Power plants – Combustion products used as motive fluid
Reexamination Certificate
1998-12-18
2001-09-11
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S737000, C060S732000, C060S750000, C060S751000
Reexamination Certificate
active
06286298
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas turbine engine combustor having at least one trapped vortex cavity and, more particularly, to an apparatus and method for injecting fuel into such cavity and providing high inlet air flows to the combustion chamber through flow passages of a dome inlet module in accordance with a Rich-Quench-Lean (RQL) process.
2. Description of Related Art
Advanced aircraft gas turbine engine technology requirements are driving the combustors therein to be shorter in length, have higher performance levels over wider operating ranges, and produce lower exhaust pollutant emission levels. One example of a combustor designed to achieve these objectives is disclosed in U.S. Pat. No. 5,619,855 to Burrus. As seen therein, the Burrus combustor is also to operate efficiently at inlet air flows having a high subsonic Mach Number. This stems in part from a dome inlet module which allows air to flow freely from an upstream compressor to the combustion chamber, with fuel being injected into the flow passage. The combustor also has inner and outer liners attached to the dome inlet module which include upstream cavity portions for creating a trapped vortex of fuel and air therein, as well as downstream portions extending to the turbine nozzle.
It will be noted in the aforementioned Burrus combustor that the fuel is injected into the trapped vortex cavities through a portion of the liner forming an aft wall of such cavity. Fuel is also injected into the flow passages of the dome inlet module via atomizers located along hollow vanes of the dome inlet module, the vanes being in flow communication with a fuel manifold. While functional for its intended purpose, it has been found that the fuel injection approach taken in the '855 patent lacks simplicity. In particular, it will be understood that this design requires the occupation of significant space within the combustor housing cavity, as separate systems are utilized for injecting the fuel into the cavities and the dome inlet module. This not only represents a large cost from a manufacturing standpoint, but extraction of fuel injectors from the engine for repair or replacement with a major tear down of the engine to expose the combustor cavity section is not permitted.
In order to address the concerns associated with the '855 combustor, a new design employing a plurality of circumferentially spaced fuel injector bars are located upstream of a modified dome inlet module is shown and disclosed in a patent application Ser. No. 09/215,863 entitled “Fuel Injector Bar For A Gas Turbine Engine Combustor Having Trapped Vortex Cavity,” which is also owned by the assignee of the present invention, hereby incorporated by reference, and filed concurrently herewith. It will be appreciated that the combustor of this concurrently filed patent application utilizes the fuel injector bars to inject fuel into the cavities in the liner, as well as the flow passages of the dome inlet module in a dual stage process.
Another method for achieving low emissions within combustor designs is a concept known as Rich-Quench-Lean (RQL). This concept features a very rich primary combustion zone with local equivalence ratios typically much greater than 1.0, which allows initiation of the mixing of the fuel with some of the combustor air and provides combustion under oxygen deprived conditions. Accordingly, formation of nitrous oxide (NOx) in the primary zone is reduced. The partially burned combustion gases from the rich primary zone then undergo a rapid dilution from the injection of significant amounts of additional fresh combustor air. The difficulty is in achieving a rapid mixing of the fresh air with the rich primary zone combustion gases to drive the overall mixture quickly to a lean state (i.e., an equivalence ratio well below 1.0). This prevents NOx formation in the dilution zone by not allowing the combustion gases sufficient time at local equivalence ratios between 0.85 and 1.15 where rapid NOx formation occurs. While RQL combustors have a significant advantage over other low emissions concepts in the area of combustion dynamics, it is known that low emissions, good combustion efficiency, and good exit gas temperature profile and pattern are difficult to achieve in the RQL concept.
Accordingly, it would be desirable for a combustor design to be developed which is compatible with use of the RQL concept. It would also be desirable for a fuel injection system to be developed in a gas turbine engine combustor having a liner with one or more trapped vortex cavities so that the RQL concept can be utilized therewith.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a fuel injection system for a gas turbine engine combustor is disclosed, wherein the combustor includes a dome inlet module having a plurality of flow passages formed therein and at least one cavity formed in a linear downstream of said dome inlet module. The fuel injection system includes a fuel supply and a plurality of fuel injector bars positioned circumferentially around and interfacing with the inlet dome module. The fuel injector bars are in flow communication with the fuel supply, with each of the fuel injector bars further including a body portion having an upstream end, a downstream end, and a pair of sides. At least one injector is formed in the downstream end of the body portion and in flow communication with the fuel supply, whereby fuel is provided to the cavities through the fuel injector bars.
In accordance with a second aspect of the present invention a method of operating a gas turbine combustor is disclosed, where the combustor includes a dome inlet module having a plurality of flow passages formed therein and at least one cavity formed within a combustion chamber by a liner downstream of the dome inlet module. The method includes the step of injecting fuel into an upstream end of the cavity so as to create a rich primary combustion zone therein, injecting air into the cavity to create a trapped vortex of fuel and air therein, igniting the mixture of fuel and air in the cavity to form combustion gases, diluting the combustion gases with a flow of air through the flow passages of the dome inlet module, and driving the overall mixture of fuel and air within the combustion chamber to a lean state.
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Burrus David L.
Johnson Arthur W.
Mongia Hukam C.
Andes William Scott
General Electric Company
Hess Andrew C.
Kim Ted
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