Geared gas turbine engine
AssigneeROLLS-ROYCE plc
InventorCraig W Bemment
Life of this patent
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Abstract
The present disclosure relates to a geared gas turbine engine for an aircraft. Example embodiments include a gas turbine engine for an aircraft including: an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan having a plurality of fan blades; and a gearbox that receives an input from the core shaft to drive the fan at a lower rotational speed than the core shaft, the gearbox having a gear ratio of around 3.4 or higher, wherein the gas turbine engine is configured such that a jet velocity ratio between a first jet velocity exiting from a bypass duct of the engine and a second jet velocity exiting from an exhaust nozzle of the engine core is within a range from around 0.75 to around 0.82.
Claims12
A method of operating a gas turbine engine on 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 receives an input from the core shaft to drive the fan at a lower rotational speed than the core shaft, the gearbox having a gear ratio of between 3.2 and 4.7,
- wherein the method comprises operating the gas turbine engine to provide propulsion under cruise conditions such that a product of a jet velocity ratio RJ and the gear ratio is between 2.4 and 4.7,
- wherein the jet velocity ratio, RJ, is determined by the following formula:
- R
- J
- =
- V
- B
-
- C
- B
- V
- C
-
- C
- C
-
- η
- L
-
- P
-
- T
-
- η
- F
- where VB is the fully expanded first jet velocity, CB is a thrust coefficient of the bypass nozzle, VC is the fully expanded second jet velocity, CC is a thrust coefficient of the core exhaust nozzle, ηLPT is an isentropic efficiency of a lowest pressure turbine of the engine core and ηF is an isentropic efficiency of compression of air into the bypass duct by the fan.
Dependencies are inferred from the claim text.