Blades made from a variety of materials

Abstract

The airfoil (3) of a turbine blade comprises a first structural resistance portion (8) formed by two end portions (11, 12) comprising leading and trailing edges (4, 5) and end strips (14, 15, 16, 17) of the suction and pressure surfaces and a core (13) joining the two end portions. The other two portions (9, 10) of the blade are made of a lightweight material, for example a composite material, between the end portions to form the complete airfoil. According to the invention, the core has an inclined or diagonal extension between the end portions.

Description

Technical Field

[0001] The subject of the invention is a blade made of a plurality of materials. Background Art

[0002] The ongoing search for lightweight turbines in the aerospace sector also extends to the blades. Various designs for hollow blades have been proposed, but the use of hollow blades is not always possible. Another way to lighten the blades is to use lighter materials, such as composite materials; however, this approach also has limitations, because lightweight materials usually do not have the required resistance to the most heavily loaded parts of the blades (such as the leading edge, which is exposed to impact and abrasion due to solid impurities entrained in the gas); moreover, lightweight materials usually do not allow the leading and trailing edges to be shaped with sufficient fineness.

[0003] It was then proposed (and this is the subject of documents FR 3035679 A etc.) to reinforce large blades made of light material by means of reinforcements made of thin foils made of resistant material, folded so as to cover the main material in small strips on the lower and upper surfaces. A blade is then obtained which is both light and sufficiently resistant to resistance in use. However, these local reinforcements also have certain disadvantages: firstly, the shaping of the foil is difficult, since such a thin and elongated part lacks rigidity and must be shaped into complex and irregular shapes, the edges of recent blades often having significant and highly variable inclinations (known as vertical angles and dihedral angles) in the axial and tangential directions; even if the reinforcements are constructed with very thin foils, they produce folds that are too thick and rounded, making it impossible to build a blade edge that is relatively thin and sharp.

[0004] An improved blade structure is also disclosed in US Pat. No. 3,294,366 A, but is improved by the present invention. Summary of the invention

[0005] According to the present invention, another structure is proposed. According to the general definition, the structure includes: a blade, the blade includes a reinforced leading edge and a trailing edge, and extends between the leading edge and the trailing edge, while being limited by a lower surface and an upper surface, the lower surface and the upper surface are two main aerodynamic surfaces of the blade, opposite in the thickness direction of the blade, and each extending from the leading edge to the trailing edge; the blade is formed by a first part, a second part and a third part, the first part is made of a first material as a single piece, the first part is composed of a first end part including the leading edge, a second end part including the trailing edge, and a core connecting the first end part to the second end part, the first end part and the second end part each including a strip of each of the main aerodynamic surfaces; the second part extends between the first end part and the second end part and is joined to the main surface of the core, the second part is composed of A second part is made of a second material that is lighter than the first material, and the second part carries the first aerodynamic surface in the main aerodynamic surface, in the area between the strips of each of the end parts of the first aerodynamic surface; a third part is similar to the second part, is made of a material that is lighter than the first material, and the third part carries the second aerodynamic surface in the main aerodynamic surface, in the area between the strips of the end parts of the second aerodynamic surface belonging to the first part; it is characterized in that the core has an inclined extension in the thickness direction over at least a part of the height of the blade, so that the thickness of the second part near the second end part is greater than the thickness near the first end part, and the thickness of the third part near the first end part is greater than the thickness near the second end part.

[0006] The leading edge and the trailing edge are constructed as rigid parts of the lower and upper surfaces over at least a large part of the extension of the leading edge and the trailing edge, rather than being formed by a bent foil. Due to the rigidity of these end parts, an easier manufacturing of the leading edge and the trailing edge is obtained, as well as the ability to construct the leading edge and the trailing edge with a sharp section. The core ensures the cohesion of the assembly by withstanding the forces occurring in the blade. The second part can be much larger than the first part, thereby enabling a significant overall lightening. The cohesion of the second part with the first part is good, because the second part is arranged in the cavity formed by the first part, between the end parts, and the end parts protrude from the core in the thickness direction of the blade. The mechanical resistance of the second part can be low, because the forces to which the blade is subjected are borne by the first part, and the second part is reasonable in order to restore the continuous main surface of the blade, thus giving the blade good aerodynamic qualities. The third part has the same characteristics as the second part.

[0007] The second portion and the third portion may both be composed of the second material.

[0008] The first end portion and the second end portion are typically selected to be solid (and thicker than the core in the thickness direction) so that the first end portion and the second end portion have sufficient strength.

