Numerical Simulation Of Gas-solid Two-phase Flow And Acoustic Measurement In Primary Air Ducts

The acoustic method measures the gas-solid two-phase flow field parameters in the coal-pulverized coal pipeline.It has the advantages of accurate,reliable,fast,non-invasive,on-line measurement,etc.For the construction of laboratory scale measurement platform,the simulation research work in this paper is divided into two parts.In the first part,in order to accurately investigate the characteristics of the pneumatic conveying flow field of the dilute phase air-pulverized coal particles in the powder conveying pipe,a reasonable range of the design parameters of the experimental platform is obtained.The coupling between CFD and DEM is used to give more close to the actual fluid flow and particle contact characteristics.Based on the modified CFD-DEM coupling model,the flow field variation of the dilute phase pneumatic conveying in the tube is studied.The research shows that when the air-pulverized coal mixed gas-solid two-phase fluid passes through the curved pipeline,the Dean vortex phenomenon,the particle rope result and the particle wall wear caused by the particle collision are related to the flow field parameters,including the air flow velocity and coal powder particle mass flow rate and pipe bending diameter ratio characteristics.The second part is to establish a scientific and comprehensive ultrasonic mechanism model for collecting ultrasonic signal inversion to obtain flow field parameters.For the dilute phase air-pulverized coal gas-solid two-phase medium in the power plant boiler powder conveying pipeline,based on the description of ultrasonic waves The coupled-phase model of two-phase medium propagation corrects and establishes the calculation formula of sound attenuation coefficient and sound velocity prediction in the mixed fluid of dilute phase pneumatic conveying in the powder pipeline,and focuses on different physical parameters(including ultrasonic frequency,two-phase density.Studies have shown that when ultrasonic waves propagate in air-powder mixed gas-solid two-phase flow medium,the energy attenuation and sound velocity change are related to many factors,including the frequency of ultrasonic waves,the density of air and pulverized coal particles,the concentration of pulverized coal particles,The particle size distribution form of pulverized coal particles,etc.