Book contents
- Unsteady Combustor Physics
- Unsteady Combustor Physics
- Copyright page
- Summary Contents
- Detailed Contents
- Acknowledgments
- Introduction
- Overview of the Book
- 1 Basic Equations
- 2 Decomposition and Evolution of Disturbances
- 3 Hydrodynamic Flow Stability I: Linear Instability
- 4 Hydrodynamic Flow Stability II: Common Combustor Flow Fields
- 5 Acoustic Wave Propagation I: Basic Concepts
- 6 Acoustic Wave Propagation II: Heat Release, Complex Geometry, and Mean Flow Effects
- 7 Flame Sheet and Flow Interactions
- 8 Ignition
- 9 Internal Flame Processes
- 10 Flame Stabilization, Flashback, Flameholding, and Blowoff
- 11 Forced Response I: Flamelet Dynamics
- 12 Forced Response II: Heat Release Dynamics
- Index
- References
9 - Internal Flame Processes
Published online by Cambridge University Press: 27 October 2021
- Unsteady Combustor Physics
- Unsteady Combustor Physics
- Copyright page
- Summary Contents
- Detailed Contents
- Acknowledgments
- Introduction
- Overview of the Book
- 1 Basic Equations
- 2 Decomposition and Evolution of Disturbances
- 3 Hydrodynamic Flow Stability I: Linear Instability
- 4 Hydrodynamic Flow Stability II: Common Combustor Flow Fields
- 5 Acoustic Wave Propagation I: Basic Concepts
- 6 Acoustic Wave Propagation II: Heat Release, Complex Geometry, and Mean Flow Effects
- 7 Flame Sheet and Flow Interactions
- 8 Ignition
- 9 Internal Flame Processes
- 10 Flame Stabilization, Flashback, Flameholding, and Blowoff
- 11 Forced Response I: Flamelet Dynamics
- 12 Forced Response II: Heat Release Dynamics
- Index
- References
Summary
Chapter 8 considered ignition, and the processes associated with autoignition and forced ignition of a nonreactive mixture. In this chapter we focus on premixed and nonpremixed flames and the key physics controlling burning rates and extinction processes. Section 9.1 summarizes basic issues associated with the structure and burning rate of steady, premixed flames in homogeneous, one-dimensional flow fields. This includes discussions of the effects of pressure, temperature, and stoichiometry on burning rates. Section 9.2 then discusses how these results are modified by inhomogeneities in mixture composition, and the competition between autoignition waves and deflagration waves. Section 9.3 discusses how these one-dimensional characteristics are altered by inhomogeneities in the flow field relative to the flame, referred to as flame stretch. We then discuss how these lead to changes in burning rate and, for large enough levels of stretch, cause the flame to extinguish. Section 9.4 treats the effects of unsteadiness in pressure, fuel/air ratio, and stretch rate. Specifically, we discuss how the flame acts as a low-pass filter to disturbances in most cases, and that its sensitivity to disturbances diminishes with increasing frequency. These results have important implications for many combustion instability phenomena, where the flame is perturbed by time-varying flow and composition variations.
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- Unsteady Combustor Physics , pp. 321 - 378Publisher: Cambridge University PressPrint publication year: 2021