EXPERIMENTAL AND NUMERICAL INVESTIGATION OF NOISE GENERATION IN HYDROGEN AND METHANE-HYDROGEN LAMINAR FLAMES

The direct combustion noise generation in hydrogen-air and methane-hydrogen-air laminar flames is investigated by means of experimental measurements and high-fidelity numerical simulations. Premixed M-shaped flames, stabilized over a cylindrical bluff-body burner at atmospheric conditions, are submitted to a weak acoustic perturbation, inducing oscillations of flame surface area and heat release rate, thus leading to noise emission. The similarities and differences in noise generation between the two fuel mixtures are investigated by comparing flames with either the same flame height or the same ratio between the flow velocity and laminar burning velocity. Under the conditions considered in this study, methane-hydrogen flames exhibit a more accentuated flame-flame interaction, and consequently a larger pressure fluctuation than hydrogen flames, even though the sound pressure levels are comparable for all cases. Moreover, the response of the hydrogen flames is in phase with the imposed acoustic excitation, while a delay is observed in the case of methane-hydrogen flames.