# US 8,783,008 B2 · Gas turbine reheat combustor including a fuel injector for delivering fuel into a gas mixture together with cooling air previously used for convectively cooling the reheat combustor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,783,008 B2 - Document ID: US8783008B2 - Status: Granted - Kind: B2 - Application number: 13/474,422 - Filed: 2012-05-17 - Published: 2012-10-18 - Granted: 2014-07-22 - Earliest claimed: 2009-11-17 - Assignees: ALSTOM Technology Ltd - Applicants: Adnan Eroglu; Thiemo Meeuwissen; Peter Flohr - Inventors: Adnan Eroglu; Thiemo Meeuwissen; Peter Flohr - Web page: https://patentgrep.com/patent/US8783008B2 ## CPC - F23R 3/286: {having fuel-air premixing devices (F23R3/30 takes precedence)} - F23R 3/34: Feeding into different combustion zones - F23R 2900/03042: Film cooled combustion chamber walls or domes - F23R 2900/03341: Sequential combustion chambers or burners - F23R 2900/03342: Arrangement of silo-type combustion chambers - 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 A reheat combustor for a gas turbine engine includes a fuel/gas mixer for mixing fuel, air and combustion gases produced by a primary combustor and expanded through a high pressure turbine. Fuel injectors inject fuel into the mixer together with spent cooling air previously used for convectively cooling the reheat combustor. The fuel mixture is burnt in an annular reheat combustion chamber prior to expansion through low pressure turbine inlet guide vanes. The fuel/gas mixer and optionally the combustion chamber define cooling paths through which cooling air flows to convectively cool their walls. The fuel injectors are also convectively cooled by the cooling air after it has passed through the fuel/gas mixer cooling paths. The low pressure turbine inlet guide vanes may also define convective cooling paths in series with the combustion chamber cooling paths. ## Claims ### Claim 1 A reheat combustor for a gas turbine engine, comprising: a fuel/gas mixer for mixing fuel with combustion gases that have been produced by a primary combustor and expanded through a high pressure turbine; a plurality of fuel injectors for injecting fuel into the fuel/gas mixer; and an annular combustion chamber downstream of the fuel/gas mixer, in which the mixture of injected fuel and combustion gases is combusted prior to expansion through a low pressure turbine; a wall of the fuel/gas mixer defining at least one convective cooling path through which cooling air flows, in use, for convectively cooling the fuel/gas mixer; and wherein the fuel injectors are arranged to inject the cooling air previously used for convective cooling of the fuel/gas mixer into mixing zones of the fuel/gas mixer together with the fuel. ### Claim 2 (depends on 1) A reheat combustor according to claim 1, wherein the wall of each fuel injector defines a fuel injector convective cooling path and the fuel injector convective cooling path is connected to receive cooling air from the at least one convective cooling path of the fuel/gas mixer. ### Claim 3 (depends on 1) A reheat combustor according to claim 1, the fuel/gas mixer comprising: an annular structure that is segmented into a plurality of discrete mixing zones, each mixing zone having at least one fuel injector, the mixing zones being angularly spaced apart around the annulus, a circumferential extent of individual mixing zones being defined by angularly spaced-apart side walls and their radial extent being defined by radially inner and radially outer walls of the fuel/gas mixer, the side walls and/or at least one of the radially inner and outer walls defining the at least one fuel/gas mixer convective cooling path through which the cooling air flows, in use, to convectively cool the fuel/gas mixer. ### Claim 4 (depends on 1) A reheat combustor according to claim 1, the combustion chamber comprising: at least one of a radially inner and a radially outer combustion chamber wall that defines a combustion chamber cooling path through which the cooling air flows, in use, to convectively cool the combustion chamber. ### Claim 5 (depends on 4) A reheat combustor according to claim 4, wherein at least one cooling path of the combustion chamber and at least one cooling path of the fuel/gas mixer are connected to enable cooling air to flow through a combustion chamber cooling path and then through a fuel/gas mixer cooling path. ### Claim 6 (depends on 1) A reheat combustor according to claim 1, comprising: an annular array of low pressure turbine inlet guide vanes (LP IGV's) provided at an exit of the reheat combustion chamber and a convective cooling path in each LP IGV communicating with at least one convective cooling path in the reheat combustion chamber. ### Claim 7 (depends on 1) A reheat combustor according to claim 1, wherein all the convectively cooled cooling paths share a common supply of cooling air. ### Claim 8 (depends on 2) A reheat combustor according to claim 2, wherein the fuel injectors extend radially into the mixing zones and are arranged to inject fuel into the mixing zones coaxially inside annular jets of the cooling air, injection being in the downstream direction. ### Claim 9 (depends