Euler–Lagrangian simulation of the fuel spray of a planar prefilming airblast atomizer

Abstract

The pollutant emissions of aircraft engines are strongly affected by the fuel injection into the combustion chamber. Hence, the precise description of the fuel spray is required in order to predict these emissions more reliably. The characteristics of a spray is determined during the atomization process, especially during primary breakup in the vicinity of the atomizer nozzle. Currently, Euler-Lagrangian approaches are used to predict the droplet trajectories in combustor simulations along with reaction and pollutant formation models. To be able to reliably predict pollutant emissions in the future, well-defined starting conditions of the liquid fuel droplets close to the atomizer nozzle are necessary. In the present work, Euler-Lagrangian simulations of a generic airblast atomizer are presented. The starting conditions of the droplets are varied in the simulations by means of a primary breakup model, which takes into account the local gas velocity when predicting the droplet diameter. The objective of this work is to determine the optimal parameters of the probability density functions for the starting position and the starting velocity of the droplets. Spray properties observed in the simulations are used to qualitatively evaluate the major effects of the distribution parameters on the spray and the suitability of the primary breakup model being applied. Hence, the spatial distribution of an experimental spray can be reproduced using a statistical model for the droplet starting conditions.

Modeling Multivariate Spray Characteristics with Gaussian Mixture Models

“…In most cases, a droplet diameter distribution based on a characteristic mean diameter is prescribed that is determined either ad hoc through experimental or numerical investigations [7][8][9][10][11], empirical correlations [12,13], or through low-order models [14][15][16][17]. Some authors employ deterministic approaches to determine droplet velocities based on the droplet diameter [9,16], others employ some stochastic methods [18], an,d in some cases, the droplet velocities are either constant [7,15] or neglected [14]. The spray is usually injected at discrete points distributed evenly around the rotation axis at one or more specified radial distances [7,16].…”