Study on a method for steam wetness measurement based on microwave resonant cavity

A method for wetness measurement based on microwave resonant cavity is presented in this paper. A specially structured resonant cavity with annular grid at its both ends was designed for the wetness measurement of flowing wet air. The pneumatic characteristic of the cavity was simulated and the S parameter of it was measured. The simulation and measurement results show that it is especially suitable for the online measurement of flowing wet air wetness. The measurement system has been developed and used to measure the saturated wet air which is especially produced for studying the performance of the system. The experimental data and theoretical value are compared and the reasons for deviation between them are analyzed. The resolution of the wet air wetness measurement can reach 1.5% in the temperature range of 29~38degC.