An enhancement in the radiation flux from porous medium burners operating with nonpremixed flames was obtained by a vane-rotary burner, in which the swirling fuel flow was confined by an air duct. By optimizing the gap distance between the swirling flow and the base of the porous medium, the relative enhancement in radiation flux reached 5.7 times. This improvement is attributed to the superior fuel-air swirl mixing, with the resulting flame efficiently transferring the heat to the solid phase, as been substantiated by the exhaust gas analysis, the radiation spectrum, flame, and solid temperatures. A significant reduction in CO and UHC concentrations was obtained at high swirl numbers, whereas the NOx emission was decreased to a level below 10 ppm. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.