Study On Gas Separation Performance Of Vortex Tube With Supersonic Inlet Nozzles

The supersonic gas separation technology is a novel gas mixture separation technology appeared in recent years.In the supersonic gas separation process,heavy components of gas mixture condense under the low-temperature condition created by supersonic gas flow itself and then separated from gas phase by the centrifugal force caused by the self-rotation of two -phase flow.This technology conducts expansion,cyclone gas/liquid separation and re-compression in a compact,tubular device with no rotating part,with the advantage including simple structure,small occupied space,low energy consumption and investment cost,and high isentropic efficiency etc.Thus,it has wide application foreground in the gas mixture separation area such as dehydration and purification of Natural Gas.However,the supersonic state of gas flow in the separation section shortens the contact and separation time of gas and condensed droplets,leading to the infaust effect on the separation performance.To overcome this shortcoming,the separation technology based on the two-phase vortex tube is proposed,combining the supersonic gas separation technology and vortex flow effects together.On the basis of two-phase vortex separating technology,a new vortex structure with supersonic nozzles is proposed.A numerical model has been established to simulate the flow behavior of gas flow in this new type of vortex tube.The numerical results indicate that the mixed gas can be separated by the new device.An experimental platform is set up to investigate the separation performance of the new device and the influential trend of operational and structural parameters on the separation performance are found out.In order to improve the performance of vortex tube with supersonic nozzle for mixed gas separation,the condensed droplet size is enlarged by adding nucleation centers.Based on the heterogeneous nucleation theory,the adoption requirements of additional nucleation centers are analyzed.Finally,the added nucleation centers are determined,i.e.micro-droplets with lower volatility which are soluble and not reacted with heavy component.Using Discrete Phase Model,the movement states of injected droplets in the vortex tube are analyzed and the influences of operational and structural parameters on the separation performance are also predicted. The gas mixture separation performance of vortex tube with supersonic nozzle using droplet enlargement method is experimentally researched.The medium is air-ethanol steam mixture and the external condensation nucleuses are micro water drops.Experimental results shows that the separation performance of the equipment is improved by a certain degree using the droplet enlargement method.The maximums of the heavy component removal rate and the dew point depression are 33.73%and 17.8K,increased by 17.85%and 3.55K respectively. Furthermore,the effects of the operational and structural parameters on the separation performance is studied,and the influence trend consistent well with the numerical prediction.