Low NO.sub.x multistage combustor

A combustor for burning a mixture of a fuel and an oxidant gas, comprising:

• a combustion chamber including an upstream end, a downstream end, and a longitudinal wall joining the ends, the downstream end including a combustion chamber outlet;
• a gaseous fuel inlet arranged to introduce a mixture of an oxidant gas and a gaseous fuel to the upstream end of the combustion chamber so as to create a vortical flow of the mixture moving towards the downstream end;
• an igniter at the upstream end of the combustion chamber igniting the mixture;
• and
• a recirculation channel, including a recirculation channel inlet downstream of the fuel inlet and upstream from the combustion chamber outlet, and a recirculation channel outlet upstream of the recirculation channel inlet, wherein the recirculation channel inlet is at a greater distance from a longitudinal central axis of the combustion chamber than the recirculation channel outlet, and wherein the vortical flow urges a recirculated portion of partially oxidized products of combustion to be extracted from the combustion chamber through the recirculation channel inlet, to pass through the recirculation channel and to be reintroduced to the combustion chamber through the recirculation channel outlet.

A combustor for burning a mixture of fuel and an oxidant gas, comprising:

• a cylindrical combustion chamber, including an upstream end, a downstream end, a longitudinal wall joining the ends, and a combustion chamber outlet at the downstream end;
• a fuel inlet arranged to introduce a flow of the fuel into the combustion chamber at the upstream end;
• at least one gas inlet arranged to introduce a flow of the oxidant gas into the combustion chamber at the upstream end, creating a flow of the fuel and oxidant mixture from the upstream end to the downstream end;
• an igniter for igniting the mixture in the combustion chamber;
• a recirculation channel inlet downstream of the gas inlet and upstream of the combustion chamber outlet, arranged to extract a portion of partially oxidized products of combustion from the combustion chamber;
• a recirculation channel outlet upstream of the recirculation channel inlet, arranged to reintroduce said portion of partially oxidized products of combustion to the combustion chamber off of a central axis thereof;
• and
• a recirculation channel connecting between the recirculation channel inlet and the recirculation channel outlet, wherein the gas inlet comprises a plurality of gas inlet openings in the cylindrical wall of the cylindrical combustion chamber, wherein the plurality of gas inlet openings are arranged to cause the mixture and the partially oxidized products of combustion to vortically flow from the upstream end to the downstream end in the combustion chamber, and wherein the vortical flow causes a portion of the partially oxidized products of combustion to recirculate through the recirculation channel.

A multiple-stage combustor, comprising:

• an upstream combustion chamber;
• a downstream combustion chamber having an end wall;
• and
• a nozzle communicating partially oxidized products of combustion from the upstream combustion chamber to the downstream combustion chamber, the nozzle protruding from the end wall into the downstream combustion chamber.

A multiple-stage combustor, comprising:

• an upstream combustion chamber;
• a downstream combustion chamber having an end wall;
• a combustion channel communicating partially oxidized products of combustion from the upstream combustion chamber through the end wall into the downstream combustion chamber;
• and
• a secondary air inlet to the downstream combustion chamber, being structured and arranged to provide a flow of secondary air to the downstream combustion chamber in a substantially annular shaped flow pattern around the partially oxidized products of combustion exiting the combustion channel.

A multi-stage combustor, comprising:

• a fuel mixing system being structured and arranged to provide a continuous flow of a fuel mixture comprised of a gaseous fuel and an oxidant with about 45% to about 90% stoichiometric oxygen, the fuel mixing system including a fuel inlet, an oxidant inlet, and a fuel mixture outlet;
• a first combustion chamber for partially oxidizing the fuel mixture and producing partially oxidized products of combustion, including a fuel mixture inlet communicating with the fuel mixture outlet, and a fuel igniter;
• and
• a second combustion chamber communicating with the first combustion chamber for further oxidizing the partially oxidized products of combustion, including a secondary oxidant inlet structured and arranged to introduce into the second combustion chamber additional oxidant sufficient to completely oxidize the partially oxidized products of combustion, wherein the first combustion chamber includes a substantially cylindrical shaped wall extending between an upstream end and a downstream end, the downstream end including an outlet for the partially oxidized products of combustion communicating with the second combustion chamber, and wherein the fuel mixture inlet comprises a plurality of fuel mixture inlet apertures near the upstream end of the cylindrical wall being structured and arranged to provide a flow of the fuel mixture into the first combustion chamber with sufficient velocity tangential to the cylindrical wall to create a vortical flow of the fuel mixture within the first combustion chamber.

A method of reducing NO.sub.X emissions while combusting a fuel, comprising:

• forming a mixture of the fuel and about 45% to about 90% stoichiometric oxygen;
• generating a vortical flow of the mixture in a first combustion chamber from an upstream end to a downstream end of the combustion chamber;
• igniting the vortically flowing mixture to form partially oxidized products of combustion;
• recirculating a portion of the partially oxidized products of combustion from the upstream end to the downstream end;
• mixing the recirculated partially oxidized products of combustion with additional mixture in the vortical flow;
• communicating a second portion of the partially oxidized products of combustion th rough an outlet at the downstream end into a second combustion chamber;
• and
• further oxidizing the second portion of the partially oxidized products of combustion in the second combustion chamber.