Shock waves in the nozzle during supersonic separation under different conditions can disrupt the flow field’s thermodynamic equilibrium.While it contributes to the recovery of pressure energy,it also leads to the di...Shock waves in the nozzle during supersonic separation under different conditions can disrupt the flow field’s thermodynamic equilibrium.While it contributes to the recovery of pressure energy,it also leads to the dissipation of mechanical energy.This study aimed to investigate the effects of changes in back pressure on the shock wave position and its subsequent impact on the refrigeration performance of nozzles.A mathematical model for the supersonic gas in a nozzle was established and evaluated via experiments.The results show that when the back pressure is less than 0.2 MPa,no shock wave is generated in the nozzle,and high refrigeration and liquefaction efficiency can be ensured while effective pressure recovery is achieved.When the back pressure(pb)is increased from 0.3 to 0.6 MPa,the refrigeration efficiency of the nozzle decreases,and the shock wave position(x shock)is advanced from 157 to 118 mm.The maximum Mach number(Ma)that can be reached by the fluid in the nozzle is reduced from 1.97 to 1.27.When the back pressure is increased from 0.2 to 0.6 MPa,the minimum temperature is increased by 55.18 K.When the back pressure is greater than 0.3 MPa,the Mach number upstream of the shock wave is reduced from 1.97 to 1.27,the shock wave intensity is weakened,and the thickness of the boundary layer separation caused by the shock wave is also decreased accordingly.Therefore,to ensure refrigeration efficiency,measures should be taken to control the back pressure within a reasonable range.展开更多
目的天然气加臭是保障天然气泄漏迅速识别和安全使用的重要手段,为保证加臭剂质量浓度符合标准规范且避免过量加臭,建立一种准确高效的分析方法对天然气中加臭剂进行检测。方法采用光离子化气相色谱法(gas chromatography with photoion...目的天然气加臭是保障天然气泄漏迅速识别和安全使用的重要手段,为保证加臭剂质量浓度符合标准规范且避免过量加臭,建立一种准确高效的分析方法对天然气中加臭剂进行检测。方法采用光离子化气相色谱法(gas chromatography with photoionization detection,GC-PID),设置操作流程,优选分析参数,通过实验室评价和现场应用,系统考察GC-PID法的有效性、抗干扰性、检出限、重复性、准确性和现场适用性,验证其对四氢噻吩和无硫加臭剂的检测能力。结果建立的方法对加臭剂具有高选择性,定量准确性高,在2.00~150.00 mg/m^(3)范围内,对四氢噻吩的相对标准偏差<1.5%,检出限为0.40 mg/m^(3)。GC-PID法具有良好的现场适用性,具有良好的数据准确性和稳定性。结论基于GC-PID法开发的该天然气中四氢噻吩和无硫加臭剂的检测方法,为加臭剂质量浓度的在线监测和便携检测提供了新途径,具有实际应用价值与推广前景。展开更多
基金supported by the National Science and Technology Major Project of China(2025ZD1406703)the Open Fund of Key Laboratory of Oil&Gas Equipment,Ministry of Education(Southwest Petroleum University)(Grant No.OGE20230206).
文摘Shock waves in the nozzle during supersonic separation under different conditions can disrupt the flow field’s thermodynamic equilibrium.While it contributes to the recovery of pressure energy,it also leads to the dissipation of mechanical energy.This study aimed to investigate the effects of changes in back pressure on the shock wave position and its subsequent impact on the refrigeration performance of nozzles.A mathematical model for the supersonic gas in a nozzle was established and evaluated via experiments.The results show that when the back pressure is less than 0.2 MPa,no shock wave is generated in the nozzle,and high refrigeration and liquefaction efficiency can be ensured while effective pressure recovery is achieved.When the back pressure(pb)is increased from 0.3 to 0.6 MPa,the refrigeration efficiency of the nozzle decreases,and the shock wave position(x shock)is advanced from 157 to 118 mm.The maximum Mach number(Ma)that can be reached by the fluid in the nozzle is reduced from 1.97 to 1.27.When the back pressure is increased from 0.2 to 0.6 MPa,the minimum temperature is increased by 55.18 K.When the back pressure is greater than 0.3 MPa,the Mach number upstream of the shock wave is reduced from 1.97 to 1.27,the shock wave intensity is weakened,and the thickness of the boundary layer separation caused by the shock wave is also decreased accordingly.Therefore,to ensure refrigeration efficiency,measures should be taken to control the back pressure within a reasonable range.
