Numerical simulation on the larger concentration difference characteristics of dense granular jet in a coaxial gas stream

Abstract

AbstractThis work is devoted to the numerical study of particle dispersion prediction of gas–solid coaxial jet with a larger concentration difference. In pulverized coal gasifier, the pulverized coal is very dense at the nozzle outlet, and its volume fraction can reach 0.3. Then, it is dispersed rapidly under the action of high‐speed annular gas, and the particle volume fraction in the space is less than 0.002. In order to better predict the motion characteristics of a gas–solid jet with a high concentration gradient, the applicability of the three models is compared. The results show that the dense discrete phase model (DDPM) and Eulerian two‐fluid model (TFM) models considering particles collision can accurately predict the dense jet flow at low annular gas velocity. The DDPM and discrete phase model (DPM) show a good simulation for the dispersion characteristics of particles at high annular velocities where the particles' collision could be ignored. Therefore, DDPM has better adaptability for coaxial jet with large concentration gradient. The DDPM was used to predict the particle velocity and concentration for different annular gas velocities and different particle mass loads. It is found that particle flow is contracted first and then dispersed gradually under the action of airflow. The particle dispersion range increases with the increase of solid loading rate, and the corresponding radial distribution of particle velocity is greater.