| Due to the relative position changes between the rotary impeller and the static components of the centrifugal pump,it will cause a strong rotor-stator interaction phenomenon in the flow field,which is the main reason for the pressure pulsation in the centrifugal pump.The pressure pulsation will induce the appearance of noise and high-frequency vibration,or even resonance,which will seriously affect the operating environment and life of the centrifugal pump.Therefore,we need to take active measures to reduce the pressure pulsation caused by rotor-stator interaction.The profile of blade outlet trailing edge has a very important effect on the rotor-stator interaction.The reasonable design of profile of blade outlet trailing edge can reduce the pressure pulsation,which is of great significance for improving the performance of the centrifugal pump.In this paper,the impeller models with different trailing edge shapes were designed according to the bionics principle.They are the original trailing edge(OTE)and the sinusoidal tubercle trailing edge(STTE).The main research contents and results are as follows:(1)Designing the impeller models.According to the principle of bionics,the sinusoidal tubercles on the pectoral fin of humpback whale have excellent hydraulic performance.It is applied to the blade trailing edge,which play the role of actively controlling the rotor-stator interaction of the blade outlet area,thereby reducing the pressure pulsation.According to the size of the sinusoidal structural characteristics of the trailing edge,the impeller models were named OTE,STTE-1,STTE-2 and STTE-3.(2)Performance test of impeller model.The changes of the external characteristic and the pressure distribution in the pump cavity were tested.The results showed that the STTE-1 impeller model has the best external characteristics.The head is consistent with OTE at low flows,but increases obviously under large flow condition.The head and efficiency of STTE-2 and STTE-3 have decreased than OTE's.The pressure distribution of the four models has similar rules in the pump chamber.The pressure values of each circumferential monitoring point decrease when the flow rates increase,and the pressure declining gradient gradually increases.The pressure gradient of the model pump STTE-1 is the smallest under the full flow condition,and it has better pressure stability,while the pressure stability of STTE-3 is poor.The maximum pressure pulsation amplitude of main frequency of the model pump STTE-3 increases by 8.9%than the original model pump OTE.The maximum pressure pulsation amplitude of the model pump STTE-1 main frequency educes by 7.1%than OTE.(3)In order to reveal the reasons of external characteristics and pressure distribution of the four impeller model tests,steady calculations were carried out.We analyzes the pressure distribution,blade surface load,velocity streamline and turbulent kinetic energy distribution under various flow rates.The results showed that different blade trailing edge shapes have significant effects on the internal flow field and energy distribution.The areas of the inlet low-pressure area of the model pumps STTE-2 and STTE-3 are reduced,which reduce the risk of cavitation at the inlet of impeller.However,the internal flow field is turbulent,resulting in increased losses and increased pressure pulsation;the model pump STTE-1 has a relatively uniform pressure distribution without obvious vortex exists in the flow channel,and has a better head performance,and there are fewer high-turbulence kinetic energy distribution areas and less energy loss.(4)Studying on internal pressure pulsation of model pump.The unsteady calculations of the four model pumps were carried out to study the pressure pulsation distribution in the flow channel and rotor-stator interaction area of the tongue by the pressure pulsation intensity coefficient.It was intuitively found that the high-intensity pressure pulsation was mainly concentrated in the rotor-stator interaction area and the impeller channel outlet area.At the same time,the time domain and frequency domain distribution of pressure pulsation of the four model pumps are quantitatively compared under design flow conditions.The time domain curves show a consistent regularity.The amplitude of pressure pulsation in tongue area is higher than other areas.By comparison,the maximum pressure pulsation amplitude of model pump STTE-1 is reduced by 8.97%than that of OTE.However,the pressure pulsation amplitude of STTE-2 and STTE-3 increase.(5)By comparing and analyzing the vortex core distribution in the trailing edge area of four models,it was found that there is a large number of shedding vortex in the blade trailing area.In this case,the original model pump OTE's shedding vortex presents large lumpy,which occupies large volume and runs fast,and generates a large pressure pulsation after impacting with the volute.The vortex core distribution in the trailing area of STTE-1 is less than that of original model pump OTE.Because the tiny sinusoidal tubercle structure at blade trailing edge can separate the large lumpy shedding vortex into several small's.The area and energy occupied by the vortex core are reduced,and the rotor-stator interaction generated by the shedding vortex is also weakened.so the pressure fluctuation decreases.The trailing edge area of STTE-3 has more vortex,enhancing rotor-stator interaction,and increasing pressure pulsation. |
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