[0009] The consideration of the resistance or stiffness to static or dynamic forces, including vibrations, is important for the precise definition of the parameters of the shape and dimensions of the blade, here in particular the core and the first part. The important idea is that the sections of the blade taken at different radii are different due to the position of the core, so that the core may be subject to buckling, that is to say a uniform or non-uniform tilting in the radial direction in the angular direction of the turbine; or a twisting (rotation) around the radial direction, from one section to another. This leads to certain specific structures, according to which:

[0010] - in a cross section taken through the blade, in the radial direction of the blade, from the lower surface to the upper surface and over a portion of the height of the blade, one of the second portion and the third portion has an increasing thickness in an outward direction in the radial direction and the other of the second portion and the third portion has a decreasing thickness in said outward direction;

[0011] - in a first cross section taken through the blade adjacent to the first end portion, in the radial direction of the blade, from the lower surface to the upper surface, and over a portion of the height of the blade, one of the second portion and the third portion has an increasing thickness in an outward direction of the radial direction, and the other of the second portion and the third portion has a decreasing thickness in the outward direction; and, in a second cross section taken through the blade adjacent to the second end portion, in the radial direction of the blade, from the lower surface to the upper surface, and over a portion of the height of the blade, one of the second portion and the third portion has a decreasing thickness in an outward direction of the radial direction, and the other of the second portion and the third portion has an increasing thickness in the outward direction.

[0012] This structure can extend in radial direction over the entire height of the blade, or only over a portion of this height. Thus, according to an advantageous structure, said portion of the height of the blade has an extension of at least 30% in height; the height varies from 0% at the radially inner end of the blade to 100% at the radially outer end of the blade; or again, said portion of the height of the blade extends between 20% of the height and 80% of the height between these ends.

[0013] According to other structural possibilities, the second portion and / or the third portion (at least over a portion of the height of the blade) has a thickness that decreases continuously towards zero in the direction of one of the end portions, that is, the core can be connected to the end portions at the lower surface or the upper surface or only to one of the end portions.

[0014] According to certain embodiments contemplated for the invention, the first and second end portions are connected to the core via rear surfaces opposite the leading and trailing edges, respectively, the rear surfaces being substantially flat and the core being a rigid plate delimited by two opposite and smooth main surfaces.

[0015] The core may also have a variable thickness from the first end portion to the second end portion, depending on the desired resistance properties of the core.

[0016] The first material is usually metallic and is selected based on the resistance of the material, while the second material (and the material of the third part, if the material of the third part is different from the second material) can be made of a composite material or a polymer (resistant to high temperatures) to provide the required lightness. Assembly of the second and third parts to the first part is usually easy because the second and third parts are located in one or more cavities of the first part, where the second and third parts can be molded or formed so as to create good cohesion by bonding to the first part. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The various aspects, features and advantages of the present invention will now be described by way of the following drawings, which illustrate certain embodiments given purely by way of illustration:

[0018] Figure 1 It is a general perspective view of the impeller blade;

[0019] Figure 2 is a cross section of a first embodiment of the present invention;

[0020] Figure 3 is a cross section of a second embodiment;

[0021] Figure 4A , Figure 4B and Figure 4C are three consecutive cross sections of the third embodiment;

[0022] Figure 5A , Figure 5B and Figure 5C are three consecutive cross sections of a fourth embodiment;

[0023] Figure 6 is a cross section of a fifth embodiment;

[0024] Figure 7 is a perspective view of a fourth embodiment of the present invention;

[0025] Figure 8 is a perspective view of the fourth claim in the opposite orientation;

[0026] Fig. 9 is a view of possible layout details;

[0027] as well as Fig.10 is another example of this detail. DETAILED DESCRIPTION

[0028] Figure 1 The general view of a blade (e.g., a compressor blade) that can be applied to the present invention is shown: the blade includes an inner platform 1 located at the inner radial end, an outer platform 2 located at the outer radial end, and a blade 3 that joins the platforms 1 and 2 and implants the present invention. The blade 3 is used to extend in a gas flow path, where it can be exposed to high temperatures and impacts from various solid impurities entrained in the gas flow. The blade includes a leading edge 4 and a trailing edge 5, and the blade is limited by two curved aerodynamic surfaces that join the leading edge 4 to the trailing edge 5, including an upper surface 6 and a lower surface 7 that are opposite in the thickness direction T of the blade 3. For each section of the blade 3 with a constant radius in the radial direction R, in addition to considering the thickness direction T, the elongation direction X extending from the leading edge 4 to the trailing edge 5 is also considered, and these three directions are perpendicular. A height parameter on the blade measured from 0% at the inner platform 1 to 100% at the outer platform 2 in the radial direction R will also be defined.

