Influence of air supply pressure on atomization characteristics and dust-suppression efficiency of internal-mixing air-assisted atomizing nozzle

In this study, the effect of air supply pressure on atomization characteristics and dust-suppression efficiency of internal-mixing air-assisted atomizing nozzle was investigated. Firstly, the FLUENT software was employed to simulate the flow field inside the nozzle and near the outlet of the nozzle under different air supply pressures. The numerical simulation results showed that as the air supply pressure increased, the pressure and air flow velocity inside the mixing chamber of the nozzle increased dramatically, while the water flow velocity at the water injection hole decreased. At the same time, with the increase of air supply pressure, the fragmentation scale of the liquid jet was continuously shortened, thus the primary atomization of the liquid was more sufficient. Secondly, the custom-developed dust suppression experimental system via spraying was used to investigate the atomization characteristics of the nozzle. According to the experimental results, when the air supply pressure increased, both the droplet size and the droplet volume fraction decreased, the air flow rate increased exponentially, and the water flow rate decrease linearly. In addition, as the air supply pressure increased, the atomization angle, the droplet velocity and the droplet number density first increased and then decreased. Finally, the dust-reduction experiment via spraying was performed under different air supply pressures. The results showed that the dust-suppression efficiency of total dust and respirable dust had a trend of first increasing and then decreasing with the increase of the air supply pressure. The classification efficiency of dust suppression via spraying first increased and then decreased with the increase in the dust particle diameter. Furthermore, as the droplet size decreased, the peak particle diameter decreased accordingly. (C) 2019 Elsevier B.V. All rights reserved.