Development of a Yagi Antenna-Based Microwave Sensor for Solid Concentration Measurement

The nonuniform solid distribution and unknown solid moisture content in gas-solid two-phase flow present challenges to the measurement of solid concentration. To address this issue, this article proposes a novel method for measuring solid concentration by developing a Yagi antenna-based microwave sensor. The dimensions of the Yagi antenna are optimized through finite element simulation to ensure good radiation performance at the working frequency. The optimized Yagi antennas are employed as transmitting unit and receiving unit, forming a novel microwave transmission sensor. Experiments are carried out to assess the sensor performance and its effectiveness in measuring solid concentrations. Experimental results indicate that the measured phase shift exhibits a high sensitivity to changes in solid concentration and is not sensitive to the nonuniform solid distribution. However, the relation between the measured phase shift and solid concentration is influenced by the moisture content of the solid. In order to eliminate the impact of moisture content on solid concentration measurement, a new parameter named normalized phase shift is defined. The relation between the solid concentration and the normalized phase shift is almost not affected by the moisture content. Consequently, the Yagi antenna-based microwave sensor, combined with the definition of normalized phase shift, allows for accurate measurement of solid concentration under varying moisture conditions.