US 11,920,514 B1
Gas turbine operation
Craig W Bemment, Derby (GB); Benjamin J Keeler, Chesterfield (GB); Kevin R McNally, Derby (GB); and Andrea Minelli, Derby (GB)
Assigned to ROLLS-ROYCE plc, London (GB)
Filed by ROLLS-ROYCE plc, London (GB)
Filed on Jun. 20, 2023, as Appl. No. 18/337,749.
Claims priority of application No. 2219390 (GB), filed on Dec. 21, 2022.
Int. Cl. F02C 7/14 (2006.01); F02C 7/16 (2006.01); F02C 7/22 (2006.01)
CPC F02C 7/14 (2013.01) [F02C 7/16 (2013.01); F02C 7/22 (2013.01); F05D 2260/213 (2013.01); F05D 2260/98 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method of operating a gas turbine engine, the gas turbine engine comprising:
a fuel delivery system that includes a pump and is arranged to provide fuel;
a combustor arranged to combust at least a proportion of the fuel;
a primary fuel-oil heat exchanger arranged to have up to 100% of the fuel provided by the fuel delivery system flow therethrough; and
a secondary fuel-oil heat exchanger arranged to have a proportion of the fuel from the primary fuel-oil heat exchanger flow therethrough, the proportion of the fuel being arranged to flow from the primary fuel-oil heat exchanger to the secondary fuel-oil heat exchanger and oil being arranged to flow from the secondary fuel-oil heat exchanger to the primary fuel-oil heat exchanger;
the method comprising heating the fuel by delivering the fuel through at least one of the primary fuel-oil heat exchanger and the secondary fuel-oil heat exchanger so as to adjust a fuel viscosity to a maximum of 0.58 mm2/s on entry to the combustor at cruise conditions.