Rotor blade arrangement
AssigneeROLLS-ROYCE plc
InventorBharat M. Lad
Life of this patent
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Abstract
The blades for a rotor of a gas turbine engine are all manufactured to the same design. However, manufacturing tolerances mean that in practice each individual blade is different to the others. It is proposed to arrange the blades around the circumference of the rotor in a manner that limits excessive stress being induced in the blades due to differences in the vibration response between a given blade and its two neighbouring blades.
Claims20
A rotor for a gas turbine engine comprising a rotor hub and a plurality of rotor blades, each rotor blade being attached to the rotor hub at a rotor blade root, wherein:
- the plurality of rotor blades are arranged circumferentially around the rotor hub such that each rotor blade has two neighbouring rotor blades;
- the plurality of rotor blades have a critical mode shape that is excited at a frequency that corresponds to an excitation frequency in use;
- each rotor blade of the plurality of rotor blades has a respective critical mode stiffness that is the stiffness of the respective blade in the critical mode shape, wherein the plurality of rotor blades define a median critical mode stiffness, and wherein the respective critical mode stiffness of each rotor blade is greater than, less than, or equal to the median critical mode stiffness;
- for a majority of rotor blades in a first set of rotor blades that have a critical mode stiffness greater than the median critical mode stiffness, at least one of the neighbouring rotor blades also has a critical mode stiffness greater than the median;
- and
- for a majority of rotor blades in a second set of rotor blades that have a critical mode stiffness less than the median critical mode stiffness, at least one of the neighbouring rotor blades also has a critical mode stiffness less than the median critical mode stiffness.
A method of assembling a rotor for a gas turbine engine, the rotor comprising a rotor hub and a plurality of rotor blades, each rotor blade of the plurality of rotor blades having a respective critical mode stiffness defined as the mode stiffness of the rotor blade for a critical mode shape that is excited at a frequency that corresponds to an excitation frequency in use, wherein the plurality of rotor blades define a median critical mode stiffness, wherein each respective critical mode stiffness is either greater than, less than, or equal to the median rotor blade critical mode stiffness, the method comprising:
- attaching each rotor blade to the rotor hub using a rotor blade root so as to arrange the rotor blades circumferentially around the rotor hub such that each rotor blade has two neighbouring rotor blades;
- and
- arranging the rotor blades such that:
- for a majority of rotor blades in a first set of rotor blades that have a critical mode stiffness greater than the median critical mode stiffness, at least one of the neighbouring rotor blades also has a critical mode stiffness greater than the median critical mode stiffness;
- and
- for a majority of rotor blades in a second set of rotor blades that have a critical mode stiffness less than the median critical mode stiffness, at least one of the neighbouring rotor blades also has a critical mode stiffness less than the median critical mode stiffness.
Dependencies are inferred from the claim text.