[0029] Figure 2 The structure of the blade 3 is described in detail. The blade consists of a first part 8 and in this embodiment a second part 9 and a third part 10. The first part 8 has the function of structural rigidity and is usually made of metal. The first part comprises a first end part 11, a second end part 12 and a core 13 joining these end parts 11 and 12. The first end part 11 comprises a leading edge 4 and two end strips 14 and 15 of the upper surface 6 and the lower surface 7, which are joined to each other at the leading edge 4. The second end part 12 comprises a trailing edge 5 and two end strips 16 and 17 of the upper surface 6 and the lower surface 7, which are joined to each other at the trailing edge 5. However, the strips 14 and 16 and the strips 15 and 17 occupy a small part of the width of the upper surface 6 and the lower surface 7 (in the direction of elongation X). The end portions 11 and 12 are solid, that is, the end portions have a solid section and extend continuously in the thickness direction T of the blade 3 from the end strip 14 or 15 of the upper surface 6 to the end strip 16 or 17 of the lower surface 7, so that the end portions occupy the entire thickness of the blade 3 at the leading edge 4 and the trailing edge 5, and are close to the entire thickness of the blade (however, the ends of the end portions opposite to the leading edge 4 or the trailing edge 5, respectively, can be connected by a flat or slightly concave rear surface 18 or 19, as shown in the figure).

[0030] The core 13 is a spacer that joins the end portions 11 and 12 by their rear faces 18 and 19. The core is made integrally with the end portions and may consist of a plate or a curved rigid airfoil extending between two main surfaces 20 and 21 which may be smooth or, on the contrary, may be ribbed. The thickness of the core is variable here, being thicker in the center than near the end portions 11 and 12. It can be determined that whether there is a progression or a change between the end portions 11 and 12 or not depends on the static or dynamic mechanical strength to be obtained for the blade, which in fact depends to a large extent on the characteristics of the core 13. In any case, the thickness of the core 13 is significantly less than that of the end portions 4 and 5, with the result that the core 13 occupies only a small part of the volume of the blade 3 between these portions. The abrupt change in thickness between the core 13 and the end portions 11 and 12 is accepted and occurs here.

[0031] The second part 9 and the third part 10 extend on opposite sides of the core 13, in a cavity defined by the core 13 and the end parts 11 and 12. The second part 9 is mainly defined by the main surface 20 of the core 13, the rear surface 19 of the second end part 12 and the strip 14 on the side of the upper surface 6 of the first end part 11. The third part 7 is mainly defined by the other main surface 21 of the core 13, the rear surface 18 of the first end part 11 and the strip 17 on the side of the lower surface 7 of the second end part 12. The second part 9 and the third part 10 carry the largest part of the area of ​​the upper surface 6 between the strips 14 and 16 and the largest part of the area of ​​the lower surface 7 between the strips 15 and 17, respectively. The second part and the third part are made of a lighter material than the first part 8, for example made of a composite material or a polymer. The second part and the third part can be molded in the cavity of the first part 8. The blade 3 is rigid due to the first part 8, is resistant due to the end parts 11 and 12, and is light due to the large volume of the second part 9 and the third part 10. The areas of the upper 6 and lower 7 surfaces belonging to the second 9 and third 10 portions extend perfectly the strips 14, 15, 16 and 17, thus giving the upper 6 and lower 7 surfaces a continuous and regular shape and good aerodynamic qualities to the blade 3. In other words, the second 9 and third 10 portions each extend between two end portions 11 and 12 and carry a portion of the aerodynamic surface of the upper 6 and lower 7 surfaces respectively, the second and third portions being positioned so as to ensure the continuity of said upper 6 and lower 7 surfaces with the strips 14, 15, 16 and 17 and to complement said upper and lower surfaces with said strips.

[0032] Other alternative embodiments will now be described.

[0033] Figure 3An alternative embodiment is shown which shows a core 23 of the first portion (now 22) which is uniform in thickness in the direction of elongation X but is otherwise similar to Figure 2 Embodiment of the invention.

[0034] Compared to blades of embodiments such as US 3 294 366 A, it is therefore proposed here to make the connecting core of the end portions inclined across the thickness dimension of the blade along the length dimension of the blade. This new design makes it possible to strengthen the blade by further giving the blade reinforcing ribs (this effect can be enhanced, for example, by giving the core a curved meander or transverse rib shape) and by increasing the cohesion of the second and third portions, the conical shape of which comprises a larger portion at one tip and a more flexible portion at the opposite tip, compared to a portion of which the thickness is more or less constant. The thickness of the core can vary in the radial direction to take into account the aerodynamic forces to which the component is subjected. The core 13 can have a varying shape depending on the section of the blade considered. This will be described in more detail by means of the following figures.

