摘要
蒸汽湿度的测量在监测蒸汽发生器产生的蒸汽品质、评判汽水分离装置工作效率、监测汽轮机级间和出口处蒸汽湿度、保证汽轮机的经济与安全运行等方面具有重要的意义。但到目前为止,无论热力学法、光学法还是微波法等测量方法,都还不能很好地解决蒸汽湿度准确测量的问题。
由电容法测量原理可知,不同湿度蒸汽的介电常数有很大不同,当其流经电容传感器时,输出电容值有较大差异。本文据此设计搭建了电容法测量流动蒸汽实验台,开发了一种同轴圆筒式电容传感器,自行研制了两种不同结构形式的蒸汽湿度调节装置,分别为A型(螺旋导流片式)和B型(插管式)。A型能够实现对蒸汽湿度较大程度的调节,B型能够实现对蒸汽湿度小范围的调节。基于热平衡原理自行设计了蒸汽湿度标定系统。
文中分别针对电容传感器水平和竖直放置进行了实验研究,研究了电容传感器的时漂以及蒸汽流量和蒸汽湿度对电容传感器输出特性的影响。结果表明:电容传感器时漂较小,输出稳定;传感器输出电容值与蒸汽流量大小无关;在所测湿度范围内,传感器水平放置时,随着蒸汽湿度增大,输出电容值呈线性增长趋势;在所测湿度范围内,传感器竖直放置时,其输出电容值随蒸汽湿度增大呈指数增长趋势。
另外,本文基于FLUENT软件,采用SIMPLE计算方法,通过UDF二次开发功能,实现了电场参数与流场参数的交换,对电容传感器内部流场和电场的耦合特性进行了数值模拟研究,并与实验结果进行了比较分析。结果表明:对于双层极板电容传感器,由于边界层的影响,蒸汽流速在传感器极板壁面附近降低,在远离壁面处流动稳定;传感器极板壁面附近蒸汽带电,远离壁面处蒸汽基本不带电。对于多极板电容传感器,电荷主要集中分布在极板壁面附近;施加外电场后,对传感器极板壁面附近蒸汽的径向流速影响较大;当蒸汽流量不同时,实验所测电容值与数值模拟电容值相近,最大相差6%;当蒸汽湿度不同时,实验所测电容变化与模拟值变化趋势基本相同,最大相差3%。
Steam humidity measurement plays an important role in monitoring the quality of steam generated by steam generator and evaluating the efficiency of separator device, and it also of great significant in monitoring the steam humidity in the turbine and outlet of the turbine, which ensure safe and economic operation of the steam turbine. Until to now, however, regard less of thermodynamics, microwave or optical measurement method, etc, there is no good solution for the accurate measurement of steam humidity.
From the capacitance measurement principle, we can see that, the steam of different humidity has a quite different dielectric constant, and when it flows through the capacitance sensor, the output capacitance values are very different. Based on this, this paper design and build a capacitance steam humidity measurement test bench, develop a coaxial cylinder-type capacitance sensor, design and make two types of humidity adjusting device, there are A (spiral chip type) and B (tube type) respectively. Type A can regulate the steam humidity in greater degree, and type B can regulate the steam humidity in small range, this paper also design a set of steam humidity calibration system.
This paper study capacitance sensor when it is placed horizontal and vertical respectively, study the capacitance sensor drift and the impact of steam flow and steam humidity on the capacitance sensor output characteristics. The results show that, the capacitance sensor drift is small and the output is stable; output capacitance value has nothing to do with the steam flow; in the range of measured steam humidity, the output capacitance value increase linearly with the steam humidity when the capacitance sensor is placed horizontally; in the range of measured steam humidity, the output capacitance value increase exponentially with the steam humidity when the capacitance sensor is placed vertically.
