| At present,although the throttle valve of the key equipment in the throttling process of natural gas wellhead gas transmission station has a good antihypertensive effect,the disadvantage is that the gas temperature drops sharply after throttling,leading to ice blockage,seriously endangering the operation of pipeline and equipment,and has to be medicated or heated,which undoubtedly increases the operation steps and operation cost.Vortex tube is widely used in cooling and heating industry with unique energy separation effect.In this paper,the physical model and operation parameters of large-diameter throttling vortex tube are simulated and optimized by software,and the energy separation effect of vortex tube is verified by cross-validation of bench test.The work and achievements are as follows:The geometry size of vortex tube that meets the requirements of gas transmission station is optimized,and a three-dimensional model is established for numerical simulation.The variation trend of temperature,pressure and velocity parameters in axial and radial positions of internal flow field is studied.It is found that: Under high pressure conditions,the vortex tube can not only throttle and reduce the pressure,but also reduce the temperature drop range before and after throttling.The high temperature gas formed can wrap the low temperature gas,and this temperature distribution gradient can avoid the phenomenon of ice blocking.Based on this model,the main components are optimized : keeping inlet high pressure and cooling rate constant,the fixed inlet flow channel type is tangent to straight pipe,and the number of changes is 2,4,6 and 8.The diameter of fixed hot end pipe is 80 mm,the length is1236,1336,1436,1536,1636,1736mm;the length of the fixed cold end pipe is 240 mm and the diameter is 36,38,40,42,44 mm,and changed the diameters to 36,38,40,42,44mm;Fixed inlet pressure and geometry,varying cooling rate from 0.1 to 0.9(0.1 interval).The comparison show that when the inlet flow channel is 4,the L/D of hot end section is1436/80 mm,the L/D of cold end section is 240/40 mm,and the cooling rate is 0.5,the effect of throttling and reducing the temperature drop interval is the best,and the externally rotating high-temperature gas flows close to the tube wall to the hot end outlet,and the internally rotating low-temperature gas flows along the axis to the cold end outlet.If the external heat transfer loss is not considered,the vortex tube can throttle the high-pressure gas of 12 MPa,298.15 K to about 9MPa,and the the temperature is barely unchanged.At the same time,the experimental model of vortex tube is made by assembly bench test.The maximum pressure is 1.0Mpa,and the inlet pressures of 0.6 MPa,0.7 MPa,0.8 MPa,0.9MPa and 1.0 MPa are selected to study the variation law of temperature at the pipe wall and the variation trend of inlet and outlet pressure.The results show that with the increase of inlet pressure,the throttling effect of vortex tube is better,and the larger the inlet pressure is,the larger the throttling range is,but the temperature drop range before and after throttling is reduced.Finally,the throttle valve and vortex tube are used as the key equipment to establish the throttle and step-down process of natural gas wellhead gas transmission station.Finally,the throttle valve and vortex tube as the key equipment to establish natural gas wellhead gas station throttling step-down process comparison found that the latter can simplify the process,reduce heating or dosing equipment,reduce enterprise investment and operating costs. |
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