Conditions for the excitation of a laminar kinetic singing flame

Experimental studies have been conducted of the concentration regimes of excitation and silence of acoustic instability of a laminar kinetic singing flame with changes in composition, flow rate, and initial temperature of a propane-air mixture. Measurements of the distribution intensity of the varying component of the emission of the CH radical at a wavelength of 4315 A and of the phase difference between oscillations of pressure and of heat-release rate along the flame height have shown that the major portion of varying heat release for sustaining and amplifying pressure oscillations, in accordance with the Rayleigh criterion, occurs as a result of periodic changes in the surface area near the tip of the flame cone. A relation has been established between the change in the phase shift and the appearance of concentrational and temperature regions of excitation and silence of acoustic oscillations.