In addition, this paper based on the FLUENT software, use the SIMPLE method, by UDF secondary development, achieve the exchange of electric parameters and flow parameters, simulate the coupling characteristics of electric field and flow field, and compare with the experimental results. The results show that, for the double-electrode capacitance sensor, because of the boundary layer thickness, the steam flow rate reduce near the plate of the sensor, and the steam flow stably away from the plate of the sensor; the steam near the plate of the sensor has electricity, and the steam away from the plate of the sensor has no electricity. For multi-electrode capacitance sensor, the charge is mainly distributed near the plate of the sensor; applying electric field has greater effect on the radial velocity of the steam near the plate; when the steam flow changes, the capacitance value of numerical simulation is close to the experimental results, and the maximum difference is 6%; when the steam humidity changes, the capacitance value of numerical simulation changes basically the same trend with the experimental results, and the maximum difference is 3%.
引文
[1]宁德亮.新型电容传感器测量蒸汽湿度的研究.哈尔滨工程大学博士学位论文.2007
[2]蔡颐年,王乃宁.湿蒸汽两相流.西安:西安交通大学出版社,1985:97页
[3]Robert Svoboda, Maurice Bodmer. Investigations into the composition of the water phase in steam turbines.14th International Conference on the Properties of Water and Steam in Kyoto.2004:594-601p
[4]刘建成,林志鸿等.汽轮机内部除湿技术的发展.热能动力工程.2005,20(1):1-5页
[5]Yoko Miyoshi, Kumiko Miyajima etc. Flexible humidity sensor in a sandwich configuration with a hydrophilic porous membrane. Sensors and Actuators B. 2009,142:28-32p
[6]Youngdeuk Kim, Bongbu Jung etc. Capacitive humidity sensor design based on anodic aluminum oxide. Sensors and Actuators B.2009,141:441-446p
[7]Jae Sung Kim, Myung Jin Lee, Moon Sik Kang etc. Fabrication of high-speed polyimide-based humidity sensor using anisotropic and isotropic etching with ICP. Thin Solid Films.2009,517:3879-3882p
[8]王雪文,张志勇编著.传感器原理及应用.北京:北京航空航天大学出版社,2004:279-280页
[9]Mikko Bjorkqvist, Jarno Salonen etc. Characterization of thermally carbonized porous silicon humidity sensor. Sensors and Actuators A.2004,112:244-277p
[10]Timothy J. Harpster, Brain Stark, Khalil Najafi. A passive wireless integrated humidity sensor. Sensors and Actuators A.2002,95:100-107p
[11]周兰欣,张明智等.汽轮机末级湿度测量方法研究现状及其发展.华北电力大学学报.2001,28(2):72-76页
[12]张弘,蔡小舒,王夕华.汽轮机内蒸汽实验测量技术现状.热力透平.2007,36(1):1-7页
[13]王乃宁.汽轮机中蒸汽湿度测量的研究和进展.上海机械学院学报.1982,2:23-39页
[14]韩中合,杨昆.汽轮机中蒸汽湿度测量方法的研究现状.华北电力大学学报.2002,29(4):44-47页
[15]黄雪峰,盛德仁等.湿蒸汽两相流湿度测量方法研究进展.电站系统工程.2006,22(5):1-4页
[16]李炎锋,王新军等.蒸汽透平中流动蒸汽湿度测量方法的分析与比较.汽轮机技术.2000,42(3):156-161页
[17]Ching Liang Dai. A capacitive humidity sensor integrated with micro heater and ring oscillator circuit fabricated by CMOS-MEMS technique. Sensors and Actuators B.2007,375-380p
[18]Pi Guey Su, Chao Jen Ho, Yi-Lu Sun. A micro machined resistive-type humidity sensor with a composite material as sensitive film. Sensors and Actuators B.2006,113:837-842p
