U-tube diffusion flame burner assembly having unique flame stabilization

Abstract

A U-tube diffusion flame burner assembly having improved flame stabilization with no undesirable acoustic effects. The burners are axial units comprised of flame holders and combustors. The flame holders includes secondary air tubes to support the flow of secondary air that have helical walls forming helical passageways along at least a portion of its inner diameter to impart a swirl to the secondary air. The helical passageways impart a swirl to the secondary air exiting the passageways while simultaneously acting as a heat exchanger to heat primary air. The flame holders includes fuel tubes having first ends connected to a fuel supply and second flame ends. A plurality of radially oriented apertures are located at the second flame ends to distribute fuel in a radial direction. Primary air tube surrounds at least the flame ends of the fuel tubes and extend axially from first air supply ends to second flame ends. Air is diverted from air supply ends of the flame burners into primary air tubes through radial apertures located at the first air supply ends of the primary air tubes. Secondary air tubes surround the primary air tubes extending from first air supply ends to second ends opposite the air supply, the secondary air tubes having inner diameters larger than the outer diameters of the primary air tubes. The secondary air tubes extend for a preselected distance beyond the second flame ends of the primary air tubes and are coupled to axially-oriented conical-shaped reducers. Flame at high velocity exits the restricted end of the reducers.