| Jet vacuum pump is a kind of important energy conversion and fluid conveying device,which is widely used in the fields of energy,power,petrochemical,refrigeration and other fields.In this paper,in view of the existing problems of jet vacuum pump,such as high gas consumption,high flow loss,the characteristics of jet pumps were studied by using of numerical simulation,and the structure optimization of the jet vacuum pump was carried out.The influences of nozzle throat diameter,angle of width,nozzle distance,mixing chamber structure and diffuser on performances of jet pump were obtained.The working process curve of jet pump was given.Numerical simulation method and optimized method of jet pump were verified by experiments;a new nozzle,which employed tangential rotary and rotary top guide element combination was put forward to improve the efficiency of pump jet ejector.The flow field structure and influence of the jet pump model of swirl nozzle were analyzed.Finally,according to the problems of cleaning,discharging,transportation and recycling of the waste oil tanks,and combined with the characteristics of the application of jet vacuum pump,a new scheme for cleaning dirt in oil storage tank was put forward.The results show that the pressure of the working fluid after the exit of the nozzle is oscillating with the pressure of the injection fluid,and shock wave in the jet pump usually appears at the beginning of the nozzle exit and the diffuser.Through numerical simulation and optimization of structure parameters of jet pump,the injection coefficient and the working performance of jet pump can be improved.After optimizing the injection coefficient of the ejector vacuum pump is 0.18,the pre injection coefficient is 0.15,the injection coefficient is increased by 20%,and the limit vacuum degree is increased by 26.7%.Under certain conditions,there exists a critical value of the outlet pressure of the jet pump and a maximum injection coefficient.When the injection coefficient is zero,there is a limit vacuum degree of the jet pump under different working fluid pressure.When the working fluid exceeds the pressure,the vacuum will not change,but the gas consumption will increase.Compared with the conventional vortex nozzle,the new swirl nozzle has a stronger suction force,which is due to the high speed rotation of the flow field,and a rotating centrifugal pressure field is generated in the radial direction of the nozzle.The position of the mixing of the two strands of the swirling jet is ahead of schedule,compared with the general free jet,it has the characteristics of high turbulence degree and strong entrainment ability.The swirl injection coefficient is better than that of ordinary injection,and the advantage is more obviously with the increase of working fluid pressure.The cleaning device of the dirt in the oil storage tank has the advantages of high flexibility,time saving,labor saving and high efficiency.The research on the structure and application of jet vacuum pump has guiding significance in engineering practice. |
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