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A combustor includes outer and inner liners joined together by a dome to define a combustion chamber. A row of air swirlers is mounted in the dome and includes corresponding main fuel injectors for producing corresponding fuel and air mixtures. Pilot fuel injectors fewer in number than the main inje

A combustor includes outer and inner liners joined together by a dome to define a combustion chamber. A row of air swirlers is mounted in the dome and includes corresponding main fuel injectors for producing corresponding fuel and air mixtures. Pilot fuel injectors fewer in number than the main injectors are mounted in the dome between corresponding ones of the swirlers. Staged fuel injection from the pilot and main injectors is used for starting the combustor during operation.

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1. A combustor comprising:annular outer and inner combustion liners joined together at upstream ends by an annular dome to define a combustion chamber therebetween; a row of air swirlers mounted in said dome for swirling air into said chamber; a row of main injectors mounted in said swirlers for inj

1. A combustor comprising:annular outer and inner combustion liners joined together at upstream ends by an annular dome to define a combustion chamber therebetween; a row of air swirlers mounted in said dome for swirling air into said chamber; a row of main injectors mounted in said swirlers for injecting fuel for mixing with said swirled air to form corresponding fuel and air mixtures; a plurality of pilot injectors fewer in number than said main injectors, and mounted in said dome between corresponding ones of said swirlers for injecting fuel into said chamber; a common fuel manifold joined to said plurality of pilot injectors and having a common flow valve to control fuel flow thereto; at least one common fuel manifold joined to said plurality of main injectors and having a common flow valve to control fuel flow thereto; and a controller operatively joined to said flow valves for staging fuel delivery to said manifolds firstly to only said pilot injectors and following in turn circumferentially to said main injectors. 2. A combustor according to claim 1 wherein:said pilot injectors are grouped in a common pilot cluster in a circumferentially minor sector of said dome, and extend through a radially outer portion of said dome; and said main injectors are grouped in first and second main clusters, each overlapping circumferentially opposite ends of said pilot cluster, and being disposed radially inwardly therefrom in a radial middle portion of said dome. 3. A combustor according to claim 2 wherein;said main injectors are further grouped in a third main cluster and interspersed in said pilot cluster, and in a fourth main cluster disposed opposite to said third cluster in said dome middle portion; said pilot cluster is joined to a first fuel manifold having a first flow valve; said first and second clusters are joined to a second fuel manifold having a second flow valve; and said third and fourth clusters are joined to a third fuel manifold having a third flow valve. 4. A combustor according to claim 3 further comprising a pair of igniters mounted in said outer portion of said dome minor sector interspersed in said main injectors and said pilot injectors.5. A combustor comprising:annular outer and inner combustion liners joined together at upstream ends by an annular dome to define a combustion chamber therebetween; a row of air swirlers mounted in said dome for swirling air into said chamber; a row of main injectors mounted in said swirlers for injecting fuel for mixing with said swirled air to form corresponding fuel and air mixtures; a plurality of pilot injectors fewer in number than said main injectors, and mounted in said dome between corresponding ones of said swirlers for injecting fuel into said chamber, said pilot injectors are grouped in a common pilot cluster in a circumferentially minor sector of said dome, and extend through a radially outer portion of said dome; and wherein said pilot injectors comprise fuel-pressure atomizing injectors extending through said dome without cooperating air swirlers therearound; and a controller operatively joined to said main and pilot injectors for staging fuel delivery thereto firstly to said pilot injectors and following in turn circumferentially to said main injectors. 6. A combustor according to claim 5 wherein said main injectors comprise airblast-atomizing injectors, each having a tip with side apertures for receiving air.7. A combustor according to claim 6 wherein said main and pilot injectors alternate circumferentially in said minor sector.8. A combustor according to claim 7 further comprising:a first fuel manifold joined to said pilot cluster; a second fuel manifold joined to said first and second main clusters; and a third fuel manifold joined to said third and fourth main clusters. 9. A combustor according to claim 8 wherein said controller is operatively joined to said first, second, and third manifolds for staging fuel flow sequentially in turn thereto.10. A method of starting said combustor according to claim 8 in a gas turbine engine including an upstream compressor joined by a rotor to a downstream turbine, comprising:operating a starter to accelerate said rotor and produce pressurized air in said compressor for flow to said combustor; staging pilot fuel to said pilot cluster for producing a pilot flame in said combustion chamber to further accelerate said rotor; staging main fuel to said first and second main clusters for mixing with said pressurized air channeled through said swirlers to produce a main flame ignited by said pilot flame to further accelerate said rotor; staging main fuel to said third and fourth main clusters for mixing with said pressurized air channeled through said swirlers to add to said main flame and further accelerate said rotor; terminating fuel flow to said pilot clusters; disconnecting said starter from said rotor; and fueling all said main clusters to further accelerate said rotor to steady state idle speed. 