容器放气过程的数值模拟及热力学模型研究
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摘要
容器放出法是一种测试气动元件流量特性的方法,因其简便、节能、高效,故具有很高的应用价值。本课题基于国际合作研究项目,对放出法进行了基础理论和实验研究,其目的在于给国际标准组织提交一种通用的测试气动元件流量特性的新方法。本文采用了有限体积数值模拟、试验研究和理论分析相结合的方法,对容器放气过程的速度场和温度场的分布及变化规律、等温容器的特性及等温容器放出法、空容器放气过程的多变指数、放气过程的热力学模型及其应用进行了系统的研究,目的在于全面、直观地认识放气过程,提高放出法的测试精度,研究内容具有重要的理论价值和实际意义。
     文中首先建立了容器放气过程的数学模型,通过将等温容器内的填充物简化为一定孔隙率的多孔介质,利用Fluent软件对空容器和等温容器的放气过程进行数值仿真,得到了放气过程中速度场分布、温度场分布以及它们的变化规律。模拟结果表明:(1)速度场主要位于放气口附近很小的区域,容器内大部分区域在放气过程中速度接近于0;(2)容器内的温度场的分布和容器形状有关,最低温度位于容器中心,并且温度梯度随放气过程不断加大;(3)等温容器放气过程的温度变化范围要比空容器小约20倍,非常接近于等温过程。最后,通过实验对仿真结果进行验证,结果表明,容器内压力曲线的仿真结果和实验结果非常吻合,容器内空气的平均温度的仿真结果和实验结果尽管有一定误差,但仍能正确反映温度变化的趋势和规律。其次,等温容器的等温特性直接决定其使用性能。因此,本文对不同条件下等温容器放气过程的温度变化规律进行了全面的研究。实验结果表明,容器内填充细金属丝可以显著增强热交换,使放气过程的温降很小,并可近似为等温过程。但放气过程的温降受到很多因素的影响,在放气初始压力和放气口固定的条件下:填充密度一定时,金属丝的线径越细等温效果越好;填充物只要是金属丝,材质影响不大;金属丝的填充密度越大,等温效果越好。另外,在充气压力和填充密度一定的情况下,放气速度越快,等温性能越差。通过实验可知:在放气初始压力为700kPa、50μm铜丝填充密度0.3kg/L的条件下,要形成等温容器,则容器的容积(L)和放气口的声速流导(×10~(-8)m~3/(s·Pa))的比值必须大于等于6。研究表明等温容器放出法能够用来测量放气电磁阀的声速流导和临界压力比,尽管忽略温度变化会引起一定的误差,但测试结果说明采用全局优化的方法,仍旧能够得到比较准确的结果。
     再次,文中还通过“停止法”对空容器放气过程声速段和整个放气过程的多变指数进行了研究。结果表明,容器的放气过程是个多变指数不断变化的过程,多变指数从1.4开始逐渐减小并趋近于1,放气过程中有热交换的存在并随着放气过程不断加强。为了提高定容积放出法的测试精度,把多变指数应用于定容积放出法测试声速流导的数据处理中,提出了部分多变指数法和完全多变指数法,结果证明:完全多变指数法所得的声速流导精确度非常高,且稳定性也很好,随测试时间点的变化幅度小于1.2%。
     文中还建立了集总参数法的空容器放气过程的热力学模型,针对模型中的难以测定的换热系数,提出了两种方法:固定换热系数模型和基于大空间自然对流换热模型。对于固定换热模型,根据停止放气后的压力曲线得到此过程的换热系数,并把这个换热系数作为放气过程中的换热系数,基于此模型的放气过程仿真结果要比绝热模型的仿真结果接近试验结果很多。基于大空间自然对流的换热模型中的热交换系数是根据自然对流换热关联式得到的,它随着放气过程的变化而变化,根据这个模型仿真得到压力曲线和温度曲线和试验结果都很一致,说明该模型能够真实反映放气过程的热交换。
     论文最后把基于大空间自然对流换热的放气热力学模型和放气压力曲线相结合,由放气的初始状态递推得到放气过程中容器内空气的平均温度和放气过程的多变指数,计算结果和实验结果非常一致,说明此方法可以替代“停止法”来确定放气过程的平均温度。基于放气热力学模型,根据放气压力曲线,通过分段函数优化的方法来辨识放气阀的声速流导和临界压力比,得到的结果和ISO6358所测的结果基本相同。研究表明,基于模型辨识的方法要比ISO6358简单、节能,且精度不低于ISO6358标准中A级精度。
Discharge method is one of methods to measure the flow rate characteristics of pneumatic components. Being simple, energy-saving and efficient, it is also highly applicable. In this internationally coordinated research project, theoretical and experimental study on the discharge method were carried out in order to provide International Organization for Standardizaion (ISO) with a novel and general-purpose method for measuring flow rate characteristics of pneumatic components. By combining finite volume simulation, theoretical analysis along with experimental study, the following specifics were systematically studied in this paper: the distribution and evolution of the velocity and temperature fields during discharge, the isothermal chamber characteristics and isothermal discharge method, the polytropic exponent, the thermodynamic model during discharge as well as their applications. The objective of this study is to accurately and roundly understand the process of discharge and improve the measurement accuracy and repeatability, which are of great theoretical and practical significance.
