Book contents
- Frontmatter
- Contents
- Preface
- INTRODUCTION
- 1 CHEMICAL THERMODYNAMICS
- 2 CHEMICAL KINETICS
- 3 OXIDATION MECHANISMS OF FUELS
- 4 TRANSPORT PHENOMENA
- 5 CONSERVATION EQUATIONS
- 6 LAMINAR NONPREMIXED FLAMES
- 7 LAMINAR PREMIXED FLAMES
- 8 LIMIT PHENOMENA
- 9 ASYMPTOTIC STRUCTURE OF FLAMES
- 10 AERODYNAMICS OF LAMINAR FLAMES
- 11 COMBUSTION IN TURBULENT FLOWS
- 12 COMBUSTION IN BOUNDARY-LAYER FLOWS
- 13 COMBUSTION IN TWO-PHASE FLOWS
- 14 COMBUSTION IN SUPERSONIC FLOWS
- References
- Author Index
- Subject Index
7 - LAMINAR PREMIXED FLAMES
Published online by Cambridge University Press: 06 July 2010
- Frontmatter
- Contents
- Preface
- INTRODUCTION
- 1 CHEMICAL THERMODYNAMICS
- 2 CHEMICAL KINETICS
- 3 OXIDATION MECHANISMS OF FUELS
- 4 TRANSPORT PHENOMENA
- 5 CONSERVATION EQUATIONS
- 6 LAMINAR NONPREMIXED FLAMES
- 7 LAMINAR PREMIXED FLAMES
- 8 LIMIT PHENOMENA
- 9 ASYMPTOTIC STRUCTURE OF FLAMES
- 10 AERODYNAMICS OF LAMINAR FLAMES
- 11 COMBUSTION IN TURBULENT FLOWS
- 12 COMBUSTION IN BOUNDARY-LAYER FLOWS
- 13 COMBUSTION IN TWO-PHASE FLOWS
- 14 COMBUSTION IN SUPERSONIC FLOWS
- References
- Author Index
- Subject Index
Summary
We now begin the study of premixed combustion. As we have learned from Chapter 6, a nonpremixed flame is supported by the stoichiometric, counterdiffusion of fuel and oxidizer. Thus, once ignited, a nonpremixed flame will situate itself somewhere between the fuel and oxidizer sources in order to satisfy this stoichiometry requirement. However, once ignition is achieved in a combustible fuel–oxidizer mixture, the resulting premixed flame tends to propagate into and consume the unburned mixture, if unrestrained through some aerodynamic means. Thus a premixed flame is a wave phenomenon.
In this chapter we shall study the simplest, idealized mode of wave propagation, namely the steady propagation of a one-dimensional, planar, adiabatic, wave relative to a stationary, combustible mixture in the doubly infinite domain. We shall call such a wave a standard wave or standard flame. In Section 7.1 we shall identify all such possible waves by constraining, through the conservation of mass, momentum, and energy, the states far upstream and downstream of the wave where the nonequilibrium processes of diffusion and reaction both vanish. Such an analysis yields the Rankine–Hugoniot relations, which show that two classes of waves can propagate in a combustible mixture, namely subsonic deflagration waves and supersonic, detonation waves. These waves have distinctively different properties.
Since the wave structure is not described at the level of the Rankine–Hugoniot analysis, the problem is not closed in that the crucial parameter of the wave response, namely the wave propagation speed, needs to be given.
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- Combustion Physics , pp. 234 - 302Publisher: Cambridge University PressPrint publication year: 2006
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