Apparatus and method for controlling the secondary injection of fuel

A method for controlling combustion in a gas turbine engine, the method comprising:

• providing a primary combustion chamber and a transition piece located downstream from the primary combustion chamber;
• injecting a first fuel into an air stream flowing through the primary combustion chamber to create a combustion stream having a first momentum in an axial direction through the primary combustion chamber and the transition piece and having a radial temperature differential at an inlet to the transition piece between an average temperature in a hotter central region of the combustion stream flowing at the inlet to the transition piece and an average temperature in a cooler peripheral region of the combustion stream flowing at the inlet to the transition piece;
• and
• injecting a second fuel into the combustion stream in a radial direction perpendicular to the axial direction within the transition piece, wherein combustion of the second fuel is effective to reduce the radial temperature differential of the combustion stream as it flows through the transition piece;
• wherein the cooler peripheral region comprises a first zone located circumferentially peripherally outward from the central region and a second zone located peripherally outward from the first zone, and wherein the injecting a second fuel comprises:
• injecting a portion of the second fuel in the first annular zone at a first momentum ratio between the injected second fuel and the combustion stream of from 30 to 50 effective to increase an average temperature in the first zone as the combustion stream flows through the transition piece;
• and
• injecting a portion of the second fuel in the second annular zone at a second momentum ratio between the injected second fuel and the combustion stream of from 25 to 45 effective to increase an average temperature in the second zone as the combustion stream flows through the transition piece, the second momentum ratio different from the momentum ratio.

A combustor for a gas turbine engine comprising:

• a primary combustion chamber for combusting a first fuel to form a combustion flow stream;
• and
• a transition piece located downstream from the primary combustion chamber, the transition piece comprising a plurality of injectors located around a circumference of the transition piece for injecting a second fuel into the combustion flow stream;
• wherein the injectors are configured to create a radial temperature profile at an exit of the transition piece having a reduced coefficient of variation relative to a radial temperature profile at an inlet of the transition piece;
• wherein the plurality of injectors comprise a center hole through which an amount of the fuel is injected radially and a plurality of injection holes angled relative to the center hole at an outlet end through which additional portions of the second amount of the fuel is injected angularly, the injectors are located at an axial position along the transition piece and are configured to ensure completion of the burning of the second fuel within the combustion flow stream within a target distance from a downstream outlet end of the transition piece;
• and
• wherein the target distance from the downstream outlet end is from 0 to 20 percent of an axial length of the transition piece;
• and
• wherein the injector injectors are located at a point from 25 to 75 percent along the axial length of the transition piece.

A transition piece for a gas turbine engine comprising a plurality of fuel injectors located between an inlet end of the transition piece and a point from 0 to 75 percent along an axial length of the transition piece from the inlet end, wherein the injectors are effective to reduce a radial temperature differential between an average temperature in a hotter central region of the combustion stream and an average temperature in a cooler peripheral region of the combustion stream as it flows through the transition piece

• wherein the plurality of injectors are located at an axial position along the transition piece and are effective to ensure completion of burning of a fuel injected by the injectors within a target distance from a downstream outlet of the transition piece, the target distance being from 0 to 20 percent of the axial length of the transition piece;
• and
• wherein the injectors are located at a point from 25 to 75 percent along the axial length of the transition piece
• wherein the injectors comprising first and second injectors, the first injectors comprising nozzles having a single center hole through which a first amount of the fuel is injected radially into the transition piece and the second injectors comprising nozzles having a center hole through which a first amount of the fuel is injected radially and a plurality of injection holes angled relative to the center hole through which additional portions of the second amount of the fuel can be injected angularly.

A combustor for a gas turbine engine comprising:

• a primary combustion chamber for combusting a first fuel to form a combustion flow stream;
• and
• a transition piece located downstream from the primary combustion chamber having the combustion stream flowing there through;
• wherein the transition piece comprises at least a central zone, a first zone located peripherally outward from the central zone, and a second zone located peripherally outward from the first zone;
• first means for injecting a first amount of the second fuel into the first zone of the transition piece, but not the central zone, the first means configured to increase an average temperature of a portion of the combustion stream in the first zone by a first amount;
• and
• second means for preferentially injecting a second amount of the second fuel into the second zone of the transition piece, but not the first zone or the central zone, the second means configured to increase an average temperature of a portion of the combustion stream in the second zone by a second amount different than the first amount;
• wherein the first and second means for injecting are configured to create a radial temperature profile at an outlet of the transition piece having a reduced coefficient of variation relative to a radial temperature profile at an inlet of the transition piece.