US-20260126008-A1 - GAS TURBINE ENGINE

US20260126008A1US 20260126008 A1US20260126008 A1US 20260126008A1US-20260126008-A1

Abstract

A gas turbine engine includes a gear assembly including planet gears arranged in a planetary configuration. Each planet gear includes a pin, a gearbox bearing, and a planet gear rim. An inner surface of the planet gear rim and an outer surface of the pin define a clearance therebetween that is greater than zero when radial, pinch, tangential, and centrifugal component forces are applied to the planet gear. Each planet gear includes a pin clearance parameter greater than or equal to zero rpm and less than or equal to 3,334 rpm. The gas turbine engine includes a primary lubrication system that supplies lubricant to the gearbox bearing of at least one planet gear during normal operation of the gas turbine engine.

Inventors

Kedar S. Vaidya
Bugra H. Ertas
Arthur W. Sibbach

Assignees

GENERAL ELECTRIC COMPANY

Dates

Publication Date: 20260507
Application Date: 20260105
Priority Date: 20220727

Claims (20)

1 . A gas turbine engine comprising: a gear assembly mechanically coupled to an LP shaft of the gas turbine engine, wherein the gear assembly comprises a sun gear, a ring gear, a carrier, and a plurality of planet gears arranged in a planetary configuration, wherein each of the plurality of planet gears comprises: a pin comprising a pin outer surface; a gearbox bearing disposed within the planet gear and at least partially surrounding the pin; an annular planet gear rim comprising an inner surface, wherein the inner surface and the pin outer surface define a clearance, wherein the clearance is greater than zero when a radial component force, a pinch component force, a tangential component force, and a centrifugal component force are applied to the planet gear; a planet gear bending stress neutral axis radius, wherein the planet gear bending stress neutral axis radius is a radius where stresses and strains within the annular planet gear rim are zero when the radial component force, the pinch component force, the tangential component force, and the centrifugal component force are applied to the planet gear; a pin clearance parameter defined by: PCP = K 1 c r ⁢ GR GR - 2 ⁢ r p 2 [ K 2 ⁢ r p 3 ⁢ Ω fan 3 - HP fan N p ⁢ ( GR - 2 GR ) 2 ] wherein “PCP” is the pin clearance parameter in rpm, “c r ” is the clearance in inches, “GR” is a gear ratio of the epicyclic gear train, “r p ” is the planet gear bending stress neutral axis radius in inches, “N p ” is a number of the plurality of planet gears, “HP fan ” is a fan power of the gas turbine engine in horsepower at takeoff conditions, “Ω fan ” is a fan speed of the gas turbine engine in rpm at takeoff conditions, K 1 is a first constant of 1.96×10 −5 per horsepower-minute-inch, and K 2 is a second constant of 4.91×10 −9 horsepower-minutes cubed per cubic inch, and wherein the pin clearance parameter is greater than or equal to zero rpm and less than or equal to 3,334 rpm; and a primary lubrication system configured to supply a lubricant to the gearbox bearing of at least one of the plurality of planet gears during normal operation of the gas turbine engine, wherein the primary lubrication system comprises a primary pump, a primary lubricant supply line, and one or more tanks, wherein the primary pump is in fluid communication with the one or more tanks and the primary lubricant supply line and is operative to pump the lubricant from the one or more tanks to the gearbox bearing of at least one of the plurality of planet gears, and wherein a gear ratio of the gear assembly is in a range from 2.5 to 5.
2 . The gas turbine engine of claim 1 , further comprising a primary lubricant return line in fluid communication with the gearbox bearing and the one or more tanks, wherein the primary lubricant return line is a sump line in fluid communication with the gearbox bearing and the one or more tanks to return lubricant that drains from the gearbox bearing to the one or more tanks.
3 . The gas turbine engine of claim 2 , further comprising a sump pump in fluid communication with the primary lubricant return line and configured to pump lubricant and air within the primary lubricant return line toward the one or more tanks.
4 . The gas turbine engine of claim 2 , wherein the primary lubricant return line includes one or more drain valves in communication with a controller and configured to be opened during normal operation to direct lubricant through the primary lubricant return line to the one or more tanks and to be closed to inhibit drainage to the one or more tanks.
5 . The gas turbine engine of claim 4 , wherein the one or more drain valves are controlled to be opened or closed based on a pressure of the lubricant in the primary lubrication system.
6 . The gas turbine engine of claim 1 , wherein the primary return line comprises a drain valve configurable between a first state that directs lubricant from the gearbox bearing to the one or more tanks and a second state that inhibits drainage to the one or more tanks.
7 . The gas turbine engine of claim 6 , further comprising an auxiliary lubrication system including an auxiliary reservoir positioned to receive lubricant draining from the gearbox bearing when the drain valve is in the second state, and a lubricant dispersion device mounted to rotate about the longitudinal centerline axis and disposed to contact lubricant within the auxiliary reservoir and disperse the lubricant toward the gearbox bearing.
8 . The gas turbine engine of claim 7 , wherein the gearbox bearing comprises a journal bearing, and wherein the primary lubrication system supplies lubricant to the journal bearing during normal operation including takeoff conditions, and the auxiliary lubrication system disperses lubricant to the journal bearing during windmilling or when the primary lubrication system is unable to supply lubricant.
9 . The gas turbine engine of claim 7 , wherein the auxiliary lubrication system comprises a lubricant dispersion device gear assembly drivingly coupling the lubricant dispersion device to the gear assembly.
10 . The gas turbine engine of claim 9 , wherein the lubricant dispersion device gear assembly has a gear ratio such that a rotational speed of the lubricant dispersion device is greater than a rotational speed of the gear assembly.
