An Experimental Study of the Stability of Laminar Flame

Citation

Curran, Donald Charles (1953) An Experimental Study of the Stability of Laminar Flame. Engineer's thesis, California Institute of Technology. doi:10.7907/6W88-7713. https://resolver.caltech.edu/CaltechETD:etd-04222003-101645

Abstract

Knowledge of laminar flame front structure is insufficient to make exact stability calculations possible. The analysis of Landau(1) indicated flame front instability under all conditions. Semi-empirical corrections to Landau's result by Markstein(2) demonstrated that a cellular flame front structure that Markstein observed experimentally might be a stable configuration. Karlovitz(3) has proposed that there is a significant additional amount of turbulence produced in turbulent flames over that found in the upstream flow. Of particular significance is the question of whether or not a flame may take on a turbulent structure in the absence of upstream turbulence. Therefore explorations concerning the conditions under which a laminar flame might become unstable were undertaken by burning premixed propane and air using a spherical flame holder. The resulting conical flame had annular waves develop in the flame front a short distance downstream from the flame holder. This distance decreased as fuel-air ratio was decreased and as gas mixture flow velocity increased. Lean high velocity flames showed a parallel result in the amplitude of the wave formed - the wave in this case developing to a large amplitude in a short distance with a tendency to roll up. Another result of the investigation was that a fairly uniform wavelength of 0.27 in. was observed even though mixture, flame holder size and flow rate were varied. The introduction of a small external turbulence source upstream of the flame front disturbed the flame - the amount of disturbance increasing with Reynolds' number of the turbulence source and with fuel-air equivalence ratio.

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