Experimental Investigation of the Influence of the Shear Layer on Direct Combustion Noise of a Turbulent Jet Flame Available to Purchase

This work presents results from experiments on direct combustion noise emitted from an unconfined, turbulent, premixed jet flame. It focuses on the influence of the shear layer and the turbulent fluctuations within this layer on the resulting noise emissions. Orifice discs of different diameter are used to change the shear layer width of the emanating jet. Using these discs, which induce and increase blockage upstream of the reaction zone, leads to significantly higher turbulent fluctuations of the velocity and subsequently to wider shear layers. As these fluctuations in the shear layer are the origin of direct combustion noise, the sound pressure levels of reacting flows increase as well. Moreover, the experiments also show the impact of the Reynolds number and equivalence ratio on noise emissions when using these discs. In general, wider shear layers yield higher sound pressure levels of the resulting combustion noise. Although amplitudes of the resulting noise emissions might differ for different conditions, the normalized sound spectra coincide proving that turbulent velocity fluctuations only govern the sound pressure levels but do not affect the shape of the resulting spectra if the geometry and fuel remain the same.