Agent for treating raw coal

Abstract

Modeling particle dispersion in turbulent flows is very complex. Several publications in this field have dealt with both the experimental and modeling aspects of turbulent particle dispersion. This paper gives a broad overview of different modeling techniques discussed in the literature in order to describe the problem of particle dispersion in dilute flows. Unlike other reviews of this subject, this paper maintains a simple approach in explaining mathematically and conceptually the complex issues involved in modeling. Some fundamental concepts, such as key characteristics of turbulent flow and the nature of interaction between turbulence and an individual particle under simplified conditions, are discussed. The authors have attempted to present several definitions (such as homogeneous flow, stationary condition, and integral time scale) that are commonly used to imply certain assumptions or as conceptual tools to derive a model. As indicated, a review of models that are capable of predicting the dispersion of dilute concentration of particles in turbulent flows is presented. The models are described in a simplistic way through use of previously explained ideas and concepts. One of the important practical applications of such dilute two-phase flow models deals with the problem of pulverized-coal combustion. The final part of the paper discusses some of the key issues involved in comprehensive pulverized-coal combustion models. The primary objective of this work is to provide a basic understanding of the subject and hence to serve as an introduction to the theoretical world of turbulent particle dispersion.