Study On Flow Field And Condensation Characteristics In Low-pressure Supersonic Cyclone Separator

In recent years,the state’s requirements for flue gas emissions from coal-fired boilers have become more stringent,and traditional flue gas purification equipment is approaching the technical bottleneck.To achieve the flue gas emission standard,according to traditional technologies,only the superimposed use of purification equipment can be used.The supersonic cyclone separator has the dual functions of condensation and separation,and has broad application prospects in the field of "dewhitening" of flue gas.In this paper,the structure of the supersonic cyclone separator is designed by using saturated humid air at atmospheric pressure,combining aerodynamic knowledge and thermodynamic theory.Numerical simulation is used to analyze the flow field in the supersonic cyclone separator at low pressure.The discrete phase model is used to study the droplet separation efficiency.A condensation model is established to study the condensation and liquefaction of water vapor in the supersonic nozzle process.Finally,a complete low-pressure dehydration experiment process of the supersonic cyclone separator is designed.The findings are as follows:(1)The angle of the swirler blade exit angle has a greater effect on the axial velocity and tangential velocity in the nozzle,and the larger the blade wrap angle,the greater the pressure loss generated by the swirler.The structure of the separator has a large impact on the flow field in the nozzle.When the B-type separator structure is used,the temperature in the supersonic swirl separator can reach a lower temperature,which is conducive to the condensation of condensable gas.(2)When a shock occurs,the temperature and pressure rise,but as the intensity of the shock increases,the pressure and temperature rise will increase,which is not good for gas condensation.As the pressure difference ratio increases and the shock position moves downstream,the gas in the nozzle can obtain better condensing conditions.As the inlet temperature rises,the overall temperature in the nozzle rises,which is not conducive to gas condensation,but it will not affect the intensity of the shock wave and the location of the shock wave.(3)There are two typical types of droplet trajectories in a supersonic cyclone;increasing the droplet radius and increasing the separator inlet length to diameter ratio can improve the droplet separation efficiency.(4)As the inlet pressure increases,the location of condensation in the nozzle advances,the droplet radius increases significantly,and the minimum content of water vapor in the nozzle decreases.Therefore,increasing the inlet pressure is beneficial to the condensation of water vapor.The inlet gas temperature is lowered,the steam condensation position is advanced,the droplet radius is significantly increased,and the number of droplets is reduced sharply,while the gas condensation depth is increased,and the water vapor content is reduced,which is beneficial to the condensation in the nozzle.As the water vapor content at the inlet increases,the location of vapor condensation advances,and the radius of the condensed droplets increases significantly.