The Study On Thermal Steam Recompression Mechanism And Supercharging Characteristics

Any discharge of salt and even high-salt wastewater has caused a serious impact on our environment,which has caused widespread concern.At present,only the thermal technology of high salt wastewater is technically feasible,and its thermal economy is the key issue.In the thermal technology,the latent heat of the secondary steam can be effectively utilized by embedding the steam recompression device into the multi-effect evaporation process of the salt wastewater,that has a significant energy saving effect.Mechanical vapor recompression technology is the best for thermal economy,but the development of core vacuum steam compressors is difficult,and this technology promotion is very slow.Thermal vapor recompression(TVR)utilizes low quality drive steam to achieve partial utilization of secondary steam latent heat that has a certain energy saving effect and a wide range of applications.Currently,the core equipment of TVR technology includes steam ejector based on steady flow and the pressure exchange ejector and the wave rotor supercharger based on unsteady flow,etc.Their supercharging and ejecting properties directly affect the thermal economy of TVR technology.This paper completes the steam ejector design verification procedure,and completes the structure of the static steam ejector and its performance with the wave rotor booster to be fully studied,based on that this paper proposes a three-space momentum exchange mechanism for driving steam and secondary steam.This paper attempts to place the swirl generation element upstream and downstream of the drive nozzle to introduce circumferential momentum exchange,enhance the momentum exchange capacity,and reduce the axial size of the steam ejector.This paper mainly through the numerical analysis and experimental research methods to complete the following related work:(1)Based on water vapor thermodynamics model,the design and verification procedures of gas dynamics and thermodynamics model are established,and the error of design result and experimental result is less than 22.5%.Based on this,the use of computational fluid dynamics to complete the steam ejector structure optimization work.It is found that the four main structural parameters of angle between the nozzle expansion section and the axial direction,the length of the constant section,the driving nozzle outlet and the constant section inlet of the mixing chamber,the constant section of mixing chamber radius have an optimal value to maximize the entrainment ratio.(2)Complete the salt water treatment experimental platform,and embedded a variety of steam ejectors and wave rotor supercharger in the salt water treatment experimental platform.Based on this experimental platform,the experimental study of traditional steam ejector and wave rotor supercharger are completed.And it was found that under the same conditions,the supercharging ratio of the wave rotor supercharger is 185% higher than that of the traditional steam ejector.However,compared with the wave rotor supercharger,the steam ejector has the advantages of simple structure,no dynamic sealing and excellent ejection performance,so it is easier to be further studied and improved.(3)In view of the shortcomings of the traditional steam ejector momentum exchange capacity,two kinds of space momentum exchange enhancement mechanism solution are proposed by placing the swirl generation element upstream and downstream in the drive nozzle to form Pre-Static Cyclone Steam Ejector(Pre-SCSE)and Post-Static Cyclone Steam Ejector(Post-CDSE).In this paper,a detailed numerical analysis and experimental study are carried out,and the relevant conclusions are as follows:(1)The Pre-SCSE and Post-CDSE can improve the space momentum exchange significantly.The effective dynamic pressure ratio(DPR)of the Post-SCSE which own 8 teeth and 1mm high teeth to Pre-SCSE increased by 17.3 times,which means that the Post-SCSE has a higher space momentum exchange capacity.(2)Under standard operating conditions,the increased DPR can short the main jet and condensate area of the Pre-SCSE,so the length of the mixing chamber can be shortened.In the chocked flow region,the increased DPR can improve the entrainment ratio of Pre-SCSE,and the entrainment ratio of Pre-SCSE is higher than that of traditional steam ejector significantly.(3)The radial turbulence intensity and turbulence range of Post-SCSE are wider in the mixing chamber,and the mixing chamber length of Post-SCSE is reduced up to 20.8% compared to the traditional steam ejector.Under standard operating conditions,the entrainment ratio of Post-SCSE in this paper are higher than those of traditional steam ejectors.The change in the number of teeth and the height of tooth have an impact on the entrainment ratio,the main jet length,the shape of the radial main jet in the mixing chamber and the near-wall condensation area of the Post-SCSE.The increase in tooth height can shorten the maximum length of the mixing chamber by 20%.(4)Based on the static cyclone steam ejector,this paper proposes a Post-Cyclone Dynamic Steam Ejector(Post-CDSE)and declares two national invention patents(201510286589.0?201710042657.8).the numerical analysis of Post-CDSE find: the length of the Post-CDSE mixing chamber could be much shorter than that of traditional steam ejector;The rectification ring at the outlet of the Post-SCSE mixing chamber could recycle the tangential velocity back to axial velocity.