Turbomachine rotor with stacked impellers and turbomachine

A rotor for a turbomachine, comprising:

• a plurality of rotor segments arranged axially adjacent to one another, each rotor segment including a central through bore;
• a tie rod extending through the through bores of the rotor segments, the tie rod having opposite first axial end and second axial end;
• a first stub shaft and a second stub shaft arranged at the first axial end and second axial end of the tie rod, each coupled to the tie rod so as to lock the rotor segments to one another and to the tie rod;
• and
• at least one intermediate support member arranged in an intermediate position between the first axial end and the second axial end of the tie rod and between the tie rod and one of the rotor segments;
• wherein the intermediate support member comprises an inner annular component coupled to the tie rod and rotating therewith, and an outer annular component adapted to co-act with said one rotor segment;
• wherein the outer annular component comprises a plurality of annular segments,
• each annular segment being coupled to the inner annular component by at least one resilient member arranged between the inner annular component and the annular segment;
• and
• wherein the inner annular component, the annular segments of the outer annular component and the resilient members are formed as a monolithic machine component,
• wherein at rest, the outer diameter of the outer annular component is smaller than an inner diameter of a bore of the rotor segment, in which the intermediate support member is housed,
• wherein when the rotor is driven into rotation, the annular segments expand under the effect of centrifugal force acting thereon and provide an intermediate support constraint for the tie rod, causing a stiffening thereof and a consequent increase of the first resonant frequency of the tie rod, and
• wherein the characteristics of the resilient members are such that the annular segments engage with the bore of the rotor segment at a rotational speed equal to or lower than 70% of the nominal rotational speed of the rotor.