【作者】 钱江波；

【导师】 韩中合；

【作者基本信息】 华北电力大学 ， 热能工程， 2012， 博士

【摘要】 湿蒸汽两相流严重影响汽轮机的安全、经济运行,蒸汽湿度的准确测量有助于确定湿蒸汽级和低压缸的运行效率,为汽轮机运行提供指导,也为除湿装置、叶片防护、湿蒸汽级以及通流结构设计提供参考。因此,汽轮机内蒸汽湿度的测量技术研究具有十分重要的意义。论文基于微波谐振腔介质微扰技术,对汽轮机排汽湿度测量方法进行了理论和实验研究。1.将电介质的复介电常数与其静介电参数、交变电磁场频率的关系引入Maxwell-Wagner非均质电介质理论,建立了湿蒸汽的等效复介电常数关系式,得到了饱和水、干饱和蒸汽和湿蒸汽的复介电常数随介质温度(压力)、微波频率的变化规律,将湿蒸汽的介电性质扩展到了交变电磁场。2.根据湿蒸汽混合物的复介电常数关系式,采用谐振腔介质微扰理论,建立了圆柱形谐振腔在TE011模式下测量蒸汽湿度的关系式。谐振腔的测量湿度与湿蒸汽的热物性、温度(压力)、谐振腔的谐振频率和相对频偏有关。3.设计了适合流动湿蒸汽湿度测量的环耦合谐振腔和孔耦合谐振腔,设计了谐振腔的分隔器结构。通过仿真计算,确定了谐振腔的有效尺寸、分隔器长度、耦合环尺寸、矩形波导尺寸和耦合孔半径等重要参数。针对不同耦合型式的谐振腔,设计了双端口传输型湿度测量系统和单端口反射型湿度测量系统。根据测量和设计要求进行了微波元器件选择、工作电路和测量控制流程设计。湿度测量数据由计算机进行处理,介绍了扫频数据和脉冲数据的处理和分析方法。4.定量分析了谐振腔温度变化引起腔体热膨胀、谐振腔内壁沉积水膜或盐垢、大水滴(水团)穿越腔体、谐振腔的取样偏差和湿蒸汽参数突变时谐振腔的传热滞后等因素对湿度测量的影响设计了一种温度自补偿微波谐振腔结构,彻底解决了谐振腔热膨胀和湿蒸汽与谐振腔换热滞后对湿度测量的影响。5.设计了汽轮机排汽取样缸外湿度测量方案和排汽缸内湿度测量方案,并进行了汽轮机排汽湿度测量实验。在缸外测量实验中,由于水滴沉积和蒸汽在壁面凝结,在器壁和管道中形成大片水膜,严重影响湿度测量。在缸内测量实验中,谐振腔的振动和热膨胀对测量影响很大,采用合理的谐振腔耦合结构和温度补偿措施可以以消除影响。测量实验证明谐振腔介质微扰技术测量蒸汽湿度的方法在实践中是可行的。更多还原

【Abstract】 Wet steam two-phase flow affects the safe and economic operation of steam turbine seriously. The accurate measurement of steam humidity is helpful to calculate the operating efficiency of the wet steam stages, as well as the low-pressure cylinder, and can provide guidance for turbine’s operation. Besides, also it can provide references for the optimization design of moisture removal device, levels protection, wet steam stages and flow passage. Therefore, measurement technology of steam humidity in turbine has very important significance. Based on the microwave resonant cavity dielectric perturbation theory, the paper has earried out theoretical and experimental research on the measurement method of the steam humidity in turbine.1. The relationship between complex permittivity and static dielectric parameters, frequency of alternating electric field was substituted into the Maxwell-Wagner non-homogeneous dielectric theory. An equivalent complex permittivity model of wet steam was established. The complex permittivity distribution of saturated water, dry saturated steam and wet steam with temperature (or pressure) and the microwave wavelength changing were obtained.2. According to the complex dielectric properties of wet steam, using microwave resonant cavity dielectric perturbation theory, a relationship of cylindrical cavity working in TE011mode for steam humidity measurement was established. Thermal properties of wet steam, temperature (or pressure), resonance frequency and relative frequency offset of the cavity affect the humidity measurement.3. The loop coupling cavity and the hole-coupling cavity which are suitable to measure the humidity of flowing wet steam were designed, as well as the slicer structure of the cavity. The important parameters of the effective size of the cavity, the length of the slicer, the size of the coupling loop, the rectangular waveguide, the radius of the coupling hole and so on, were also determined by the simulation. The measurement system used to measure steam humidity of flowing wet steam was designed.The microwave devices were chosen, and the operating circuit and control process of the measurement system were designed according to the design and measurement requirements. The measured data from the measurement system was sented to the computer to be analyzed. Besides, the methods of processing and analysis about the frequency sweep data and the pulse data were introduced.4. The influences which caused several factors on the humidity measurement were analyzed quantitatively. The factors include the expansion of the cavity when the temperature changed, the deposition water film or salt depositing on the cavity wall, large water droplets (water mass) passing through the cavity, the sampling bias of the cavity and heat transfer lag of the cavity when wet steam parameters abrupt changed and so on. A microwave cavity with automatic temperature compensation structure was designed. Therefore, the effects of the cavity thermal expansion and the heat transfer lag between the cavity and wet steam to humidity measurement were solved completely.5. The experimental program of wet steam sampling, measurement outside and the experimental program of measurement in exhaust cylinder were designsed, and the steam humidity measurement experiment was earried out. In the external cylinder measurement experiment, due to the droplets deposition and the steam condensation on the wall, large areas of water film formed in the wall and pipe, and it affected the humidity measurement seriously. In the interior cylinder measurement experiment, the vibration and thermal expansion of the cavity had a great effect on the measurement. The influence can be eliminated by using proper coupling structure and the temperature compensation method. The meaurement experiment shows that it is feasible to use the cavity medium perturbation techniques to measure the steam humidity.更多还原