Development of ring-shaped electrostatic coupled capacitance sensor for the parameter measurement of gas-solid flow

This paper develops a novel non-intrusive ring-shaped electrostatic coupled capacitance sensor (ECCS) for the parameter measurement of gas-solid flow to eliminate the temperature drift of traditional capacitance sensor and to improve the reliability of velocity measurement. In ECCS, one source electrode and two detection electrodes are housed in a sensing head to simultaneously derive two pairs of capacitance and electrostatic signals, which can achieve the simultaneous measurement of the particle velocity, concentration and mass flow rate within the same sensing space of gas-solid flow system. The effects of the isolation electrodes on the capacitance sensitivity and the temperature drift of the sensor standing capacitance are further investigated. Then, a weighted velocity is determined by fusing the capacitance correlation velocity and the electrostatic correlation velocity based on the correlation coefficients, which are useful for the reliable measurement of gas-solid flow. Finally, experiments are carried out to test the performance of the developed ring-shaped ECCS. Results demonstrate that the developed ECCS triples the capacitance sensitivity for the radial position from -15 mm similar to 15 mm. The temperature drift of the capacitance signal is less than 0.075 mV/C-o from the room temperature to 65 C-o, and thus the sensor standing capacitance is almost impervious to the temperature. After calibrating the relationship between the particle concentration and the capacitance signal, the developed ECCS can measure the particle mass flow rate with a relative error less than +/- 8%.