Hydraulic Performance Optimization And Experiment On The Model Pump Of The Fourth Generation Main Nuclear Molten-salt Pump

The molten salt reactor is one of the fourth generation nuclear reactors.Nuclear reactor coolant main circulating pump(nuclear main pump)is the only high-speed rotating equipment in the main circuit system,and is known as the "heart" of nuclear power plant.Molten salt main pump is different from the general pump,its design needs to consider the physical properties of high temperature molten salt,hydraulic requirements and operating conditions,which give higher requirements of the design.The design and experimental study of the hydraulic model pump are the prerequisite for the study of the real machine of the molten salt pump.Therefore,in order to provide theoretical reference to the fourth generation nuclear pump of China.this paper has researched the numerical simulation,the experiment and the hydraulic performance optimization of the model pump of the molten salt main nuclear pump.The main research work and achievements of this paper are as follows:1.The development of nuclear power trends,as well as the pressure pulsating radial force,axial force and vibration noise have been summarized.2.Based on CFD,the whole flow field unsteady numerical calculation of the model pump is carried out,and the external characteristics,internal flow field,radial force and pressure pulsation of different conditions are analyzed.The results indicate that: the calculated efficiency is 73.22% and the head is 16.11 m.The shape of the radial force vector of the guide vane and the annular vortex chamber is hexagonal star(the number of the guide vane blades is 6),and there are five coincident curves(the number of impeller blades is 5)in all.But its distribution in the four quadrants is not uniform.The pressure pulsating fluctuations of the same location in different flow channel of guide vane are the same.And the more close to the guide vane imports,the more intense fluctuations.The pressure pulsation in the annular spiral chamber which are symmetric by the guide vane center line is the same.3.The model pump is manufactured,and its external characteristics,cavitation,pressure pulsation,vibration and noise were tested.The results indicate that the efficiency is 71.47%.The NPSHr of the pump were 2.82 m,3.46 m and 3.8m under0.6Qd,0.8Qd and 1.0Qd.The pressure amplitude of the outlet diffusion section is larger..A wide frequency as the center of 450 Hz is appeared of export flange due to the instability of the vortex.The arrangement of vibration intensity is: import and export flange> bearings> motor base> pump base> pump casing.The fluid induced vibration affected by the unchamfe annular volute will produce the collision and impact in the actual flow and result in the increase of vibration intensity.The vibration grade of the model pump is B.4.In order to improve the hydraulic performance of the model pump,the hydraulic performance of the model pump is optimized and the numerical calculation is carried out.The results show that the calculation efficiency of the second scheme is the highest,which is 6.37 percentage points higher than the original model.The axial force is affected by the cut of impeller back-blade,and the axial force of the original model and that of the second scheme can be balanced about 89.47% and 62.74%under design condition.The fluctuations of pressure pulsation and radial force have been improved after optimization,and the radial force vector distribution is more uniform.5.The second scheme was been verified by experiment.The results show that the efficiency is 5.26 percentages higher than the original model.The amplitude of the pressure fluctuation is decreased and the fluctuation condition is improved.After optimization,the wide band frequence of M1 disappears and the wide band frequence of other points decreases or disappears.The harmonic frequency decreases.The vibration intensity of the export flange is 4% higher than that of the original model because of the increase of the export pressure after optimization,and the vibration intensity on both sides of the bearing decreases by 14.2% and 17.5%.After optimization,the vibration level of the pump is Grade A,the optimization effect is obvious.The NPSHr is 5.67%,6.64% and 6.82% lower than the original pump.