Experimental investigation of structure and heat transfer in cellular flame of rich and lean propane-butane-air mixtures

We studied a lean propane-butane-air mixture ascending through a round hole of 10-mm diameter, covered by a brass mesh as a single element of the multicellular flame. Gas temperature was measured by the CARS method (Coherent anti-Stokes Raman Scattering) with original software for spectra processing. The vertical and horizontal velocity components were measured by the PIV method (Particle Image Velocimetry). Distributions of heat release intensity and heat fluxes, which cannot be obtained in direct measurements, were estimated using balance relationships in the energy equation. The results were compared with the data obtained for the rich mixture flame in experiments with the same burner. Convective and molecular heat fluxes were considered separately. It was shown that when the rich air mixture with propane-butane burns, the heat flux caused by thermal conductivity reach a maximum at the center of the heat-release zone. Their intensity is substantially lower in comparison with the convective fluxes behind the flame front, which in turn are almost twice as weak as the convective flux in the flame of a lean mixture. The maximal intensities of heat release in the flame of a rich mixture are lower than in the lean one.