1. Field of the Disclosure
The present disclosure relates to a bladed rotor, and more particularly relates to a bladed rotor for a turbo-machine such as a gas turbine engine. The disclosure is particularly suited for use in gas turbine compressor rotors, although it is to be appreciated that the disclosure is not limited to compressor rotors and could find application in other types of bladed rotors for use in other types of turbo-machines.
2. Description of the Related Art
Conventional axial compressor rotors for gas turbine engines typically comprise a number of discs which are bolted or welded together to form an integral rotatable drum. Each disc can be considered to represent a central hub around which a plurality of rotor blades of aerofoil configuration are mounted. Each rotor blade is normally attached to the hub using a mechanical connection known as a root fixing. One such type of arrangement involves axially fixing the rotor blades to the periphery of the hub and involves the provision of a series of slots which are machined into the peripheral region of the hub and which are generally elongate parallel to one another. The slots are typically arranged so that they extend in a lengthwise direction which makes an acute angle of between 10 and 30 degrees to the rotational axis of the hub. Each slot is configured to receive a dove-tail or fir-tree shaped root fixing of a respective rotor blade.
A radially outwardly biased sprung retaining ring is normally used to secure the root portions of the rotor blades within their respective mounting slots. The retention ring locates within radially inwardly open grooves formed around the hub at positions located between the blade mounting slots, under its radially outward bias. Similar grooves are provided on the rotor blades and so the retaining ring also locates in the blade grooves to axially retain the root portions of the blades in the mounting slots.
It is important for integrity reasons that during operation of the rotor that the retaining ring does not apply radial load to the blades within the blade grooves. The retaining ring must at all times remain radially inwardly spaced from the radially outmost region of each blade groove by a clearance gap. It is therefore normal to configure the arrangement such that the retaining ring only bears against the radially outmost regions of the hub grooves.
However, it has been found that during service the retaining rings of the above-described type of axial fixing arrangement can be susceptible to wear on their radially outmost surfaces, as also can the inner surfaces of the hub grooves within which the rings locate. Over time, this wear can reduce the size of the radial clearance gap between the retaining ring and the blade grooves which, as indicated above, cannot be allowed to occur due to integrity concerns.