Research on a new-designed Venturi ejector and dazomet particle motion characteristics for dilute-phase pneumatic conveying systems based on CFD-DEM

To disperse dazomet, a commonly used soil fumigant for soil disinfection, over large soil surfaces, dilute-phase pneumatic conveying can be utilized. Currently, most research has focused on pneumatic conveying systems for large particles, such as coal conveying or pneumatic seeding However, there has been almost no research on the dilute-phase pneumatic conveying of dazomet particles. Therefore, a coupled simulation model based on computational fluid dynamics and discrete element method (CFD-DEM) was established to study the effect of the structural parameters of the Venturi ejector on the motion of particles and airflow fields variation characteristics for the pneumatic conveying system of dazomet particles. Based on the Box-Behnken experimental design method, a 3-factor and 3-level response surface simulation experiment was carried out by selecting the contraction angle, throat diameter, and diffusion angle of the Venturi ejector as factors. The suction-flow ratio, average velocity of particles, average coordinates of particles in the vertical direction, and corresponding standard deviation at the outlet of the pipeline were chosen as response indexes. Multiple linear regression models were established between each factor and response index. The simulation results showed that the impact of factors on the 4 response indexes from strong to weak were throat diameter, contraction angle, and diffusion angle. With decreasing throat diameter, the suction flow ratio and average velocity of the particles increased. The average coordinates of the particles in the vertical direction decreased, while the standard deviation increased, indicating that the pneumatic conveying performance of the system increased. The optimal structural parameters for the contraction angle, throat diameter, and diffusion angle were 34.5 degrees, 15 mm, and 12.0 degrees, respectively. The experimental results demonstrated that the application precisions of the optimised Venturi ejector were 99.23%, 98.46%, and 98.56% at application rates of 15, 20, and 25 g/s, respectively. The results provide a theoretical reference for the structural optimisation of the Venturi ejector and operational performance evaluation of the pneumatic conveying system for dazomet particles.