US 12,140,084 B2
Geared gas turbine engine
Craig W Bemment, Derby (GB)
Assigned to ROLLS-ROYCE plc, London (GB)
Filed by ROLLS-ROYCE PLC, London (GB)
Filed on Feb. 12, 2024, as Appl. No. 18/439,253.
Application 18/439,253 is a continuation of application No. 18/135,526, filed on Apr. 17, 2023, granted, now 11,994,075.
Application 18/135,526 is a continuation of application No. 17/870,270, filed on Jul. 21, 2022, granted, now 11,761,384, issued on Sep. 19, 2023.
Application 17/870,270 is a continuation of application No. 17/411,617, filed on Aug. 25, 2021, granted, now 11,434,832, issued on Sep. 6, 2022.
Application 17/411,617 is a continuation of application No. 16/526,221, filed on Jul. 30, 2019, granted, now 11,131,250, issued on Sep. 28, 2021.
Claims priority of application No. 1907256 (GB), filed on May 23, 2019.
Prior Publication US 2024/0191661 A1, Jun. 13, 2024
This patent is subject to a terminal disclaimer.
Int. Cl. F02C 9/24 (2006.01); F01D 19/00 (2006.01); F02C 7/268 (2006.01); F02C 7/36 (2006.01); F02C 9/18 (2006.01)
CPC F02C 9/24 (2013.01) [F01D 19/00 (2013.01); F02C 9/18 (2013.01); F02C 7/268 (2013.01); F02C 7/36 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method of operating a gas turbine engine on an aircraft, the gas turbine engine comprising:
an engine core comprising a turbine, a combustor, 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;
a nacelle surrounding the engine core and defining a bypass duct and a bypass exhaust nozzle; and
a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, wherein the method comprises operating the gas turbine engine to provide propulsion such that a jet velocity ratio, RJ, of a first jet velocity exiting from the bypass exhaust nozzle to a second jet velocity exiting from an exhaust nozzle of the engine core is defined as:

OG Complex Work Unit Math
where VB is a fully expanded first jet velocity, CB is a thrust coefficient of the bypass exhaust nozzle, VC is a fully expanded second jet velocity, CC is a thrust coefficient of the engine core exhaust nozzle, ηLPT is an isentropic efficiency of a lowest pressure turbine of the engine core and ηF is an isentropic efficiency of a fan tip;
the jet velocity ratio, RJ, is between around 0.75 and 1.3 at maximum take-off conditions;
each fan blade has a radial span extending from a hub to a tip, and a ratio of a radius of each fan blade at its hub to a radius of each fan blade at its tip is in a rang of 0.25 to 0.4;
a bypass ratio, defined as a ratio of a mass flow rate of a flow through the bypass duct to a mass flow rate of a flow through the core at cruise conditions, is in a range of 10 to 17;
a fan tip loading defined as dH/Utip2 is between 0.28 and 0.38 at cruise conditions, where dH is an enthalpy rise across the fan and Ud is a translational velocity of the leading edge of a fan tip; and a specific thrust, defined as a net thrust of the engine divided by a total mass flow through the engine, is between 80 Nkg-1s and 110 N kg−1s at the cruise conditions.