Experimental study of combustion of hydrogen–syngas/methane fuel mixtures in a porous burner

Lean premixed combustion of hydrogen–syngas/methane fuel mixtures was investigated experimentally to demonstrate fuel flexibility of a two-section porous burner. The un-insulated burner was operated at atmospheric pressure. Combustion was stabilized at the interface of silicon-carbide coated carbon foam of 26 pores per centimeter (ppcm) and 4 ppcm. Methane (CH4) content in the fuel was decreased from 100% to 0% (by volume), with the remaining amount split equally between carbon monoxide (CO) and hydrogen (H2), the two reactive components of the syngas. Experiments for different fuel mixtures were conducted at a fixed air flow rate, while the fuel flow rate was varied to obtain a range of adiabatic flame temperatures. The CO and nitric oxide (NOxNOx) emissions were measured downstream of the porous burner, in the axial direction to identify the post-combustion zone and in the transverse direction to quantify combustion uniformity. For a given adiabatic flame temperature, increasing H2/CO content in the fuel mixture decreased both the CO and NOxNOx emissions. Presence of H2/CO in the fuel mixture also decreased temperature near the lean blow-off limit, especially for higher percentages of CO and H2 in the fuel.