Patent Application
20080080967
Generally, during operation, air flows axially through fan assembly 12, in a direction that is substantially parallel to a central axis 34 extending through engine 10, and compressed air is supplied to high pressure compressor 14. The highly compressed air is delivered to combustor 16. Combustion gas flow (not shown in
Gas turbine engine 10 also includes an active clearance control system 100. In the exemplary embodiment, clearance control system 100 is coupled to a fan frame hub 40 associated with fan blades 24, and clearance control system 100 includes an inlet assembly 102 and at least two active clearance control supply pipes 104 and 106. Specifically, in the exemplary embodiment, a first active clearance control supply pipe 104 and a second active clearance control supply pipe 106 extend downstream from inlet assembly 102 to channel airflow towards a portion of high pressure turbine 18 and low pressure turbine 20, respectively. Specifically, in the exemplary embodiment, first pipe 104 is coupled to high pressure turbine casing manifold 108, and second pipe 106 is coupled to low pressure turbine casing manifold 110. In the exemplary embodiment, first pipe 104 includes a first control valve 112 and second pipe 106 includes a second control valve 114. Valves 112 and 114 each modulate airflow during engine operation.
Inlet assembly 102 is coupled to a portion of fan frame hub 40 to channel air discharged from fan assembly 12 towards high pressure turbine 18 and low pressure turbine 20 to facilitate controlling thermal expansion of first and second casing manifolds 108 and 110. More specifically, as shown in
In the exemplary embodiment, a portion of air discharged from the fan blades 24, is channeled through an intake side 122 of inlet assembly 102 for delivery into pipes 104 and 106. Specifically, in the exemplary embodiment, air intended for use with pipes 104 and 106 enters inlet assembly 102 from the same circumferential location, i.e. a single inlet location, for use with both high pressure turbine 18 and low pressure turbine 20. The use of a single inlet location facilitates reducing the complexity of clearance control system 100. In one embodiment, the single inlet location is located adjacent an outlet guide vane hub exit.
Inlet assembly 102 includes a plurality of louvers 130 that are aerodynamically designed and oriented to channel air from the fan discharge stream into inlet assembly 102 such that the air captured maintains a higher pressure facilitating optimizing dynamic head recovery of the captured air. Specifically, in the exemplary embodiment, louvers 130 are oriented at an angle with respect to central axis 34 of engine 10 that enables air to be “scooped” or channeled from the fan discharge stream. In the exemplary embodiment, louvers 130 are semi-elliptically-shaped and are oriented to channel a portion of the fan discharge stream into inlet assembly 102. Alternatively, louvers 130 may be of any suitable shape and/or may be positioned at any suitable angle within inlet assembly 102 that enables clearance control system 100 to function as described herein. The shape and position of louvers 130 facilitates increasing the pressure of the air that may be captured from the fan discharge stream. Additionally, as shown in
Inlet assembly 102 also includes an anchor plate 140 that circumscribes inlet assembly 102 adjacent intake side 122. More specifically, in the exemplary embodiment, anchor plate 140 is positioned upstream from louvers 130. Anchor plate 140 includes a plurality of openings 141 that are sized to receive at least one fastening mechanism (not shown) therethrough for coupling inlet assembly 102 to fan frame hub 40. In the exemplary embodiment, anchor plate 140 also includes a contoured inlet wall 142 that assists in channeling air into inlet assembly 102 with an enhanced pressure recovery. Countered inlet wall 142 extends into both sets of louvers 134 and 136. Inlet tube 121 extends in sealing contact between anchor plate 140 and plenum 125. The combination of inlet tube and plenum 125 facilitates reducing significant pressure losses of air by channeling the air directly from inlet assembly 102 into pipes 104 and 106 without passing through a dead air gap, as is common in known active control systems.
In the exemplary embodiment, each pipe 104 and 106 extends from plenum 125 and includes at least one bend 152 that turns air flowing therein. In the exemplary embodiment, the smooth curvature of each bend 152 facilitates channeling air through pipes 104 and 106 while minimizing pressure losses therein. Furthermore, the orientation, configuration, and size of contoured inlet wall 142, inlet tube 121, and plenum 125 also facilitate preventing pressure losses of air channeled therethrough.
In the exemplary embodiment, plenum 125 also includes retaining member 160 that circumscribes the exterior of pipes 104 and 106, and plenum 125. Retaining member 160 facilitates enhancing the structural support to pipes 104 and 106 and facilitates aligning pipes 104 and 106 with respect to each other. Specifically, in the exemplary embodiment, pipes 104 and 106 are adjacent each other near inlet assembly 102 and separate a distance apart as pipes 104 and 106 extend outward from inlet assembly 102 towards turbines 18 and 20.
