Blade arrangement of a jet engine or an aircraft propeller

Abstract

A blade arrangement of a jet engine or an aircraft propeller including a blade with a root portion and an aerofoil portion, wherein the aerofoil portion includes a suction side and a pressure side. The blade arrangement further includes a retention structure that is configured to radially retain the blade in case of a structural blade failure, wherein the retention structure is secured to the root portion and/or to a structure adjacent to the root portion and extends in the radial direction along the suction side and along the pressure side of the aerofoil portion. The retention structure forms a loop that runs at least around the root portion, along the suction side and along the pressure side of the blade.

Claims

1. A blade arrangement of a jet engine or an aircraft propeller, comprising: a blade with a root portion and an airfoil portion, wherein the airfoil portion comprises a suction side, a pressure side and a blade tip, a retention structure for radially retaining the blade in case of a structural blade failure, wherein the retention structure: is secured to at least one chosen from the root portion and a structure adjacent to the root portion and extends in a radial direction along the suction side and along the pressure side of the airfoil portion, forms a loop that runs at least around the root portion, along the suction side and along the pressure side of the blade, and includes a textile band or ribbon that forms a full loop which runs around the root portion, along the suction side, along the pressure side and around the blade tip, wherein the band or ribbon runs around the blade tip by looping over the blade tip or by running through an opening formed in the blade tip.

2. The blade arrangement of claim 1, wherein the band or ribbon is attached to the root portion with a fastening device.

3. The blade arrangement of claim 1, wherein the band or ribbon is tapered towards the blade tip.

4. The blade arrangement of claim 1, wherein the band or ribbon is made out of a material that is lower in weight than a material out of which the airfoil portion is made.

5. The blade arrangement of claim 1, wherein the airfoil portion comprises on both the suction side and the pressure side at least one groove or indentation, wherein the band or ribbon is arranged in the at least one groove or indentation.

6. The blade arrangement of claim 5, wherein the retention structure is formed integrally with the blade.

7. The blade arrangement of claim 5, wherein the band or ribbon is pretensioned in the radial direction.

8. The blade arrangement of claim 1, wherein the blade is a jet engine fan blade or a jet engine propeller blade.

9. A jet engine comprising the blade arrangement of claim 1.

10. The blade arrangement of claim 1, wherein a thickness of the band or ribbon decreases towards the blade tip.

11. The blade arrangement of claim 5, and further comprising an adhesive joining the band or ribbon to the at least one groove or indentation.

12. The blade arrangement of claim 11, wherein a final shape of the blade includes a smooth aerodynamic external profile achieved by the band or ribbon being joined to the at least one groove or indentation with the adhesive.

13. The blade arrangement of claim 11, wherein the band or ribbon is tapered towards the blade tip.

14. The blade arrangement of claim 13, wherein the band or ribbon is made out of a material that is lower in weight than the material out of which the airfoil portion is made.

15. The blade arrangement of claim 11, wherein the band or ribbon is made out of a material that is lower in weight than the material out of which the airfoil portion is made.

16. The blade arrangement of claim 14, wherein the retention structure is formed integrally with the blade.

17. The blade arrangement of claim 16, wherein the band or ribbon is pretensioned in the radial direction.

18. The blade arrangement of claim 1, wherein the retention structure is formed integrally with the blade.

19. The blade arrangement of claim 1, wherein the band or ribbon is pretensioned in the radial direction.

20. The blade arrangement of claim 5, wherein a thickness of the band or ribbon decreases towards the blade tip.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and embodiments of the invention are described with reference to the drawings.

(2) FIG. 1 is a partially sectional view of an embodiment of a fan stage of a jet engine, wherein the fan stage includes a fan with blades that comprise a retention structure.

(3) FIG. 2 is a schematic sectional view of the root portion of a fan blade of FIG. 1, wherein the root portion comprises an inner dovetail root fixing with a retention structure looped around.

(4) FIG. 3 is a cross-sectional view of an embodiment of a blade that comprises a retention structure at the section side and at the pressure side of the blade.

(5) FIG. 4 shows a schematic sectional view of a gas turbine engine.

(6) FIG. 5 is a perspective view of a fan blade.

(7) FIG. 6 is a perspective view of a propeller of a turbo-prop engine.

DETAILED DESCRIPTION

(8) The invention will be described in the following by way of example primarily with respect to a fan blade of a fan of a dual-flow jet engine. However, the principles of the present invention apply similarly to blades of other components of a jet engine such as the blades of a compressor and to blades of a propeller.

