Structure Design And Flowfield Simulation Of Supersonic Swirling Separator

Natural gas dehydration and heavy hydrocarbon separation are twoimportant processes in surface operations of gasfiled. Traditionallow-temperature separation has been proven to be inefficient and require highcapital and operating cost. It is difficult to prevent freezing by heating wet gasand consumes amount of antihydrate agent. In order to solve those problems, anew gas conditioning process—supersonic swirling separator has beendeveloped.Based on the theory of gas dynamics, thermodynamics and fluiddynamics, the paper analyses the basic working principle of supersonicseparator and set up the mechanic models of compressible gas flow in Lavalnozzle, stabilizing tube, supersonic wing section and diffuser. By using CFDsoftware-FLUENT, the paper studies the distributions of velocity, temperatureand pressure in nozzle, wing section, diffuser and the whole separator. Bycomparison and analysis of different nozzles design methods, the paperpresents the optimum design method for the Laval nozzle. Subsonicconvergent section of Laval nozzle is designed according to double cubiccurve method, throat is designed as a smooth circular arc, and supersonicdivergent section is designed according to Foelsch method. The stream from this type of nozzle has preferable uniformity of velocity, less energy loss anddesigned Mach number after boundary-layer correction. The supersonic wingdesigned according to axial turbomachinery blade method is optimized, sothat centrifugal acceleration and swirl ratio can be increased. The simulationsof supersonic wing sections with single wing and double wings has been done.the results indicate the average tangential velocity more than 135m/s and swirlratio exceeding 0.35 at the outlet of wing section can be achieved, the swirlingseparation result is well. The comparison and analysis of different diffuserstructure show that the second throat diffuser has higher pressure recoverycapability, less pressure loss, and better brearing capability of pressurefluctuation.According to the swirling separation efficiency in the wing section, of water and of heavy hydrocarbon can be separated accordingto simulated computation. Hydrate formation will not occur because themaximum residence time of liquid droplets from the nozzle outlet to thediffuser outlet is about 9.6 milliseconds due to relatively slow hydrate-crystalgrowth. So the supersonic swirling separator can prevent freezing withoutantihydrate agent. As is shown by the simulation of Hysys, when the outletpressure is 4MPa the dew point of hydrocarbon decreases to whilehydrate formation temperature is 1.17 .The paper studies the distributions of the velocity, the temperature andthe pressure in the supersonic swirling separator by simulation and analysis.The shock wave is controlled between the supersonic wing and diffuser nearthe diffuser inlet. The shock wave dissipates the kinetic energy of the fluid stream, increases the swirl ratio and the swirling separationg efficiency, whichis the key factor to design the separator. The pressure recovery ratio iscontrolled between 40% and 47%, the separator can be in normal operation.