Direct Numerical Simulation of Turbulent Spray Combustion in the SpraySyn Burner: Impact of Injector Geometry

Abstract

Spray combustion is one of the most important applications connected to modern combustion systems. Direct numerical simulations (DNS) of such multiphase flows are complex and computationally very challenging. Ideally, such simulations account for atomization, breakup, dispersion, evaporation, and finally ignition and combustion; phase change, heat and mass transfer should be considered as well. Considering the complexity of all those issues, and to simplify again the problem, virtually all DNS studies published up to now replaced the injector geometry by an approximated, simple configuration, mostly without any walls within the DNS domain. The impact of this simplification step is not completely clear yet. The present work aims at investigating the impact of a realistic injector geometry on flow and flame characteristics in a specific burner (called SpraySyn burner). For this purpose, two cases are directly compared: one DNS takes into account the inner geometry of the injector, including walls of finite thickness; a second one relies on a simplified description, as usually done in the literature. It has been found that considering the details of the geometry has a noticeable impact on the evaporation process and ultimately on the flame structure. This is mostly due to the effect of recirculation zones appearing behind thick injector walls; though quite small, they are sufficient to impact the evolution of the flow and of all connected processes.

Multiscale Simulation of the Formation of Platinum-Particles on Alumina Nanoparticles in a Spray Flame Experiment

“…Here, dρ I /dt is given by Equation (11), N A is the Avogadro constant, ρ Pt the density of platinum and δ d 1 the Dirac measure.…”

“…Until now, these remained the only LES of the flame spray pyrolysis process. Very recently, Abdelsamie et al [11] presented a direct numerical simulation (DNS) of the SpraySyn burner, but without modeling the particle dynamics. It should, however, be stressed that even with LES, closure modeling of nanoparticle synthesis is in its early development, and that more sophisticated models will be needed in the future.…”

Compact, Global–Skeletal Reaction Mechanisms for Combustion of o-Xylene/Air and 1-Butanol/Air

“…Rittler et al presented a large eddy simulation of the FSP process for silica formation from hexamethyldisiloxane dissolved in ethanol using a tabulated reaction kinetics approach. When the standardized SpraySyn burner was introduced, also the number of validation targets increased, causing further interest in detailed simulations of the process flame − or for subprocesses, like single droplet evaporation and combustion. − Parallel to the SpraySyn development, Apazeller et al introduced a novel matrix burner for the investigation of flat, laminar, low-pressure flames seeded with a droplet aerosol . While the matrix burner allows investigation of a low-pressure flame, the SpraySyn burner is operated at pressures close to ambient pressure.…”

Direct numerical simulation of SpraySyn burner: Impact of liquid solvent

“…For the SpraySyn burner configuration, most existing simulations rely on large eddy simulations, like, for instance, those documented by Schneider et al, 5 Rittler et al, 9 Prenting et al, 18 and Sellmann et al 23 The present authors are involved as well in this collaborative DFG project, with the ultimate objective of providing direct numerical simulation (DNS) results for conditions as close as possible to those found in the real SpraySyn burner as it has been documented in our recent publications. 24,25 The latter publications can be considered as the first DNS of nanoparticle production in the SpraySyn burner.…”