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An annular combustor and a method for operating a gas turbine engine over a power demand range facilitate combustion in a lean direct ignition (LDI) mode over an extended range of operating fuel air ratios. The flow primary combustion air admitted into the primary combustion zone is varied in respon

An annular combustor and a method for operating a gas turbine engine over a power demand range facilitate combustion in a lean direct ignition (LDI) mode over an extended range of operating fuel air ratios. The flow primary combustion air admitted into the primary combustion zone is varied in response to power demand from a maximum air flow rate of high power demand to a minimum flow air rate of low power demand, while the flow of dilution air into a quench zone downstream of the primary combustion zone is increased from a minimum air flow rate at high power demand to a maximum air flow rate at low power demand.

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1. An annular combustor for a gas turbine engine, comprising: a diffuser;an inboard liner extending circumferentially and extending longitudinally fore to aft;an outboard liner extending circumferentially and extending longitudinally fore to aft and circumscribing the inboard liner;a bulkhead extend

1. An annular combustor for a gas turbine engine, comprising: a diffuser;an inboard liner extending circumferentially and extending longitudinally fore to aft;an outboard liner extending circumferentially and extending longitudinally fore to aft and circumscribing the inboard liner;a bulkhead extending between a forward end of the inboard liner and a forward end of the outboard liner and in cooperation with the inboard liner and the outboard liner defining the annular combustion chamber;a plurality of primary combustion air admission nozzles downstream of and operatively coupled with the diffuser, and opening through the bulkhead for admitting air into a forward region of the annular combustion chamber, each air admission nozzle of the plurality of air admission nozzles including a throat having a radially variable flow area geometry by radially translating a mechanism;a plurality of first dilution air admission holes formed in the outboard liner at a location downstream of the forward region of the combustion chamber and arranged in at least one circumferential row at circumferentially spaced intervals;a plurality of second dilution air admission holes formed in the inboard liner at a location downstream of the forward region of the combustion chamber and arranged in at least one circumferential row at circumferentially spaced intervals;wherein a flow area geometry of each dilution air admission hole of the plurality of first dilution air admission holes is variable and additionally, or alternatively, the flow area of each dilution air admission hole of the plurality of second dilution air admission holes is variable; anda plurality of plugs having a conically shaped outside surface, each plug of the plurality of plugs operatively associated with a corresponding dilution air admission hole of the plurality of first or second dilution air admission holes to adjust the flow area geometry of the corresponding dilution air admission hole. 2. The annular combustor as recited in claim 1 wherein the radially variable flow area geometry of the throat is variable between a maximum airflow area at high power demand and a minimum airflow area at low power demand. 3. The annular combustor as recited in claim 2 wherein the radially variable flow area geometry of the throat is continuously variable between the maximum airflow area at high power demand and the minimum airflow area at low power demand. 4. The annular combustor as recited in claim 2 wherein the radially variable flow area geometry of the throat is step-wise variable between the maximum airflow area at high power demand and the minimum airflow area at low power demand through at least one intermediate airflow area at an intermediate power demand. 5. The annular combustor of claim 1 wherein each air admission nozzle of the plurality of air admission nozzles further includes an air passage downstream of the throat, and a fuel injector circumferentially surrounded by the associated air passage, the fuel injector located downstream of the throat and extending along the centerline of the air admission nozzle. 6. The annular combustor of claim 2 wherein radially translating the mechanism causes a narrowing of the throat at low power demand and a widening of the throat at high power demand. 7. The annular combustor of claim 6 wherein the narrowing of the throat creates the minimum airflow area at low power demand and the widening of the throat creates the maximum airflow area at high power demand. 8. The annular combustor as recited in claim 1 wherein the plurality of second dilution air admission holes is offset circumferentially from the plurality of first dilution air admission holes. 9. The annular combustor of claim 1 wherein at least one of the plurality of first dilution air admission holes is circumferentially aligned with the fuel injector. 10. The annular combustor of claim 1 wherein at least two of the plurality of second dilution air admission holes are circumferentially located between each of the plurality of air admission nozzles.