US 11,988,148 B2
Low noise gas turbine engine
Alastair D Moore, Derby (GB); and Robert J Telling, Derby (GB)
Assigned to ROLLS-ROYCE plc, London (GB)
Filed by ROLLS-ROYCE plc, London (GB)
Filed on May 28, 2019, as Appl. No. 16/423,253.
Claims priority of application No. 1820941 (GB), filed on Dec. 21, 2018.
Prior Publication US 2020/0200089 A1, Jun. 25, 2020
Int. Cl. F02C 7/24 (2006.01); F02C 6/02 (2006.01); F02C 7/36 (2006.01)
CPC F02C 7/24 (2013.01) [F02C 6/02 (2013.01); F02C 7/36 (2013.01); F05D 2260/96 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A gas turbine engine for an aircraft, the 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 extending from a hub, a diameter D of the fan being in a range of from 220 cm to 290 cm; and
a gearbox that receives 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:
a ratio L/D is in a range of 0.33 to 0.48, L being an intake length defined as an axial distance between a leading edge of an intake of the engine and a leading edge of the plurality of fan blades at the hub, and D being the diameter of the fan;
during operation of the gas turbine engine, air is drawn into a front of the engine and exhausted from a rear of the engine as a jet;
a combined contribution of the jet and the turbine to an Effective Perceived Noise Level (EPNL) at a take-off lateral reference point, defined as a point on a line parallel to and 450 m from a runway centre line where the EPNL is a maximum during take-off, is in a range of from 3 EPNdB to 15 EPNdB lower than a total engine EPNL at the take-off lateral reference point, the contribution of the turbine to the EPNL at the take-off lateral reference point being non-zero;
the turbine that drives the fan via the gearbox comprises four, five, or greater than five axially separated rotor stages; and
the contribution of the turbine to the EPNL at the take-off lateral reference point is in a range of from 27 EPNdB to 33 EPNdB lower than contribution of fan noise emanating from the rear of the engine to the EPNL at the take-off lateral reference point.