| China is a country with imbalanced distribution of water resources and moderate water shortage.The water level of river bed and groundwater decreases year by year and falls to-8m or less in many regions.As a kind of high lift pumping devices,jet pump devices are widely used and its absorbing height can reach to several decameter.It has many advantages,reliable operation,convenient maintenance and low cost included,and can run with other power instead of electricity.But efficiency is low due to its work principle.So in order to improve the performance of the jet pump devices,the structure of the jet pump was improved and a new type of swirling jet pump was designed.Then we researched the performance of this device.The main contents were as follows:(1)Velocity and pressure attenuation of the swirling jet,entrainment ability and mixing effects were analyzed and a new jet pump was designed.The results show that the diffusion attenuation in jet pump with weak swirling jet was weaker than jet pump with strong swirling jet.Entrainment ability and mixing effects of swirling jet pump were much stronger than irrotational jet,which helped to improve the performance of jet pump device.Based on the swirling jet theory and the work principle,fixed guide vane number of swirling jet pump z=2,guide vane height hv=100mm,working water inflow angle α=40°,guide vane thickness d1=1mm and guide vane width d2=10mm were decided by cylindrical coordinate design method.(2)A comparative study of swirling jet pump with three different area ratio and the corresponding irrotational jet pump(m=4.37、3.13、2.35)was carried out on the same test bed.The experimental results show that the optimal area ratio of the swirling jet pump was smaller than the irrotational jet pump.The high efficiency area of the swirling jet pump device was larger than the irrotational jet pump.The swirling jet pump had lower pressure loss and better performance under the same area ratio and operating conditions.The maximum value of pressure ratio could be increased by 0.01 which was comparable with the pressure ratio 5%~10% of irrotational jet pump,Efficiency could increased by 4% which was the equivalent to about the efficiency 25% of irrotational jet pump.(3)A feasible numerical simulation method was proposed and was used to compare and analyze the internal flow of the swirling jet pump and the irrotational jet pump with different area ratio.The results show that compared with the irrotational jet pump,pressure loss of the swirling jet pump was smaller under the same area ratio,and pressure loss decreased with the decrease of area ratio.Velocity of working water in the swirling jet pump was larger before flowing through the nozzle.After expelled from the nozzle,center velocity attenuation in the throat and diffuser pipe was weaker and was weakened with the decrease of area ratio.There was an obvious vortex in the junction of diffuser and straight pipe and inner flow of the swirling jet pump was very smooth.The numerical simulation results were consistent with the experimental results,and pressure ratio and efficiency of the swirling jet pump were higher.(4)The orthogonal test of four factors and three levels was designed and pressure ratio and efficiency were chosen as the experimental indexes.Structure sizes of the swirling jet pump were optimized and their influences on experimental indexes were researched based on CFD.The results show that area ratio had significant effects on indexes above while the influences of fixed guide vane number,guide vane height and working water inflow angle were not obvious,especially guide vane height.The better structure size program of swirling jet pump device was confirmed. |
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