Premixed Combustion Noise Scaling: Total Power and Spectra

Abstract

Turbulent premixed combustion processes are inherently unsteady and, thus, a source of acoustic radiation. The objective of this paper is to examine the basic scaling of the flame’s acoustic emission spectra and establish its dependence upon geometric and flow variables using a piloted Bunsen burner. The results show that the flame's acoustic spectrum has a nearly universal shape that can be character ized by four parameters: the total acoustic power, OASPL, the frequency of peak emissions, fpeak , and the power law scaling of the spectra in the low ( f fpeak ) frequency regime. The frequency of peak emissions scales with Strouhal number , St = fpeak . L f/U ave , where Lf and Uave denote the flame length and axial flow velocity, respectively. The OASPL of combustion noise scales as fpeak . Q, where Q denotes the average heat release from the flame. The high frequency acoustic emissions sca les as f