Patent Application
20070110568
The present invention relates to a gas turbine engine and, more particularly, to a shroud in a turbine section of the gas turbine engine.
A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power an aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine may include, for example, a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section is positioned at the front of the engine, and includes a fan that induces air from the surrounding environment into the engine and accelerates a fraction of this air toward the compressor section. The remaining fraction of induced air is accelerated into and through a bypass plenum, and out the exhaust section.
The compressor section is configured to raise the pressure of the air to a relatively high level and includes an impeller that has a plurality of blades extending therefrom that accelerate and compress the air. The compressed air then exits the compressor section, and is energized by the combustor section. Next, the energized air is directed into the turbine section, which includes a rotor and a plurality of turbine blades that are mounted thereto. The air impinges the turbine blades and causes the rotor to rotate and to generate energy.
To protect the rotor blades from tip loss, a suitably sized annular shroud surrounds the rotor blades. Typically, the annular shroud and blades define a radial clearance gap therebetween that is sufficiently large to allow the blades to rotate without contacting the shroud, while small enough to optimize engine efficiency. Thus, maintaining the annular shroud in a particular position relative to the blades is preferable.
In one positioning configuration, the annular shroud is coupled to a cylindrical flowpath housing that is mounted around the rotor. Both the turbine shroud and flowpath housing include pilots that mate with each other to ensure proper radial positioning of the shroud on the flowpath housing. In many cases, the shroud pilot is an annular protruding ring formed on the shroud inner surface and the flowpath housing pilot is a corresponding structure formed on the flowpath housing outer surface. In many gas turbine engine configurations, the flowpath housing also includes a plurality of support struts that radially extend at least partially therethrough.
During engine operation, exposure to the energized air from the combustor section may cause the flowpath housing struts to expand radially outwardly at a rate that is faster than the radial expansion rate of the cylindrical flowpath housing. Accordingly, the flowpath housing may become misshapen, and may consequently form a rectangular-shaped component. As a result, the annular shroud may become misshapen, thereby undesirably altering the configuration of the clearance gap and the positioning of the shroud relative to the flowpath housing.
Therefore, there is a need for a shroud that allows the flowpath housing to radially expand without compromising the configuration of the clearance gap. Additionally, it is desirable for the shroud to be simple and inexpensive to manufacture and to implement.
The present invention provides a turbine section of an engine that includes a shaft, a plurality of blades extending radially from the shaft, a bearing assembly, a flowpath housing, and a shroud. The bearing assembly is mounted to the shaft adjacent to the plurality of blades. The flowpath housing is coupled to the bearing assembly and includes an inner cylinder, an outer cylinder, and a strut. The inner and outer cylinders each include a strut attachment point between which the strut is coupled, and the outer cylinder includes an outer surface. The shroud is disposed concentric to the outer cylinder and has an inner surface including a groove formed therein that is substantially aligned with the outer cylinder strut attachment point. The groove has a depth that provides and maintains a gap between the outer cylinder outer surface and the shroud inner surface when the flowpath housing is exposed to heat and the strut radially expands.
In another embodiment, and by way of example only, the turbine section of the engine includes a shaft, a plurality of blades extending radially from the shaft, a bearing assembly mounted to the shaft adjacent to the plurality of blades, a flowpath housing coupled to the bearing assembly, and a shroud. The flowpath housing includes an inner cylinder, an outer cylinder, and a plurality of struts, where the inner and outer cylinders each includes a plurality of strut attachment points between which the plurality of struts extend, and the outer cylinder includes an outer surface and an annular protrusion formed on the outer surface. The shroud is disposed concentric to the outer cylinder and has an inner surface and an annular protrusion formed on the inner surface. The shroud annular protrusion is configured to mate with the flowpath housing annular protrusion and includes a plurality of grooves formed therein, where at least one groove corresponds to and aligns with selected ones of the outer cylinder strut attachment points and has a depth that provides a gap between the outer cylinder outer surface and the shroud inner surface that is maintained when the flowpath housing is exposed to heat and the strut radially expands.
In still another embodiment, and by way of example only, the turbine section includes a shaft, a plurality of blades extending radially from the shaft, a bearing assembly mounted to the shaft adjacent to the plurality of blades, a flowpath housing, and a shroud. The flowpath housing is coupled to the bearing assembly and includes an inner cylinder, an outer cylinder, and a plurality of struts, where the inner and outer cylinders each includes strut attachment points between which the plurality of struts are coupled, the outer cylinder includes an outer surface, and the plurality of struts are disposed in a predetermined pattern. The shroud is disposed concentric to the outer cylinder and includes an inner surface having a plurality of grooves formed therein. At least one of the plurality of grooves is aligned with selected ones of the outer cylinder strut attachment points and has a depth that is configured to provide a gap between the outer cylinder outer surface and the inner surface that is maintained when the flowpath housing is exposed to heat and the strut radially expands.
Other independent features and advantages of the preferred turbine section will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.
Turning now to the description, and with reference first to
The high-pressure compressed air then enters the combustor and turbine module 130, where a ring of fuel nozzles 114 injects a steady stream of fuel. The injected fuel is ignited by a burner (not shown), which significantly increases the energy of the high-pressure compressed air. This high-energy compressed air then flows first into a high pressure turbine 115 and then a low pressure turbine 116, causing rotationally mounted turbine blades 118 on each turbine 115, 116 to turn and generate energy. The energy generated in the turbines 115, 116 is used to power other portions of the engine 100, such as the fan module 110 and the compressor module 120. The air exiting the combustor and turbine module 130 then leaves the engine 100 via the exhaust module 140. The energy remaining in the exhaust air aids the thrust generated by the air flowing through the bypass 112.
With reference now to
The bearing assembly 208 is disposed between the turbines 204, 206 and each includes inner rings 218, corresponding outer rings 220, and a plurality of bearings 222 disposed therebetween. The inner and outer rings 218, 220 and bearings 222 are disposed within a bearing housing 224 that is supported by, and coupled, to the flowpath housing 226.
The flowpath housing 226, a close up of which is provided in
As briefly mentioned above, the plurality of struts 242 (only one of which is shown) extend between and are couple to the cylinders 238, 240 at the strut attachment points 248, 254, respectively. The struts 242 may be integrally formed as part of the cylinders 238, 230 or alternatively may be separately manufactured and subsequently welded thereto. Although a single strut 242 is shown in
As shown in more detail in
With reference to
Preferably, the axially extending ring 262 has an inner surface 266 that includes two sections 268, 270. The first section 268 surrounds the blades 214 and defines a radial gap 260 therewith. The second section 270 is configured to cooperate with the lip 264 for coupling the shroud 212 to the flowpath housing outer cylinder 240. In this regard, the second section 270 includes a pilot 272 that is an annular protrusion extending radially inwardly and is configured to correspond to and mate with the flowpath housing pilot 256. Shown in phantom in
The lip 264 extends radially outwardly from an aft end of the axially extending ring 262. It will be appreciated that the lip 264 may extend from any suitable section of the axially extending ring 262 and the particular placement of the lip 264 may depend on the configuration of the flowpath housing fastener flange 244. The lip 264 may be annular or may alternatively be radially extending pieces. In any case, the lip 264 includes at least one fastener opening 276 that corresponds with at least one of the fastener openings 258 of the fastener flange 244 to thereby couple the shroud 212 to the flowpath housing 226.
A shroud has now been provided that protects turbine blades while allowing the flowpath housing to radially expand without compromising the configuration of the clearance gap. Additionally, the shroud is simple and inexpensive to manufacture and to implement. Moreover, the shroud configuration may alternatively be retrofitted into existing shrouds.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
