Microwave Differential System Research On Wetness Measurement With Microwave Resonant Cavity

The accurate measurement of steam wetness has great significance in long-term stability operation and its life for a steam turbine. In this paper, at first, the measurement principle of the humidity of wet stream has been researched. The differential measurement system of the steam humidity has been studied and analyzed. The analysis showed that the differential measurement system can avoid frequency offset brought by thermal expansion, the output of the system can meet the experiment requirements. According to the needs of measuring system and also in order to reduce the cost of the system, a phase offset signal extraction circuit has been designed to take place of the phase lock amplifier. In addition, this circuit has been simulated in Multisim10, the results of output and signal processes in different input and output conditions have been compared. Finally two kinds of design have been determined and the circuits have been built. According to the analysis of the design, actual operations have been carried out. Compared with the theoretical value, the experimental results made the phase offset signal extraction possible. Then the system has been built, the phase offset signal extraction circuit has been connect in. The result should that this system can work normally. At last a double holes incentive microwave resonator with open loop ends has been designed. The main body of this resonator is a cylindrical cavity. It works at the mode of TE011, and couples with two rectangle waveguide through elliptical holes. In order to improve the performance, we put short circuit separators at the two recessed ends. All parts of the resonator have been designed. ANSOFT HFSS9.0software has been used to implement the model and simulation. According to the simulation, field distribution and the curve of S parameter showed that the design of resonant cavity can achieve theory demands9.6GHz. Then this cavity has been optimized, kinds of different situations in HFSS simulation for optimization have been carried out, results have been compared, finally the resonator has been totally designed. It can reach the theory demands9.6GHz,suitable for the measurement of the humidity of the flowing wet steam.