Numerical Study On The Influence Of The Structure Of The Guide Vane And Case On The Performance Of Nuclear Main Pump

Nuclear power is a safe,clean and efficient energy.It will get a broad demand.Nuclear power technology should also continue to progress.The nuclear main pump is used to drive the coolant to circulate in the reactor coolant system,and transmit a large amount of energy generated from the primary loop of the nuclear power plant to the second stage circulation loop.It`s performance and reliable operation directly affect the power generation capability and safety of the nuclear power plant.Therefore,the research and development of the hydraulic model of the nuclear main pump with good performance and stable operation is of great significance for the efficient and stable operation of the nuclear power plant.In this paper,the internal flow characteristics of the designed nuclear main pump model pump under steady and unsteady conditions were analyzed by the combination of CFD numerical simulation technology and experimenta l research.The numerical simulation method was verified by the test method.Based on this,the influence of the variation of the structure of the vane and the case on the performance of the nuclear main pump was further studied,which provides an important theoretical basis for the optimal design of the nuclear main pump.In this paper,the following three aspects were studied.(1)Internal flow characteristics and pressure fluctuation of nuclear main pump.Based on the self-designed CAP1400 nuclear main pump model,the flow analysis of the whole working condition were carried out,and the experimental comparison was made.The similarity between the numerical simulation method and the actual experiment was analyzed.At the same time,on the basis of steady-state simulation,the internal pressure fluctuation of the unsteady flow of the simulated pump is further monitored,and the causes of pressure fluctuation are analyzed.(2)Influence of the geometric parameters of the guide vane axial surface on the performance of the nuclear main pump.By changing the width of guide vane outlet and referring to the design method of front and rear cover plate streamline of centrifugal pump impeller axial flow passage,we redesign guide vane axial flow path.By checking the area change of the cross-section,we can ensure that the cross-section area of guide vane axial flow passage changes smoothly.It is concluded that the efficiency and head of the model pump with smaller guide vane outlet width will be greatly reduced under the condition of large flow rate,under 0.8Q_d and 0.9Q_d,the maximum difference of head of each comparison scheme is 0.05m and 0.33m respectively,and the efficiency gap is also small.Compared with the original scheme,the model with smaller guide vane outlet width at 1.1Q_d and 1.2Q_d has lower head by 1.19m and 1.24m.The efficiency was reduced by 6.86%and 7.77%.With the increase of the outlet width of the guide vane,the flow loss in the guide vane will increase,and the flow loss in the case will decrease.The change of the efficiency of the whole pump is the result of t he joint effect of the two aspects.As the width of the vane outlet increases,the interference of the flow in the case to the flow state at the outlet of the vane increases,causing back flow and vortex at the exit position of the vane.This is the main r eason for the increase in the loss within the vane under conditions where the vane outlet is too wide.(3)Influence of the change of axial area of case on the performance of nuclear main pump.The case of the nuclear main pump is an annular case of equal section.This causes the flow in the case to be the most chaotic of the entire pump section,and the interior is filled with a large number of vort ex of various scales.The full flow field hydraulic calculation is carried out for the design schemes with different cross-sectional areas.The conclusion is as follows,Under the design conditions,the variation of the cross-sectional area within a certain range has little effect on the operating state of the nuclear main pump,The head and efficiency of the three schemes are basically the same.The head values are 17.96m,17.92m and 17.95m respectively,and the efficiency values are 85.14%,85.23%and 85.31%respectively.However,deviation from the design conditions,the change in the cross-sectional area of the case will have a greater impact on the head and efficiency of the nuclear main pump.Appropriate increase of cross-sectional area can improve the head and efficiency of the nuclear main pump,for example,under the condition of 1.2Q_d flow rate,the head and efficiency of the scheme with larger cross-section area are increased by 0.6m and 2.15%respectively compared with the original scheme,and optimize the indoor flow structure of the pressurized water,reduce the pressure gradient in the case,reduce the flow velocity in the case,and make the pressure distribution and velocity distribution in the case more evenly.A small cross-sectional area will increase the loss in the case.