US 12,331,685 B2
Fuel viscosity
Craig W Bemment, Derby (GB); Alastair G Hobday, Derby (GB); Benjamin J Keeler, Chesterfield (GB); Christopher P Madden, Derby (GB); Andrea Minelli, Derby (GB); Andrew T Smith, Derby (GB); Peter Swann, Derby (GB); and Martin K Yates, Derby (GB)
Assigned to ROLLS-ROYCE plc, London (GB)
Filed by ROLLS-ROYCE plc, London (GB)
Filed on Apr. 12, 2024, as Appl. No. 18/634,305.
Application 18/634,305 is a continuation of application No. 18/337,516, filed on Jun. 20, 2023, granted, now 11,988,144.
Claims priority of application No. 2219425 (GB), filed on Dec. 21, 2022.
Prior Publication US 2024/0263582 A1, Aug. 8, 2024
Int. Cl. F02C 7/14 (2006.01); F02C 7/224 (2006.01); F02C 7/36 (2006.01)
CPC F02C 7/14 (2013.01) [F02C 7/224 (2013.01); F02C 7/36 (2013.01); F05D 2220/323 (2013.01); F05D 2260/213 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A method of operating a gas turbine engine, the gas turbine engine comprising:
an engine core comprising a turbine, a compressor, a combustor arranged to combust a fuel, and a core shaft connecting the turbine to the compressor;
a fan located upstream of the engine core;
a fan shaft;
a gearbox that receives an input from the core shaft and outputs drive to the fan via the fan shaft;
a primary oil loop system arranged to supply oil to the gearbox;
a heat exchange system comprising:
an air-oil heat exchanger through which oil in the primary oil loop system flows; and
a fuel-oil heat exchanger through which the oil in the primary oil loop system and the fuel flow such that heat is transferred between the oil and the fuel, and wherein the primary oil loop system branches such that a proportion of the oil can flow along each branch and the air-oil and fuel-oil heat exchangers are arranged in a parallel configuration on different branches of the primary oil loop system; and
a modulation valve arranged to allow the proportion of oil sent via each branch to be varied,
wherein the method comprises controlling the heat exchange system so as to transfer between 200 and 600 KJ/m3 of heat from the oil to the fuel at cruise conditions, wherein
the gas turbine engine further comprises:
an integrated drive generator; and
a secondary oil loop system arranged to provide oil to the integrated drive generator;
the heat exchange system further comprises:
a secondary fuel-oil heat exchanger arranged to receive the fuel and oil from the secondary oil loop system; and
the method comprises transferring heat between the oil from the secondary oil loop system and the fuel using the secondary fuel-oil heat exchanger.