ME745A

MODELLING OF TURBULENT COMBUSTION



Introduction to Turbulence, review of turbulence models: RANS, LES, DNS, simple closure of chemical source terms, mixture fraction based modeling of turbulent nonpremixed combustion: flamelet model and CMC method, PDF and Monte Carlo methods, scalar mixing models, turbulent premixed flames, droplet and spray combustion.
Lecturewise breakup (considering the duration of each lecture is 50 minutes)
I. Introduction (6 lectures):

Objectives and outline of the course

Review of thermodynamics

Review of chemical kinetics: elementary and overall reactions, reaction rate, combustion of hydrocarbons, reaction mechanisms

Turbulence theory: Characteristics of turbulence, examples of turbulent flows

Complexities associated with turbulent combustion, statistical description of turbulent flows
II. Review of Turbulence Models (6 lectures):

Derivation of the Reynolds and Favre averaging of NavierStokes equations

Turbulence models, length/time scales of turbulent flows, Kolmogorov hypotheses

Turbulence closure: zero equation, one equation and twoequation models

Transport equation for kinetic energy and dissipation rate

Large eddy simulation, models for the subgrid stress tensor, examples

Transport equation for reactive scalars, closure issues for the chemical source terms

Simple closure for the chemical source terms: EBU, EDC models
III. Turbulent nonpremixed combustion (9 lectures):

Introduction: flame structure, definition of conserved scalar, mixture fraction

Characteristics of turbulent nonpremixed flame, functional dependencies of reactive scalars with mixture fraction: infinite fast chemistry, equilibrium chemistry, frozen chemistry, shape of the PDF for nonpremixed combustion

Derivation of transport equations for mean and variance of mixture fraction

Closure models for the unclosed terms, model for the scalar dissipation rate

Flamelet concept, derivation of the flamelet equations

Functional dependence of the reactive scalars with mixture fraction and scalar dissipation rate

Estimation of the averaged quantities, overall solution algorithm, some applications of the flamelet models

Conditional moments and its usefulness, introduction to conditional moment closure (CMC) method

Some examples of CMC method and its shortcomings
IV. Probability Density Function based approaches for turbulent combustion (6 lectures):

Introduction to statistics: probability, mean, variance, skewness and flatness of a random variable, probability density function, cumulative distribution function, Bayes theorem, joint PDF, marginal PDF, conditional PDF, conditional expectation

Derivation of the transport equation for the PDF

Closure of various unclosed terms: chemical source terms, conditional velocity

Mixing models: IEM, CURL
V. Turbulent premixed combustion (7 lectures):

Introduction: turbulent premixed flames, turbulent flame speed, structure and characteristics of turbulent premixed flame, different regimes of turbulent premixed flame

Modeling of turbulent premixed flames: BML model

G equation / levelset approach and closure models
VI. Droplet evaporation and spray combustion (6 lectures):

Applications, simple model of droplet evaporation

Simple model for burning droplet, burning rate constant and droplet lifetime

Droplet burning in convective environments

Realworld effects on droplet burning rate

Spray phenomena

Modeling of turbulent sprays
References:

Turbulent Combustion, N. Peters, Cambridge University Press

Computational models for turbulent reacting flows, R. O. Fox, Cambridge University Press

An Introduction to Combustion: Concepts and Applications by S. R. Turns, McGrawHill Science/Engineering/Math; 3 edition (January 24, 2011)

Combustion by I. Glassman, Academic Press; 4 edition (September 8, 2008)

Combustion: Physical and Chemical Fundamentals, Modeling and Simulation, Experiments, Pollutant Formation by J. Warnatz, U. Mass and R. W. Dibble, Springer; 4th edition (November 9, 2010)
