Effect Of Blade Rectification On Vortex Tube Performance

Vortex tube is an energy separation device in field of dehydration and dehydro carbonation of natural gas.According to investigations,high-speed swirl in the tube will lead to energy dissipation and viscous loss,which would degenerate the performance of vortex tube.Therefore,a three-dimensional blade rectifier is designed and proposed for the flow phenomena at the inlet and outlet of the vortex tube,which converts the swirl into parallel flow to achieve efficient recovery of energy.Combining theory,simulation and experiment,the whole process includes designing detailed structure of the rectifier and the swirl tube based on the principle of gas dynamics and energy transfer,building experimental platform and studying the effect of the rectifier on the cooling efficiency and structure size of the swirl tube.The specific contents and main conclusions are as follows:(1)The internal flow law of the swirl tube was analyzed and the structure of threedimensional blade rectifier was designed.It is found that the flow field inside the swirl tube changes obviously to different pressure ratios.When the pressure ratio is low,the horizontal angle of tangential velocity of airflow is small,so the refrigeration efficiency is higher when the inlet angle of the rectifier blade is small.When the pressure ratio is high,the horizontal angle of tangential velocity of the airflow is large,so the refrigeration efficiency is higher when the inlet angle of the rectifier blade is larger.The intermediate alignment was added to smooth the blade transition and reduce the air impact loss.Gradual diffuser is used among blades to further recover gas energy.(2)The influence of different structure parameters and installation position of rectifier on the cooling efficiency of vortex tube was determined by numerical simulation.As for number of blades of the rectifier,according to the simulation results,when the number of blades is 4,the rectification effect is the most obvious.When the number is less than 4,the rectification effect decreases,while when the number is higher than 4,the flow loss among blades increases and the comprehensive refrigeration efficiency decreases.According to the simulation analysis of the inner and outer diameters of the swirl tube blades,it is found that the optimum inner and outer diameters of the cold-end rectifier are 10 mm and 40 mm respectively,while the optimum inner and outer diameters of the hot-end rectifier are 6 mm and 20 mm respectively.Increasing or decreasing the size will have adverse effects on the flow.For the hot-end rectifier,the installation in front of the hot-end valve will increase the refrigeration efficiency most.(3)The experimental platform of vortex tube was set up and different structures and operation parameters were adjusted for relevant research.The results show that when rectifiers are installed at both ends at the same time,the refrigeration efficiency is obviously improved.For the pressure ratio of 3,the installation of rectifier can increase the unit refrigeration capacity by 65% and the refrigeration temperature effect by 35%.For the fixed working conditions,under the premise of meeting the refrigeration efficiency requirements,by increasing the rectifier structure,the length-diameter ratio of the hot end tube can be significantly shortened,the space utilization ratio of the equipment can be improved,and the equipment investment can be reduced.