Rotating machinery with adaptive bearing journals and methods of operating
A method for operating a rotating machinery comprising a rotor, a rotor shaft, and at least one journal bearing supporting the rotor shaft is disclosed. The bearing comprises a bearing housing, a bearing surface in the bearing housing, a sleeve torsionally and axially fitted on the shaft, and a lubrication oil film filling a clearance between the outer surface of the sleeve and the bearing surface. The method comprises the step of modifying the clearance by modifying a radial dimension of the outer surface of the sleeve as a function of a rotation speed of the shaft.
1. A method for operating a rotating machinery comprising a rotor, a rotor shaft, and at least one journal bearing supporting the rotor shaft and comprised of a bearing housing, a bearing surface in the bearing housing, a sleeve torsionally and axially fitted on the shaft, the sleeve having an outer surface facing the bearing surface and an inner surface facing the shaft, and a lubrication oil film filling a clearance between the outer surface of the sleeve and the bearing surface; the method comprising the step of;
modifying the clearance by modifying a radial dimension of the outer surface of the sleeve as a function of a rotation speed of the shaft;
wherein the radial dimension of the outer surface of the sleeve is modified by at least one of: at least by effect of centrifugal forces generated by the rotation of the shaft and pressurized fluid between the journal and the shaft.
2. The method of claim 1 , wherein the step of modifying the clearance comprises the steps of: increasing a rotation speed of the shaft from a first rotation speed to a second rotation speed, reducing the clearance while increasing the rotation speed.
3. The method of claim 2 , wherein the step of increasing the rotation speed between the first rotation speed and the second rotation speed comprises crossing at least one critical rotation speed of the rotor.
4. The method of claim 1 , wherein the step of modifying the clearance comprises the steps of: reducing the rotation speed of the shaft from a second rotation speed to a first rotation speed; and increasing the clearance while reducing the rotation speed.
5. The method of claim 4 , further comprising the step of maintaining the rotation speed of the shaft at an intermediate rotation speed between the second rotation speed and the first rotation speed to cool the shaft and increase the clearance.
6. The method of claim 1 , further comprising the step of fitting the sleeve on the shaft with a degree of interference variable in an axial direction.
7. The method of claim 6 , further comprising the steps of fitting at least one axial end portion of the sleeve on the shaft with a higher interference than an axial intermediate portion of the sleeve.
8. The method of claim 7 , further comprising the step of forming an annular cavity between the inner surface of the sleeve and the shaft.
9. The method of claim 8 , further comprising the step of pressurizing the annular cavity with a pressurized fluid and modifying the pressure of the fluid as a function of the rotation speed to increase or decrease the outer diameter of the sleeve thus reducing or increasing the clearance.
10. The method of claim 9 , further comprising the step of removing heat from the bearing by means of the pressurized fluid.
11. A rotating machine comprising
a rotor;
a rotor shaft; and
at least one journal bearing supporting the shaft, the journal bearing comprising:
a bearing housing with a bearing surface, the shaft being rotatingly housed in the bearing housing;
an outer sleeve torsionally and axially constrained to the shaft and rotating therewith, the outer sleeve having an outer surface facing the bearing surface and an inner surface facing the shaft; and
a lubrication oil-filled clearance between the outer surface of the sleeve and the bearing surface;
wherein the outer surface of the sleeve is radially deformable when the shaft is rotating, such that a radial dimension of the lubrication oil-filled clearance reduces when the shaft rotation speed increases; and
wherein the outer surface of the sleeve is radially deformable by at least one of: under the effect of centrifugal forces generated by rotation of the journal and a pressurised fluid.
12. The rotating machine of claim 11 , wherein the sleeve has a first end portion, a second end portion and an intermediate portion between the first end portion and the second end portion, and wherein at least one of the first end portion and the second end portion is fitted on the shaft with an interference greater than an interference between the intermediate portion and the shaft.
13. The rotating machine of claim 12 , wherein the other of the first end portion and the second end portion is fitted on the shaft with an interference smaller than the interference between the one of the first end portion and second end portion.
14. The rotating machine of claim 12 , wherein an annular cavity is provided between the inner surface of the sleeve and the shaft at the intermediate portion of the sleeve.
15. The rotating machine of claim 14 , further comprising a duct for delivering a pressurized fluid in the annular cavity.
16. The rotating machine of claim 15 , wherein a pressure control arrangement is provided, for controlling the pressure of the pressurized fluid as a function of the rotation speed of the rotor.
17. The rotating machine of claim 11 , wherein the sleeve has a radial thickness which varies along the axial development thereof.
18. The rotating machine of claim 11 , wherein the sleeve has a first end portion, a second end portion and an intermediate portion between the first end portion and the second end portion, and wherein at least one of the first end portion and the second end portion is fitted on the shaft with an interference greater than an interference between the intermediate portion and the shaft.