A study of axial oscillations in laminar pre-mixed hydrocarbon-air flames

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In recent years, a great deal of work has been done on the problem of flame stability. Although the phenomenon of combustion is very complex, the use of linear stability analysis and high speed electronic computers has provided for advances in theoretical explanations. However, even with these recent advances, the theory is just now becoming sophisticated enough to address systems capable of being easily produced in the laboratory. As in all areas of scientific investigation, the need for experimental data is critical as an aid to the theoretician. This paper addresses this problem by presenting the results of an experimental study on one time-dependent mode of propagation - axial oscillations in laminar, pre-mixed flames. Using a flat flame burner in a low-pressure (.4 atm) combustion chamber, axial oscillations in the range of 20 - 100 Hz were observed for wide ranges of flow parameters. These oscillation frequencies were measured as a function of equivalence ratio and flow rate. These experiments have shown that axial oscillations are widespread, occurring in methane, propane and isobutane flames for the appropriate parameter ranges. A relationship between measured values of the frequency and the flow parameters is discussed.