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Non-steady behavior of a flame spreading from a point in a two-dimensional duct


Subbaiah, Malladi Venkata (1980) Non-steady behavior of a flame spreading from a point in a two-dimensional duct. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/se8q-9c70.


Non-steady behavior of a flame stabilized in a two-dimensional duct is studied in this thesis. The problem is formulated by an integral technique in which the governing equations are integrated across the duct to obtain integral relations for the mean flow variables. The flow fields on either side of the flame sheet are matched by appropriate matching conditions. Fluid flow through the flame surface causes the integral relations to explicitly involve the fluid velocities at the flame. An independent description of the flame shape and the irrotational flow field upstream of the flame is provided by a source distribution on the duct axis.

The integral relations are analyzed by a perturbation technique, in which the dominant order solution represents the steady flame development. The steady flame configuration is perturbed by an acoustic wave incident on the compact flame region. The time dependent counterpart of the integral relations describes the ensuing non-steady flow fields. The flame perturbation exhibits a travelling wave pattern with considerable amplification along the flame zone. A simple model to describe the growth of the flame perturbation is put forth, by considering the flame surface as an unstable shear layer.

Acoustic reflection and transmission coefficients of the flame region are obtained utilizing the time-dependent flame calculations. The response spectra exhibit active responses at certain well defined frequencies. The non-steady flame model is incorporated in a rudimentary afterburner configuration to investigate the low frequency behaviour of the afterburner. The results suggest a possible mechanism of low frequency instability in a combustion system.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Marble, Frank E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:19 May 1980
Record Number:CaltechETD:etd-11012006-152708
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4362
Deposited By: Imported from ETD-db
Deposited On:27 Nov 2006
Last Modified:16 Apr 2021 22:12

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PDF (Subbaiah_mv_1980.pdf) - Final Version
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