| In recent years,the Supersonic Gas Separation(SGS) Technology for gas mixture separation has attracted great attention.It conducts expansion,cyclone gas/liquid separation and re-compression in a compact,tubular device with no rotating part.The low temperature needed by the condensation of heavy component is generated by the supersonic gas flow state and is lower than that of turboexpander.Comparing with thetraditional gas mixture separation technology,such as solvent absorption by liquid and solid,membrane separation and condensing separation,it has advantages including simple structure,small occupied space, low energy consumption and investment cost,and high iso-entropic efficiency etc.However, at present,the foreign and domestic studies are at confidential and beginning stage respectively so that little research work on this technology has been done.This dissertation is aimed to study rotating supersonic condensing flow behavior of gas mixture during the supersonic gas separation process,deveople new structure of the SGS device,and explore effective method for the improvement of device separation performance.To accomplish these objectives,a three-Dimensional numerical model for the rotating supersonic condensing flow of gas mixture has been set up and it can be used to predict the feasibility and the factor influences of SGS device.A novel SGS device with ring-section supersonic nozzle has been proposed and two effective strategies have been put forward to improve device separation performance.Series of simulations and experiments are carried out to study the separation performance of proposed SGS device and validate the two mentioned strategies.The main research work and achievements are as following.①An Eulerian two-fluid model for the spontaneous condensing flow of gas mixture is put forward.In this model,the governing equations of two phase flow are established based on the Eulerian-Eulerian method,considering the velocity slip between phases and thus actually revealing the flow field of droplet phase.CNT is adopted to describe the spontaneous nucleation of vapor,simulating the phase change behavior of gas mixture during the complex condensation and flow process.A RNG k-ε-k_p model is set up to close the turbulent two phase flow,introducing the influence of tense rotation and compressibility of gas phase and the influence of droplets on the flow turbulence.CFD software is employed to solve the governing equations of two phase turbulent flow,so the model is able to conduct the simulation of condensing gas flow with complex three-dimensional characteristic.An interface program is compiled using C language to add droplet governing equations and the phase change model into CFD software.The simulation results of this model are in good accordance with the experimental data,and more closer to the reality than the one-dimensional simulation results.Furthermore,the multi-dimension distribution of gas condensation and flow parameters and the influence of boundary on the condensing flow can also be obtained.②In virtue of the established Eulerian two-fluid model,the rotating supersonic condensing flow of gas mixture is simulated.It is found that in this process,the distribution of flow and condensation parameters on the nozzle cross-section is unsymmetrical.The existence and enhance of rotation make the spontaneous condensation happen closer to the nozzle throat,the maximum nucleation rate decrease and the length of condensation zone shorten.Decreasing inlet temperature and increasing inlet pressure,the area ratio of nozzle outlet to throat as well as inlet relative humidity make the spontaneous condensation happen closer to the nozzle throat and the length of condensation zone shorten.Increasing the inlet temperature and the area ratio of nozzle outlet to throat,and decreasing the inlet pressure and relative humidity can make the maximum nucleation rate increase.③In virtue of the established Eulerian two-fluid model,the feasibility of four designed supersonic nozzles with circular-section is predicted,and a novel SGS device,the SGS Device with Inner Pyramid,is proposed.This device has ring-section supersonic nozzle and the convergence and divergence of cross-section area is actualized by changing outer diameter of the inner pyramid.Comparing with the existed supersonic nozzle with circular section,the supersonic nozzle with ring section has the advantages including easy to machining,low pressure loss and short settlement distance for droplets.Furthermore,the condensation and flow of moist air in the SGS Device with Inner-Pyramid is simulated,based on which,an effective strategy for the improvement of device separation performance,enlarging size of condensed droplet,is brought forward.④Aiming at the strategy of enlarging the size of condensed droplet,the method of adding nucleation center is proposed.By the theoretical analysis,inertia micro droplets which are mutually soluble with the vapor component are determined as the nucleation centers.A simplified model for liquid injection is set up,based on which,the spray process of injected liquid in the gas flow of air-ethonal is simulated combining with the Descerate Partical Model. By synthetically analyzing the size and movement of sprayed droplets and the supersaturation state of gas phase,the liquid injection location of SGS Device with Inner-Pyramid is determined,on the outer wall of inner-pyramid near the throat of supersonic nozzle.⑤The experiment apparatus and the related experiment technique of supersonic gas separation process are established to study the separation performance of SGS Device with Inner-Pyramid.The experimental results show that the separation performance of SGS Device with Inner-Pyramid is obviously better than that of the SGS Device with circular-setion supersonic nozzle.Comparing to the SGS Device with circular iso-diameter and iso-diameter diverging alternated separation tube,the separation performance of SGS Device with Inner-Pyramid is much better with the removal rate and dew point depression of about 21.8%, 4.3K and 13.7%,2.7K respectively.After the proposed droplet enlargement method is adopted,the separation performance of SGS Device with Inner-Pyramid is ulteriorly improved and the removal rate and dew point depression can reach 52.1%and 29.0K,with the improvement of 30.3%and 8.1 respectively.
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