Research On The Velocity Measurement Of Gas-Solid Two-phase Flow Based On Spatial Filtering Effect

Particle velocity is an important parameter describing the flow state of gas-solids two-phase flow. Real-time detection of particle velocity is of great importance to know the flow condition, to save energy, and to control production process. It can be widely used in the process of metallurgy industry, electric power industry and energy industry.In recent years, velocity measurement methods of gas-solid two phase flow mainly include cross-correlation, spatial filtering, microwave, tracer method and so on. Because of the simple measurement installation and convenient date processing, spatial filtering method has been widely studied. In comparison with other principles, the capacitive sensing approach is widely used for its advantageous behavior in terms of noninvasive sensing, costs and harsh environment capabilities. So in this thesis, capacitive sensor is used to design particle velocity measurement based on spatial filtering effect.In this thesis, the relationship between the frequency characteristics of the output power frequency signal of the capacitive sensor and particle velocity is deeply analyzed in theory. Finite element analysis software COMSOL is used to simulate the characteristics of the spatial filtering effect. And finally experiments are to validate the simulation results. The main works are as follow:(1) The principle of spatial filtering is analyzed in theory. The effects of geometry parameters of the sensor, number of the electrodes on the spatial filtering characteristics including sensitivity, spectral bandwidth, central frequency are investigated, which provides theoretical basis for the design of the spatial filtering sensor.(2) Aimed at optimizing the sensitivity of sensor, the structure parameter of the semi-ring capacitive sensor based on the FEM software COMSOL is investigated. The most important parameter n (number of the sensors) is also deeply studied in this paper. Meanwhile, the best number of the sensor, according to its influence on the central frequency deviation of the power spectral sensitivity is finally confirmed.(3) The impact of the pedestal on the central frequency deviation in the output signal is analyzed in theory. To eliminate the pedestal frequency which affects the accuracy of velocity measurement, differential measurement technology is adopted in this paper.(4) A new capacitive measurement method based on differential excitation increasing the output signal amplitude is proposed.(5) Spatial filtering velocity measurement system based on virtual instrument technology is built in the lab. Relevant software program is written to measure the particle velocity. Experiments verify the novel spatial filtering method is applicable to capacitive velocity measurement.