Mesoscopic model and flow characteristics of sequential double chord grid wires

Abstract

The crushing of beneficiation plants will produce a large amount of dust containing hot air flow, seriously polluting the atmospheric environment if discharged directly without treatment. The key to control is to dust and cool the exhaust. In order to improve the efficiency of the device, the airflow disturbance between the chord grid should be enhanced to promote the collision probability between the dust and the droplet and the surface of the chord grid. Based on the above analysis, the lattice Boltzmann method (LBM) is used to simplify the chord grid wire into an infinitely long cylinder structure, and a mesoscopic model is established to explore the flow characteristics of the airflow through the wet chord grid wires. The results show that there is a critical flow direction spacing ratio of L/D = 2.5; when the critical spacing is exceeded, vortex shedding occurs on the upstream cylinder, the boundary layer is separated, and the time-average drag coefficient C_d-M on the cylinder surface changes sharply, when the spacing ratio is less than this critical ratio, the downstream cylinder is immersed in the near wake region of the upstream cylinder. The gap flows smoothly from the downstream cylinder gap. The sequential double-chord grid wires show the flow characteristics around a single blunt body, and the time-average drag coefficient of the cylinder surface changes smoothly. According to the research results, the wet chord grid wires purification and heat dissipation device is applied to the beneficiation plants. The parameter design is carried out to make the flow direction spacing ratio (FDSR) L/D ≥ 3.5 to ensure that the development and migration of vortices in the wake of the upstream cylinder are not inhibited by the downstream cylinder. The longitudinal spacing ratio (LSR) is 1.35≤W/D ≤ 2.5 to ensure that the velocity ratio behind the upstream cylinder is u/u₀ ≥ 0.5 to promote the mixing of the fluid. The test results show that when the concentration of exhaust dust in the beneficiation plants is 38.27 mg/m³, the dust concentration of outlet air will be reduced to 0.39 mg/m³ after the wet chord grid wires purification and heat treatment, the total dust removal efficiency is 98.98%, the inlet air temperature is 32 °C, and the outlet air temperature is about 27 °C. The maximum temperature drop is 5 °C, and the air quality meets environmental emission standards.

Keywords: Chord grid wires; Flow around circular cylinder; Flow field structure; Mesoscopic model; Sequential arrangement; Spacing ratio.