Unsteady Contribution of Water Vapor Condensation to Heat Losses at Flame-Wall Interaction

This study addresses experimentally the influence of a second-order phenomenon concerning wall heat losses in combustion chambers, namely water vapour phase change, that is likely to occur subsequently to flame-wall interaction. For this purpose, flame quenching experiments are carried out on methane-air mixtures in a constant volume combustion chamber, using heat gauges based on surface thermometry. The transient effect of condensation on wall heat flux, that was already predicted using numerical simulation, is evidenced in our experiments. Its evolution and magnitude are quantified and compared to the relevant literature. Although the time evolution of condensation heat flux was poorly predicted by numerical simulation, its magnitude is well estimated thanks to mass diffusion across the quenched layer at the wall. In the conditions investigated, the contribution of condensation to wall heat flux reaches about 0.1 MW/m(2), which represents around 6% of conductive wall heat flux at quenching and up to 23% during the cooling phase after combustion.