Reports: ND1051768-ND10: Super-Adiabatic Combustion in Porous Media with Catalytic Enhancement for Thermoelectric Power Conversion

Nina Orlovskaya, University of Central Florida

Ruey-Hung Chen, University of Central Florida

In the course of the project the novel porous combustor was designed and developed and is now in use for the experiments on heat to electricity conversion. The combustion of ultra-lean fuel/air mixtures provides an efficient way to convert the chemical energy of hydrocarbons and low-calorific fuels into useful power. Matrix-stabilized porous medium combustion is an advanced technique in which a solid porous medium within the combustion chamber accumulates heat from the hot gaseous products and preheats incoming reactants. This heat recirculation extends the standard flammability limits, allowing the burning of ultra-lean fuel mixtures. The heat generated may be converted into electricity with thermoelectric generators. The design of a porous media burner coupled with a thermoelectric generator and its testing were developed where combustion-zone media was a highly-porous alumina matrix interposed between upstream and downstream honeycomb structures with pore sizes smaller than the flame quenching distance. The honeycomb structures were used to prevent the flame from propagating outside of the central section. Experimental results include temperature distributions inside the combustion chamber and across a thermoelectric generator; along with associated current, voltage and power output values. Measurements were obtained for a catalytically-inert Al2O3 medium and a SiC-coated medium, which was tested for the ability to catalyze the super-adiabatic combustion. In certain experiments, LaFeO3 based perovskite powders doped with Ru, Co, and other cations, were deposited on Al2O3 and SiC surfaces in order to facilitate the combustion reactions. The combustion efficiency was obtained for stoichiometric and ultra-lean (near the lean flammability limit) mixtures of CH4 and air. The thermoelectrics were used to harness heat produced in superadiabatic combustion in porous media. A second prototype of the porous combustor was also developed with a specific goal of achieving liquid fuel utilization, such as kerosene. A liquid fuel delivery section was specifically designed allowing the pre-evaporation of the liquid fuel and its further utilization in combustion.