In the exemplary embodiment, retaining member 160 is coupled to fan frame hub 40. Specifically, retaining member 160 circumscribes plenum 125 and includes a lip 162 that includes a plurality of openings 166 that are each sized to receive retaining mechanisms (not shown) therethrough to enable retaining member 160 to be coupled to fan frame hub 40.
During assembly, inlet assembly 102 is coupled to inlet tube 121 in a sealed joint. Inlet tube 121 is then coupled to plenum 125 and pipes 104 and 106 are each coupled to plenum 125. In the exemplary embodiment, plenum 125 is coupled to pipes 104 and 106 in a sealed joint to facilitate preventing air from leaking out of inlet assembly 102 and into a cowl support plenum 150.
Clearance control system 100 is then coupled to fan frame hub 40 with a plurality of retaining mechanisms (not shown) inserted through openings 141. Additionally, retaining mechanisms are inserted through openings 166 to couple plenum 125 and retaining member 160 to fan frame hub 40. Specifically, retaining member 160 is positioned adjacent an inner portion 172 of fan frame hub 40 and retaining mechanisms are used to secure retaining member 160 to inner portion 172 such that lip 162 contacts inner portion 172.
During operation, a portion of air discharged from fan blades 24 is channeled from fan assembly 12 towards clearance control system 100. Specifically, air discharged from fan assembly 12 is directed into clearance control system 100 through inlet assembly 102 and at a single inlet location. Air entering inlet assembly 102 is discharged downstream towards high pressure turbine casing manifold 108 and low pressure turbine casing manifold 110. Louvers 130 facilitate channeling air discharged from fan assembly 12 into clearance control system 100. The aerodynamic shape of louvers 130 facilitates capturing air from the fan discharge stream while maintaining an enhanced pressure recovery for the air entering clearance control system 100. The efficiency of clearance control system 100 is at least partially dependent on system pressure ratio and pressure recovery. Additionally, contoured inlet wall 142 aids in channeling a portion of the fan discharge stream into inlet system 102 such that the captured air from the fan stream has enhanced pressure when the air enters into clearance control system 100. Once air has entered inlet assembly 102, air is channeled through inlet tube 121 and into plenum 125. Plenum 125 provides a sealed area for air to flow into first and second pipes 104 and 106. Moreover, tube 121 and plenum 125 prevent air entering inlet assembly 102 from leaking out of clearance control system 100. Air is then channeled from plenum 125 into pipes 104 and 106.
In the exemplary embodiment, air flows through each pipe 104 and 106 towards turbines 18 and 20. The smooth curvature of bends 152 facilitates guiding the air into pipes 104 and 106 such that pressure losses associated with channeling the airflow are facilitated to be reduced. Air in pipes 104 and 106 flows toward each respective control valve 112 and 114. In the exemplary embodiment, control valves 112 and 114 are fully modulated and each valve 112 and 114 may be in either an open position or a closed position. When in the open position, cooling air continues to flow through pipes 104 and 106 towards respective manifolds 108 and 110. Directing cooling air towards manifolds 108 and 110 facilitates controlling thermal expansion of the rotor and stator assemblies. As a result, tighter blade clearances within turbines 18 and 20 are achieved through enhanced control and cooling of case manifold 108 and 110. As such, engine 10 performance is enhanced.
The method for operating a gas turbine engine herein includes channeling a portion of air discharged from the fan through a clearance control system including an inlet assembly that includes a plurality of louvers, and directing air from the inlet assembly into a first pipe and second pipe coupled to the inlet assembly such that pressure losses associated with the airflow are facilitated to be reduced.
The clearance control system described herein facilitates maintaining a clearance gap defined between static casing assemblies and adjacent rotating components. Cooling air supplied towards the static casing assemblies from the clearance control system can come from any cooling source inside the engine. Moreover, the clearance control system facilitates enhanced control of thermal expansion rates, which ultimately facilitates maintaining tighter clearances during engine operation.
The above-described clearance control system provides a cost-effective and reliable means for increasing the source pressure for turbines than known bleed air systems without negatively impacting bypass fan efficiency. This is achieved by directing air from the fan stream into bleed air system at the same bleed location to increase the amount of pressure within the air captured from the fan stream. Additionally, the shape and position of louvers increases the pressure captured from the fan stream. Furthermore, contoured inlet wall, inlet tube, and gentle bend prevent pressure loss once air from the fan stream has entered bleed air system. Thus, the clearance control system facilitates increasing turbine efficiency a cost-effective and reliable manner.
An exemplary embodiment of a bleed air system for a clearance control system is described above in detail. The system illustrated is not limited to the specific embodiments described herein, but rather, components of each system may be utilized independently and separately from other components described herein.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
