| When the centrifugal pump operates under various operating conditions,the pressure pulsation induced by the internal unsteady flow is not conducive to the safety and stability of centrifugal pump,which can cause the vibration and noise of the pump system and even damage the equipment.The interaction between the impeller trailing edges and the tongue of centrifugal pump volute is the main factor to stimulate the pressure pulsation.The study is supported by National Natural Science Funds of China(Grant No.BK51409123).The effect of the blade trailing profiles on pressure pulsation in centrifugal pump was studied with the combination of numerical simulation and experimental measurement.The main researches are as follows:(1)By numerical simulation for the different blade trailing edge profile cases,the influence of different blade trailing edge profiles on the flow characteristics of centrifugal pump was studied with numerical simulation.The pressure distribution,velocity distribution and turbulent kinetic energy distribution of the internal flow field were obtained.The result shows that different trailing edge profiles have a significant influence on the pump head.The pressure difference between inlet and outlet of square blade trailing edge centrifugal pump is the largest and turbulence intensity at the pressure side of blade is the strongest.Therefore,the energy conversion rate of the square blade trailing edge centrifugal pump is the largest,and the pump head is the highest under all working conditions.(2)Comparing the time and frequency domain of centrifugal pumps with 4 kinds of trailing edge profiles,it is found that the time domain pulsation amplitude of in the centrifugal pump with the square blade trailing edge at each monitoring point is the largest.Thus,it shows that the interaction between impeller and tongue is the strongest and the internal flow field is the most unstable in square impeller trailing edge centrifugal pump.The phenomenon indicates that the profile of blade trailing edge has great influence on the interaction between impeller and tongue as well as the pressure pulsation of centrifugal pump.(3)A closed test rig for measuring the external characteristics and pressure pulsation of centrifugal pump has been set up.With high precision dynamic torque used to collect torque and speed signal,the dynamic pressure pulsation signal is monitored with high frequency dynamic pressure sensor in the inlet and outlet position as well as volute wall surface.The speed,torque,flow rate and pressure signal test program was written by Labview software to monitor and record real-time dynamic signal.And repeatability test was carried out to verify the reliability and accuracy of test results.In addition to the original model,3 kinds of impeller with other trailing edge profiles were processed by rapid prototyping technology.The uncertainty of the test rig is analyzed.The uncertainty of the rig is small and the value is less than 0.3%.The measurement accuracy of each parameter meets the GB3216(B)standard,and the test parameters can be measured accurately.(4)The dynamic pressure fluctuation signals of different models under different operating conditions were analyzed by time domain analysis,frequency domain analysis and time-frequency analysis.The amplitude of pressure pulsation is large on the blade passing frequency f=297Hz and harmonic frequencies.Through the method of time-frequency analysis,it is found that the amplitude of pressure pulsation in the model with square blade trailing edge is the most obvious,and the smallest is found in the curved blade trailing edge centrifugal pump.So,the appropriate blade trailing edge profile can effectively reduce the pressure pulsation energy of blade frequency and harmonic frequency. |
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