Patent ID: 8784096

Claim:
An air-fuel burner comprising a heat-transfer tube formed to include an interior region and adapted to discharge heat to an adjacent medium located outside the heat-transfer tube when exposed to heat from a flame generated in the interior region, an air-fuel mixing chamber adapted to mix air from an air supply and fuel from a fuel supply to establish a combustible air-fuel mixture therein, and an air-fuel nozzle coupled to the air-fuel mixing chamber and arranged to extend into the interior region of the heat-transfer tube, the air-fuel nozzle being configured to provide means for forming three nozzle exits communicating with a combustion chamber defined in the interior region and located between the air-fuel nozzle and the heat-transfer tube to cause the combustible air-fuel mixture to exit from the air-fuel nozzle into the combustion chamber through a first nozzle exit formed in the air-fuel nozzle to establish, when a portion of the combustible air-fuel mixture flowing through the first nozzle exit is ignited, a detached first flame extending in radially outward directions in the combustion chamber from the air-fuel nozzle toward the heat-transfer tube, and the detached first flame includes a root positioned to lie between the air-fuel nozzle and the heat-transfer tube and a tip arranged to stabilize on an interior surface of the heat-transfer tube, a second nozzle exit formed in the air-fuel nozzle and arranged to lie in spaced-apart relation to the first nozzle exit in a downstream direction away from the air-fuel mixing chamber to establish, when a portion of the combustible air-fuel mixture flowing through the second nozzle exit is ignited, a detached second flame extending in radially outward directions in the combustion chamber from the air-fuel nozzle toward the interior surface of the heat-transfer tube, and the detached second flame includes a root positioned to lie between the air-fuel nozzle and the heat-transfer tube and a tip arranged to stabilize on the interior surface of the heat-transfer tube, and a third nozzle exit formed in the air-fuel nozzle and arranged to lie in spaced-apart relation to the second nozzle exit in the downstream direction to locate the second nozzle exit between the first and third nozzle exits and to establish, when a portion of the combustible air-fuel mixture flowing through the third nozzle exit is ignited, an attached third flame extending in the downstream direction away from the air-fuel nozzle and the detached first and second flames, and the attached third flame includes a root stabilized on the air-fuel nozzle and a tip extending in the downstream direction.