Measurement Method And Error Analysis Of Steam Humidity In Microwave Cylindrical Cavity

Wet steam humidity has a serious impact on the safe and economic operation of steam turbines.Therefore,accurate measurement of steam humidity is of great significance.The thesis first analyzes the equivalent complex permittivity model of wet steam,and obtained the relationship between steam humidity and wet steam dielectric constant.The principle of steam humidity measurement is described.Based on the cavity media perturbation theory,the relationship between resonance frequency offset and humidity in TE₀₁₁mode is obtained.And the relationship between water film thickness and resonance frequency offset in TE₁₁₁and TE₀₁₁modes.Secondly,the elite retention strategy and the dynamic genetic algorithm of crossover and mutation are used to solve the relationship between water film thickness and wet steam,and the water film thickness is solved quickly and accurately.Next,thermal analysis is used to simulate the thermal deformation at different temperatures.According to the deformation value of the inner surface of the effective part of the cavity,the influence of the cavity deformation on the resonant frequency of the cavity is analyzed.In order to eliminate the influence of temperature to some extent,a reference cavity was introduced,and a dual-mode/four-channel system measurement model was designed.The influence of different reference frequencies on humidity measurement was analyzed.The measurement cavity and reference were simulated and analyzed.The shape variable of the cavity is calculated and analyzed for the error of the measurement of the system due to the difference between the reference cavity and the measurement cavity.Finally,according to the state of the alternating medium in the resonant cavity,the polarization process in the dielectric under the alternating electric field is analyzed,and the expression of the electric field in the dielectric under the alternating electric field is derived.Based on the electric field equation in the dielectric under the derivation of the alternating electric field,the cavity perturbation formula of the cavity is improved.The HFSS software is used to simulate and analyze the variation of the electric field in the medium before and after the perturbation of the coaxial cavity and the cylindrical cavity at different frequencies and different media.The correctness of the electric field equation in the dielectric under the alternating electric field is proved.Based on the medium perturbation formula after the change of the fruit,the simulation data is compared with the theoretical data before and after the improvement of the medium perturbation formula,and the applicability of the improved medium perturbation formula is proved,and improved humidity measurement accuracy...