Test blade

Abstract

A test blade for use in a blade-release test in which the blade is mounted on a rotatable hub and at least a portion of the blade is released therefrom by the action of a controlled explosion. The blade has a root portion for mounting on said rotatable hub and the root portion comprises a radially inner surface having a channel extending at least partly along or proximal the camber line. The channel is for receiving at least one explosive charge and at least one detonator which may be contained within a charge carrier.

Claims

1. A test blade for use in a blade-release test in which the blade is mounted on a rotatable hub and at least a portion of the blade is released therefrom by the action of a controlled explosion, the blade having a root portion for mounting on said rotatable hub, wherein the root portion comprises a radially inner surface having a channel extending at least partly along or proximal a camber line, said channel for receiving at least one explosive charge and at least one detonator within a charge carrier, the charge carrier having a first portion for insertion into the channel and a second portion having a surface for abutting the radially inner surface of the root portion.

2. The test blade according to claim 1 wherein the channel extends along or proximal the entire length of the camber line of the radially inner surface to the leading edge and the trailing edge of the root portion.

3. The test blade according to claim 1 wherein the channel has a curved profile at its radially outermost inner surface.

4. The test blade according to claims 1 wherein the root portion increases in thickness (in the circumferential direction) towards the radially inner surface such that the leading and trailing edges of the root portion increase in surface area towards the radially inner surface.

5. The test blade according to claim 1 wherein the root portion further comprises at least one axially extending slot provided towards at least one of axially outer ends of the channel.

6. The test blade according to claim 1 wherein the root portion comprises axially extending slots extending from each of the leading and trailing edges of the root portion at each of the suction and pressure surfaces.

7. The test blade according to claim 6 wherein one or more of the axially extending slots extends through the root portion in the thickness (circumferential) direction to join the channel.

8. The test blade according to claim 1 wherein the charge carrier has an axial extension coincident with the channel.

9. The test blade according to claim 1 wherein the first portion has smaller dimensions than the channel such that there is spacing between the first portion and the channel.

10. The test blade according to claim 1 wherein the first portion has an upper section shaped as a semi-circular segment for location proximal the radially outermost inner surface of the channel.

11. A test apparatus comprising the test blade according to claim 1 and the rotatable hub, wherein the root portion of the blade is mounted in a groove on said rotatable hub.

12. The test apparatus according to claim 11 wherein the groove has a narrower width towards the radially outer surface of the hub.

13. A charge carrier for insertion into a test blade for use in a blade-release test in which the blade is mounted on a rotatable hub and at least a portion of the blade is released therefrom by the action of a controlled explosion, the blade having a root portion for mounting on said rotatable hub, wherein the root portion comprises a radially inner surface having a channel extending at least partly along or proximal a camber line, said channel for receiving at least one explosive charge and at least one detonator, the charge carrier comprising: a first axially extending portion for insertion into the channel; and a second portion projecting laterally from the first portion and having a surface for abutting the radially inner surface of the root portion.

14. The charge carrier according to claim 13 wherein the first portion has an upper section shaped as a semi-circular segment.

15. The charge carrier according to claim 13 wherein the second portion comprises at least one axially extending flange.

16. The charge carrier according to claim 15 wherein the second portion comprises two axially extending flanges on opposing axially extending sides of the first portion.

17. The charge carrier according to claim 13 comprising at least one bore and/or at least one channel extending parallel to the axial extension of the first portion.

18. A method of preparing a test blade for use in a blade release test in which the blade is mounted on a rotatable hub and at least a portion of the blade is released therefrom by the action of a controlled explosion, the method comprising providing the blade with a channel extending at least partly along or proximal a camber line along a radially inner surface of a root portion of said blade, the root portion for mounting on said rotatable hub and the channel for receiving at least one explosive charge and at least one detonator within a charge carrier, the charge carrier having a first portion for insertion into the channel and a second portion having a surface for abutting the radially inner surface of the root portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 shows a perspective view of a test blade according to a first embodiment;

(3) FIG. 2 shows a radial cross-sectional view through the test blade shown in FIG. 1;

(4) FIG. 3 shows the test blade of FIGS. 1 and 2 mounted in a rotatable hub;

(5) FIGS. 4 to 6 show perspective or cross-sectional views of a charge carrier for use with a test blade;

(6) FIG. 7 shows a front perspective view of a test blade according to a second embodiment; and

(7) FIG. 8 shows a back perspective view of a portion of a test blade according to the second embodiment.

DETAILED DESCRIPTION

(8) A first embodiment of a test blade 1 is shown in FIGS. 1 and 2.

