## 5 Results and Discussion
### Particle Removal Efficiency  
Factors affect the efficiency of particle assimilation in the secondary airflow circulating in the complete system during operation of the regenerative air sweeper. In regenerative air sweepers, the speed of movement is of great importance for clearing dust particles on city roads. Figure 8 shows the effect of changes in the conveyor belt speed on the particle suction efficiency. The measurements and analyses indicated that the computational and experimental results were relatively close to each other. The suction efficiency of the particles was high at a conveyor belt speed of 6-10 km/h. The absorption efficiency of the particles reached a lower value when the movement speed exceeded 12 km/h. The results of the calculations and experiments show that the suction efficiencies of the particles at a speed of 6-8 km/h are very close to each other, and the difference between the results is 1%. The conveyor speed was between 10 and 12 km, and the difference between the simulation and experimental results was 2%. At a speed of 14 km/h, the difference was 5%. When the conveyor belt speed was 16 km/h, the difference between the particle absorption efficiency calculation and experimental results was 8%. Sand particles smaller than \(<\)200 \(\upmu\)m were used in the simulation and experimental results. Because the simulation result was higher than the experimental results with increasing speed, the values entered with the FLUENT code did not lead to a sharp decrease in the result, but a relatively faster decrease in the result with an increase in speed in the real working mode during the experiment. An increase in the conveyor belt speed had two effects on the overall particle suction efficiency. On the one hand, the relative velocity between the particles and the moving pickup head increased with the conveyor belt speed. The high speed of the cleaner encouraged the particles to move towards the rear narrow slot at a greater impact angle. The suction port of the pickup head cannot collect more particles smoothly with airflow, and most particles escape from the pickup head rear narrow slot into the environment. A high sweeping speed is less efficient than a slow sweeping speed owing to the reduction in particle reception time on the road surface. Figure 7: Velocity and trajectory of particles moving through the suction port. Many factors affect particle suction efficiency, one of which is the airflow rate. Insufficient airflow in the pickup head suction duct is ineffective for moving and collecting particles on the road surface. The dust extraction efficiency will be higher if the suction mouth airflow rate is higher than the particle movement speed for efficient collection of particles on the road surface. Figure 9 shows the effect of airflow rate on particle suction efficiency. Although the airflow rate at 15 m/s calculation result was higher than the experimental results, the experimental results were higher than the calculated results after the airflow rate exceeded 20 m/s. The higher the airflow rate in the suction mouth, the higher the efficiency owing to the movement and absorption of more dust particles on the road surface, leading to an increase in the experimental results with an increase in the airflow rate. When we compared the simulation and experimental results, the differences between the results were very similar. The difference between simulation and experimental results was 2% at airflow velocity of 15 m/s; at 20 m/s, the difference was 1.5%. The airflow velocity was 2% at 35 m/s and the particle suction efficiency was 0.9 \(\eta\). In the experimental study, the particle suction efficiency was 0.95 \(\eta\). For high particle suction efficiency, the suction port airflow velocity should be higher than the initial velocity of the particles. Figure 8: Comparison of the particle suction efficiency on different driving speeds between simulation and experiment. Figure 9: Comparison of the particle suction efficiency on different airflow rate between calculation and experiment.