The effect of heat transfer on acoustics in burner stabilized flat flames

Modern central heating systems use low NOx premixed burners with a largemodulation range. This can lead to noise problems which cannot be solved viatrial and error, but need accurate modelling. An acoustic analysis as part ofthe design phase can reduce the time-to-market considerably, but the acousticresponse of the flame is an unknown and complex key-factor.A large class of burners currently used in boiler equipment is formed bysurface burners. On these burners (nearly) one-dimensional flat flames can bestabilized. This will lead to heat transfer from the flame to the burner, andconsequently a cooler flame and reduced NO$_x$ emissions. However, the heatloss towards the burner has a significant influence on the behavior of theflame when the flow velocity is acoustically disturbed. In that case at certainfrequencies a feedback loop can occur and the velocity fluctuations areamplified.In this study, the influence of a the heat transfer between the gas and theburner on the acoustic transfer coefficientis studied numerically and compared to experimental results for burnerswith different volumetric heat transfer coefficients. It is found that thisinfluence is significant and that for the materials studied the heat transfercannot be neglected