     At first, the physical models for empty and isothermal chambers have been established under the assumption that the stuffers in the isothermal chamber serve as porous media, numerical simulations were thus carried out with Fluent software. The velocity and temperature distribution and their profiles are obtained. Simulation results indicate that the velocity gradient locates primarily at the vicinity of discharge orifice while the velocity in the chamber is almost uniformly zero. The temperature distribution in the chamber is associated with the shape of the chamber. The lowest temperature is located at the center of chamber, with increasing temperature gradient during the process of discharge. The temperature drop of isothermal chamber is about 20 times less than that of empty tank, which indicate that the discharge process of isothermal chambers is very close to isothermal process. To validify the simulation results, the experimental pressure curves in the chambers agree well with the simulations. Despite a certain error, simulations of the average air temperature profiles inside the chamber during discharge exhibit the same evoluting trend and norm to those by experiments.
     Secondly, the temperature change of isothermal chambers is critical to their usability and it is therefore systematically studied under various conditions. The results show that the metal thread stuffed in chamber can greatly enhance heat transfer during discharge, which can dramatically decrease the temperature drop so that the discharge process can be regarded as an isothermal process. The isothermal characteristic of isothermal chamber is influenced by many factors under fixed charge pressure and discharge orifice. The material has little effect on isothermal characteristic as long as the stuffer is metal. The finer metal thread and the higher stuff density yield better isothermal characteristic. The higher discharge velocity, the worse isothermal characteristic is. Under the condition of an initial pressure 700 kPa and a stuff density 0.3kg/L of copper threads, the ratio of chamber volume (L) and the sonic conductance (×10-8m3/(s·Pa)) should be greater than or equal to 6 in order to be eligibly treated as an isothermal chamber. The isothermal chamber discharge method can be used to measure the sonic conductance and critical pressure ratio of the discharge valve. Although neglecting temperature change might lead to some error, the accurate results can be obtained with global optimization.
     Next, the polytropic exponent during sonic discharge and the whole discharge is studied experimentally. The polytropic exponent during discharge keeps varying from 1.4 to 1, indicating the existence of heat transfer as the heat flux enhances with the progression of the discharge. Furthermore, by appling the polytropic exponent to the data processing of discharge method in order to improve the accuracy of constant volume discharge method, partial polytropic exponent method and complete polytropic exponent method are proposed. The accuracy and stability of sonic conductance obtained with complete polytropic exponent are very high, at a standard deviation of less than 1.2% throughout the whole measurement process.
     In addition, the thermodynamic model for tank discharge is founded with lumped parameter. In order to determine the heat transfer coefficient which is difficult to obtain experimentally, two kinds of heat transfer models were given: fixed heat transfer coefficient model and natural convection model. In the fixed heat transfer coefficient model, the coefficient is determined with the pressure curve after stopped discharge. The discharge process was simulated with this model, and the result is very close to that of the experiments when compared with the simulation results of the adiabatic model. The heat transfer coefficient in the natural convection model is determined on the basis of relationship of natural-convection, and it changes with the discharge process. The pressure and temperature curve obtained with simulation based on this model match well with those of the experiments, which indicated that natural convection model can reflect the real discharge quite well.
