| The jet pump is a fluid machine and a hybrid reaction device that uses high-speed jets as a power to transmit kinetic energy and mass,which has no moving parts,with a simple structure,easy installation,reliable work,long life and other advantages,in many process applications has the superiority and irreplaceability,plays an important role in the development of the national economy.However,the disadvantage of the jet pump is that the mixing of the working fluid(jet)and the fluid(jet fluid)will lose a lot of energy,resulting in a lower efficiency of the pump,which limits the application of the jet pump to a certain extent.In this paper,the finite element software FLUENT17.0 was used to simulate the internal flow field of the liquid jet pump.The effects of the primary nozzle exit position(NXP),area ratio,nozzle structure and nozzle installation form on the flow pattern of the jet pump were studied,seeking the structural parameters and reasonable working conditions when the efficiency of the jet pump is high The main work was carried out as follows:Based on the single variable method,the fluid flow model of the liquid jet jet pump with different NXP and area ratio was constructed.The models are introduced into ICEM-CFD to be meshed and the various boundaries of the jet pump were set.The Mixture multiphase flow model and the standard k-? turbulence model are taken for numerical simulation.Using CFD-Post to extract the pressure and velocity distribution in the pump,extract the inlet and outlet pressure and mass flow data.The flow field performance of liquid-air jet pump with different structure size(area ratio,throat distance)is compared and analyzed,and the optimal NXP and area ratio is obtained under the better efficiency.Under the optimal NXP and optimal area ratio,the performance of the cosine,conical and cylindrical nozzles is compared,it was concluded that the change of the wall pressure of the cylindrical nozzle jet pump and the pressure change on the axis are larger than the cosine,the cone nozzle jet pump was larger The cylindrical nozzle due to the working fluid through the contraction section,the energy loss was the largest,the efficiency was lower than cosine and the cone nozzle.The flow characteristics of cosine and cone nozzle jet pump were similar,taking into account the cosine nozzle was not easy to process,cone nozzle was more reasonable for jet pump.Based on the optimal NXP and optimal area ratio of the jet pump,the internal flow field characteristics of the multi-nozzle liquid-jet jet pump were designed.The circular three nozzles,the triangular three nozzles,the ring four nozzles,the center four nozzles and the six nozzles,the total nozzle area of these five multi-nozzle jet pumps was equal to the single nozzle and simulate at the same boundary conditions.It could be concluded that the cylindrical three nozzles was the most efficient and the triangular three nozzles were the least efficient.To study the efficiency of the jet pump under different working conditions,the working fluid pressure and the mixed fluid outlet pressure were changed in turn to find a reasonable working fluid pressure range.It was founded that too high or too low working fluid pressure would reduce the efficiency of the pump;appropriate to reduce the mixed fluid outlet pressure could improve the efficiency of the jet pump,but too large outlet pressure could reduce the efficiency of the pump.Therefore,the pump inlet pressure and outlet pressure were needed to be strictly controled,to ensure the normal operation of the pump even efficienty.In this paper,the flow field of the liquid-jet pump was simulated and analyzed,the flow field distribution law of the NXP,the area ratio,the nozzle shape,the number of nozzles and the flow field of different working conditions(different working fluid pressure and mixed fluid outlet pressure)could be selected for the jet pump better structural parameters and operating conditions,the conclusions could provide a theoretical basis for the design for the jet pump. |
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