US 12,258,910 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 Jul. 28, 2023, as Appl. No. 18/227,648.
Application 18/227,648 is a continuation of application No. 17/889,158, filed on Aug. 16, 2022, granted, now 11,746,707.
Application 17/889,158 is a continuation of application No. 17/231,676, filed on Apr. 15, 2021, granted, now 11,448,137, issued on Sep. 20, 2022.
Application 17/231,676 is a continuation of application No. 16/443,942, filed on Jun. 18, 2019, granted, now 11,002,194, issued on May 11, 2021.
Claims priority of application No. 1902795 (GB), filed on Mar. 1, 2019.
Prior Publication US 2023/0366356 A1, Nov. 16, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. F02C 7/36 (2006.01); F01D 15/12 (2006.01); F02C 3/113 (2006.01)
CPC F02C 7/36 (2013.01) [F01D 15/12 (2013.01); F02C 3/113 (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 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,
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 an overall pressure ratio of the gas turbine engine at cruise conditions is between 30 and 60,
wherein the jet velocity ratio, RJ, is determined by the following formula:

OG Complex Work Unit Math
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 a bypass duct by the fan,
the overall pressure ratio is defined as a ratio of a stagnation pressure upstream of the fan to a stagnation pressure at an exit of the highest pressure compressor,
the overall pressure ratio at cruise conditions is in the range 40 to 60, and
the jet velocity ratio RJ is between 0.75 and 1.3 at cruise conditions.