Burner for liquid or gaseous fuel - uses air velocity and swirl to slow combustion and lower peak temp. and minimise nitrous oxides

摘要

The burner for liquid or gaseous fuels comprises an axial fuel pipe (1) surrounded for part of its length by a coaxial cylindrical casing (2) closed at one end and containing an air swirler (4) with blades set at between 45 and 75 to the axis. The swirler may be fixed or free to rotate. Air enters the casing at the side and leaves via a flanged conical extension (5) on the furnace front. In this conical portion the flow area is reduced by between 40 and 80%. The swirled air is thus accelerated before it enters the furnace through a cylindrical duct (7). The air exit velocity is between 20 and 60 m/sec and in any case greater than the flame propagation speed with the fuel in question. The end of the fuel pipe should be between 0.1 and 4.0 (pref. 0.5-1.0) air duct dias. upstream of the duct end. In combination these measures slow down the initial combustion rate, flatten the combustion temp. curve and reduce its peak value. This in turn inhibits the formation of oxides of nitrogen.