(9) FIG. 4 is a schematic sectional view of a dual-flow jet engine 1. The jet engine 1 comprises a fan stage 10 with a fan as a low-pressure compressor, an intermediate-pressure compressor 20, a high-pressure compressor 30, a combustion chamber 40, a high-pressure turbine 50, an intermediate-pressure turbine 60 and a low-pressure turbine 70. The intermediate-pressure compressor 20 and the high-pressure compressor 30 each include a plurality of compressor stages, each compressor stage having a rotor stage and a stator stage. In one alternative, the jet engine 1 may include an additional low-pressure compressor in the core engine before the intermediate-pressure compressor 20.

(10) The fan stage 10 comprises a fan 11 with fan blades 12 which are attached to a fan disc 13. The fan stage 10 further comprises a fan containment casing 15.

(11) In a conventional manner, the dual-flow jet engine forms a secondary flow duct or bypass duct 4 and a primary flow duct or core duct 3. Air is accelerated by the fan 11 to produce two airflows, a first airflow flowing into the primary flow duct 3 and a second airflow which passes through the bypass duct 4 to provide propulsive thrust. In the bypass duct 4, a guide vane 45 and/or struts are arranged. The high-pressure, intermediate-pressure and low-pressure turbines 50, 60, 70, respectively, drive the high-pressure and intermediate-pressure compressors 30, 20 and the fan 11 by suitable interconnecting high-pressure, intermediate-pressure and low-pressure shafts, as is well-known to the person skilled in the art.

(12) In the context of the present invention, there is provided a particular construction of the fan blades 12, as will be described with respect to FIGS. 1 to 3.

(13) FIG. 1 is a partial sectional view of an embodiment of the invention, wherein FIG. 1 depicts a fan 11 and the initial sections of a bypass duct 4 and a core duct 3. The fan 11 comprises a plurality of fan blades 12 which are each connected to a fan disc 13. The connection of the fan blades 12 to the fan disc 13 may be in a conventional manner, i.e. by means of dovetail fixings. The fan blades 12 by themselves or together with the fan disc 13 are also referred to as a blade arrangement.

(14) Each blade 12 comprises a root portion 121, an aerofoil portion 122, a tip portion 123, a leading edge 124, a trailing edge 125, a suction side 126 and a pressure side 127.

(15) According to the invention, the blade 12 further comprises a retention structure 14 that is formed by a high-tensile band. The high-tensile band may be a textile such as a high-tensile woven fabric. The high-tensile band 14 forms a loop that runs around the root portion 121, along the suction side 126, along the pressure side 127 and around the tip 123 of the blade. To run around the tip 123 of the blade, the tip portion 123 in one embodiment comprises an opening in the form of a slit 16. Alternatively, the high-tensile band may loop over the tip 123 of the blade 12. Generally, the high-tensile band 14 tapers in the radial direction towards the tip portion 123, as can be seen in FIG. 1.

(16) To connect to the root portion 121 of the blade 12, in one embodiment, the high-tensile band 14 runs up around the aerofoil portion 122 and down around the root portion 121. This is shown in the sectional view of FIG. 2. As is shown in FIG. 2, the high-tensile band 14 completely loops around the root portion 121, which in the shown embodiment is in the form of an inner dovetail root fixing.

(17) Such embodiment has a plurality of advantages. First, as the high-tensile band loops around the root portion 121, there is a reliable connection of the retention band 14 to the blade. Second, by looping around the inner dovetail root fixing of the blade, the material normally holding the blade in place is now used to retain it after fracture of the usual load bearing material. Third, during high speed rotation just after a fan blade off event, a high load that will act on the dovetail contact flanks 121a and thus press the band 14 between these flanks 121a and the respective surface of the fan disc will additionally help to retain the fractured aerofoil in place. In this respect, there may be provided load spreader sheets 130 next to the flanks 121a to protect the high tension band 14 at the root contact position from friction and abrasion. The load spreader sheets 130 may be formed, e.g., of a soft metallic material or a hard plastic material. The load spreader sheets 130 also allow for easy service replacement.

(18) FIG. 2 further shows one potential fracture path 150 in case of a blade fracture. In case of such fracture, a high tension force F is exerted on the retention band 14 following a fan blade off event.

(19) In the aerofoil portion 122 of the blade, the retention band 14 extends radially both along the suction side 127 and along the pressure side 126. If a blade is metallic, the band 14 may be applied after the metallic manufacturing process in a pre-machined valley or groove together with an adhesive, wherein a smooth aerodynamic external profile of the blade 12 is provided for. In case of a composite blade, the band 14 could be built into the progressive composite lay-up of the blade and be co-cured with the other layers of the blade. In case of a composite blade, alternatively, the band 14 could also be applied after curing as with a metallic blade.

