Patent Application
20130205799
The invention relates generally to gas turbines and, more particularly, to an interface between an inlet flow conditioner and a compressor discharge air passage in a gas turbine.
Gas turbine engines typically include a compressor for compressing an incoming airflow. The airflow is mixed with fuel and ignited in a combustor for generating hot combustion gases. The combustion gases in turn flow to a turbine. The turbine extracts energy from the gases for driving a shaft. The shaft powers the compressor and generally another element such as an electrical generator.
Cold air from a flow sleeve enters into the combustor headend region and is distributed among a plurality of nozzles. Generally, air passes through an inlet flow conditioner (IFC) and becomes uniform in circumferential direction. Subsequently, it is rotated by axially placed vanes, and fuel is injected into the flow through holes in the vanes for premixing of fuel and air.
In existing designs, the end cap to fuel nozzle IFC interface does not make a seamless transition. The step or cavity recess allows for substantial flow turning disturbances and losses to impact the uniformity of the flow turning into the fuel nozzle IFC. It would be desirable to smooth the flow of headend air to minimize pressure losses, avoid flow trips and reduce flow field disturbances.
In an exemplary embodiment, a compressor discharge air passage in a gas turbine includes a cap baffle positioned radially inward of the forward casing, where the cap baffle and forward casing define an upstream passage for compressor discharge air. A cap back plate is disposed at an end of the cap baffle and includes a curved exterior surface to facilitate turning the compressor discharge air. An inlet flow conditioner (IFC) is cooperable with the cap back plate and is positioned and shaped to direct the compressor discharge air toward a swirler inlet. An end of the IFC includes a curved exterior surface that is continued from the curved exterior surface of the cap back plate.
In another exemplary embodiment, a gas turbine includes a forward casing coupled with a compressor discharge casing, an end cover coupled with the forward casing, a plurality of fuel nozzles coupled with the end cover, and the compressor discharge air passage including the cap baffle, the cap back plate, and the IFC cooperable with the cap back plate.
In yet another exemplary embodiment, an interface between an inlet flow conditioner and a compressor discharge air passage in a gas turbine includes a cap back plate including a curved exterior surface, and an IFC cooperable with the cap back plate, where an end of the IFC includes a curved exterior surface that is continued from the curved exterior surface of the cap back plate.
A casing surrounds each combustor 14 to contain the compressed working fluid from the compressor 12. Nozzles are arranged in an end cover, for example, with outer nozzles radially arranged around a center nozzle. The compressed working fluid from the compressor 12 flows between the casing and a liner to the outer and center nozzles, which mix fuel with the compressed working fluid, and the mixture flows from the outer and center nozzles into upstream and downstream chambers where combustion occurs.
An upstream air passage 26 is defined by a cap baffle 28 positioned radially inward of the forward casing 20. In a conventional construction, headend compressor discharge air is directed via the upstream passage 26 to the end cover 24. The head end air is turned approximately 180° and is directed into the fuel nozzle to be mixed with fuel for downstream combustion. With existing designs, the cap baffle includes a curved end or tip to facilitate turning the headend air toward the fuel nozzle. Existing designs, however, allow for substantial flow turning disturbances and losses, which adversely impact the uniformity of the flow turning into the fuel nozzle.
The compressor discharge air passage shown in
The upstream air passage 26 is an annular passage that provides inlet air for the fuel nozzles. The IFC 32 generally comprises a bell mouthed cylindrical component that extends annularly across the annularly-arranged outer nozzles.
Preferably, the IFC 32 is coupled with the cap back plate 30 via a tongue and groove connection or the like. That is, the end 36 of the IFC 32 is engageable with a corresponding slot or groove 38 in the cap back plate 30. Preferably, the slot 38 is sized to accommodate stack up variations of gas turbine components. The slot 38 is also sized to accommodate variations in IFC height and position.
As shown, the IFC 32 is connected between the cap back plate 30 and the fuel nozzle inlet 34 (swirler inlet).
By providing the interface between the upstream passage and the inlet flow conditioner, headend air flow can be smoothly turned to minimize pressure losses, avoid flow trips and minimize field disturbances. The structure results in added pressure and air supply as well as more uniform air supply into the fuel nozzle, resulting in more uniform combustion. This result is especially advantageous with quat fuel injection systems due to elevated flame holding risks.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