[19]Che Hsin Lin, Ching-Hsiu Chen. Sensitivity enhancement of capacitive-type photoresistor-based humidity sensors using deliquescent salt diffusion method. Sensors and Actuators B.2008,129:531-537p
[20]李世武,康芹.凝结式干度测量方法与应用.化工学报.2007,58(10):2608-2612页
[21]李炎锋,王新军,徐廷相.流动蒸汽湿度的加热法测量方法与及其装置.中国电力.1997,30(10):16-19页
[22]王建国,郝铭等.等容加热式饱和蒸汽湿度监测仪研制.工业仪表与自动化装置.2000,3:56-58页
[23]王升龙,杨善让.汽轮机排汽湿度的在线监测方法及工业试验研究.中国机电工程学报.2005,25(17):83-87页
[24]王升龙.汽轮机排汽湿度在线监测方法及应用研究.华北电力大学博士学位论文.2005:7-15页
[25]李炎锋.流动蒸汽湿度测量的理论与实践.西安交通大学博士学位论文.1999
[26]Lina Xu, Joseph C. Fanguy, Krunal Soni etc. Optical fiber humidity sensor based on evanescent-wave scattering. Optics Letters.2004,29(11):1191-1193p
[27]Shinzo Muto, Osamu Suzuki, Takashi Amano etc. A plastic optical fiber sensor for real-time humidity monitoring. Measurement Science and Technology.2003,14:746-750p
[28]王乃宁.用光学探针测量汽轮机内的蒸汽湿度和水滴直径.工程热物理学报.1985,6(1):99-103页
[29]Sunil K. Khijwania, Kirthi L. Srinivasan, Jagdish P. Singh. An evanescent-wave optical fiber relative humidity sensor with enhanced sensitivity. Sensors and Actuators B. 2005,104:217-222p
[30]M. Schatz, M. Casey. Design and testing of a new miniature combined optical/pneumatic wedge probe for the measurement of steam wetness. American Institute of Physics. 2007:464-479p
[31]卫敬明,张卫国,蔡小舒等.应用光学法饱和蒸汽湿度仪测量汽轮机末级蒸汽湿度.动力工程.1997,17(4):71-75页
[32]唐贵基,曹静等.光学测量法和微波测量法在湿度测量中的应用.仪器与分析监测.2007,2:23-26页
[33]夏林泉,莫国钧.大亚湾核电站一、二号机组蒸汽湿度测量.核电工程与技术.1995,8(3):13-17页
[34]刘子列,耿国山等.浅析非放射性示踪法在主蒸汽湿度测定实验中的应用.黑龙江电力.2003,25(3):168-171页
[35]田松峰.汽轮机组微波谐振腔湿度测量方法实验研究.华北电力大学博士学位论文.2009
[36]Caroline Buschmuller, Wolfgang Wiedey etc. In-line monitoring of granule moisture in fluidized-bed dryers using microwave resonance technology. European Journal of Pharmaceutics and Biophramaceutics.2008,69:380-387p
[37]韩中合,钱江波等.谐振腔微扰法测量汽轮机排汽湿度技术的关键问题.动力工程.2005,25(3):387-391页
[38]张淑娥,王红云,亢丽娜.基于微波谐振腔微扰法的汽轮机蒸汽湿度测量.电力自动化设备.2008,28(2):33-36页
[39]田松峰,韩中合,杨昆.流动蒸汽湿度谐振腔微扰法测量的实验研究.中国动力工程学报.2005,25(2):254-257页
[40]M. Penza, G. Cassano. Relative humidity sensing by PVA-coated dual resonator SAW oscillator. Sensors and Actuators B.2000,68:300-306p
[41]T.Venugopalan, T L Yeo, F.Basedau etc. Evaluation and calibration of FBG-based relative humidity sensor designed for structural health monitoring.20th International Conference on Optical Fibre Sensors.2009,7503:1-10p
[42]Pascal Kronenberg, Pramod K. Rastogi, Philippe Giaccari etc. Relative humidity sensor with optical fiber Bragg gratings. Optics Letters.2002,27(16):1385-1387p
[43]黄雪峰,盛德仁等.布拉格光纤光栅测量湿蒸汽两相流温/湿度的理论数学模型.中国机电工程学报.2006,26(7):40-46页
[44]盛德仁,黄雪峰等.一种基于布拉格光纤光栅测量湿蒸汽两相流湿度场的新方法.中国机电工程学报.2005,25(5):136-140页
[45]Robert Cerny. Time-domain reflectometry method and its application for measuring moisture content in porous materials:A review. Measurement. 2009,42:329-336p
