Alternative fuel combustor with recirculation zone

A gas turbine comprising:

• a compressor section;
• a turbine section;
• and
• a combustion section disposed downstream of the compressor section and upstream of the turbine section, the combustion section including at least one combustor, wherein the at least one combustor comprises:
• a combustion liner extending along an axial centerline from a forward end to an aft end, the combustion liner defining a combustion chamber, wherein the combustion liner includes a first portion and a second portion, the first portion extending from the forward end to the second portion, the second portion extending radially outwardly from the first portion;
• a center fuel nozzle extending along the axial centerline at least partially within the combustion chamber such that the combustion chamber includes an annular portion defined between the center fuel nozzle and the combustion liner, the annular portion extending from the forward end to a downstream end of the center fuel nozzle;
• a plurality of outer fuel nozzles surrounding the center fuel nozzle, the plurality of outer fuel nozzles terminating at the forward end;
• a vortex generating element configured to induce a recirculation zone for the stabilization of a flame;
• a fuel injector coupled to the combustion liner downstream of the forward end;
• and
• an air injector coupled to the combustion liner downstream of the fuel injector.

A method of operating a combustor in a gas turbine, the combustor comprising a combustion liner that defines a combustion chamber extending between a forward end and an aft end, wherein the combustion liner includes a first portion and a second portion, the first portion extending from the forward end to the second portioin, the second portion extending radially outwardly from the first portion, the method comprising:

• providing, with one or more fuel nozzles including a center fuel nozzle, fuel and an oxidant to the combustion chamber having a first equivalence ratio that is rich, the center fuel nozzle extending along an axial centerline of the combustor at least partially within the combustion chamber such that the combustion chamber includes an annular portion defined between the center fuel nozzle and the combustion line, the annular portion extending from the forward end to a downstream end of the center fuel nozzle;
• conveying the fuel and oxidant over a vortex generating element disposed within the combustion chamber, whereby a recirculation zone is induced aft of the vortex generating element;
• providing fuel into the combustion chamber with a fuel injector coupled to the combustion liner at least partially downstream of center fuel nozzle;
• and
• providing additional oxidant to the combustion chamber aft of the fuel injector such that the fuel and oxidants have a second equivalence ratio that is lean.