The effect of equivalence ratio on sound generation by turbulent premixed flames

Abstract

Direct numerical simulation (DNS) is used to study sound generation by open, turbulent premixed flames. Two cases of methane/air combustion with different equivalence ratios (φ = 0.7 and 1 ) are considered. The computational grid is set up such that both the near and far fields are fully resolved. A simple-chemistry model is used to reduce the computational cost. The results show that flame annihilation events are significant monopolar sources of noise. Spectral analysis of the radiated sound shows a broadband spectrum where the observed frequency of the peak amplitude matches that observed experimentally. Furthermore, it is observed that the stoichiometric flame (φ =1) is a much stronger source of noise than the lean flame (φ = 0.7 ).