# US 2014/0196465 A1 · Lean-rich axial stage combustion in a can-annular gas turbine engine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0196465 A1 - Document ID: US20140196465A1 - Status: Published application - Kind: A1 - Application number: 13/739,316 - Filed: 2013-01-11 - Published: 2014-07-17 - Earliest claimed: 2013-01-11 - Assignees: Siemens Energy, Inc. - Inventors: Walter R. Laster; Peter Szedlacsek - Web page: https://patentgrep.com/patent/US20140196465A1 ## CPC - F23R 3/346: {for staged combustion} - F23R 3/286: {having fuel-air premixing devices (F23R3/30 takes precedence)} - F23R: GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS (fluidised bed combustion apparatus specially adapted for operation at superatmospheric pressures F23C10/16) ## Abstract An apparatus and method for lean/rich combustion in a gas turbine engine (10), which includes a combustor (12), a transition (14) and a combustor extender (16) that is positioned between the combustor (12) and the transition (14) to connect the combustor (12) to the transition (14). Openings (18) are formed along an outer surface (20) of the combustor extender (16). The gas turbine (10) also includes a fuel manifold (28) to extend along the outer surface (20) of the combustor extender (16), with fuel nozzles (30) to align with the respective openings (18). A method (200) for axial stage combustion in the gas turbine engine (10) is also presented. ## Claims ### Claim 1 A method for axial stage combustion in a gas turbine engine comprising: mixing a lean air-fuel mixture in a first stage of combustion of a can-annular combustor of the gas turbine engine, wherein the lean air-fuel mixture has an equivalence ratio of less than one; igniting the lean air-fuel mixture at the first stage of combustion to create hot combustion gas having a first temperature and free radicals; mixing a rich air-fuel mixture with an equivalence ratio of greater than one; injecting the rich air-fuel mixture into the hot combustion gas at a second stage of combustion of the can-annular combustor downstream from the first stage; and igniting the rich air-fuel mixture in the hot combustion gas at the second stage of combustion, such that the first temperature and the free radicals of the hot combustion gas promote combustion of the rich air-fuel mixture within a predetermined hydrocarbon emissions limit, and the first temperature of the hot combustion gas increases to a second temperature. ### Claim 2 (depends on 1) The method of claim 1, wherein the rich air-fuel mixture has an equivalence ratio between 3 and 10. ### Claim 3 (depends on 2) The method of claim 2, wherein the rich air-fuel mixture has an equivalence ratio between 3 and 5. ### Claim 4 (depends on 1) The method of claim 1, wherein an equivalence ratio of the rich air-fuel mixture is reduced as it diffuses into the hot combustion gas and the equivalence ratio of the rich air-fuel mixture is selected to be high enough so that the second temperature is less than an emission threshold temperature. ### Claim 5 (depends on 1) The method of claim 1, wherein the first temperature is in a range of 1300-1500 degrees C. and wherein the second temperature is in a range of 1500-1700 degrees C. ### Claim 6 (depends on 1) The method of claim 1, wherein the igniting of the lean air-fuel mixture generates a first degree of an emission in the hot combustion gas, wherein the igniting of the rich air-fuel mixture increases the first degree of the emission to a second degree of the emission, and wherein the second degree of the emission is within a predetermined emission limit. ### Claim 7 (depends on 6) The method of claim 6, wherein the emission comprises NOx. ### Claim 8 (depends on 1) The method of claim 1, wherein a split of a total amount of air between the lean air-fuel mixture and the rich air-fuel mixture is between 0.5% and 3.5% in the rich air-fuel mixture; and wherein a split of a total amount of fuel between the lean air-fuel mixture and the rich air-fuel mixture is between 5% and 20% in the rich air-fuel mixture. ### Claim 9 (depends on 8) The method of claim 8, wherein the split of the total amount of air is between 0.5 and 2% in the rich air-fuel mixture and wherein the split of the total amount of fuel is between 5 and 15% in the rich air-fuel mixture. ### Claim 10 A gas turbine engine comprising: a can-annular combustor; a transition in fluid communication between the combustor and a turbine; a combustor extender in fluid communication between the combustor and the transition; a plurality of wall openings formed through the combustor extender; and a fuel manifold extending along an outer surface of the combustor extender, said fuel manifold comprising a plurality of fuel nozzles aligned to deliver fuel through the respective plurality of wall openings. ### Claim 11 (depends on 10) The gas turbine engine of claim 10, further comprising: a mixer positioned between the fuel manifold and the outer surface of the combustor extender at each of the plurality of openings, said mixer including a first opening aligned with the respective fuel nozzle to receive fuel from the respective fuel nozzle and a second opening to receive an air flow; and a scoop positioned at each of the plurality of openings, said scoop configured to receive the fuel and the air flow from the mixer, said scoop is further configured to direct an air-fuel mixture of the fuel and the air flow into the respective opening. ### Claim 12 (depends on 11) The gas turbine engine of claim 11, wherein the second opening of the mixer is an annular opening to receive the air flow and wherein the first opening is formed in a central cross sectional region of the mixer. ### Claim 13 (depends on 11) The gas turbine engine of claim 11, wherein the scoop takes a conical shape that is angled inward toward an interior of the combustor extender. ### Claim 14 (depends on 11) The gas turbine engine of claim 11, wherein each fuel nozzle of the fuel manifold includes a valve to adjustably vary a volumetric flow rate of fuel directed into the first opening and to adjustably vary an equivalence ratio of the air-fuel mixture directed into the respective opening. ### Claim 15 (depends on 10) The gas turbine engine of claim 10, wherein the plurality of openings are formed along an outer circumference of the outer surface of the combustor extender and wherein the fuel manifold is configured to extend along the outer circumference of the outer surface of the combustor extender. ### Claim 16 (depends on 10) The gas turbine engine of claim 10, further comprising: a sleeve around an outer surface of the combustor, said sleeve including a supply line to direct fuel to the fuel manifold; a controller to supply fuel through the supply line to the fuel manifold, based on a load of the gas turbine engine exceeding a threshold load. ### Claim 17 (depends on 10) The gas turbine engine of claim 10, wherein the plurality of openings formed through the combustor extender are oval shaped. ### Claim 18 A method for axial stage combustion in a gas turbine engine comprising: igniting a lean air-fuel mixture at a first stage of combustion of the gas turbine engine to create hot combustion gas having a temperature below a predetermined NOx production threshold limit; mixing a rich air-fuel mixture with an equivalence ratio greater than or equal to three; injecting the rich air-fuel mixture into the hot combustion gas at a second stage of combustion downstream from the first stage; and utilizing heat of the hot combustion gas and free radicals therein to ignite the rich air-fuel mixture such that the rich air-fuel mixture is combusted within a predetermined hydrocarbon emissions limit and the temperature of the hot combustion gas is increased by a threshold amount to a temperature still below the NOx production threshold limit. ### Claim 19 (depends on 18) The method of claim 18, wherein the temperature of the hot combustion gas is increased from within a range of 1300-1500 degrees C. to within a range of 1500-1700 degrees C.