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A mechanism for high-frequency oscillation in ramjet combustors and afterburners

Rogers, Don E. and Marble, Frank E. (1956) A mechanism for high-frequency oscillation in ramjet combustors and afterburners. Jet Propulsion, 26 (6). pp. 456-462. ISSN 0095-8751.

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An experimental investigation was made of the behavior of a small two-dimensional combustion chamber, burning a uniform mixture of air and fuel vapor under conditions of high-frequency oscillation or screech. Measurements were made of the limits of stable screech, the amplitude and frequency of pressure oscillations over a wide range of mixture ratio, inlet air temperature, and combustor flow rate. Spark schlieren photographs and high-speed motion pictures taken of the combustion process showed, in agreement with other investigations, that the high-frequency oscillation is accompanied by vortices shed periodically from the flameholder lip with the same frequency as the oscillation. The following mechanism of exciting the oscillations is suggested. A mode of transverse oscillation is excited as the result of periodic transport of combustible material, associated with the vortices, into the hot wake of the flameholder. The vortices, in turn, are generated at the flameholder lips by the fluctuating transverse velocity. When the ignition time delay lies in the proper range, the phase relationship between oscillations in transverse velocity and combustion intensity is such that the oscillation is amplified.

Item Type:Article
Additional Information:© 1956 American Rocket Society. Received Sept. 15, 1955.
Group:Guggenheim Jet Propulsion Center
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Guggenheim Jet Propulsion Center UNSPECIFIED
Issue or Number:6
Record Number:CaltechAUTHORS:20110114-111632665
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21763
Deposited By: Ruth Sustaita
Deposited On:27 Jan 2011 17:42
Last Modified:03 Oct 2019 02:29

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