     At last, by combining the discharge thermodynamic model base on natural convection with the discharge pressure curve, the temperature and polytropic exponent during discharge can be obtained from initial state,which were quite closed to those from experiments. Therefore,it can be concluded that this method can be a very good substitute to the“stop method”in determining the average temperature during discharge. The sonic conductance and critical pressure ratio of discharge valve can be identified by optimization based on discharge thermodynamic model and discharge pressure curve, where the results are basically the same as those by ISO 6358. This identification method is simpler and more energy-saving than ISO 6358, and its accuracy is equal or higher than that the A grade in ISO 6358.
引文
[1] 路甬祥. 流体传动与控制技术的历史进展与展望. 机械工程学报,2001,10: 1-9
    [2] 徐炳辉. 2003 年 PTC 展览会观后感——气动部分. 液压气动与密封,2004,1: 9-10
    [3] SMC(中国)有限公司. 国外气动技术发展的新动向. 现代制造,2002,16: 32-34
    [4] 杨晓林,尹殊勇. 气动技术在工业生产中的应用. 建材技术与应用,2004,4: 19-20
    [5] Stout K J, Barrens S M. The design of aerostatic bearings for application to nano -meter resolution manufacturing machine systems. Tribology Int.,2000,33( 22): 803-809
    [6] Auge Brian K, Lallas Costas D, Pietrow Paul K, etc. In vitro comparison of standard ultrasound and pneumatic lithotrites with a new combination intracorporeal lithotripsy device. Urology,2002,60: 28-32
    [7] Kapoor, C., Tesar, D.. Integrated teleoperation and automation for nuclear facility cleanup. Industrial robot,2006,33: 469-484
    [8] Pu J, Moore P R, Wong C B. Smart components-based servo pneumatic actuation systems Microprocessors and Microsystems,2000,24: 113-119
    [9] Hφier, C.K., Sonnenborg, T.O., Jensen, K.H. etc. Experimental investigation of pneumatic soil vapor extraction. Journal of contaminant hydrology,2007,89: 29-47
    [10] 赵彤. 气动技术的发展及在新领域中的应用. 液压气动与密封,2004,2: 1-5
    [11] 王祖温. 日本气动技术的现状和发展. 液压与气动,1993,2: 1-3
    [12] 路甬祥. 气动技术的发展方向. 液压与气动,1991,4: 2-3
    [13] 周洪. 气动技术的新发展. 液压气动与密封,1999,10: 2-12
    [14] 裘华徕. 气动技术的近期发展及其影响因素. 液压气动与密封,2002,3: 1-3
    [15] 李小宁. 气动技术发展的趋势. 机械制造与自动化,2003,3: 1-4
    [16] 李建藩. 气压传动系统动力学. 广州: 华南理工大学出版社, 1991: 48-51
    [17] 赵明. 气动元件及系统的流量特性研究. [学位论文],杭州,浙江大学,2003
    [18] DeRose, D. Typical proportional and servo valve control systems. Fluid power journal,2003,10: 15-18
    [19] Araki, Kenji. Yamamoto A. Model reference adaptive control of a pneumatic servo with a constant trace. Algorithm. Journal of fluid control,1990,20( 4): 30-48
    [20] Paul, Arun K., Mishra, J.K., Radke, M.G. Reduce order sliding mode control for pneumatic actuator. IEEE Transactions on control systems technology,1994,2: 271-276
    [21] Yang, G., Li, B., Fu, X. Research on dynamic characteristics of a pneumatic muscle actuator. Zhongguo jixie gongcheng,2006,17: 1294-1298