[0035] Let us consider Figure 1 , and are taken at three different heights of the blade in the radial direction R, and these three sections are compared. In certain embodiments of the present invention, as Figure 4A , Figure 4B and Figure 4C As shown, the core (now 33) has a twisted shape, that is to say, successive sections of the core are derived from each other by rotation about a radial direction R, which causes the core to be transformed from, for example, a core similar to Figure 3 Switch the shape to Figure 4C The opposite shape of Figure 3 In the embodiment, the core is joined to the first end portion 31 on the lower surface and to the second end portion on the upper surface. Figure 4C In the embodiment, the core is joined to the first end portion 31 at the upper surface and to the second end portion 32 at the lower surface; there is an intermediate shape between these two heights, such as Figure 4B As shown, according to this intermediate shape, the core 33 joins the two ends 31 and 32 approximately at an intermediate thickness. In other words, the thicknesses e2 and e3 of the second portion 34 and the third portion 35 of the blade are respectively measured in the outer radial direction (towards the outer platform 2) along the first radial section ( Figure 1 CR1-CR1 taken along the radial direction R and the thickness direction of the blade, adjacent to the first end portion 31) decreases and increases (e 21 and e 31 ), along another radial section (CR2-CR2, adjacent to the second end portion 32), respectively increases and decreases, wherein the thickness e of the second portion 34 and the third portion 3522 and e 32 Increase and decrease in the outer radial direction respectively.

[0036] Figure 5A , Figure 5B and Figure 5C Another possible structure is shown, according to which the core (now 43) has an airfoil shape inclined in the angular direction of the turbine, that is, the successive sections of the core are derived from each other mainly by rotation in the axial direction and in the thickness direction of the blade, the core 43 being Figure 5A In the lower surface, Figure 5B In the Figure 5C In other words, the thickness e2 of the second portion 44 decreases in the outer radial direction, and the thickness e3 of the third portion 45 increases. In addition, this evolution is irregular along each cross section of the core 43, and the position of the core 43 in the thickness direction and the height direction of the blade varies greatly near the first end portion 41, and varies little, if at all, near the second end portion 42. Figure 7 and Figure 8 This embodiment is described more fully.

[0037] The opposite evolution is possible.

[0038] The structure of the core will generally be selected for its resistance to static or aerodynamic forces, or its rigidity to vibrations, associated with the particular embodiment of the blade; it will be determined by tests or calculations on a model.

[0039] Different and possibly more complex structures than those described here can also be proposed. This is why the varying shape may involve only a portion of the core, with the additional portion then having a regular shape in the radial direction R. The evolution of the shape may be present only over a portion of the height of the blade, for example in the range of 30% of the total height, or for example also in the region between 20% and 80% of the height between the inner platform 1 and the outer platform 2, at 0% and 100% of the height.

[0040] There are also no rules regarding the thickness of the core, which may be variable or non-variable in the radial direction as well as in the vertical direction, for example thicker at the platform (or generally at the radial ends) than at mid-height, or thicker at the connection of the end parts than at the mid-length between these parts.

[0041] Bonding of the second and third parts to the first part may be achieved in various ways: by overmolding, bonding or interlocking protruding portions of the second and third parts in corresponding recesses of the first part (eg, visible on rear surfaces 18 and 19).

[0042] A completely different way of ensuring the uniformity of the blades is to provide a core, such as core 13, with a hole 50 which enables the second and third parts, such as 9 and 10, to be joined directly, the material of the second and third parts filling the hole 50. Overmoulding is a particularly suitable manufacturing method. Fig. 9 A structure with two radially and axially opposed holes 50 is shown, Fig.10 A structure with eight holes distributed in a regular rectangular array is shown. The number, arrangement and width of the holes 50 are chosen according to the required cohesion; like any thickness variation at locations where mechanical stress is low, the holes also have the effect of lightening the core and thus the blade. Fig. 9 and Fig.10 It also shows Figure 3 An embodiment in which the core 13 has almost overlapping sections over the entire height, the core joining the first end portion 11 at the upper surface 6 and the second end portion 12 at the lower surface 7, but similar holes can be made in all other embodiments considered here.

