Abstract
The effects of swirled inflows on the evaporation of dilute acetone droplets dispersed in turbulent jets are investigated by means of direct numerical simulation. The numerical framework is based on a hybrid Eulerian–Lagrangian approach and the point-droplet approximation. Phenomenological and statistical analyses of both phases are presented. An enhancement of the droplet vaporization rate with increasing swirl velocities is observed and discussed. The key physical drivers of this augmented evaporation, namely dry air entrainment and swirl-induced centrifugal forces acting on the droplets, are isolated with the aid of additional simulations in which the inertial properties of the droplets are neglected. The correlation between swirl and dry air entrainment rate is found to be responsible for the increase of the global evaporation rate and the spray penetration length reduction, while swirl-induced centrifugal forces are found to be effective only in the jet shear layer, close to the injection orifice, for the analyzed cases.
Highlights
Turbulent sprays are complex multiphase flows playing an essential role in several technological devices as well as in natural processes
The effects of swirled inflows on turbulent jets laden with acetone droplets are investigated by means of direct numerical simulations
The numerical method is based on the low-Mach number expansion of the Navier-Stokes equations for the Eulerian carrier phase, coupled with a Lagrangian description of the dispersed phase based on the point-droplet model
Summary
Turbulent sprays are complex multiphase flows playing an essential role in several technological devices as well as in natural processes. Different studies have examined the dynamics of swirling jets laden with solid/ liquid particles, archival literature lacks in works focusing on the detailed investigation of the evaporation process and preferential segregation of liquid droplets dispersed in swirling jet sprays, at least with the richness of details achievable in a 3D, DNS framework. The effects of the enhanced entrainment rate and the radial forces induced by the swirled motion on the evaporation dynamics of dispersed liquid droplets need to be further investigated. This work aims at characterizing and quantifying the relative importance of these two processes on the evaporation rate and provide detailed physical insights, which are expected to be relevant for the development of RANS and LES sub-grid models to be employed in numerical simulations of power plants and aeronautical engines combustion chambers, in which a swirl motion is given to the reactants inflow
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