    [22] James E. Bobrow, Brian W. McDonell. Modeling identification and control of a pneumatically actuated, force controllable robot. IEEE Transactions on robotics and automation,1998,14:732-742
    [23] 陶国良,毛文杰,王宣银. 气动伺服系统机理建模的实验研究. 液压气动与密封,1999,5: 26-31
    [24] 董晓倩,郭淑娟. 气动比例/伺服系统的建模研究. 机床与液压,2003,1: 222-223
    [25] 武卫,吴强,祈晓野等. 气动比例控制系统的机理建模与实验研究. 液压与气动,2005,9: 34-37
    [26] 李宝仁,朱玉泉,许耀铭. 气动位置伺服系统的自适应控制研究. 中国机械工程,1998,Vol.9,3: 4-8
    [27] 石运序,李小宁. 排气回收速度控制系统的建模及仿真. 液压与气动,2005,2: 25-28
    [28] Edmond Richer. A high performance pneumatic force actuator system. Journal of dynamic systems measurement and control,2000,22(3): 416-425
    [29] 傅晓云,刘浩,李宝仁. 摆动气缸位置伺服控制系统的建模与仿真. 机床与液压,2004,8: 48-49
    [30] 汪淑兰. 导弹气动舵机系统的建模与仿真. 计算机仿真,1994,1: 37-46
    [31] 邱仁辉,王克奇,黄祖泰等. 全自动纸浆模塑餐具生产线气动系统设计. 林业机械与木工设备,2002,Vol.30,6: 4-6
    [32] Chen, J.-C., Chao, C.-G. Numerical simulation and experimental investigation for design of a carbon fiber tow pneumatic spreading system. Carbon,2005,43(12):2514-2529
    [33] 许伟达,凌勇坚. 气动控制系统的设计和使用. 液压与气动,2003,3: 23-24
    [34] 徐文灿. 气缸充(排)气回路中的元件尺寸设计. 液压与气动,1998,4: 29-31
    [35] 陈昱,黄伟明,夏运芳. 气动元件流通能力的实验方法及测试装置综述. 1986,3: 12-16
    [36] 小根山. 空気圧機器の流量特性. フル一ドパワ一,2001,15 巻 4 号: 20-25
    [20] Paul, Arun K., Mishra, J.K., Radke, M.G. Reduce order sliding mode control for pneumatic actuator. IEEE Transactions on control systems technology,1994,2: 271-276
    [21] Yang, G., Li, B., Fu, X. Research on dynamic characteristics of a pneumatic muscle actuator. Zhongguo jixie gongcheng,2006,17: 1294-1298
    [22] James E. Bobrow, Brian W. McDonell. Modeling identification and control of a pneumatically actuated, force controllable robot. IEEE Transactions on robotics and automation,1998,14:732-742
    [23] 陶国良,毛文杰,王宣银. 气动伺服系统机理建模的实验研究. 液压气动与密封,1999,5: 26-31
    [24] 董晓倩,郭淑娟. 气动比例/伺服系统的建模研究. 机床与液压,2003,1: 222-223
    [25] 武卫,吴强,祈晓野等. 气动比例控制系统的机理建模与实验研究. 液压与气动,2005,9: 34-37
    [26] 李宝仁,朱玉泉,许耀铭. 气动位置伺服系统的自适应控制研究. 中国机械工程,1998,Vol.9,3: 4-8
    [27] 石运序,李小宁. 排气回收速度控制系统的建模及仿真. 液压与气动,2005,2: 25-28
    [28] Edmond Richer. A high performance pneumatic force actuator system. Journal of dynamic systems measurement and control,2000,22(3): 416-425
    [29] 傅晓云,刘浩,李宝仁. 摆动气缸位置伺服控制系统的建模与仿真. 机床与液压,2004,8: 48-49
    [30] 汪淑兰. 导弹气动舵机系统的建模与仿真. 计算机仿真,1994,1: 37-46
    [31] 邱仁辉,王克奇,黄祖泰等. 全自动纸浆模塑餐具生产线气动系统设计. 林业机械与木工设备,2002,Vol.30,6: 4-6
    [32] Chen, J.-C., Chao, C.-G. Numerical simulation and experimental investigation for design of a carbon fiber tow pneumatic spreading system. Carbon,2005,43(12):2514-2529
    [33] 许伟达,凌勇坚. 气动控制系统的设计和使用. 液压与气动,2003,3: 23-24
    [34] 徐文灿. 气缸充(排)气回路中的元件尺寸设计. 液压与气动,1998,4: 29-31
    [35] 陈昱,黄伟明,夏运芳. 气动元件流通能力的实验方法及测试装置综述. 1986,3: 12-16
    [36] 小根山. 空気圧機器の流量特性. フル一ドパワ一,2001,15 巻 4 号: 20-25
