Sadaf Sobhani

Investigation of Lean Combustion Stability, Pressure Drop, and Material Durability in Porous Media Burners

The operational stability and thermal durability of combustion in two-zone porous media burners (PMBs) is examined experimentally and computationally. Long-term material durability tests at constant and cycled on-off conditions are performed, along with a characterization of combustion stability, pressure drop and pollutant emissions for a range of equivalence ratios, mass flow rates, and burner setups. Experimental thermocouple temperature measurements and pressure drop data are presented and compared to results obtained from one-dimensional volume-averaged simulations. Experimental and model results show good agreement for temperature profiles and pressure drop evaluated using the Darcy-Forchheimer equation with Ergun’s relations. Enhanced flame stability is observed for burners with Yttria-stabilized Zirconia Alumina (YZA) upstream and Silicon Carbide (SiC) in the downstream combustion zone. Measurements of product gas concentrations illustrate highest emissions of CO at conditions close to flash-back and, as expected, higher NOx emissions with increasing equivalence ratios. ∗Address all correspondence to this author. NOMENCLATURE Di j Species i binary diffusion coefficient (m/s) MFR Mass flux rate (kg/m2s) Pe Peclet number (Pe = SLdp,e f f ρgcg λg ) SL Laminar flame speed (m/s) Xi Species i mole fraction Yi Species i mass fraction c Specific heat capacity (J/KgK) dp Pore diameter (m) hv Volumetric heat transfer coefficient (W/m3K) ṁ Mass flow rate (kg/s) q̇ Heat release rate (W/m3) u Volume-averaged fluid velocity (m/s) ε Porosity λ Thermal conductivity (W/mK) κ Radiative heat extinction coefficient (W/m2K) Ω Scattering albedo ω̇i Species i production rate per unit volume (kg/m3s) φ Equivalence ratio ρ Density (kg/m3) σ Stefan-Boltzmann constant (W/m2K4) 1 Copyright