Wavelet analysis of flame blowout of a liquid-fueled swirl burner with quarls

Lean swirl combustion is the leading burner concept today, used in several steady-operating applications to ensure a wide operating range and low pollutant emissions. Approaching lean blowout is highly desired by design to achieve the lowest possible NOx emission. It was shown earlier that quarls could significantly extend the operating regime of liquid-fueled swirl burners. In the present study, the accompanying acoustic noise is evaluated by continuous wavelet transformation to show the effect of various quarl geometries on lean flame blowout. However, the desired flame shape of swirl burners is V, first, and a straight flame, and then a transitory regime can be observed before the developed V-shaped flame through increasing the swirl number. If the axial thrust is excessive, blowout might occur in earlier stages. Presently, the characteristic bands before blowout were analyzed and evaluated at various quarl geometries, swirl numbers, and atomizing pressures. The latter parameter also acts as an axial thrust control to adjust the swirl number. (C) 2019 Institute of Noise Control Engineering.