A Combined Eulerian and Lagrangian Method for Prediction of Evaporating Sprays

Abstract

Polydisperse sprays in complex three-dimensional flow systems are important in many technical applications. Numerical descriptions of sprays are used to achieve a fast and accurate prediction of complex two-phase flows. The Eulerian and Lagrangian methods are two essentially different approaches for the modeling of disperse two-phase flows. Both methods have been implemented into the same computational fluid dynamics package which is based on a three-dimensional body-fitted finite volume method. Considering sprays represented by a small number of droplet starting conditions, the Eulerian method is clearly superior in terms of computational efficiency. However, with respect to complex polydisperse sprays, the Lagrangian technique gives a higher accuracy. In addition, Lagrangian modeling of secondary effects such as spray-wall interaction enhances the physical description of the two-phase flow. Therefore, in the present approach the Eulerian and the Lagrangian methods have been combined in a hybrid method. The Eulerian method is used to determine a preliminary solution of the two-phase flow field. Subsequently, the Lagrangian method is employed to improve the accuracy of the first solution using detailed sets of initial conditions. Consequently, this combined approach improves the overall convergence behavior of the simulation. In the final section, the advantages of each method are discussed when predicting an evaporating spray in an intake manifold of an internal combustion engine.

A study of transient processes in a closed vessel due to injection of hot liquid sprays

“…It is the aim of this work to present a companion analysis based on the first approach discussed above, by simultaneously solving energy and mass balance equations for a single evaporating droplet and its associated gas/vapour phase. Similar problems have been analysed previously [5][6][7], but the investigations were either theoretical or the geometries used did not allow measurements of significant thermal parameters, such as pressure and temperature. The advantage of the present approach is that the geometry and the initial and boundary conditions are well defined, thus allowing direct comparison between theoretical results and numerical data.…”

Experimental investigation of the evaporation characteristics of the fuel in a direct-injection spark ignition engine subjected to a direct-start process

“…The spray dynamics were simulated using a discrete droplet method in which the Lagrangian method was adopted to solve the differential equations. 17 The simulations of a dispersed twophase flow are based on the tracking of statistically significant droplet parcels in the gas flow. Each parcel is represented by one droplet and is determined by discretization of the continuous spectra of the initial conditions of droplets in the near field of the atomizer.…”

Modeling and Simulation of Effects of Turbulence on Vaporization, Mixing and Combustion of Liquid-Fuel Sprays

“…However, the study of the effect of the turbulence on the modification of the droplet interface transport is rather rare, although the turbulence is one of the major factors controlling droplet dispersion, formation of droplet high concentration regions and thus sprays flame structure [11,14,27,[43][44][45]. In internal combustion engines, available results are usually limited to those of the experiments of turbulence augmentation by additional injections of air or gaseous fuel or by adjusting the swirl intensity without investigating deeply the modification of interface transport and the influence of the turbulence modulation process on it (e.g., [4]). The effect of turbulence on vaporization and mixing of liquid-fuel sprays has been experimentally investigated in [11,44].…”