Lubrication of epicyclic gear system for gas turbine engine
An epicyclic gear system includes a sun gear, a ring gear, and two or more star gear assemblies enmeshed between the sun gear and the ring gear. Each star gear assembly includes a star gear and a journal bearing supportive of the star gear. The journal bearing includes one or more lubricant passageways to deliver a flow of lubricant to a selected location of the star gear assembly, wherein a first cross-sectional area of a lubricant passage of a first journal bearing of the two or more star gear assemblies is greater than a second cross-sectional area of the corresponding lubricant passage of a second journal bearing of the two or more star gear assemblies.
1. An epicyclic gear system comprising:
a sun gear;
a ring gear; and
two or more star gear assemblies enmeshed between the sun gear and the ring gear, each star gear assembly including:
a star gear; and
a journal bearing supportive of the star gear;
wherein the journal bearing includes one or more lubricant passageways to deliver a flow of lubricant to a selected location of the star gear assembly, wherein a first cross-sectional area of a lubricant passage of a first journal bearing of the two or more star gear assemblies is greater than a second cross-sectional area of the corresponding lubricant passage of a second journal bearing of the two or more star gear assemblies; and
wherein the first journal bearing is positioned vertically higher than the second journal bearing;
wherein the one or more lubricant passageways includes:
an axially-extending lubricant passageway; and
a radially-extending lubricant passageway fluidly connected to the axially-extending lubricant passage; and
wherein the first cross-sectional area is a cross-sectional area of the radially extending lubricant passageway of the first journal bearing and the second cross-sectional area is a cross-sectional area of the radially-extending lubricant passageway of the second journal bearing.
2. The epicyclic gear system of claim 1 , wherein the selected location is an interface defined between a radial inner surface of the star gear and a radial outer surface of each journal bearing.
3. The planetary gear system of claim 2 , wherein the one or more lubricant passages are configured to deposit a film of lubricant at the interface having a thickness in a range of 100 microinches to 2000 microinches.
4. The epicyclic gear system of claim 1 , wherein each journal bearing is fluidly connected to a lubricant manifold.
5. The epicyclic gear system of claim 1 , further comprising a carrier to which the two or more star gear assemblies are coupled.
6. The epicyclic gear system of claim 1 , further comprising five star gear assemblies enmeshed between the sun gear and the ring gear.
7. The epicyclic gear system of claim 6 , wherein the cross-sectional areas of the lubricant passageways of the journal bearings varies with vertical position of the journal bearings in the epicyclic gear system.
8. A fan and compressor assembly of a gas turbine engine including a combustor section and a turbine section, the fan and compressor assembly comprising:
a fan section including a fan shaft;
a compressor section including a compressor shaft; and
an epicyclic gear system to couple the fan section to the compressor section, the epicyclic gear system including:
a sun gear connected to the compressor shaft;
a ring gear connected to the fan shaft; and
two or more star gear assemblies enmeshed between the sun gear and the ring gear, each star gear assembly including:
a star gear; and
a journal bearing supportive of the star gear;
wherein the journal bearing includes one or more lubricant passageways to deliver a flow of lubricant to a selected location of the star gear assembly, wherein a first cross-sectional area of a lubricant passage of a first journal bearing of the two or more star gear assemblies is greater than a second cross-sectional area of the corresponding lubricant passage of a second journal bearing of the two or more star gear assemblies; and
wherein the first journal bearing is positioned vertically higher than the second journal bearing.
wherein the one or more lubricant passageways includes:
an axially-extending lubricant passageway; and
a radially-extending lubricant passageway fluidly connected to the axially-extending lubricant passage; and
wherein the first cross-sectional area is a cross-sectional area of the radially extending lubricant passageway of the first journal bearing and the second cross-sectional area is a cross-sectional area of the radially-extending lubricant passageway of the second journal bearing.
9. The fan and compressor assembly of claim 8 , wherein the selected location is an interface defined between a radial inner surface of the star gear and a radial outer surface of each journal bearing.
10. The fan and compressor assembly of claim 9 , wherein the one or more lubricant passages are configured to deposit a film of lubricant on the interface having a thickness in a range of 100 microinches to 2000 microinches.
11. The fan and compressor assembly of claim 8 , wherein each journal bearing is fluidly connected to a lubricant manifold.
12. The fan and compressor assembly of claim 8 , further comprising a carrier to which the two or more star gear assemblies are coupled.
13. The fan and compressor assembly of claim 8 , further comprising five star gear assemblies enmeshed between the sun gear and the ring gear.
14. The fan and compressor assembly of claim 13 , wherein the cross-sectional areas of the lubricant passageways of the journal bearings varies with vertical position of the journal bearings in the epicyclic gear system.
15. A gas turbine engine, comprising:
a low pressure unit including:
a low pressure compressor;
a low pressure turbine; and
a low pressure shaft connecting the low pressure compressor and the low pressure turbine;
a high pressure unit including:
a high pressure compressor;
a high pressure turbine; and
a high pressure shaft connecting the high pressure compressor and the high pressure turbine;
a fan section including a fan disposed on a fan shaft; and
an epicyclic gear system to couple the fan section to the low pressure compressor unit, the epicyclic gear system including:
a sun gear connected to the compressor low pressure shaft;
a ring gear connected to the fan shaft; and
two or more star gear assemblies enmeshed between the sun gear and the ring gear, each star gear assembly including:
a star gear; and
a journal bearing supportive of the star gear;
wherein the journal bearing includes one or more lubricant passageways to deliver a flow of lubricant to a selected location of the star gear assembly, wherein a first cross-sectional area of a lubricant passage of a first journal bearing of the two or more star gear assemblies is greater than a second cross-sectional area of the corresponding lubricant passage of a second journal bearing of the two or more star gear assemblies; and
wherein the first journal bearing is positioned vertically higher than the second journal bearing.
16. The gas turbine engine of claim 15 , wherein the one or more lubricant passageways includes:
an axially-extending lubricant passageway; and
a radially-extending lubricant passageway fluidly connected to the axially-extending lubricant passage.
17. The gas turbine engine of claim 16 , wherein the first cross-sectional area is a cross-sectional area of the radially extending lubricant passageway of the first journal bearing and the second cross-sectional area is a cross-sectional area of the radially-extending lubricant passageway of the second journal bearing.
18. The gas turbine engine of claim 15 , wherein the one or more lubricant passages are configured to deliver the flow of lubricant to the journal bearing.
19. The gas turbine engine of claim 18 , wherein the one or more lubricant passages are configured to deposit a film of lubricant at the journal bearing having a thickness in a range of 100 microinches to 2000 microinches.
20. The gas turbine engine of claim 18 , further comprising a distribution recess disposed between an interface surface of the journal bearing and the star gear;
wherein the flow of lubricant is deposited on the distribution recess.