THE COMBUSTION OF LIQUID FUELS WITHIN A POROUS-MEDIA RADIANT BURNER

The combustion of liquid fuels within the porous inert media (PIM) of a radiant burner was examined. Existing designs of porous radiant burners have typically relied on premixed mixtures of gaseous fuels and air. A radiant burner was built, and various design configurations were tested using the following types of porous ceramics: magnesia-stabilized zirconia, silicon carbide, and yttrium-stabilized zirconia. The fuel heptane was impinged on the combustion section using an oil spray nozzle with a fixed flow rate of approximately 0.025 Ipm. The burner had an insulated combustion section that was 10.0 cm in diameter and consisted of several 2.5-cm-thick ceramics. Stable complete combustion was achieved for heptane at equivalence ratios of 0.57-0.67. Temperature measurements taken across the exit plane of the combustion section were typically within 50 degrees C of each other, indicating radially uniform combustion. For an equivalence ratio of 0.64, axial temperature measurements taken down the side of the combustion section showed relatively low temperatures, 1170-1370 degrees C. Very low emissions of both CO and NOx were measured for the range of stable equivalence ratios. Corrected for 3% oxygen, CO varied from 3 to 7 ppm and NOx varied from 15 to 20 ppm. Several variations of the burner were tested, including higher fuel flow rates, prevaporized fuel, and a quartz-enclosed ceramic section.