TURBOMACHINERY ROTOR BLADE

Abstract

A turbomachinery rotor blade is provided having an aerofoil body, and a hole penetrating the aerofoil body from a suction surface to a pressure surface thereof. The hole is suitable to receive a lacing wire. The blade further has a protrusion from the suction or pressure surface. The protrusion extends in a downstream direction from a downstream side of the hole and/or extends in an upstream direction from an upstream side of the hole, thereby disturbing the suction or pressure surface to locally thicken the aerofoil body adjacent the hole. The maximum radial extent of the protrusion in the radially outward direction of the blade is radially coterminous with the outboard side of the hole, and the maximum radial extent of the protrusion in the radially inward direction of the blade is radially coterminous with the inboard side of the hole.

Claims

1. A turbomachinery rotor blade having an aerofoil body, and a hole penetrating the aerofoil body from a suction surface to a pressure surface thereof, the hole being suitable to receive a lacing wire; wherein a protrusion from the suction or pressure surface extends in a downstream direction from a downstream side of the hole and/or extends in an upstream direction from an upstream side of the hole, the protrusion disturbing the suction or pressure surface to locally thicken the aerofoil body adjacent the hole, the maximum radial extent of the protrusion in the radially outward direction of the blade being radially coterminous with the outboard side of the hole, and the maximum radial extent of the protrusion in the radially inward direction of the blade being radially coterminous with the inboard side of the hole.

2. A blade according to claim 1, wherein the protrusion extends from the hole in the downstream direction, and the thickening produced by the protrusion reduces with increasing downstream distance from the hole.

3. A blade according to claim 1, wherein the protrusion extends from the hole in the upstream direction, and the thickening produced by the protrusion reduces with increasing upstream distance from the hole.

4. A blade according to claim 1, wherein the width of the protrusion in the radial direction of the blade reduces with increasing downstream distance from the hole.

5. A blade according to claim 1, wherein the protrusion extends in a downstream direction from the downstream side of the hole a distance which is less than four times the diameter of the hole as measured in the radial direction of the blade.

6. A blade according to claim 1, wherein the protrusion extends in an upstream direction from the upstream side of the hole a distance which is less than four times the diameter of the hole as measured in the radial direction of the blade.

7. A blade according to claim 1, wherein the maximum height of the protrusion above the adjacent undisturbed aerofoil surface is less than half the diameter of the hole as measured in the radial direction of the blade.

8. A blade according to claim 1, wherein the blade has a protrusion from the suction surface and a protrusion from the pressure surface.

9. A blade according to claim 1, wherein the blade is a turbine rotor blade or a compressor rotor blade.

10. A rotor having a row of blades according to claim 1, and further having a lacing wire received in the holes of the blades.

11. A turbocharger having the rotor of claim 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

[0025] FIG. 1 shows neighbouring turbine blades with a lacing wire;

[0026] FIG. 2 shows schematically (a) a row of blades viewed from the pressure side and (b) a close-up view of one of the blades viewed from the suction side;

[0027] FIG. 3 shows (a) pressure side and (b) suction side calculated strain contours from finite element modelling of a typical lacing wire inertial loading at the hole of the blade of FIG. 2; and

[0028] FIG. 4 shows (a) pressure side and (b) suction side calculated strain contours from finite element modelling of a similar lacing wire inertial loading at the hole of a conventional blade with no protrusions.

DETAILED DESCRIPTION AND FURTHER OPTIONAL FEATURES

[0029] FIG. 2 shows schematically (a) a row of blades for an axial flow turbocharger turbine rotor viewed from the pressure side and (b) a close-up view of one of the blades viewed from the suction side. Each blade 11 has an aerofoil body 13 with a pressure surface 15 and a suction surface 17. A hole 19 penetrates through the aerofoil body from the suction surface to the pressure surface such that a lacing wire can be passed through the hole to link the blade to neighbouring blades.

[0030] The blade 11 has a protrusion 21 from the pressure surface 15 and another similar protrusion 21 from the suction surface 17. The protrusions are local thickenings of the aerofoil body and extend in a downstream direction from the downstream side of the hole. Advantageously, these local thickenings increase the contact area between the blade and a wire inserted through the hole 19, reducing the stresses produced in the blade by the inertial load of the wire. Although not shown here, another option is to have a single protrusion from either the pressure or the suction side of the blade.

[0031] Each protrusion 21 extends downstream a distance which is less than four times the diameter of the hole 19 as measured in the radial direction of the blade, and more preferably, a distance which is less than two times said diameter. However, each protrusion also extends a distance which is greater than one quarter of said diameter, and preferably greater than one half of said diameter.

[0032] Both the width of each protrusion 21 in the radial direction of the blade 11 and the height of each protrusion above the respective surface 15, 17 reduces with increasing downstream distance from the hole 19. The maximum height of each protrusion above the adjacent undisturbed aerofoil surface is less than half the diameter (and preferably less than one quarter of the diameter) of the hole measured in the radial direction of the blade, but greater than one sixteenth (and preferably greater than one eighth) of said diameter.

[0033] The pressure 15 and suction 17 surfaces adjacent to the hole 19 have undisturbed aerofoil surfaces in the upstream, inboard and outboard directions, i.e. there is no thickening in an upstream direction from the upstream side of the hole, radially inwards from the inboard side of the hole or radially outwards from the outboard side of the hole. Thus, advantageously, the protrusions 21 reduce the disruption of the gas stream flowing across the aerofoil surface 15, 17 because, in use, they sit in the wake of the lacing wire inserted through the hole 19. In this way, the aerodynamic performance of the blade 11 can be improved.

[0034] FIG. 3 shows (a) pressure side and (b) suction side calculated strain contours from finite element modelling of a typical lacing wire inertial loading at the hole of the blade of FIG. 2, and for comparison FIG. 4 shows (a) pressure side and (b) suction side calculated strain contours from finite element modelling of a similar lacing wire inertial loading at the hole of a conventional blade with no protrusions. Relative to the blade having no protrusions, at the downstream side of the hole the protrusions 21 are able to usefully alter the pattern of strain experienced by the blade and reduce the maximum strain. Further, the protrusions can displace the point of maximum strain on the downstream side of the hole from a location at the suction side to a less damaging location within the hole. Both these effects can increase the fatigue life of the blade.

[0035] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. For example, although not shown in the drawings, to further increase the fatigue life of the blade, the or each protrusion may also extend in a similar fashion in the upstream direction from the upstream side of the hole. Although upstream of the hole the protrusion is not in the wake of the lacing wire, at this location the streamlines of the flow approaching the wire either stagnate on the wire or divert around it. Indeed, although less preferred, the or each protrusion may extend in the upstream direction instead of the downstream direction. Moreover, the invention is not limited to turbine applications but may be used for other applications. For example, the blade may be used in a low pressure axial flow compressor in a gas turbine engine. Further, the invention is not limited to axial flow devices but may be used in other devices. For example, a rotor blade according to the present invention may be used in a radial or mixed flow device such as a water turbine or a radial flow turbine in a turbocharger. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.