[0043] Finally, the core does not have to join the end portions at the lower or upper surface: the second and third portions can maintain a non-zero thickness at these locations and at all heights of the blade, as shown in Figure 6 shown.

Claims

1. A blade comprising a reinforced leading edge and a trailing edge and extending between said leading edge and said trailing edge while being limited by a lower surface and an upper surface, said lower surface and said upper surface being two main aerodynamic surfaces of said blade, opposite in the thickness direction (T) of said blade and each extending from said leading edge to said trailing edge; The blade is formed by a first portion (8, 22), a second portion and a third portion, the first portion being made in one piece from a first material, the first portion being made of a first end portion (11) comprising the leading edge (4), a second end portion (12) comprising the trailing edge (5), and a core connecting the first end portion (11) to the second end portion (12), the first end portion and the second end portion each comprising a strip (14, 15, 16, 17) of each of the main aerodynamic surfaces (6, 7), a second portion extending between the first end portion and the second end portion and joined to a first main surface (20) of the core, the second portion being made of a second material that is lighter than the first material and carrying a region of a first of the main aerodynamic surfaces (6, 7) between the strips of the first aerodynamic surface belonging to each of the first end portion and the second end portion; The third portion is joined to a second main surface (21) of the core opposite to the first main surface, and carries a second aerodynamic surface of the main aerodynamic surface in an area between strips of the second aerodynamic surface belonging to each of the first end portion and the second end portion, the third portion being made of a material lighter than the first material; characterized in that the core has an inclined extension in the thickness direction over at least a portion of the height of the blade, the second portion having a greater thickness near the second end portion than near the first end portion, and the third portion having a greater thickness near the first end portion than near the second end portion.

2. The impeller according to claim 1, characterized in that: The first and second end portions are connected to the core by rear surfaces (18, 19) opposite the leading and trailing edges, the rear surfaces being substantially flat.

3. The impeller according to claim 1 or 2, characterized in that: The core is a rigid plate defined by the first (20) and second (21) main surfaces which are opposite and smooth.

4. The impeller according to claim 3, characterized in that: The rigid plate has a variable thickness between the first end portion and the second end portion.

5. The impeller according to claim 1 or 2, characterized in that: The second portion and the third portion are both made of the second material.

6. The impeller according to claim 1 or 2, characterized in that: The first material is metallic.

7. The impeller according to claim 1 or 2, characterized in that: The second material and the material of the third portion are made of composite materials or polymers.

8. The impeller according to claim 7, characterized in that: The second portion and the third portion are molded or formed in the first portion.

9. The impeller blade according to claim 1 or 2, characterized in that: The first end portion (11) and the second end portion (12) are solid and thicker than the core in the thickness direction.

10. The impeller according to claim 1 or 2, characterized in that: In a cross section taken through the blade, in the radial direction of the blade, from the lower surface to the upper surface, and over a portion of the height of the blade, one of the second portion and the third portion has an increasing thickness (e3) in an outward direction of the radial direction, and the other of the second portion and the third portion has a decreasing thickness (e2) in the outward direction.

11. The impeller blade according to claim 1 or 2, characterized in that: In a first cross section taken through the blade adjacent to the first end portion, in the radial direction of the blade, from the lower surface to the upper surface, and over a portion of the height of the blade, one of the second portion and the third portion has an increased thickness in an outward direction of the radial direction, and the other of the second portion and the third portion has a decreased thickness in the outward direction; and, in a second cross section taken through the blade adjacent to the second end portion, in the radial direction of the blade, from the lower surface to the upper surface, and over a portion of the height of the blade, one of the second portion and the third portion has a decreased thickness in an outward direction of the radial direction, and the other of the second portion and the third portion has an increased thickness in the outward direction.

12. The impeller according to claim 1 or 2, characterized in that: The second portion and / or the third portion has, at least over a portion of the height of the blade, a thickness which decreases continuously towards zero in the direction of one of the first end portion and the second end portion.

13. The impeller according to claim 10, characterized in that: The height portion of the vane has an extension of at least 30% in height, the height varying from 0% at the radially inner end of the vane to 100% at the radially outer end of the vane.

14. The impeller according to claim 11, characterized in that The height portion of the vane has an extension of at least 30% in height, the height varying from 0% at the radially inner end of the vane to 100% at the radially outer end of the vane.

15. The blade according to claim 13 or 14, characterized in that: The height portion of the bucket extends between 20% of the height and 80% of the height between the radially inner end and the radially outer end of the bucket.

16. The impeller according to claim 1 or 2, characterized in that: The vane includes a hole (50) through the core, the second portion and the third portion being joined by the hole.

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