(9) The blade 1 comprises a radially extending leading edge 2 and trailing edge 3 axially spaced by a (concave) pressure surface 4 and a circumferentially opposed (convex) suction surface 5. The camber line extends from the leading edge 2 to the trailing edge 3 of the blade 1 midway between the pressure and suctions surfaces 4, 5 of the blade 1.

(10) The blade 1 has a root portion 6 for mounting on a rotatable hub 10 (shown in FIG. 3).

(11) The root portion 6 comprises a radially inner surface 7 having a channel 8 extending along the entire length of the camber line of the radially inner surface 7 to the leading edge 2′ and the trailing edge 3′ of the root portion 6.

(12) By providing a channel on the radially inner surface 7 of the root portion 6, the ease of manufacture of the test blade 1 is improved because it is much easier to machine a channel 8 into the surface of the root portion than drill bores into the root portion 6. This means that it is possible to apply the channel to either a straight-rooted blade (as shown in the figures) or to a curved-rooted blade. By positioning the channel 8 on the camber line and thus spacing it from the pressure and suction faces 4′, 5′ of the root portion 6, the structural integrity and strength of the root portion 6 is maintained.

(13) The channel 8 extends radially into the root portion 6 of the blade 1 and has a curved profile at its radially outermost inner surface 9.

(14) The root portion 6 increases in thickness (in the circumferential direction) towards the radially inner surface 7 such that the leading and trailing edges 2′, 3′ of the root portion 6 increase in surface area towards the radially inner surface 7.

(15) In some embodiments, the pressure and suction face 4′, 5′ of the root portion 6 comprise a glass reinforced plastic coating 23 (see FIG. 3).

(16) The test blade 1 is mounted in a rotatable hub 10 within a groove 11 as shown in FIG. 3.

(17) The groove 11 has a narrower width towards the radially outer surface 24 of the hub 10. The root portion 6 is held in a dovetail arrangement within the groove 11 so that it is in compression under application of centrifugal force.

(18) Prior to mounting the root portion 6 within the groove, 11, a charge carrier 12 housing at least one explosive charge and at least one detonator is fitted into the channel 8.

(19) The open nature of the channel 8 (compared to a bore within the root portion) allows flexibility in the size, position and orientation of the explosive charge/detonator.

(20) The charge carrier 12 is also under compression within the groove 11 and thus increases the load carrying capabilities of the root portion.

(21) Suitable charge carriers are shown FIGS. 4-6.

(22) The charge carrier 12 has a first portion 13 for insertion into the channel 8. The first portion 13 may has smaller dimensions than the channel 8 such that there is spacing between the first portion 13 and the channel 8 which can be filled with adhesive and/or damping material.

(23) The first portion 13 has an upper section 14 shaped as a semi-circular prism for location proximal the curved radially outermost inner surface 9 of the channel 8. The radius of curvature of the upper section 14 is less than that of the curved radially outermost inner surface 9 of the channel 8 such that upper section 14 is spaced from the curved radially outermost inner surface 9 of the channel 8.

(24) The charge carrier 12 has a second portion 15 comprising flanges 16, 16′ for abutting the radially inner surface 7 of the root portion 6 either side of the channel 8.

(25) The charge carrier 12 may comprise a plurality of bores 17, 17′, 17″ as shown in FIG. 4

(26) The charge carrier 12 may comprise two bores 17, 17′ and two channels 18, 18′ extending parallel to the axis of the charge carrier 12 as shown in FIG. 5. The two channels 18, 18′ are provided in the upper section 14 of the first portion 13 of the charge carrier 12 on opposing curved surfaces 19, 19′ of the semi-circular prism.

(27) The charge carrier 12 may comprise two bores 17, 17′ and a channel 20 extending perpendicularly to the axis of the charge carrier 12 from the second portion 15 into the first portion 13 from an end face 21 of the charge carrier 12 as shown in FIG. 6.

(28) In an explosive release test, the explosive charge detonation results in almost instantaneous release of the blade in a controlled manner. A clean failure surface is left at the blade root.

(29) In the second embodiment shown in FIGS. 7 and 8, the root portion 6 further comprises axially extending slots 22 extending from both the leading and trailing edges 2′, 3′ on both the suction surface 5′ and pressure surface 4′ of the root portion 6.

(30) Each axially extending slot 22 extends through the root portion 6 in the thickness (circumferential) direction (from the pressure surface 4′ or the suction surface 5′ of the root portion 6) to join the channel 8.

(31) The axial slots 22 in the second embodiment are to provide areas of radial weakness at the axially outer ends of the channel which is where, in use, the detonators are positioned. The force of the explosion is reduced in these areas (by the absence of explosive charge) and the slots are provided to ensure cleaving of the blade from the root portion in these areas especially in static tests (where no centrifugal force is applied to the test blade).

(32) 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. 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.

(33) All references referred to above are hereby incorporated by reference.