Suppression of Burner Oscillations by Acoustical Dampers

Abstract

Abstract Tests on the suppression of burner oscillations are described. The work was not all inclusive but did produce several positive conclusions which may help in quieting particular combustion installations, or may be of help in preventing waste of effort in trying ineffective methods. The effectiveness of a quarter-wave tube was found to be critically dependent on length, but relatively insensitive to location, as long as the tube is placed in the region of the pressure antinode. Similarly, the effectiveness of a Helmholtz resonator depended critically on volume for a particular neck, but is quite insensitive to location. In neither case did the suppressor have to be placed near the particular antinode where energy was fed into the oscillation. The degree of suppression obtained was approximately proportional to the cross-sectional area of the tube; the same conclusion appears to be warranted with regard to the cross-sectional area of the throat of a Helmholtz resonator. Almost complete suppression was obtained with holes drilled in the side of the tube and placed within 10 per cent of a wave length from a pressure antinode. It was found that the diameter of the hole need not be greater than about 1/10 to 1/15 of the diameter of the combustion chamber, but should be greater than the wall thickness for best suppression.