11. A combustor comprising:annular outer and inner combustion liners joined together at upstream ends by an annular dome to define a combustion chamber therebetween; a row of air swirlers mounted in said dome for swirling air into said chamber; a row of main injectors mounted in said swirlers for injecting fuel for mixing with said swirled air to form, corresponding fuel and air mixtures; a plurality of pilot injectors fewer in number than said main injectors, and mounted in said dome between corresponding ones of said swirlers for injecting fuel into said chamber; a common fuel manifold joined to said plurality of pilot injectors and having a common flow valve to control fuel flow thereto; and two fuel manifolds joined to said plurality of main injectors and having corresponding flow valves to control fuel flow thereto. 12. A method of starting said combustor according to claim 11 comprising:staging pilot fuel firstly to said pilot injectors; staging main fuel secondly to said main injectors following in time fuel commencement to said pilot injectors; and terminating fuel flow to said pilot injectors following in time fuel commencement to said main injectors. 13. A combustor comprising:annular outer and inner combustion liners joined together at upstream ends by an annular dome to define a combustion chamber therebetween; a row of air swirlers mounted in said dome for swirling air into said chamber; a row of main injectors mounted in said swirlers for injecting fuel for mixing with said swirled air to form corresponding fuel and air mixtures; and a plurality of pilot injectors fewer in number than said main injectors, and mounted in said dome between corresponding ones of said swirlers for injecting fuel into said chamber; and said pilot injectors are grouped in a common pilot cluster in a circumferentially minor sector of said dome; and said main injectors are grouped in first and second main clusters each overlapping circumferentially opposite ends of said pilot cluster. 14. A combustor according to claim 13 wherein said main injectors are further grouped in a third main cluster and interspersed in said pilot cluster, and in a fourth main cluster disposed opposite to said third cluster.15. A combustor according to claim 14 further comprising:a first fuel manifold joined to said pilot cluster; a second fuel manifold joined to said first and second main clusters; and a third fuel manifold joined to said third and fourth main clusters. 16. A combustor according to claim 15 further comprising a controller operatively joined to said first, second, and third manifolds for staging fuel flow sequentially in turn thereto.17. A method of starting said combustor according to claim 15 comprising:staging pilot fuel firstly to said first manifold for discharge from said pilot injectors; staging main fuel secondly to said second manifold for discharge from said main injectors in said first and second clusters; staging main fuel thirdly to said third manifold for discharge from said main injectors in said third and fourth clusters; and terminating fuel flow to said pilot injectors following fuel flow to all said main clusters. 18. A combustor according to claim 14 further comprising a pair of igniters mounted in said dome minor sector interspersed in said main injectors and said pilot injectors.19. A combustor according to claim 18 wherein said main and pilot injectors alternate circumferentially in said minor sector.20. A combustor according to claim 14 wherein said pilot injectors comprise fuel-pressure atomizing injectors extending through said dome without cooperating air swirlers therearound.21. A combustor according to claim 20 wherein said main injectors comprise airblast-atomizing injectors.22. A method of starting said combustor according to claim 14 in a gas turbine engine including an upstream compressor joined by a rotor to a downstream turbine, comprising:operating a starter to accelerate said rotor and produce pressurized air in said compressor for flow to said combustor; staging pilot fuel to said pilot cluster for producing a pilot flame in said combustion chamber to further accelerate said rotor; staging main fuel to said first and second main clusters for mixing with said pressurized air channeled through said swirlers to produce a main flame ignited by said pilot flame to further accelerate said rotor; staging main fuel to said third and fourth main clusters for mixing with said pressurized air channeled through said swirlers to add to said main flame and further accelerate said rotor; terminating fuel flow to said pilot clusters; disconnecting said starter from said rotor; and fueling all said main clusters to further accelerate said rotor to steady state idle speed. 23. A method according to claim 22 wherein said third and fourth are fueled after commencement of fueling of said first and second clusters.24. A method according to claim 23 wherein said first and second clusters are fueled simultaneously, and said third and fourth clusters are fueled simultaneously.