    [54] 陈才元. 气动节流阀流量特性试验方法研究. 液压与气动,1991,2: 41-44
    [55] 王雪松,彭光正. 气动调速阀流量特性试验研究. 机床与液压,2006,7: 154-156
    [56] 柴喜燕,彭光正,范伟. 一次填充法测量减压阀的流量特性研究. 机床与液压,2005,8: 113-114
    [57] 小根山. 減圧弁の流量特性. フル一ドパワ一,2002,16 巻 1 号: 20-25
    [58] Kagawa, T., Cai, M., Kawashima, K., etc. Extended representation of flow-rate characteristics for pneumatic components and its measurement using isothermal discharge. Bath workshop on power transmission and motion control, PTMC 2004, 271-282
    [59] 腾燕,李小宁. 针对 ISO6358 标准的气动元件流量特性表示式的研究. 液压与气动,2004,2: 6-9
    [60] Mitsuru Senoo, Huping Zhang, Naokake Oneyama. Study and suggestions on pneumatic component flow-rate characteristics. The fifth JFPS international symposium,2002: 67-72
    [61] 腾燕,孟国香,张护平等. 气动元件合成流量特性的相关研究. 液压与气动,2004,12: 28-30
    [62] K.A. Park, Y.M Chai, H,M Choi, etc. The evaluation of critical pressure ratios of sonic nozzles at low Retynoids numbers. Flow measurement and instrumentation,2001,12 : 37-40
    [63] Salvador de las Heras. A new experimental algorithm for the evaluation of the true sonic conductance of pneumatic components using the characteristics unloading time. International Journal of Fluid Power,2001,2 :17-24
    [64] Kuroshita, K., Oneyama, N.. Improvements of test method of flow-rate characteristics of pneumatic components. Proceedings of the SICE annual conference,2004,415-420
    [65] Kenji Kawashima, Yukio Ishii, Tatsuya Funaki, Toshiharu Kagawa. Determination of flow rate characteristics of pneumatic solenoid valves using an isothermal chamber. ASME transaction: Journal of Fluids Engineering,2004,126: 273-279.
    [66] Han, B., Fujita, T., and Kawashima, K. Flow rate characteristics measurement of pneumatic valve by pressure response. Proceedings of the fifth international conference on fluid power transmission and control,2001,200-204
    [67] Kenji Kawashima, Toshinori Fujita, Toshiharu Kagawa. Flow rate measure -ment of compressible fluid using pressure change in the chamber. Trans. of the society ofInstrument and control engineers,2001,E-1(1): 1-7
    [68] Kuroshita K, Sekiguchi Y, Oshiki K, Oneyama N 2004 Development of new test method for flow rate characteristics of pneumatic components Bath workshop on power transmission and motion control,PTMC 2004,Code 64431,243-256
    [69] 黒下. 真空を利用した有効断面積の測定法. 油圧と空気圧,1995,26 巻 6号: 586-691
    [70] 黒下. 充填法による空圧用電磁弁の流量特性の測定. 油空圧技術,2002,41 巻 10 号: 25-30
    [71] 王祖温,郭晓晨,包钢等. 基于流场的气动换向阀流量特性研究. 机械工程学报, 40(2): 1-4
    [72] Jyh-Chyang Ren, Chih-Hung Hsiao. Experimental and CFD study on the mass flow-rate characteristic of gas through orifice-type restrictor in aerostatic bearings. Tribology international,2004,37: 309-315
    [73] 川嶋健嗣, 藤田壽憲, 香川利春. 等温化圧力容器を用いた空気の非定矨髁?発生装置. 計測自動制御学会論文集,1998,34(12): 1773-1778.
