# Study on the Influence of Different Factors on Pneumatic Conveying in Horizontal Pipe
## 4 Simulation Results and Analysis
### Simulation Results and Analysis of Different Particle Sizes  
In order to study the influence of particle size on the conveying characteristics of particles, the particle size of other working conditions is set to 2 mm, 4 mm, or 5 mm based on the benchmark working conditions, and the control variable method is used for simulation analysis. The simulation results are as follows. Figure 15a is the fluid dynamic pressure cloud diagram under different particle sizes in the sampling section. Figure 15b shows the cloud diagram of particle mass concentration changes under different particle sizes in the sampling section. It can be seen from Figure 15 that the dynamic pressure of the fluid in the three zones has little change under different particle sizes, while the mass concentration of the particles in the low-speed zone changes significantly when the particle size increases from 4 mm to 5 mm. When the mass flow rate of particles is the same, the change of particle size will affect the number of particles. If the mass flow rate is the same, the total mass of different particle sizes in unit time is the same. Under the condition of constant density, the larger the particle size, the larger the mass of a single particle, so the total number of  
Figure 14: Velocity and pressure drop change curve with pipe diameter. (**a**) Variation of average value of final stable velocity with pipe diameter; (**b**) variation of pipe pressure drop with pipe diameter. Figure 15: Distribution cloud diagram of fluid dynamic pressure and solid mass concentration under different particle sizes. (**a**) Fluid dynamic pressure cloud diagram, Pa; (**b**) particle mass concentration cloud diagram, kg/m\({}^{3}\). particles will be reduced. In Figure 15a, the dynamic pressure of particles with different particle sizes changes little, indicating that the total energy obtained by particles has little difference, that is, the average velocity difference of particle groups is small. In Figure 15b, the abrupt change of particle mass concentration in the low-speed region indicates that the total mass of particles with 5 mm diameter is more than that of particles transported out of the pipeline in the same time. Figure 16 shows the relationship between the average velocity of particles in the 0.5 m pipes length in the three zones with time under different particle sizes. As can be seen from Figure 16, the first time for particles of different sizes to reach the sampling segment varies slightly in the three zones. The first arrival time of particles with different sizes in the low-speed zone is almost the same, while the time when the high-speed zone and the transition zone first reach the sampling section is significantly different than that in the low-speed zone. In addition, the average velocity of 2 mm particle group in the sampling section reaches dynamic equilibrium first. Figure 17a shows the average value of the final stable velocity of the particles in the three zones with the change of the particle sizes, Figure 17b shows the pressure drop of fluid along the pipe under different particle sizes in the sampling section 7.5 m to 8 m away from the inlet. It can be seen from Figure 17a that the average velocity of particle groups in the three zones decreases approximately linearly with the increase of particle size, and the change trend is consistent. The decreases in the three zones are 2.26, 2.23, and 2.28 respectively. It can be seen from Figure 17b that the pressure drops inside the 0.5 m length pipe gradually increases with the increase of particle size, and the pressure drop increases by 0.8, 0.5, and 1.2, respectively. The pressure drop increases the most when the particle size increases from 4 mm to 5 mm. From the analysis of particle mass concentration, when the particle size increases from 4 mm to 5 mm, the mass concentration of particles in the low-speed zone changes greatly, indicating that there is a large difference in the quantity of particles in the conveying pipe, so the pressure drop is large.