1. Technical Field
The present disclosure relates to a turbomachine blade production method.
More specifically, the present disclosure relates to a method of producing a lightweight rotor or stator blade for a compressor or front fan of an aircraft turbine engine, to which use the following description refers purely by way of example.
2. Description of the Related Art
As is known, rotor and stator blades of aircraft turbine engine compressors substantially comprise a coupling root designed to fit and lock rigidly to the compressor hub or center blade mounting disk; and an airfoil-shaped oblong member, which cantilevers from the coupling root, so as to cantilever radially outwards of the blade mounting hub or disk when the coupling root is fixed inside the hub or center blade mounting disk.
Stator blades also have an upper coupling head, which is located at the top end of the airfoil-shaped oblong member, i.e. at the opposite end to the coupling root, and is designed to fit and lock rigidly to the outer blade mounting ring of the compressor.
Having to withstand fairly severe mechanical stress and heat, the lower coupling root, the airfoil-shaped oblong member, and the upper coupling head (if there is one) are usually formed in one piece from a single block of high-strength metal, which is forged and then milled to shape the blade as required.
To reduce inertia and the overall weight of turbine engines, some aircraft turbine engine manufacturers have opted over the past few years to employ blades with hollow airfoil-shaped oblong members in parts of the engine, so as to drastically reduce the amount of metal needed to make the blade.
Patent Application US2006/039792 describes a method of producing a lightweight aircraft turbine engine blade, which comprises:
Producing a lightweight blade from a single block of metal, however, is an extremely painstaking, time-consuming, high-cost job, because of the large amount of material the numeric-control milling machine has to remove to shape the part as required.
It is therefore an object of the present disclosure to provide a method of producing a lightweight turbomachine blade, designed to significantly reduce the manufacturing cost of blades of this sort.
According to the present disclosure, there is provided a method of producing a turbomachine blade, as defined in claim 1 and preferably, though not necessarily, in any one of the claims dependent on claim 1.
A non-limiting embodiment of the present disclosure will be described by way of example with reference to the attached drawings, in which:
With reference to
Lightweight blade 1 is made of metal, and substantially comprises a lower coupling root 2 designed to fit and lock rigidly to the turbine engine hub or center blade mounting disk (not shown); an airfoil-shaped oblong member 3 which cantilevers from coupling root 2, so as to cantilever substantially radially outwards of the hub or blade mounting disk (not shown) when coupling root 2 is fixed inside the hub or center blade mounting disk, and inside has a large closed weight-reducing cavity 4, the three-dimensional shape of which preferably, though not necessarily, substantially reproduces, to a smaller scale, the three-dimensional shape of airfoil-shaped oblong member 3 as a whole; and an upper coupling head 5, which is located at the second end of airfoil-shaped oblong member 3, i.e. at the opposite end to coupling root 2, and is designed to fit and lock rigidly to the turbine engine outer blade mounting ring (not shown).
In other words, airfoil-shaped oblong member 3 is designed to joint/connect coupling root 2 rigidly to coupling head 5.
In the example shown, in particular, coupling root 2, airfoil-shaped oblong member 3, and coupling head 5 are preferably, though not necessarily, made of titanium alloy, aluminum alloy, or special high-strength steel.
Airfoil-shaped oblong member 3, in turn, comprises a substantially airfoil-shaped, main plate-like element 6 which connects directly to coupling root 2 and coupling head 5, and which, substantially in the center of one of its two major faces, has at least one hollow weight-reducing seat 6a of predetermined shape; and a cover plate 7 which closes the opening of hollow seat 6a to form the inner cavity 4 and complete the outer profile of airfoil-shaped oblong member 3.
More specifically, hollow weight-reducing seat 6a preferably extends over more than 40% of the total area of the major face of main plate-like element 6 in which hollow seat 6a is formed.
Preferably cover plate 7 instead is complementary in shape to, and serves to airtight seal, the opening of hollow seat 6a.
More specifically, cover plate 7 is preferably fixed irremovably to the opening of hollow seat 6a in main plate-like element 6 by a weld bead 8 preferably extending seamlessly along the whole peripheral edge of cover plate 7.
Preferably, though not necessarily, the shape of hollow seat 6a also roughly reproduces, to a smaller scale, the three-dimensional shape of airfoil-shaped oblong member 3 as a whole.
With reference to
More specifically, the lower edge 11a of center plate-like body 11 and the ridge 9a of lower connecting fin 9 are complementary in shape, and are butt welded to each other so that center plate-like body 11 forms one piece with lower connecting fin 9; and the upper edge 11b of center plate-like body 11 and the ridge 10b of upper connecting fin 10 are complementary in shape, and are butt welded to each other so that center plate-like body 11 forms one piece with upper connecting fin 10.
More specifically, lower edge 11a of center plate-like body 11 and ridge 9a of lower connecting fin 9 preferably extend from the leading edge 3a to the trailing edge 3b of airfoil-shaped oblong member 3 along a curved, preferably, though not necessarily, substantially Ω (omega) shaped path.
Likewise, upper edge 11b of center plate-like body 11 and ridge 10b of upper connecting fin 10 preferably also extend from the leading edge 3a to the trailing edge 3b of airfoil-shaped oblong member 3 along a curved, preferably, though not necessarily, substantially Ω (omega) shaped path.
With reference to
As used herein, “over-approximates” and “over-approximating” refer to approximating with a larger value or size.
