气液混合流体的体积弹性模量理论模型研究
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摘要
气液混合流体的体积弹性模量是流体本身的物理性质,直接影响流体传动的准确性、快速性和稳定性。建立准确的气液混合流体体积弹性模量理论模型是实现流体机械设计和优化的基础,具有重要的理论和工程应用价值。通过分析流体空化演变过程,在亨利定律的基础上,运用五次多项式法建立流体内气相组分含量与压力间的数学模型,推导出气液混合流体体积弹性模量理论模型(Model1)。结合物理试验样本数据,选取三种流体体积弹性模量理论模型与Model1的计算结果进行对比,并分析初始含气量和流体压力对气液混合流体体积弹性模量的影响规律。研究结果表明:Wylie与Nykanen模型在等温条件下的体积弹性模量差别很小,在全压力范围内的体积弹性模量均比较接近;Ruan模型在高压区的体积模量预测结果偏大,而在低压区与Wylie模型比较接近;所建立的Model1模型的体积弹性模量预测结果与物理试验实测点更接近,且在考虑低压区流体呈现气态特性的基础上,给出了更加准确的低压区气液混合流体体积弹性模量预测方法。本项研究可为建立准确的气液混合流体体积弹性模量理论模型提供参考。
The bulk elastic modulus of the air and liquid mixing fluid is the inherent physical property, and it has direct effects on the accuracy, rapidity and stability of fluid driving. An accurate model to calculate the bulk elastic modulus is the basis for the design and optimization of the fluid machinery, and it is of great value to the theory and engineering. By analysing the evolution process of the cavitation in the fluid and Henry's law, a quintic polynomial is proposed to fit the theoretical relationship air content and pressure, and then a theoretical model(Model 1) to calculate the bulk elastic modulus of the air and liquid mixing fluid is obtained. Compared with the experimental date, the results of different models are analysed and the effects of the pressure and air content on the fluid bulk elastic modulus are revealed. The investigation shows that Wylie and Nykanen models have a little difference under isothermal conditions, and the bulk elastic modulus of both are approximate within the full pressure range; the values of Ruan model are larger within high pressure range and close to the values of Wylie model within low pressure range; the values of Model1 is the closest model to the experimental data, and it provides a more accurate method to predict the bulk elastic modulus of the fluid within law pressure range, in which the liquid phase will turn into gas phase. The investigation will provide the reference to a better prediction of the bulk elastic modulus of the air and liquid mixing fluid.
The bulk elastic modulus of the air and liquid mixing fluid is the inherent physical property, and it has direct effects on the accuracy, rapidity and stability of fluid driving. An accurate model to calculate the bulk elastic modulus is the basis for the design and optimization of the fluid machinery, and it is of great value to the theory and engineering. By analysing the evolution process of the cavitation in the fluid and Henry's law, a quintic polynomial is proposed to fit the theoretical relationship air content and pressure, and then a theoretical model(Model 1) to calculate the bulk elastic modulus of the air and liquid mixing fluid is obtained. Compared with the experimental date, the results of different models are analysed and the effects of the pressure and air content on the fluid bulk elastic modulus are revealed. The investigation shows that Wylie and Nykanen models have a little difference under isothermal conditions, and the bulk elastic modulus of both are approximate within the full pressure range; the values of Ruan model are larger within high pressure range and close to the values of Wylie model within low pressure range; the values of Model1 is the closest model to the experimental data, and it provides a more accurate method to predict the bulk elastic modulus of the fluid within law pressure range, in which the liquid phase will turn into gas phase. The investigation will provide the reference to a better prediction of the bulk elastic modulus of the air and liquid mixing fluid.
引文
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[12]路甬祥.液压气动技术手册[M].北京:机械工业出版社,2002.LU Yongxiang.Hydraulic pneumatic technical manual[M].Beijing:China Machine Press,2002.
[2]CHEN Y,WANG N,GU L.On-line measuring method of effective bulk modulus in hydraulic system based on frequency analysis[J].International Journal of Fluid Machinery&Systems,2018,11(1):13-20.
[3]ZHOU J,VACCA A,MANHARTSGRUBER B.A novel approach for the prediction of dynamic features of air release and absorption in hydraulic oils[J].Journal of Fluids Engineering,2013,135(9):1790-1791.
[4]SINGHAL A.Mathematical basis and validation of the full cavitation model[J].Journal of Fluids Eng.,2002,124(3):617-624.
[5]ZHAO Yu,WANG Guoyu,HUANG Biao,et al.Acavitation model for computations of unsteady cavitating flows[J].Acta Mechanica Sinica,2016,32(2):273-283.
[6]WYLIE E B,STREETER V L.Fluid transients[M].Osborne McGraw-Hill,1978.
[7]魏超,周俊杰,苑士华.液压油体积弹性模量稳态模型与动态模型的对比[J].兵工学报,2015,36(7):1153-1159.WEI Chao,ZHOU Junjie,YUAN Shihua.Comparision of steady and dynamic models for the bulk modulus of hydraulic oils[J].Acta Armamentarii,2015,36(7):1153-1159.
[8]RUAN J,BURTON R.Bulk modulus of air content oil in a hydraulic cylinder[C]//ASME 2006 International Mechanical Engineering Congress and Exposition Nov.5-10,2006.Fluid Power Systems and Technology,2006:259-269.
[9]YANG Huayong,FENG Bin,GONG Guofang.Measurement of effective fluid bulk modulus in hydraulic system[J].Journal of Dynamic Systems Measurement&Control,2011,133(6):061021.
[10]HRUZIK L,VASINA M,BURECEK A.Evaluation of bulk modulus of oil system with hydraulic line[C]//European Physical Journal Conferences.EDP Sciences,2013:333-336.
[11]KIM S,MURRENHOFF H.Measurement of effective bulk modulus for hydraulic oil at low pressure[J].Journal of Fluids Engineering,2012,134(2):021201.
[12]路甬祥.液压气动技术手册[M].北京:机械工业出版社,2002.LU Yongxiang.Hydraulic pneumatic technical manual[M].Beijing:China Machine Press,2002.