Research On 16 Electrode Electrostatic Imaging System For Gas-Solids Two Phase Flow Measurement

Electrostatic tomography(EST)is a new information detection technology,which has the advantages of simple structure,real-time high-speed imaging,non-excitation and non-invasive measurement.At present,electrostatic tomography can be applied to the flow parameters measurement of gas-solid two-phase flow,such as the parameters of flow velocity,concentration,mass and flow pattern etc.And the focus of this paper is the application of electrostatic tomography in the flow pattern monitoring of gas-solid two-phase flow,which has a wide range of applications in the electrical and chemical industries.Based on the analysis of electrostatic tomography technology principle,and the simulation research of the array electrostatic sensor,a new type of electrostatic imaging system is designed and manufactured in this paper.This electrostatic imaging system includes 16 electrode array electrostatic sensor,hardware circuit device for data acquisition,and the PC platform software integrated with image reconstruction algorithm.The function of this system is tested and verified on the simulated particle two-phase flow device,and many useful experimental conclusions and results are obtained,which are described as follows.Based on the three-dimensional simulation results of electrostatic sensor's space sensitivity,the main structure and size of electrostatic sensor and the shape and size of 16 array electrodes are optimized and designed,and the electrostatic sensor is fabricated.Based on the analysis of the designed electrostatic sensor,the sensor signal acquisition circuit is designed,this circuit consists of three parts,including charge amplification,programmable amplification and rectification filtering,which can effectively measure and obtain the induced charge signal of the electrostatic sensor electrode.Through analyzing the data acquisition requirements of electrostatic imaging system,a 16-channel parallel data acquisition and control circuit is designed based on the 16-Bit A/D converter AD7606 and the ARM Cortex-M4 core controller STM32F407,compared with the channel switch acquisition mode used by the previous researchers in electrostatic imaging system,this circuit is able to obtain analog output signal of the 16 electrodes array electrostatic sensor in parallel way,which makes the obtained imaging data meet the real-time and accuracy requirements of electrostatic imaging system.Reconstruction and Optimization of the flow fattern distribution image.Including the analysis and solution to the forward problem of image reconstruction,the inverse problem of image reconstruction using the iterative Tikhonov regularization algorithm,in addition,there are binarization of reconstruction image based on local threshold and cubic spline interpolation of the reconstruction image,which are mainly used to improve the accuracy and recognition of reconstruction image.The system PC platform software integrated with data transmission and processing function and image reconstruction function is designed and developed,and the overall design of electrostatic imaging system is completed.According to the designed electrostatic imaging system,the function and actual measurement performance of this system are tested and studied on the simulation experiment platform of gas-solid particle flow,and the feasibility of the electrostatic imaging system for flow pattern monitoring of gas-solid two phase flow is verified by the experimental results.