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Reacting Flows

Oxycoal flame structure 

Oxycoal flame structure with inset captions

 Credit: Simone Hochgreb

The image is a photo of a co-fired coal flame, surrounded by a pilot gas flame. We are studying how coal burns under O2/CO2 atmospheres, as this could be a useful means of preparing for carbon capture. We perform laser Doppler (LDA) velocity measurements in two directions, using the two-colour crossed beams as shown. The scattered light is most pronounced where the flow is seeded with particles (outside) or with coal (inside). Further measurements using Mie scatter (inset left), PIV and OH planar laser-induced fluorescence (inset right) have also been made on the same flame, to understand its structure. Velocity measurements made with LDA and PIV complement the set. See: Balusamy et al. (2015).

 


Bluff body burner with added swirl

Bluff body burner flow, with added swirl

 Credit: Simone Hochgreb

Bluff body burner, comparing non-reacting flow (top) and reacting flow (bottom).

Using high speed PIV, we obtain the fluctuating velocity field, shown left. The first two Proper Orthogonal Decomposition (POD) modes of the axial fluctuating kinetic energy are shown in the centre (Mode 1 upper, Mode 2 lower), while the rightmost figures show the corresponding 3-d reconstructed iso-phase surfaces.

We see a helical mode rising from the bluff body in the non-reacting case. These helical modes, which contribute to mixing with the outer flow, are suppressed in the reacting case, owing to the stabilizing effect of the low density hot central region. See: Kamal et al. (2014).