Modeling and Simulation of Droplet and Spray Combustion

Abstract

Abstract This chapter provides a survey on both droplet and spray models, as droplet heating, evaporation and motion are the underlying processes of both nonreacting and reacting spray flows. Attention is focused on the modeling and simulation of turbulence and turbulent mixing, as well as the interaction of evaporation with the turbulent flow field and chemical reactions. The principal approaches to modeling sprays in a turbulent flow field, such as Reynolds‐averaged Navier–Stokes equations (RANS), direct numerical simulation (DNS), and large eddy simulation (LES) are addressed. Details of the Reynolds stress models (RSM) and probability density function (PDF) models are also presented and discussed. These approaches may serve both as general spray models and subgrid models for LES. In order to address environmental concerns, detailed chemical kinetics must be considered to account for the prediction of pollutant emission, and its reduction. Appropriate methods such as direct closure and (spray) flamelet models for turbulent spray flames are addressed, together with reduced chemical mechanisms. It is shown that most often, gas flame models are not appropriate for spray flame modeling, because of the major impact that spray dynamics and evaporation have on spray combustion. The chapter also compares, by example, numerical results using different models and experimental data, mainly of research burners, with an aim to evaluate the present models, and also to identify future areas of research.