气体喷射压缩器变工况激波特性分析与试验
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摘要
为了解不同操作压力下的激波特性,采用试验与数值分析相结合的方法,测得不同出口压力下(0.105,0.110,0.115,0.120,0.125,0.130,0.135 MPa)的喷射系数;采用FLUENT赫数分布;对试验值与仿真值进行对比分析,平均误差率为12.5%,验证了模型的准确性。结果表明:受操作工况的影响,压缩器喷嘴出口处和扩散器内出现了激波,且在工作压力和引射压力一定的情况下,喷嘴出口处的激波是不随出口压力的变化而改变的;压缩器出口压力为0.105～0.12 MPa激波,双激波使得流体由超音速减至亚音速时消耗了大量的能量,而单激波时消耗能量则较少;压力为0.135 MPa时,喷射器出现回流,不能正常工作;在出口压力为0.125 MPa,吸入口压力为0.074 MPa,当工作压力为0.4 MPa时,压缩器内部出现微弱激波,且工作压力越大,激波现象越严重。
In order to understand the characteristics of shock wave at different operating pressures,the method of combination of experimental analysis with numerical analysis was used to measure the entrainment ratio under different outlet pressures(0.105,0.110,0.115,0.120,0.125,0.130,0.135 MPa) by a throttle valve. The computational fluid dynamics(CFD)software FLUENT was adopted to analyze internal static pressure distribution and Mach number distribution under different outlet pressures and working pressures. The experimental values were compared with the simulated values for fitting analysis. The average error rate is 12.5%,which verified the accuracy of the model. The results show that shock waves appeared at the nozzle outlet of the air ejector and within the diffuser due to the impact of the operating conditions,and under a fixed working pressure and ejection pressure,the shock waves at the nozzle outlet did not change with the change of outlet pressure. When the outlet pressure of the ejector was 0.105 MPa～0.12 MPa,double shock waves appeared within the diffuser. When the pressure was 0.125～0.13 MPa,single shock waves appeared within the diffuser,the double shock waves consumed a lot of energy in the diffuser section when the flow speed was reduced from supersonic speed to subsonic speed,whereas the single shock waves consumed less energy. But when outlet pressure was 0.135 MPa,reverse flow appeared and the air ejector was unable to operate. The weak shock wave occurred at the outlet pressure of 0.125 MPa,the suction pressure of 0.074 MPa and working pressure of 0.4 MPa,and the higher the working pressure,the more severe the shock wave.
In order to understand the characteristics of shock wave at different operating pressures,the method of combination of experimental analysis with numerical analysis was used to measure the entrainment ratio under different outlet pressures(0.105,0.110,0.115,0.120,0.125,0.130,0.135 MPa) by a throttle valve. The computational fluid dynamics(CFD)software FLUENT was adopted to analyze internal static pressure distribution and Mach number distribution under different outlet pressures and working pressures. The experimental values were compared with the simulated values for fitting analysis. The average error rate is 12.5%,which verified the accuracy of the model. The results show that shock waves appeared at the nozzle outlet of the air ejector and within the diffuser due to the impact of the operating conditions,and under a fixed working pressure and ejection pressure,the shock waves at the nozzle outlet did not change with the change of outlet pressure. When the outlet pressure of the ejector was 0.105 MPa～0.12 MPa,double shock waves appeared within the diffuser. When the pressure was 0.125～0.13 MPa,single shock waves appeared within the diffuser,the double shock waves consumed a lot of energy in the diffuser section when the flow speed was reduced from supersonic speed to subsonic speed,whereas the single shock waves consumed less energy. But when outlet pressure was 0.135 MPa,reverse flow appeared and the air ejector was unable to operate. The weak shock wave occurred at the outlet pressure of 0.125 MPa,the suction pressure of 0.074 MPa and working pressure of 0.4 MPa,and the higher the working pressure,the more severe the shock wave.
引文
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[21]Zhu YW,Wen C,Li Y.Simplified ejector model for control and optimization[J].Energy Conversion and Management,2008,49(6):1424-1432.
[2]许树学,马国远,刘挺,等.带有喷射器的热泵冷冻干燥装置设计与性能分析[J].农业机械学报,2008(11):225-226.
[3]杨勇,李熠桥,沈胜强,等.蒸汽喷射器中的激波效应[J].工程热物理学报,2014(7):1419-1423.
[4]Bartosiewicz Y,Aidoun Z,Desevaux P,et al.Numerical and experimental investigation on supersonic ejectors[J].International Journal of Heat and Fluid Flow,2005,26(1):56-70.
[6]丁学俊,刘书勇,徐鑫.蒸汽喷射器的CFD数值模拟[J].流体机械,2011,39(4):21-25.
[6]王静,韩立夫,刘道启,等.结构参数对大气喷射器性能影响的数值模拟分析[J].内蒙古师范大学学报(自然科学汉文版),2011(3):243-245.
[7]黄思,罗力,杨国蟒.液环泵喷射器三维流场数值模拟分析[J].机械设计与制造,2012(5):111-112.
[8]李金梦,郑宏亮,刘霞,等.基于计算流体力学模拟的蒸汽喷射器结构优化[J].流体机械,2016,44(7):42-46.
[9]田静,刘祥灿,杜丽超,等.蒸不同温度气体喷射特性的PIV试验研究[J].流体机械,2016,44(10):9-18.
[10]王鹏,王忠,瞿磊,等.高压喷射喷孔结构参数对空化现象的影响[J].排灌机械工程学报,2017,35(12):1063-1068.
[11]李海军,沈胜强.蒸汽喷射制冷系统中喷射器内特殊流动现象的研究[J].工程热物理学报,2006(3):454-456.
[12]张军强.蒸汽喷射凝结流动模拟研究[D].锦州:辽宁工业大学,2014.
[13]薛凤娟.气液两相喷射器的试验研究[D].大连:大连理工大学,2008.
[14]Yosr Allouche,Chiheb Bouden,Szabolcs Varga.A CFD analysis of the flow structure inside a steam ejector to identify the suitable experimental operating conditions for a solar driven refrigeration system[J].International Journal Refrigeration,2014,39(3):186-195.
[15]Pianthong K,Seehanam W,Bahnia M,et al.Investigation and improvement of ejector refrigeration system using computational fluid dynamics technique[J].Energy Conversion and Management,2007,48(9):1160-1166.
[16]Bartosiewicz Y,Aidoun Z,Mercadier Y.Numerical assessment of ejector operation for refrigeration applications based on CFD[J].Applied Thermal Engineering,2006,26(5-6):604-612.
[17]Rusly E,Aye L,Charters WWS,et al.CFD analysis of ejector in a combined ejector cooling system[J].International Journal Refrigeration,2005,28(7):1092-1101.
[18]Sriveerakul T,Aphornratana S,Chunnanond K.Performance prediction of steam ejector using computational fluid dynamics:part2.Validation of the CFD result[J].International Journal of Thermal Science,2007,46(8):823-833.
[19]Sriveerakul T,Aphornratana S,Chunnanond K.Performance prediction of steam ejector using computational fluid dynamics:part1.Validation of the CFD result[J].International Journal of Thermal Science,2007,46(8):812-822.
[20]周良富,周立新,薛新宇,等.射流式在线混药装置汽蚀特性数值分析与试验[J].农业工程学报,2015(7):60-65.
[21]Zhu YW,Wen C,Li Y.Simplified ejector model for control and optimization[J].Energy Conversion and Management,2008,49(6):1424-1432.