Gearboxes for aircraft gas turbine engines
AssigneeROLLS-ROYCE plc
InventorMark Spruce
Life of this patent
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Abstract
Gearboxes for aircraft gas turbine engines, in particular to arrangements for journal bearings such gearboxes, and to related methods of operating such gearboxes and gas turbine engines. Example embodiments include a gearbox for an aircraft gas turbine engine, the gearbox including: a sun gear; a plurality of planet gears surrounding and engaged with the sun gear; and a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a bearing.
Claims20
A method of operating a gas turbine engine for an aircraft, the gas turbine engine comprising:
- an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;
- a fan located upstream of the engine core, the fan comprising a plurality of fan blades;
- and
- a gearbox that is configured to receive an input from the core shaft and provide an output drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, the gearbox comprising:
- a sun gear;
- a plurality of planet gears surrounding and engaged with the sun gear;
- a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin, wherein:
- the internal or external sliding surface of the journal bearing has a surface coating, and
- the method comprises operating the gas turbine engine at maximum take-off conditions such that a Journal Bearing Efficiency Density is in a range of 0.0003 to 0.0033, the Journal Bearing Efficiency Density being defined as:
- Journal
-
- Bearing
-
- Efficiency
-
- Density
- =
- Power
-
- loss
-
- per
-
- planet
- (
- P
-
- V
- )
- *
- (
- Journal
-
- Bearing
-
- Projected
-
- Area
- )
- where:
- the power loss per planet is in MW,
- P is a specific bearing load in MPa,
- V is a sliding speed of the journal bearing in m/s, and
- the Journal Bearing Projected Area is a length L of the journal bearing in m multiplied by a diameter D of the journal bearing in m.
A gearbox for an aircraft gas turbine engine, the gearbox comprising:
- a sun gear;
- a plurality of planet gears surrounding and engaged with the sun gear;
- a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin, wherein:
- the gearbox is arranged such that if the aircraft gas turbine engine were to be operated at maximum take-off conditions, a Journal Bearing Efficiency Density is in a range 0.0003 to 0.0033, the Journal Bearing Efficiency Density being defined as:
- Journal
-
- Bearing
-
- Efficiency
-
- Density
- =
- Power
-
- loss
-
- per
-
- planet
- (
- P
-
- V
- )
- *
- (
- Journal
-
- Bearing
-
- Projected
-
- Area
- )
- where:
- the power loss per planet is in MW,
- P is the specific bearing load in MPa,
- V is the sliding speed of the journal bearing in m/s, and
- the Journal Bearing Projected Area is the length L of the journal bearing in m multiplied by the diameter D of the journal bearing in m.
Dependencies are inferred from the claim text.