[46]Chris D. Hahm, Bharat Bhushan. Lubricant film thickness mapping using a capacitance technique on magnetic thin-film rigid disks. REVIEW OF SCIENTIFIC INSTRUMENTS. 1998,69(9):3339-3349p
[47]杨柳,杨明皓,刘嫣红.利用边缘电场的电容式谷物水分传感器的研究.中国农业大学学报.2007,12(2):58-61页
[48]曹英荣.虚拟式电容测厚系统的研制.华中科技大学硕士学位论文.2006:7-16页
[49]Uksong Kang, Kensall D. Wise. A high-speed capacitive humidity sensor with on-chip thermal reset. IEEE TRANSACTIONS ON ELECTRON DEVICES. 2007,47(4):702-710p
[50]Alireza Hassanzadeh, Robert G. Lindquist. Relative humidity measurement using capacitive sensors. IEEE.2008:396-398p
[51]Yun Wang, Seungwoo Park, John T.W. Yeow etc. A capacitive humidity sensor based on ordered macroporous silicon with thin film surface coating. Sensors and Actuators B. 2010,149:136-142p
[52]沈逸,李小昱等.电容式水流泥沙含量传感器数据融合的研究.华中农业大学学报.2004,23(4):459-462页
[53]金峰,张宝芬,王师.电容式气-固两相流相浓度传感器的优化设计.清华大学学报.2002,42,(3):380-382页
[54]宁德亮,庞凤阁,阎昌琪等.新型湿度测量仪在气-水系统中的应用.哈尔滨工程大学学报.2006,27(6):825-829页
[55]董向元,郭淑青著.电容层析成像技术及其应用.郑州:黄河水利出版社,2008:11-25页
[56]黄雷.电容层析成像系统的研制及其在两相流参数检测中的应用研究.浙江大学学 报.2003:46-68页
[57]胡红利,周屈兰等.电容式气固两相流浓度测量系统.仪器仪表学报.2007,28(11):1947-1950页
[58]胡红利,陈夏,白涛.基于径向基网络和小波变换的电容层析图像重构算法.西安交通大学学报.2010,44(2):1-5页
[59]张洪润主编.传感器技术大全.下册.北京:北京航空航天大学出版,2007:1274-1289页
[60]Mark A. Nurge, Stephen A. Perusich. In-line capacitance sensor for real-time water absorption measurements. Sensors and Actuators B.2010,150:105-111p
[61]刘华,梁宝社等.同轴圆柱形电容器的最佳尺寸设计.河北建筑科技学院学报.2002,19(1):59-62页
[62]V. Ramaprabhu, R. P. Roy. A computational model of a combined cycle power generation unit. Journal of Energy Resources Technology.2004,126:231-240p
[63]Yi Heng Wang, Carey J. Simonson, Robert W. Besant etc. Transient humidity measurements for flow through an energy wheel. American Society of Heating, Refrigerating and Air-Conditioning Engineers Transactions.2005,3:353-369p
[64]R. Ionescu, A. Vancu, A. Tomescu. Time-dependent humidity calibration for drift corrections in electronic noses equipped with SnO gas sensors. Sensors and Actuators B. 2000,69:283-286p
[65]F. Bakhtar, H. Mashmoushy. O. C. Jadayel. Calibration characteristics of a three-hole probe and a static tube in wet steam. International Journal of Heat and Fluid Flow. 2001,22:537-542p
[66]Christoph Deml. Input and reverse transfer capacitance measurement of MOS-Gated power transistors under high current flow. IEEE.1999:1093-1097p
[67]刘文卿.实验设计.北京:清华大学出版社.2005:1-11页
[68]A. Cataldo, G. Cannazza, E. De Benedetto etc. Metrological assessment of TDR performance for moisture evaluation in granular materials. Measurement.2009, 42:254-263p
[69]J Lovell-Smith. The propagation of uncertainty for humidity calculations. Metrologia. 2009,46:607-615p
[70]A.J. White, M.J. Hounslow. Modeling droplet size distributions in poly dispersed wet-steam flows. International Journal of Heat and Mass Transfer.2000,43:1873-1884p
[71]陈秉乾,舒幼生,胡望雨.电磁学专题研究.北京:高等教育出版社.2001:259-262页
[72]陈义成.电磁学及其计算机辅助教学(CAI).北京:科学出版社.2002:83-85页
[73]陈效鹏,程久生,尹协振.电流体动力学研究进展及其应用.科学通报2003,48(7):637-645页
[74]陶文铨.数值传热学.西安:西安交通大学出版社.2001:165-166,347-353页