    [74] Kenji Kawashima, Toshiharu Kagawa, Toshinori Fujita. Instantaneous flow rate measurement of ideal gases. Transactions of the ASME: Journal of dynamic systems,measurement,and control,2000,122: 174-178.
    [75] Kenji Kawashima, Toshiharu Kagawa. Unsteady flow generator for gases using an isothermal chamber. Measurement,2003,33: 333-340.
    [76] Funaki, T., Yamazaki, s., Kawashima,K. etc. Development of continuous flow generator using isothermal chamber. Proceeding of the SICE annual conference,,2005,3068-3073
    [77] 金英子. 气动系统结露问题的研究. 博士学位论文,哈尔滨工业大学,1998
    [78] 李军. 气动系统内部结露机理的研究. 博士学位论文,哈尔滨工业大学,1999
    [79] 金英子,李军,包钢,王祖温。气动系统充放气过程中传热系数的测定及其影响。哈尔滨工业大学学报,1998,30(1): 15-19
    [80] 李军,李玉军,王祖温。气动充放气系统的流场计算。机床与液压,1999,2: 24-26
    [81] Tucker P.G. and Hewit J.R. CFD techniques and their relevance to mechatronics. Mechatronics,1996,6(2):193-207
    [82] 王福军. 计算流体力学分析,北京,清华大学出版社,2004
    [83] 韩占忠,王敬,兰小平,FLUENT 流体工程仿真计算实例与应用,北京,北京理工大学出版社,2004
    [84] Megerlin, F.E., Murphy R. W. and Bergles, A. E. Augmentation of heat transfer in tubes by use of mesh and brush inserts. Journal heat transfer,1974,145-151
    [85] Devarakonda Angirasa. Experimental investigation of forced convection heat transfer augmentation with metallic fibrous materials. International journal of heat and mass transfer,2002,45: 919-922
    [86] 林瑞泰. 多孔介质传热传质引论. 北京: 科学出版社,1995
    [87] 李亨,张锡文,何枫. 论多孔介质中流体流动问题的数值模拟方法. 石油大学学报(自然科学版),2000, 24(5): 111-116
    [88] 姜培学,李勤,司广树. 空气在多孔介质中对流换热的数值模拟. 工程热物理学报,2001, 22(5): 609-611
    [89] Mehmet Sozen, T. M. Kuzay. Enhanced heat transfer in round tubes with porous inserts. International journal heat and fluid flow,1996,17(2): 124-128
    [89] 李亨,张锡文,何枫. 考虑气体压缩性的多孔材料渗透率和惯性系数的测定. 试验力学,2002, 17(3): 326-332
    [90] 李忠全,周桂芬,陈木兰。多空材料气体渗透性的测定。粉末冶金技术,1996, 14(1): 52-57
    [91] John D.Anderson,JR. 计算流体力学入门,北京,清华大学出版社,2002
    [92] 陶文铨,数值传热学,第二版,西安,西安交通大学出版社,2001
    [93] Fluent 6.2 User guide
    [94] 汪敏生,LabVIEW 基础教程,北京,电子工业出版社,2002
    [95] 云周工作室,MATLAB 数学建模基础教程,北京,人民邮电出版社,2001
    [96] 丁振良. 误差理论与数据处理. 哈尔滨,哈尔滨工业大学出版社,2002
    [97] Y G Shin. Estimation of instantaneous exhaust gas flowrate based on the assumption of a polytropic process. Proceedings of the institution of mechanical engineers, PartD: Journal of automobile engineering,2001,215: 637-643
    [98] 金英子,朱祖超,杨庆俊,王祖温. 气动系统充放气过程中气体状态多变指数的简化与确定. 机械工程学报,2005,41: 76-80
    [99] 范伟,彭光正,王涛,赵彤. 利用声速排气法进行容积辨识的研究. 机床与液压, 2001,6: 136-138
    [100] 徐文灿. 充排气特性方程组及其应用. 北方工业大学学报,1992,4(1): 80-88
    [101] 朱明善,刘颖,林兆庄,彭晓峰。工程热力学。北京:清华大学出版社,1994
    [102] 杨世铭,传热学,第二版,北京,高等教育出版社,1987

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