Experimental analysis of a porous burner operating on kerosene–vegetable cooking oil blends for thermophotovoltaic power generation

Abstract

An experimental work was conducted to evaluate the performance and combustion characteristics of a porous burner for the cogeneration of heat and TPV applications. The main component comprised a novel tubular combustor that is designed to operate on several mixtures of gravity-fed liquid fuels and is integrated into an array of gallium antimonide (GaSb) TPV cells. Four mixtures of kerosene–vegetable cooking oil (VCO) were prepared and evaluated, as follows: 100% kerosene (100 kerosene), 90%/10% kerosene–VCO (90/10 KVCO), 75%/25% kerosene–VCO (75/25 KVCO), and 50%/50% kerosene–VCO (50/50 KVCO). The fuel–air equivalence ratios were varied from the rich blow-off condition to the lean region, and the corresponding electrical output and combustion characteristics were assessed. The maximum electrical efficiency of 1.03% was achieved using 50/50 KVCO, but the maximum radiant efficiency of 31.5% was obtained by using 100 kerosene. Experimental results indicated that increased fuel–air equivalence ratio adversely affected thermal efficiency. However, this shortcoming offsets the achievement of radiant power and efficiency. The thermal efficiency peaked at around stoichiometric mixture for all tested fuel blends. The combustion characteristics of the burner were clarified by analyzing the axial temperature profiles and emissions of carbon monoxide (CO) and nitrogen oxides (NOx). The temperature at the surface of the porous alumina was significantly higher than the developed flame temperature and the temperature at the exit of the burner. The CO emission fluctuated between 220 and 380ppm in the lean region, but appreciably increased as the fuel–air equivalence ratio was gradually enriched. The NOx emission reflected the pattern of the temperature at the burner exit, and the values recorded were in the range of 6–31ppm.