Noise Generation by Open Turbulent Flames

Abstract

In order to provide fundamental data on the acoustic energy released by combustion processes, measurements were made of the noise arising from open turbulent flames. These studies of the acoustic radiation from premixed open flames, which relate the characteristics of the noise to the various geometric and fluid-flow parameters defining the flames, are described. Examination of the combustion-noise spectra showed that their peaks could be expressed by a constant value of the Strouhal number (fmax⋅D/Ub), where D is the burner-port diameter and Ub the normal burning velocity. The acoustic power (P) generated by a turbulent flame was found to be related to the fluid-flow parameters by the expression P∝q2⋅Ufn(Ub), where q is the mixture flow rate and U the flow velocity. In this expression, the exponent of the mixture velocity varies in such a way that the rate of increase in acoustic-power output with mixture velocity is greatest for low values of the combustion velocity, and is reduced as the combustion velocity increases. [This work was supported by the Joint Research Committee of the Gas Council and by The University of Leeds.]