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US 10,975,802 B2Granted
Geared gas turbine engine
AssigneeROLLS-ROYCE plc
InventorsAlastair D Moore, Robert J Telling
Life of this patent
Estimating the term…
Abstract
A gas turbine engine generates noise during use, and one particularly important flight condition for noise generation is take-off. A gas turbine engine that has high efficiency provides low noise, in particular from the fan and the turbine that drives the fan. Values are defined for a noise parameter NP that results in a gas turbine engine having reduced combined fan and turbine noise.
Claims29
A gas turbine engine for an aircraft, the engine comprising:
- an engine core comprising a turbine having three or four axially separated rotor stages, 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 gearbox that receives input from the core shaft and drives the fan at a lower rotational speed than the core shaft;
- a bypass duct defined between an inner flow boundary formed by the engine core and an outer flow boundary formed by a nacelle of the gas turbine engine;
- and
- an intake defined as a radially outer flow boundary of flow into the gas turbine engine upstream of tips of leading edges of the plurality of fan blades, wherein:
- a minimum number of rotor blades in any single rotor stage of the three or four axially separated rotor stages of the turbine is NTURBmin;
- a diameter of the fan, which is a diameter of a circle swept by the tips of the leading edges of the plurality of fan blades, is ϕfan (m);
- a gear ratio of the gearbox is GR and is in a range of from 3.1 to 3.7;
- a noise parameter NP is defined as:
- NP
- =
- GR
- ×
- NTURB
-
-
- min
- ϕ
-
-
- fan
- where:
- 2.4 m≤ϕfan≤4.2 m
- and
- 95 m−1≤NP≤175 m−1;
- a bypass noise attenuation proportion L is defined as:
- L
- =
- J
- +
- H
- 2
-
- G
- where:
- G is an axial length between tips of trailing edges of the plurality of fan blades and a trailing edge of the nacelle;
- H is a total axial length of acoustic attenuation material provided to the outer flow boundary formed by the nacelle over an axial extent between the tips of the trailing edges of the plurality of fan blades and the trailing edge of the nacelle;
- and
- J is a total axial length of acoustic attenuation material provided to the inner flow boundary formed by the engine core over the axial extent between the tips of the trailing edges of the plurality of fan blades and the trailing edge of the nacelle;
- an intake noise attenuation proportion K is defined as:
- K
- =
- E
- F
- where:
- E is a total axial length of acoustic attenuation material provided to the intake;
- and
- F is an axial length of the intake;
- and
- a forward to rearward noise attenuation proportion M is in a range of from 0.8 to 2.5, where:
- M
- =
- K
- L
- .
53 more elements
Dependencies are inferred from the claim text.