11 . The gas turbine engine of claim 7 , wherein the auxiliary lubrication system comprises a clutch that engages the lubricant dispersion device such that the lubricant dispersion device rotates or that disengages the lubricant dispersion device to prevent the lubricant dispersion device from rotating.
12 . The gas turbine engine of claim 11 , wherein the clutch engages the lubricant dispersion device when the primary lubrication system is unable to supply the lubricant to the gearbox bearing of at least one of the plurality of planet gears.
13 . The lubrication system of claim 12 , wherein the clutch disengages the lubricant dispersion device when the primary lubrication system is supplying the lubricant to the gearbox bearing of at least one of the plurality of planet gears.
14 . The gas turbine engine of claim 1 , wherein the pin clearance parameter is greater than or equal to zero rpm and less than or equal to 3,000 rpm.
15 . The gas turbine engine of claim 1 , wherein the pin clearance parameter is greater than or equal to 48 rpm and less than or equal to 1,334 rpm.
16 . The gas turbine engine of claim 1 , wherein the pin clearance parameter is greater than or equal to 80 rpm and less than or equal to 1,300 rpm.
17 . The gas turbine engine of claim 1 , wherein the number of the plurality of planet gears is three, four, five, or six; and the gas turbine engine has a bypass ratio in a range from 12 to 15.
18 . The gas turbine engine of claim 1 , wherein the gas turbine engine further comprises a HP compressor disposed aft of the gear assembly, wherein the HP compressor comprises eight, nine, or ten HP compressor stages, and wherein the gas turbine engine further comprises a LP turbine coupled to the LP shaft and comprising a plurality of LP turbine stages, wherein the number of the plurality of LP turbine stages is three, four, five, or six.
19 . The gas turbine engine of claim 18 , wherein the gas turbine engine further comprises: a fan shaft coupled to the carrier of the gear assembly; and a fan coupled to the fan shaft, wherein the fan comprises a fan diameter that ranges from 80 inches to 95 inches.
20 . The gas turbine engine of claim 19 , wherein the fan diameter ranges from 85 inches to 90 inches.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 19/007,093, filed Dec. 31, 2024, issuing as U.S. Pat. No. 12,516,627, which is a continuation-in-part of U.S. patent application Ser. No. 17/981,219, filed Nov. 4, 2022, now U.S. Pat. No. 12,276,228, which claims the benefit of Indian Patent Application number 202211043036, filed Jul. 27, 2022, each of which is incorporated by reference herein in its entirety. FIELD The present disclosure relates to lubricated gearbox bearings for a gas turbine engine. BACKGROUND Aircraft engines typically include a fan, a low pressure compressor, and a low pressure turbine rotationally coupled in a series configuration by a low pressure shaft. The low pressure shaft is rotationally coupled to the low pressure turbine and a power gear box. The power gear box includes a plurality of planet gears and is rotationally coupled to the low pressure fan and the low pressure compressor. Each planet gear surrounds a gearbox bearing. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other features and advantages will be apparent from the following, more particular, description of various exemplary embodiments, as illustrated in the accompanying drawings, wherein like reference numbers generally indicate identical, functionally similar, or structurally similar elements. FIG. 1 is a schematic cross-sectional diagram of a gas turbine engine, taken along a longitudinal centerline axis of the gas turbine engine, according to the present disclosure. FIG. 2 is a schematic axial end cross-sectional view of a lubrication system for a gearbox assembly for the gas turbine engine of FIG. 1, taken along a latitudinal centerline axis of the gearbox assembly, according to the present disclosure. FIG. 3 is a schematic cross-sectional aft view of a lubricant dispersion device of the lubrication system of FIG. 2, taken along plane 2B-2B in FIG. 2, and isolated from the lubrication system, according to the present disclosure. FIG. 4 is a schematic axial end cross-sectional view of a lubrication system for a gearbox assembly, taken along a latitudinal centerline axis of the gearbox assembly, according to another embodiment. FIG. 5A is a schematic axial end cross-sectional view of a lubrication system for a gearbox assembly for a gas turbine engine, taken along a latitudinal centerline axis of the gearbox assembly, according to another embodiment. FIG. 5B is a schematic cross-sectional aft view of a lubricant dispersion device of the lubrication system of FIG. 5A, taken along plane 5B-5B in FIG. 5A, and isolated from the lubrication system, according to the present disclosure. FIG. 6 is a flow diagram of a method of operating a lubrication system, according to the present disclosure. FIG. 7 shows a schematic diagram of a gear assembly of the gas turbine engine shown in FIG. 1, according to one example. FIG. 8 shows a partial schematic diagram of the gear assembly shown in FIG. 7, according to one example. FIG. 9 shows a schematic diagram of the planet gear shown in FIG. 8 with the resultant tangential, radial, pinch, and centrifugal forces causing the planet gear rim to deform, according to one example. FIG. 10 shows exemplary pin clearance parameters for exemplary gear assemblies, according to one example. FIG. 11 shows exemplary ranges of values for gear assembly characteristics, according to one example. DETAILED DESCRIPTION For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatuses, and systems should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatuses, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present or problems be solved. Features and characteristics described in conjunction with a particular aspect, embodiments, or examples are to be understood to be applicable to any other aspect, embodiment, or example described herein unless incompatible therewith. A person having ordinary skill in the relevant art will recognize that any of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by