on 8) A reheat combustor according to claim 8, wherein the fuel injector convective cooling paths are defined between an inner fuel passage and an outer wall of each fuel injector and fuel is injectable into the mixing zones through a plurality of radially spaced-apart fuel injector tubes that extend from a fuel passage through corresponding holes in the outer wall, the holes being of larger cross-section than the tubes, whereby in use cooling air exits from the fuel injector cooling path into the mixing zones as annular jets of air surrounding jets of fuel. ### Claim 10 (depends on 8) A reheat combustor according to claim 8, wherein the fuel injectors are dual fuel injectors each fuel injector comprising: an outer wall; a first fuel passage for a first fuel; and a second fuel passage for a second fuel; wherein the second fuel passage is located inside the first fuel passage; the fuel injector convective cooling paths are defined between the first fuel passage and the outer wall of each fuel injector; a first fuel is injectable into the mixing zones through a plurality of radially spaced first injector tubes that extend from the first fuel passage through the outer wall of the fuel injector; a second fuel is injectable into the mixing zones through a plurality of radially spaced second injector tubes that extend from the second fuel passage through a wall of the first fuel passage and the outer wall of the fuel injector, the second injector tubes being of smaller cross-section than the first injector tubes and extending concentrically through the first injector tubes; and each first injector tube projects through a corresponding hole in the outer wall of the fuel injector, the holes being of larger cross-section than the first injector tubes, whereby in use cooling air exits from the fuel injector cooling path into the mixing zones as annular jets of air surrounding jets of the first and/or second fuel. ### Claim 11 A gas turbine engine, comprising: a low pressure compressor; a high pressure compressor; a primary combustor; a high pressure turbine for expanding combustion gases produced by the primary combustor; a reheat combustor for reheating the combustion gases following expansion through the high pressure turbine; and a low pressure turbine for expanding the reheated combustion gases wherein the reheat combustor comprises: a fuel/gas mixer for mixing fuel with combustion gases that have been produced by the primary combustor and expanded through the high pressure turbine; a plurality of fuel injectors for injecting fuel into the fuel/gas mixer; an annular combustion chamber downstream of the fuel/gas mixer, in which the mixture of injected fuel and combustion gases is combusted prior to expansion through a low pressure turbine; wherein a wall of the fuel/gas mixer defines at least one convective cooling path through which cooling air flows, in use, to convectively cool the fuel/gas mixer; and the fuel injectors are arranged to inject the cooling air previously used for convective cooling of the fuel/gas mixer into mixing zones of the fuel/gas mixer together with the fuel. ### Claim 12 (depends on 11) A gas turbine engine according to claim 11, wherein the wall of each fuel injector defines a fuel injector convective cooling path and the fuel injector convective cooling path is connected to receive cooling air from the at least one convective cooling path of the fuel/gas mixer. ### Claim 13 (depends on 11) A gas turbine engine according to claim 11, wherein the cooling air for convective cooling is supplied by the low pressure compressor. ### Claim 14 A method of cooling a reheat combustor including a mixer for mixing fuel with combustion gases that have been produced by a primary combustor in a gas turbine engine, comprising: injecting cooling air by fuel injectors into mixing zones of the reheat combustor together with fuel, wherein the injected cooling air was previously used for convectively cooling at least part of a wall of the mixing zone of the mixer downstream of the fuel injectors, the wall defining at least one convective cooling path through which the cooling air flows. ### Claim 15 (depends on 14) A method according to claim 14, comprising: convectively cooling the fuel injectors by the cooling air before it is injected into the mixing zones with the fuel. ### Claim 16 A method of cooling a reheat combustor in a gas turbine engine, comprising: injecting cooling air previously used for convectively cooling at least a part of the reheat combustor by fuel injectors into mixing zones of the reheat combustor together with fuel; convectively cooling a combustion chamber downstream of the mixing zones; convectively cooling mixing zones with cooling air therefrom; convectively cooling low pressure turbine inlet guide vanes (LP IGV's) downstream of the combustion chamber; and convectively cooling the combustion chamber with cooling air therefrom. ### Claim 17 (depends on 16) A method according to claim 16, comprising: supplying the cooling air from a single source. ### Claim 18 (depends on 16) A method according to claim 16, comprising: supplying the cooling air from a low pressure compressor of the gas turbine engine.