Research On Measurement Method Of Particle Flow Parameters Based On Interdigital Electrostatic Sensor

Sandstorms in nature,dust flying in the air,flue gas emitted from factories,coal injection systems in blast furnaces,and gas-solid two-phase flow can be seen everywhere in daily life and industrial production.Particle flow velocity is an important parameter of gas-solid two-phase flow characteristics.How to achieve accurate measurement is of great significance for understanding the characteristics of gas-solid two-phase flow and realizing process monitoring.In view of the problem that the different spatial positions of particles in the current electrostatic sensor will affect the velocity measurement results,for example,the output signal of the ring-shaped electrostatic sensor contains four kinds of information:the size of the particle charge,the spatial position of the particle,the particle size,and the particle velocity.It is very difficult to separate these four kinds of information.Based on this,this paper proposes a new type of interdigital electrostatic sensor structure in order to eliminate the influence of particle spatial position and particle size on the velocity measurement results.In addition,in order to further enhance the sensor's anti-interference ability and improve the signal-to-noise ratio,an electrostatic sensor structure with a differential design of a two-finger electrode array will be adopted.First,the finite element software COMSOL is used to model and simulate the interdigital electrostatic sensor,analyze the spatial sensitivity of the interdigital electrostatic sensor,and obtain the functional expressions of its static sensitivity and dynamic sensitivity.Analyze the influence of the axial width We of the finger electrode and the axial distance Le of the finger electrode on the spatial sensitivity distribution characteristics and use the principle of similarity to establish a dimensionless model of the sensor.Secondly,study the spatial filtering velocity measurement method of the interdigital electrostatic sensor,and the simulation shows that the change of the particle spatial position and size has no effect on the peak frequency of the power spectrum of the sensor output signal.The velocity formula of the spatial filtering method of the interdigital electrostatic sensor is derived.Verified the correctness of the simulation conclusions through experiments,and analyzed the velocity measurement results of the spatial filtering method.The experimental results show that in the drop height range of 0.45m to 1.25m,in the single particle experiment,the relative error of the spatial filtering method for velocity measurement is between 0.04%and 4.34%,and the relative standard deviation of repeated measurements is less than 2.6%;in the multi-particle experiment,the relative error of spatial filtering method of velocity measurement is between 1.17%and 4.88%,and the relative standard deviation of repeated measurement is less than 5%.Finally,the cross-correlation velocity measurement method of the interdigital electrostatic sensor is studied.The velocity measurement experiments of single particle and multi-particle were carried out on the experimental device of gravity conveying particle flow.The experimental results show that,in the range of reference velocity 2.97m/s to 4.95m/s,in the single particle experiment,the relative error of the cross-correlation method for velocity measurement is between 0.15%and 1.77%,and the relative standard deviation of repeated measurements is less than 2.9%;in the multi-particle experiment,the relative error of the cross-correlation method is between 5.18%and 8.65%,and the relative standard deviation of repeated measurements is less than 4%.Comparing and analyzing the two velocimetry methods of spatial filtering and cross-correlation,it can be found that the accuracy of the cross-correlation method in the single-particle experiment is better,and the repeatability is slightly worse;the accuracy of the spatial filtering method in the multi-particle experiment is better,the repeatability is slightly worse.