Acoustic response of bluff body stabilised turbulent premixed flames

Dowling, Mastorakos, Kaminski, Balachandran (UCL)

The understanding and quantification of the response of flames to acoustic perturbations is a major component of the description of combustion-induced oscillations. As part of a larger effort in the Engineering Department led by Prof. Dowling, we perform measurements of flame transfer function on bluff-body stabilised premixed flames subject to large-amplitude acoustic excitations. The phase averaged OH PLIF Images captured over one time period in Fig.1 shows typical cyclic reponse of flame subjected to strong acoustic forcing.

[Click here to view a movie showing cyclic variation of phase-averaged Flame Surface Density (FSD) evaluated from instantaneous OH PLIF images. The movie also shows a comparison of heat release fluctuation measured using OH* chemilumenscence and FSD.]

Figure 1.  Simultaneous instantaneous (a) and phase averaged (b) images of OH, CH2O, the heat release rate (RX) and flame contour at 40 degrees phase angle with reference to the forcing signal: <U> = 9.9 m/s, Φ = 0.55, f = 160 Hz and A = 0.64.