In other words, the method of producing lightweight blade 1 comprises twisting and curving a flat plate 100 by means of a forming process (i.e. plastic deformation of the plate, with no appreciable reduction in its nominal thickness) so that the centerline surface M of the resulting blank plate 101 substantially matches the centerline surface P of the designed center plate-like body 11.
Where the ‘centerline surface’ is the locus/set of points inside the center plate-like body, which are locally equidistant from the surfaces forming the two major faces of the center plate-like body.
The centerline surface M of blank plate 101 is therefore the curved surface formed by the points locally equidistant from the two faces of blank plate 101. And the centerline surface P of center plate-like body 11 is the curved surface formed by the points locally equidistant from the surfaces of the two faces of center plate-like body 11, also taking into account the depression formed by the portion of hollow weight-reducing seat 6a in center plate-like body 11.
In other words, the three-dimensional shape of centerline surface P of center plate-like body 11 is also determined by the shape of the portion of hollow weight-reducing seat 6a formed in center plate-like body 11.
In the example shown, thickness s of flat plate 100 preferably over-approximates the maximum thickness of center plate-like body 11 of blade 1.
More specifically, the difference between the thickness s of flat metal plate 100 and the maximum thickness of center plate-like body 11 must preferably be less than 2 mm (millimeters).
Preferably, though not necessarily, the thickness s of flat plate 100 ranges between 5 mm and 40 mm (millimeters).
In the example shown, flat metal plate 100 of constant thickness over-approximating the maximum thickness of center plate-like body 11 is preferably obtained by appropriately cutting a large flat metal plate (not shown) of constant thickness greater than the maximum thickness of the center plate-like body 11 of the airfoil-shaped oblong member 3 of the to-be-made blade 1.
In other words, the method of producing blade 1 comprises cutting, from a large flat metal plate (not shown) of constant thickness over-approximating the maximum thickness of center plate-like body 11, a plate portion with a contour over-approximating the contour, flat spread-out on the laying plane, of the center plate-like body 11 of the airfoil-shaped oblong member 3 of the blade 1 to be made, thus to obtain the flat plate 100.
In the example shown, the thickness of the flat metal plate preferably over-approximates the maximum thickness of center plate-like body 11 of blade 1, and preferably ranges between 5 mm and 40 mm (millimeters).
With reference to
With reference to
More specifically, in the example shown, the method of producing blade 1 preferably comprises shaping the lower edge 101a of blank plate 101 and the ridge 103a of projecting appendage 103, so that they extend from the leading edge 3a to the trailing edge 3b of airfoil-shaped oblong member 3 along a curved, preferably, though not necessarily, substantially Ω (omega) shaped path.
With reference to
With reference to
More specifically, in the example shown, the method of producing blade 1 preferably comprises shaping the upper edge 101b of blank plate 101 and the ridge 105b of projecting appendage 105, so that they extend from the leading edge 3a to the trailing edge 3b of airfoil-shaped oblong member 3 along a curved, preferably, though not necessarily, substantially Ω (omega) shaped path.
With reference to
More specifically, during the step of removing excess material from the part formed by butt-welding blank plate 101 to the two semifinished parts 102 and 104, the method of producing blade 1 comprises:
With reference to
More specifically, in the example shown, the method of producing blade 1 preferably comprises:
Plate-like element 106 thus forms the cover plate 7 of the airfoil-shaped oblong member.
In the example shown, the method of producing blade 1 comprises preferably fixing plate-like element 106 irremovably to main plate-like element 6 by means of a weld bead preferably extending seamlessly along the entire peripheral edge of plate-like element 106; and then trimming/machining, by milling or other material-removing machining operation, excess metal off the weld between plate-like element 106 and main plate-like element 6.
In the example shown, the method of producing lightweight blade 1 preferably provides to obtain plate-like element 106 by cutting, from a large flat, preferably 1-4 mm (millimeter) thick metal sheet (not shown), a plate portion complementary in shape to the contour of the opening of hollow seat 6a.
The method of producing blade 1 as described has numerous advantages.
Firstly, making center plate-like body 11 of main plate-like element 6 by sheet metal forming the flat plate 100, i.e. by press-forming flat plate 100 with no appreciable reduction in the nominal thickness of the plate, greatly reduces the manufacturing cost of blade 1. Which cost saving is considerable in the case of large-size blades 1.
Sheet metal forming of a flat plate, in fact, is a processing technique which is different from forging, which produces a plastic deformation of the plate with no appreciable reduction in its nominal thickness, and which requires much less energy, with all the economic advantages this entails.
Secondly, twisting and curving flat plate 100 to form a blank plate 101 in which the three-dimensional shape of centerline surface M of the plate substantially matches the three-dimensional shape of the centerline surface P of center plate-like body 11, minimizes the amount of metal that has to be milled or otherwise machined off to obtain center plate-like body 11.
Last but not least, the method of producing blade 1 allows the semifinished parts 102 and 104, eventually forming coupling root 2 and coupling head 5 of blade 1, to be produced separately using production processes best suited to the three-dimensional shape and desired mechanical characteristics of each part.
Clearly, changes may be made to blade 1 and to the method of producing it, without, however, departing from the scope of the present disclosure.
For example, with reference to
Number | Date | Country | Kind |
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TV2013A000030 | Feb 2013 | IT | national |