## 6 Conclusions  
This study was conducted to improve the particle suction efficiency while reducing the distribution of secondary particulate airflow into the atmosphere by controlling the airflow in a regenerative air sweeper. The computational simulation results were validated by conducting experiments using a specially developed setup. A turbulence model was used to simulate the airflow in the dust suction port, and physical values such as air velocity and pressure were analyzed. The main conclusions following the experimental findings in this study are summarized below:  
1. The overall dust collection efficiency decreases as the conveyor belt speed increases. When the speed changed from 6 to 16 km/h, the overall efficiency of dust collection decreased from 96% to 81% in the simulation results, and from 95% to 75% in the experimental results. 2. The road sweeper has a high efficiency during its operation at speeds of 6-10 km/h, while the intermediate difference is positive compared to the simulation and experimental results. Furthermore, when the pressure drop increased, dust removal efficiency increased. 3. The efficiency of dust cleaning depends significantly on the change in the particle structure. For instance, wood particles increased from 81% to 98%, sand particles increased from 76% to 95%, and clay (wet) particles increased from 69 to 90% when the pressure increased from 1200 to 2400 Pa.
4. In addition, the velocity of the airflow through the pickup head suction port is critical for improving the particle removal efficiency. The particle removal efficiency was 93% when the airflow rate through the suction port was increased to 35 m/s. 5. Furthermore, the particle structure and density significantly affected the starting particle removal velocity. With a particle size of 0.25 m, a particle starting removal velocity of 4.3 m/s was obtained, and when the particle size was 2000 m, the particle removal velocity was 12.3 m/s, which corroborates earlier findings. Sand particles with a density of 1650 kg/m\({}^{3}\) and size of 30 mm had a particle starting velocity of 33.5 m/s, whereas the starting removal velocity of granite particles with a size of 30 mm and density of 2600 kg/m\({}^{3}\) was 42.3 m/s. 6. It is worth mentioning that high efficiencies were obtained when the particle suction port for the pickup head was designed at an inclination angle of 30\({}^{\circ}\). By controlling the airflow in the sweepers, the amount of harmful PM\({}_{2.5}\) particles released into the  
Figure 19: The secondary airflow duct that distributes the airflow separation device to the environment is filtered. environment can be minimized by recirculating 40-70% of the secondary airflow in the system. Future research should consider a regenerative air vacuum sweeper by modeling the secondary airflow control mechanism, including dust suction and dust collection mechanisms, particle filtration mechanisms, and secondary toxic airflow control systems. Hopefully, this type of road cleaner will allow the commercialization and effective cleaning of city roads to reduce the amount of harmful dust that spreads into the environment. Conceptualization, J.V.F. and G.T. ; methodology, J.V.F. ; software, P.K.A. ; validation, J.V.F., G.T. and F.J.A. ; formal analysis, J.V.F. ; investigation, F.J.A. and Y.W. ; resources, J.V.F. and G.T. ; data curation, P.K.A. ; writing--original draft preparation, J.V.F. ; writing--review and editing, Y.W. and F.J.A. ; visualization, P.K.A. ; supervision, G.T. ; project administration, G.T. ; funding acquisition, G.T. All authors have read and agreed to the published version of the manuscript. This study was funded by Ningxia Key R&D Planning Project (2019 BFH0204) of China. Not applicable. The authors acknowledge the Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan 430070, China; School of Automotive Engineering, Wuhan University of Technology, Wuhan 430070, China; and Suizhou-WUT Industry Research Institute, Suizhou 441300, China.