Patent Application
20080075590
Fan assembly 12 includes an array of fan blades 24 extending radially outward from a rotor disk 26. Gas turbine engine assembly 10 has an intake side 28 and an exhaust side 30. Fan assembly 12, booster 22, and low-pressure turbine 20 are coupled together by a first rotor shaft 31, and compressor 14 and turbine 18 are coupled together by a second rotor shaft 32.
In operation, air flows through fan assembly 12 and a first portion of the airflow is channeled through booster 22. The compressed air that is discharged from booster 22 is channeled through compressor 14 wherein the airflow is further compressed and delivered to combustor 16. Hot products of combustion (not shown in
Shaft 31 also includes a first end 120 that is coupled to fan assembly 12 and a second end 122 that includes shaft splines 110 that is coupled to low-pressure turbine 20. In the exemplary embodiment, flange splines 108 are female splines and shaft splines 110 are male splines configured to mesh with the female splines. Optionally, shaft splines 110 are female splines and flange splines 108 are male splines. As used herein, splines are denote a series of ridges that are formed on a shaft or through a disk that mesh with and equalize the rotational speed of the pieces splined together, thereby transferring torque.
In the exemplary embodiment, shaft 31 is configured to accommodate an oversized high-pressure turbine 18. More specifically, since high-pressure turbine 18 has an inner diameter 130 that is substantially smaller than known high-pressure turbines, shaft 31 is selectively sized to accommodate the substantially larger high-pressure turbine. As such, shaft first end 120 has an outer diameter 132 that is greater than the inner diameter 130 of high-pressure turbine disk 18, and shaft second end 122 has an outer diameter 134 that is less than outer diameter 132. This configuration enables shaft second end 122 to be installed through a bore 136 formed through high-pressure turbine 18 and coupled to low-pressure turbine 20.
To maintain the structural strength of shaft 31, and thus reduce shaft flexing, first portion diameter 132 is substantially greater than second portion diameter 134. For example, in one embodiment, first portion 100 has a diameter 132 that is approximately 4.5 inches, and second portion 102 has a diameter 134 that is approximately 3.5 inches. However, it should be realized that second diameter 134 is selected based on the inner diameter 130 of high-pressure turbine 18, and as such, may be either increased or decreased to ensure that shaft 31 is capable of being inserted through high-pressure turbine bore 136 and coupled to low-pressure turbine 20.
Moreover, first portion 100 has a length 140 that is greater than a length 142 of second portion 102. Thus, the thickness or diameter 132 of first shaft portion 100 along length 140 is substantially larger than diameter 134 of second shaft portion 102 along length 142. More specifically, since fan assembly 12 and high-pressure turbine 18 are separated by a distance, the length 140 of first portion 100 is selected such that the diameter 132 of first portion 100 can be maximized between the fan assembly 12 and the high-pressure turbine 18, wherein the diameter of shaft 31 is reduced to allow shaft 31 to extend through disk bore 136 and be coupled to low-pressure turbine 20. As such, the length 140 of first portion 100 is substantially greater than the length 142 of second portion 102.
As discussed above, shaft 31 includes first, second, and third portions 100, 102, and 104, respectively. In one embodiment, first, second, and third portions 100, 102, and 104, are fabricated as separate components that are coupled together using a welding or brazing procedure, for example. In the exemplary embodiment, first, second, and third portions are formed as single unitary shaft 31.
As shown in
Described herein is a gas turbine engine assembly that includes a fan assembly, a core gas turbine engine, a low-pressure turbine, and a shaft coupled between the fan assembly and the low-pressure turbine. Specifically, the gas turbine engine described herein includes a low-pressure turbine shaft that enables a high-pressure turbine having a smaller flange bore diameter to be utilized. As a result, the life span of the high-pressure turbine is increased by reducing stress, while still maintaining an acceptable speed margin between operating speed and the first critical.
Specifically, the diameter of the high-pressure turbine flange is decreased by utilizing a low-pressure turbine shaft that is splined to the low-pressure turbine flange at the aft end of the gas turbine engine assembly, whereas known gas turbines includes splines at the forward end of the low-pressure turbine shaft. As a result, a reduced shaft diameter occurs at the end of the shaft which allows the high-pressure turbine disk to be designed with a smaller bore radius and therefore increase the life of the high-pressure turbine.
The gas turbine engine described herein also includes a differential bearing that is coupled between the low-pressure turbine shaft and the high-pressure turbine at the aft end of the gas turbine engine. The differential bearing is configured to support the high-pressure turbine and thus eliminate the need for a turbine midframe which is typically used to support the high-pressure turbine. This configuration reduces the complexity of engine assembly and disassembly. For example, since the low-pressure turbine shaft is splined at the aft end, the shaft may be installed and removed from the front of the gas turbine engine, thus improving assembly and disassembly of the gas turbine engine. The reduced complexity of assembly and disassembly may allow for the elimination of the lower low-pressure turbine torque cone flange thus reducing cost and weight, which are replaced by circumferential bosses which provide a bolting surface for the seals. Weight savings will also occur by incorporating smaller bolts used to hold the seals since the flange required for transmitting full low-pressure shaft torque has been eliminated.
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.
