Research On The Effect Of Stator And Rotor Cascade Clearance On The Performance Of Nuclear Main Pump

Under the premise of maintaining a relatively high growth in energy demand at this stage,the development and utilization of nuclear energy have become increasingly prominent in industrial production and life,among which nuclear power has the advantage that other energy sources cannot be substituted.In a nuclear power plant,the nuclear main pump is the only high-speed rotating equipment in the reactor and is the heart of the nuclear island.Its performance and stability directly affect the power generation capacity and safety of the nuclear power plant.Therefore,it is of great significance to study the performance of the nuclear main pump hydraulic model to improve the efficiency of the nuclear main pump in practical applications.In order to improve the hydraulic performance of the nuclear main pump,this article takes a specific pump with a ratio of 388 as the main pump of the 0.4-core pump as the research object,and studies the internal flow and energy of the nuclear main pump through numerical calculation and related experimental data.The conversion characteristics,as well as the effect of the rotor and static clearance on the performance of the model pump,internal flow field,energy conversion and pressure pulsation,provide an effective reference for the subsequent optimization of nuclear main pump design.The main research contents and the conclusions obtained are as follows:1.Analysis of internal flow characteristics and energy conversion characteristics of nuclear main pumpThe energy loss in the guide vanes and the annular pressurized water chamber of the main pump and the internal flow field changes in the impeller,guide vane and pressurizing chamber were studied under different working conditions.The variation of the pressure from the inlet to the outlet of the middle streamline of the impeller and guide vane 0.5lspan was analyzed.The results show that with the increase of the flow rate,the static pressure recovery in the guide vane shows a trend of increasing first and then decreasing,and the total pressure loss shows a trend of decreasing first and then increasing.The loss of the annular pressure water chamber shows a gradually increasing trend.The higher velocity region of the impeller is always concentrated on the back of the impeller blade.The low velocity region is mainly distributed near the working surface of the impeller blade.Under small flow conditions,the velocity gradient of the impeller flow channel is larger,and the flow velocity is larger at high flow rates.The gradient decreases.The pressure of the fluid at the inlet of the impeller blade is the minimum.As the radial distance increases,the pressure value increases linearly and uniformly.The pressure at the inlet surface of the impeller blade decreases with the increase of the flow rate.2.Effect of stator and rotor cascade clearance on hydraulic performance of nuclear main pumpThe influences of five different stator and rotor cascade clearances on the hydraulic performance of the main pump and the internal flow field structure were studied,and the optimal clearance of the impeller and guide vane was obtained.The results show that the stator and rotor cascade clearance has a great influence on the lift and efficiency of the model pump under design condition.The clearance has less influence on the impeller lift and efficiency than the pump,and has a greater impact on the hydraulic loss in the guide vane and on the pressure water loss in the water room.When the clearances are different,the relative velocity of each point of the impeller exit has the same change trend.The relative velocity from the front shroud flow line to the rear shroud flow line is basically monotonously decreasing,and the overall clearance is d=8.5mm.The relative change of export speed is the most gentle,and the relative velocity of each point of the guide vane inlet is consistent with the relative velocity of the impeller outlet,and both show a monotonous decreasing trend.The clearance change has a more obvious influence on the relative velocity of the guide vane inlet.With the change of the stator and rotor cascade clearance,the pressure distribution from the inlet of the impeller to the outlet of the annular pressure water chamber is not the same.When the fluid flows from the guide vane to the outlet of the pressure chamber,the position of the diversion point when the fluid diverges near the partition tongue is related to the size of the gap between the stator and rotor cascade.When the clearance is equal to 8.5mm,the flow condition of the fluid is best.In summary,the performance of the model pump is optimal when the clearance is around d=8.5mm.3.Effect of stator and rotor cascade clearance on the rotor-stator interaction of nuclear main pumpThe variation of pressure pulsation on the working face and back face of the impeller blade under unsteady conditions and the effect of the stator and rotor cascade clearance on the impeller outlet,impeller-guide vane clearance and inlet vane inlet pressure pulsation were studied.The following conclusions are drawn: During one cycle of impeller blade rotation(approximately 0.041s),five peaks and valleys appear on the working face and back pressure of the impeller blades,which is the same as the number of impeller blades.The pressure pulsation gradually decreases along the impeller blade inlet to the outlet.The maximum amplitude of pressure pulsation occurs at the inlet section of the working face of the impeller blade.The pressure changes of the four measuring points arranged circumferentially at the stator and rotor cascade clearances have obvious periodicity;the pressure fluctuations are mainly composed of main fluctuations and sub-fluctuations.The main fluctuations in one rotation cycle are 5,and the minor fluctuations are 1 to 3.With the increase of stator and rotor cascade clearance,the pressure distribution at the outlet of the impeller is basically the same.The pressure pulsation in the gap changes periodically.When the clearance is 13.5mm,the fluctuating energy amplitudes at the four monitoring points are at each frequency multiplication point.At minimum,the change in pressure at the inlet of the vane is similar to that at the outlet and clearance of the impeller.