Crossflow evaporating sprays in gas-solid flows: Effect of aspect ratio of rectangular nozzles

摘要

Many industrial applications of rapidly evaporating sprays in gas-solid suspensions involve the use of rectangular spray nozzles and crossflow spray injection. This paper presents a numerical study on the effects of aspect ratio of rectangular nozzles on the spray characteristics and phase interactions in such spray-gas-solid three-phase flows. The gas-solid flow is simulated via Eulerian two-fluid modeling and the spray is tracked via Lagrangian trajectory approach. Our study shows that the effect of aspect ratio has a significant impact on the penetration length and trajectories of the spray jet under the same flow conditions. The vertically oriented rectangular nozzles (i.e., nozzles with aspect ratios less than unity) have deeper penetration than the horizontally oriented ones (i.e., nozzles with aspect ratios more than unity) with the same nozzle injection area whereas the effect of aspect ratio has little impact on the spray deflection. The spray cross-section maintains the rectangular shape that expands basically following the original fan angle of the nozzle jet. The simulation also shows some strong phase interactions caused by the rapid spray evaporation, such as the formation of a dense layer of solids around the spray from the compression effect of vapor expansion and rigid wall of gas-solids flow chamber and the existence of a large diluted solids region in the vicinity of downstream of nozzle from the combined effects of evaporation and vapor crossflow convection. (c) 2006 Elsevier B.V All rights reserved.