湿蒸汽湿度测量传感器及控制系统的设计与实现.pdf

华北电力大学(保定)
硕士学位论文
湿蒸汽湿度测量传感器及控制系统的设计与实现
姓名:夏秋月
申请学位级别:硕士
专业:通信与信息系统
指导教师:张淑娥
2011-03
华北电力大学硕士学位论文
摘要
湿蒸汽湿度的准确测量对常规电站中大型冷凝式蒸汽透平具有重要意义。在本
文中,首先研究了湿蒸汽湿度测量原理及其相应的系统。从理论上分别阐述了单通
道测湿系统和双通道测湿系统的工作原理,比较了两者实现的难易程度,理论结果
表明采用双通道能避免因热膨胀导致的频率偏移,使系统输出信号满足实验测量要
求。然后,对系统核心部件微波谐振腔进行设计。设计了圆柱形谐振腔,其工作模
式为 TE011 模,用两个小孔将圆柱形谐振腔和矩形波导的窄壁相耦合,在谐振腔的
侧面开多个窄缝以使湿蒸汽自由通过谐振腔;使用 ANSOFT 对传感部件谐
振腔进行设计;分析了由测量方法和测量仪器引起的系统误差;依据谐振腔的等效
原理设计了谐振腔的等效电路,对谐振腔的结构和等效电路进行了仿真,得到在谐
振频率为 时,TE011 模的品质因数为 30537,适合作为测量流动湿蒸汽湿
度的传感器。最后,设计了湿度测量系统。介绍了频率跟踪和频率测量模块的原理,
以 MSP430F157 单片机为核心,设计了频率跟踪和频率测量两个模块,频率跟踪模
块实现了 VCO 的输出频率与谐振腔的谐振频率实时相等,在频率测量模块中采用多
周期同步测量与量化延迟法相结合的测量方法,使测量分辨率达到了 Hz;利用
串行通信接口实现了 PC 机与单片机之间的通信,调试结果表明频率测量和频率跟
踪模块能正常工作并且其性能指标满足测量系统的要求。

关键词:湿蒸汽;湿度测量;谐振腔;频率测量;频率跟踪
I
华北电力大学硕士学位论文
Abstract
It is great significant to have accurate measurement of the humidity of wet stream of
large condensing steam turbine in conwntional pawer plant. In this paper, at first, the
measurement principle and corresponding system of the humidity of wet stream are
researched. The operating principle of the moisture measurement system with
single-channel and dual-channel are elaborated theoretically, respectively, and the
difficulty level of this two moisture measurement system pared, the core
microwave cavity of this system is optimized, to avoid frequency offset cased by its
thermal expansion, in order to meet the experiment requirements. Then, the microwave
cavity is designed. A cylindrical cavity is designed, whose operating mode is the TE011
mode, and two holes coupled the cylindrical cavity with the narrow wall of rectangular
waveguide, there are several narrow slit in the side of the cavity so that the wet stream
can through it freely; the cavity of the sensor is designed by ANSOFT ; the
systematic errors caused by measurement methods and instruments are analysed; the
equivalent circuit of the cavity is designed on equivalence principle