| Vortex pump is a kind of vane pump rely on vortex flow to transfer energy,compared with the centrifugal pump,vortex pump is not only a small flow,the characteristics of high head,at the same time also has strong self-priming performance and gas-liquid mixing transmission performance,therefore they are widely used in petrochemical,aerospace and other small flow and have volatile or air content transmission medium.The complex vortex flow structure in the vortex pump can not only play the role of energy transfer,but also cause vortex loss.The viscosity of the medium has an important impact on the structure and performance of the vortex flow in the pump.The hydraulic performance and internal flow field evolution mechanism of CLDB240-768 vortex pump under different flow conditions and medium viscosity were analyzed.On this basis,the change mechanism of internal flow field and hydraulic performance of vortex pump under different viscosity,different blade number and different blade section shape is analyzed and studied.The main contents and conclusions are summarized as follows:(1)The performance test bench of the vortex pump was set up,and the variation law of the hydraulic performance of the vortex pump and the pressure pulsation phenomenon were studied experimentally.The comparison between the numerical simulation and experimental results shows that the variation trend of the numerical simulation data is basically consistent with the experimental data under different working conditions.Because tip clearance leakage flow was not considered in numerical simulation,the experimental test value was lower than the simulation value.The vortex pump runs more smoothly at low speed and small flow,and the peak value of pressure pulsation is smaller.The main frequency of pressure pulsation of vortex pump under different working conditions is axial frequency and frequency doubling.(2)The flow field structure and hydraulic performance of vortex pump under different medium viscosity and different flow conditions were analyzed by numerical simulation method.The results show that the flow in the impeller and the side channel of each longitudinal section tends to be stable from the inlet to the outlet along the impeller rotation direction,and there are obvious longitudinal vortexes and radial vortexes on each meridian plane.With the increase of flow rate,the intensity of longitudinal vortex and radial vortex in the impeller and the side channel gradually decreases,the power capacity of the impeller gradually decreases,and the head of the pump gradually decreases.The turbulent kinetic energy dissipation in the impeller and the vorticity distribution in the impeller decrease with the increase of flow rate,With the increase of medium viscosity,the intensity of longitudinal vortex and radial vortex on each meridian plane gradually decreases,and the turbulent kinetic energy dissipation in vortex pump vary more significantly with the viscosity,which increases significantly with the increase of medium viscosity.Under different flow conditions,the head and efficiency of vortex pump decrease with the increase of medium viscosity.At low flow rate,the head and efficiency decrease gently with the increase of viscosity,but at high flow rate,the head and efficiency decrease sharply with the increase of viscosity.(3)The internal flow field structures and hydraulic performance of vortex pump with different medium viscosity and different blade numbers were analyzed by numerical simulation.The analysis results show that the influence of blade number on pump head and efficiency is basically the same under different medium viscosity,which increases first and then decreases.Under different blade number,the head and efficiency of vortex pump decreases with the increase of medium viscosity.The longitudinal vortex intensity and radial vortex intensity in the impeller and side channel increase first and then decrease with the increase of the number of blades,so the head of the pump increases first and then decreases,the turbulent kinetic energy dissipation in the impeller decreases first and then increases,and the vorticity distribution in the impeller decreases with the increase of the number of blades.The high vorticity in the vortex pump is mainly concentrated in the impeller,and the vorticity at the root of the impeller is stronger than that at the top of the impeller.(4)The internal flow field structures and hydraulic performance of vortex pump with different medium viscosity and blade section shapes were analyzed by numerical simulation.The results show that the head and efficiency of the vortex pump decrease with the increase of the viscosity of the medium,but the C-shaped vortex pump has the best overall performance and is more suitable for conveying the medium with high viscosity.The transient pressure energy of the vortex pump with three different blade section shapes is analyzed.It is found that the transient pressure energy fluctuates periodically,and the frequency of fluctuation is exactly consistent with the frequency of blade sweep.C-shape blade vortex pump pressure rise sharply at the exit,causing pressure difference,the largest import and export of head,biggest different blade section shape of the turbulent kinetic energy and vorticity distribution trend is consistent,are the weakest when trapezoidal blades,C-shape blade of longitudinal vortex and radial vortex intensity is stronger,and produce area bigger,C-shaped blade vortex least resistance,Therefore,the corresponding head and efficiency are maximum. |
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