Investigation on the thermal flame thickness for lean premixed combustion of low calorific H2/CO mixtures within porous inert media

Abstract The lean premixed combustion of hydrogen and carbon monoxide (H 2 /CO) mixtures within a porous inert media model-burner was investigated for ranges of H 2 /CO volumetric ratios from 2 to 4, inert volumetric concentrations in the fuel stream from 85% to 90%, thermal loads of 400 kW/m 2 (2 kW) and 1000 kW/m 2 (5 kW), constant reactants temperature of 673 K and an equivalence ratio of ϕ  = 0.5. Experimental measurements and numerical predictions of temperature profiles and temperature gradients along the axial center-line of the combustion zone are presented and the thermal flame thickness is estimated and analyzed for the effect of thermal load, inert components in the fuel stream and H 2 /CO ratios. The adopted numerical model uses a volume-averaged approach and solves both the gas- and solid-phase energy balances explicitly and accounts for the radiative heat transport in the solid-phase. The thermal flame thickness results are compared with the respective laminar free flame values and differences between the flame thickness of free flames and flames inside a porous inert media are discussed.