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 arrangements for journal bearings such gearboxes, and related methods of operating such gearboxes and gas turbine engines, including 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 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.
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;
- 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 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,
- wherein a fan tip loading is defined as dH/Utip2, where dH is the enthalpy rise across the fan and Utip is the velocity of the fan tip, and the fan tip loading at cruise conditions is in a range of from 0.30 Jkg−1/(ms−1)2 to 0.35 Jkg−1/(ms−1)2,
- and wherein the method comprises operating the engine at maximum take-off conditions such that a specific loading multiplied by a sliding speed for each journal bearing is greater than around 240 MPa m/s.
A method of operating a gas turbine engine for an aircraft, the gas turbine engine comprising:
- an engine core comprising a turbine, a compressor, a combustor, 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;
- 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 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,
- wherein the method comprises operating the engine at maximum take-off conditions such that:
- a specific loading multiplied by a sliding speed for each journal bearing is less than around 720 MPa m/s;
- and
- and the temperature of the flow at exit of the combustor is in a range from 1850 K to 1950 K.
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;
- 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 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,
- wherein an overall pressure ratio of a gas turbine engine, defined as the ratio of the stagnation pressure upstream of the fan to the stagnation pressure at the exit of the highest pressure compressor, is in a range from 45 to 55 at cruise conditions,
- and wherein the method comprises operating the engine at maximum take-off conditions such that a specific loading multiplied by a sliding speed for each journal bearing is greater than around 240 MPa m/s.
Dependencies are inferred from the claim text.