Influence Of Parameters Of Guide Vane Diffusion Section On Hydraulic Performance Of Nuclear Main Pump

Nuclear power plays an increasingly important role in the energy structure.In-depth research on the internal flow mechanism and performance optimization of nuclear main pumps is of great significance for realizing the localization of China's energy equipment.In this paper,the prototype of nuclear main pump is taken as the research object.The combination of numerical simulation and experiment is used to study the nuclear main pump from three aspects:numerical algorithm,internal flow field and radial vane.By changing the grid dimension of the near wall,selecting different turbulence models and considering whether the flow state is constant,the three factors affecting the calculation accuracy of the nuclear main pump performance are discussed comprehensively.For the RNG k-?turbulence model and the standard wall function method,the highest calculation accuracy can be obtained when the near-wall mesh scale y plus value is around 50.For the RNG k-?enhanced wall function method,low Reynolds number k-?(AKN)and SST k-?,the turbulence model can directly solve the boundary layer flow,and the enhanced wall function method has higher calculation accuracy,while the low Reynolds number k-?turbulence model has low computational accuracy.The standard wall function method with y~+=50 has higher calculation accuracy than the enhanced wall function method with y~+<10.Therefore,the RNG k-?turbulence model and the standard wall function method are more suitable for nuclear main pump performance prediction.The constant calculation has a large calculation error in the partial working condition.The unsteady calculation can reflect the main characteristics of the performance curve.The unsteady calculation is more suitable for the performance prediction of the nuclear main pump.Taking the calculation results of RNG k-?turbulence model and near-wall mesh scale?y=0.4mm as an example,the internal flow fields of the main over-current components of the nuclear main pump are selected from three operating conditions of0.8Q_d,1.0Q_d and 1.2Q_d analysis.The absolute pressure in the center plane of the impeller and the vane gradually increases along the radial direction.The larger the flow rate at the same position on the center plane,the smaller the absolute pressure is.The relative velocity from the working surface of the impeller blade to the back is gradually increased,and the velocity distribution in the guide vane is compared.Disorder,the velocity in the pressurized water chamber is affected by the velocity distribution in the guide vane flow channel.The pressure gradient of the anterior chamber is evenly distributed,and the pressure increases approximately uniformly along the radial direction;the pressure gradient of the back cavity gradually increases along the radial direction;the pressure gradient in the gap of the orifice is obvious and the flow rate is smaller;the pressure gradient is smaller;The lower part flows into the impeller inlet through the gap between the front and the mouth.There is a distinct low-speed region near the left side of the inlet of the pressure tube diffusion tube,and a large local high-speed low-pressure region with a large gradient is formed around the left and right sides of the fluid diffusion tube.The hydraulic loss in the impeller accounts for a large proportion.After increasing the flow rate,the hydraulic loss in the impeller decreases,and the hydraulic loss in the guide vane and the pressurized water chamber increases gradually.The pressure distribution on the different blades of the impeller is similar,the working face pressure is greater than the back pressure,and the pressure from the blade inlet to the outlet gradually increases.The pressure on the working surface of the vane blade in the small flow condition rises sharply at a relative flow line position of 0.4 and then decreases slightly.The pressure distribution at the corresponding position on the back of the different vane vanes is greatly different;the design conditions and the large flow conditions are different.The pressure distribution at the corresponding position on the leaf blade is similar.The influence of different diffusion parameters on the hydraulic performance of the nuclear main pump was studied by controlling the diffusion of the integrated parameter guide vanes of the shape of the guide vane.The head of the nuclear main pump increases with the increase of the inlet area of the guide vane diffusion section,and the efficiency increases first and then decreases with the increase of the inlet area of the diffusion section;the impeller efficiency decreases with the increase of the inlet area of the guide vane diffusion section;The static pressure recovery capacity increases with the increase of the inlet area of the diffusion section;the hydraulic loss of the pressurized water chamber decreases first and then increases with the increase of the inlet area of the guide vane diffusion section.The head and efficiency of the nuclear main pump generally increase first and then decrease with the increase of the outlet area of the guide vane diffusion section;the impeller efficiency decreases first and then increases with the increase of the outlet area of the diffusion section,and the change of the outlet area of the diffusion section The hydraulic performance of the impeller is less affected;the hydrostatic recovery of the vane generally increases first and then decreases with the increase of the outlet area of the diffuser;the hydraulic loss of the pressurized water chamber decreases first with the increase of the outlet area of the vane diffusing section.When it is enlarged,the outlet area of the diffusion section is small,which can significantly increase the hydraulic loss of the pressurized water chamber.The head of the nuclear main pump first decreases and then increases with the increase of the length of the guide vane diffusion section.The change of the length of the diffusion section has little effect on the efficiency of the pump and has no obvious influence law.The impeller efficiency increases with the increase of the length of the guide vane diffusion section.Large;the variation of the length of the diffusion section on the static pressure recovery of the vane is not obvious.The relative hydraulic loss of the pressurized water chamber fluctuates with the increase of the length of the diffusion section.Generally,the change of the length of the diffusion section has little effect on the hydraulic performance of the pressurized water chamber.The head and efficiency of the nuclear main pump generally increase first and then decrease with the increase of the diffuser of the guide vane.The diffusion of the vane between 0.027 and 0.031 can ensure the high efficiency of the nuclear main pump.The pump has the highest efficiency when the leaf diffusivity is 0.03,and the highest efficiency point is increased by 0.45%compared with the original guide vane scheme.