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Show 2 A metal fiber plate is a porous material and has a high heat resistance and back-fire resistance, and has been used for radiant burners. In the radiant burner, flames form on the surface of the porous plate, and the surface is heated by the flames. However, the surface temperature of the upstream side of the burner is kept relatively low because the percolation flow cools the surface and also the material has a low heat conductivity in the flow direction. Thus, these burners have a high back-fire resistance. However, such burners can only operate at a low firing rate of less than 1 Mw/m2 as radiant burners. In contrast, premixed combustion burners, which have many holes or slits on the porous plates, have a high combustion performance. In this case, the burner is not considered to be a radiant burner, but rather a high intensity low NOx burner. The schematic of this burner is shown in Fig. 1. Perforated porous burners can operate at a surface load greater than 15 MW/m2 while keeping NOx (02 = 0%) below 40 ppm. The flame-stabilizing mechanism of the new type burner, however, is not yet understood well. In order to construct the basic technology for the next generation of burners, this paper investigates the flame stabilizing mechanism of perforated porous burners. The combustion range of both of a perforated porous plate burner and a non-porous plate burner perforated in the same way were measured and compared. The flow rate of the percolation from the porous plate and the port flow rate from the ports were also measured. The flame stabilizing mechanism was investigated by visualizing of the flames using direct photographs and high speed video photographs. The state of the flow above the perforated porous plate was also observed by laser Port flow ~ Percolation flow I *~ & i~ ~ ,~ rtbn. '=&e"e~ ~ ~ I ~l l 1\ ~ I I I I I ,I I f Flame port Porous plate tomography using a tracer of Ti02. Fig.1 Cross section of a perforated porous plate EXPERIMENTAL SYSTEM Figure 2 shows the experimental burner system. Combustion air and city gas ( CH4 88.50/0, C2H6 4.60/0, C3HS 5.4%, C4H10 1.5% )were mixed by a mixer, and after straightened by a flow straightener the mixture was burned over a burner plate. The combustion range was measured by burning in a water cooled furnace. The air and city gas flow rates |