to improve the hydraulic performance of nuclear main pump,the guide vanes with different structures are designed,and the external characteristics and internal flow field characteristics of the model pump with different schemes are compared and analyzed under the high speed n=2850r/min.The results show that the hydraulic efficiency of the nuclear main pump with twisted guide vane is the highest in the design operating point,which show that the design parameters of the twisted guide vane and impeller are more match,and the impact loss of fluid in the guide vanes is reduced.Cutting the radial blade near the volute outlet can reduce the impact of loss of fluid in the volute tongue.Thickening guide vanes can strengthen the control of fluid,and can reduce the complex flow of vortex.The turbulent kinetic energy intensity is mainly concentrated in the transition region of the impeller outlet and theinlet of the guide vane and near the volute tongue.Finally,in order to discuss the influence of the guide vane structure on the pressure pulsation of the model pump,the pressure fluctuation characteristics of different positions of the model pump are compared and analyzed.The results show that: under low speed condition n=1450r/min,the nuclear main pump which cutting guide vanes close to volute outlet has the highest hydraulic efficiency,which is 1%higher than the original model.Under high speed condition n=2850r/min,the hydraulic efficiency of the nuclear main pump with twisted vane is the highest,which is 0.97% higher than the original model.Half guide vanes either in low design speed or high design speed,the hydraulic efficiency of the model pump is worse than the scheme one,which probably because there's a whirlpool in the gap between vanes and the front cover of half guide vanes and there is flow separation phenomenon at the exit of the guide vanes.The pressure pulsation of the impeller and guide is mainly affected by the number of leaves and the rotation of the impeller.The amplitude of the pressure fluctuation at the rim of impeller inlet is higher than at the hub,the dynamic and static interference effect between the impeller and the guide vane is the main factor affecting the pressure pulsation.The twisted guide vane can reduce pulsation amplitude of the impeller outlet,guide vane and volute than the straight guide vane,and its effect is the most obvious,which is conducive to long-term safe and stable operation of the nuclear main pump.Cutting the blade near the volute outlet can decrease the amplitude of pressure fluctuation at the inlet and outlet of guide vane.Thickening guide vanes are favorable for the fluid to flow out from the volute.