(20) Also, in case of a composite blade, a groove or valley may be formed in the outside surface of the blade by precision forging. Alternatively, a groove or valley may be machined into the blade after manufacturing.

(21) Further, the blade 12 may be formed such that only after application of the band 14 the final blade shape is achieved. This is shown by way of example in FIG. 3. FIG. 3 shows a sectional view of a blade, wherein the dotted line 128 indicates the initial blade profile before application of the band 14. The initial blade profile thus leaves space for the band material on each side 126, 127 of the blade. Only after the band material together with adhesive has been filled in the spaces provided for, the final blade shape 129 is achieved. Accordingly, in the embodiment of FIG. 3, the aerofoil is formed such that only after addition of the retention structure and glue the blade receives its final blade shape.

(22) Accordingly, in case of a fan blade off event, the high-tensile strength band 14 looped in the radial direction around the fan blade 12 will retain the aerofoil in space even at high rotational speeds. In the embodiment shown in FIGS. 1 and 2, such retaining of the fan blade after breakage is further supported by the root portion 121 forming a dovetail fixing, wherein the high-tensile band 14 is pinched between the dovetail contact flanks 121a and the corresponding surface of the fan disc.

(23) However, it is pointed out that the connection of the retainer band 14 to the root portion 121 of the blade 12 may also be provided for in other manners. For example, the high-tensile band 14 could alternatively run through an appropriate opening in the fan disc 13 and be retained inside an inner disc bore instead. In such case, the band 14 would in a similar extend in the radial direction along the suction side 126 and along the pressure side 127 of the aerofoil portion to radially retain the blade 12 in case of a fan blade off.

(24) In another alternative, the band 14 does not loop around the root portion 121, but is formed by two band elements, wherein one element extends radially at the pressure side 127 and one element extends radially at the suction side 126 of the blade, and wherein each of the elements is secured to the root portion 121 of the blade 12, e.g., by means of pins, hooks or other fastening means. However, even if the retention band 14 is looped around the root portion 121, reinforcing through thickness pinning or similar means could be applied to increase the retention strength if required.

(25) The band 14 may be tapered towards the tip portion 123 of the blade 12, as already mentioned. Further, the thickness of the retention band 14 may decrease towards the tip portion 123. For example, the retention band 14 may have a thickness of 1 to 2 mm at the root portion 121 and may gradually become thinner towards the tip portion 123 to achieve a thickness of, e.g., about one half millimeter at the tip portion 123. Further, the retention band 124 may be thinner towards the leading edge 124 and towards the trailing edge 125 of the blade 12, as shown with respect to FIG. 3.

(26) The retention band 14 may be made out of a material that is lower in weight than the material of which the aerofoil section 122 is made. In particular, the retention band 124 may be made out of Kevlar, in particular a woven Kevlar fabric.

(27) In a further embodiment, pretention may be applied to the band 14. Such pretention is associated with two advantages. First, in case of a fan blade off event, pretention of the band 14 reduces any radial movement of fractured blade fragments and thus decreases rotor out of balance loads. Second, pretensioning the band 14 has the effect that the band 14 takes some of the steady state loading on the blade during normal operation of the blade and thus allows a reduction in load and weight of the normal load bearing material.

(28) FIG. 5 shows a fan 11 with blades 12 that include a retention structure in accordance with the present invention, the retention structure is not being shown in FIG. 5. The blades 12 are connected with their root portions 121 to a fan disc 13, as has been discussed before. There is also shown a central hub portion 18 of the fan. In the embodiment of FIG. 5, the fan 11 further includes a ring wall 19 which separates the root portion 121 from the aerofoil portion 122 which is used to accelerate the incoming air. However, such ring wall 19 is optional only.

(29) The principles of the present invention can be similarly applied to other blades, such as the blades of a propeller as shown in FIG. 6. The propeller of FIG. 6 may be the propeller of a turbo-prop engine and comprises a central hub portion 80 which is driven by the turbo-prop engine and from which radially extend a plurality of similarly shaped propeller blades 12 which are formed in accordance with the present invention.

(30) It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. In particular, the invention is not limited to the illustrated embodiments described above. For example, the retention structure that is configured to radially retain the blade in case of a structural blade failure may be formed in a different manner than described with respect to the Figures. For example, the retention structure could be formed by a plurality of parallel bands or ribbons instead of one band. Also, the retention structure may be made out of a different material than a textile. For example, the retention structure could alternatively be formed from a high-tensile plastic material. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.

(31) All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. Various features of the various embodiments disclosed herein can be combined in different combinations to create new embodiments within the scope of the present disclosure. Any ranges given herein include any and all specific values within the range and any and all ranges within the given range.