微带缝隙实现汽轮机蒸汽湿度测量的研究

Study on Turbine Wetness Measurement Implementation by Microstrip Slot

汽轮机蒸汽湿度的在线测量,直接影响汽轮机工作的安全性和经济性。通过HFSS电磁仿真软件研究空气介电常数对微带缝隙等效电容产生影响,提出一种利用微带缝隙模型测量汽轮机蒸汽湿度的方法。由于蒸汽湿度变化导致微带线空气介电常数改变,设计微带缝隙谐振器,仿真得到不同空气介电常数下的谐振频率,并得到其变化关系曲线;加宽微带线并在信号输入端设计渐变线阻抗变换器,以对设计的加宽微带缝隙谐振器进行优化,得到约为原谐振器1.6倍的频偏值。研究及实验仿真结果表明:微带缝隙谐振器模型适用于汽轮机蒸汽湿度的在线测量;在微带缝隙宽度不变的条件下,增大微带线宽度可有效加大空气介电常数对微带缝隙谐振器的影响,有利于蒸汽湿度的准确测量。

The on-line measurement of steam wetness of steam turbine directly affects the safety and economy of steam turbine. The effect of the air dielectric constant on the microstrip slot equivalent capacitance is studied by HFSS electromagnetic simulation software. A method of measuring steam wetness of steam turbine by the model of microstrip slot was proposed. The microstrip slot resonator was designed on the change of the air dielectric constant of microstrip line with the change of steam wetness, simulation to get the resonant frequency under different air dielectric constants and the relationship curves. Broadening the microstrip line and designing a gradient line impedance transformer at the signal input terminal is to optimize the design of widened microstrip slot resonantor. In this way, we can obtain the frequency deviation increased around 1.6 times than the original resonator. The study and results of simulation experiments show that ： the model of microstrip slot resonator is applied to on-line measurement of steam wetness of steam turbine. If the width of microstrip slot is unchanged, increasing the width of microstrip line can increase the influence of the air dielectric constant on the microstrip slot resonator effectively, and in favour of the accuracy of steam wetness measurement.