Suppression of Rijke tube oscillations by delay coupling

This study experimentally analyzes the cessation of self-sustained periodic oscillations of gas columns in delay-coupled Rijke tube oscillators. The Rijke tube oscillator comprised an open-ended resonance tube with a Bunsen burner inserted into it. Delay coupling was introduced using acoustic waves propagating through a gas-filled tube with both ends connected to the resonance tubes. Two coupling methods, single- and double-tube coupling, were tested for comparison. A significant reduction in the acoustic amplitude was observed with relatively narrow tubes in double-tube coupling when the tube lengths were equal to half the wavelength and one wavelength of the acoustic waves of the uncoupled oscillator. The experimental results were analyzed using the theoretical model of the delay-coupled Rijke tube oscillators, whose coupling strength varied with the delay time. The present results would be useful in establishing a simple method for suppressing unwanted acoustic oscillations observed in various combustors.