WO2019092679A1

WO2019092679A1 - Method for the construction of stator and rotor elements of turbomachines

Info

Publication number: WO2019092679A1
Application number: PCT/IB2018/058909
Authority: WO
Inventors: Stefano SALGAROLLO
Original assignee: Exergy S.P.A.
Priority date: 2017-11-13
Filing date: 2018-11-13
Publication date: 2019-05-16

Abstract

The present invention relates to a method for the construction of rotor and stator elements of turbomachines, comprising: readying an ingot (1) of material to be machined; performing cuts in the ingot (1) so as to delimit blocks (10) of material interposed between portions of material intended to form blades (2) of the rotor or stator element; removing said blocks (10) freeing passages (11) between the portions of material; finishing the portions of material until the final shape is given to said blades (2) and to the passages (11). Execution of the cuts comprises: making first slots (6) on a first side (3) of the ingot (1), wherein the first slots (6) penetrate only partially through a thickness (t) of the ingot (1) to delimit into said ingot (1) a first half-block (7) of material joined to the ingot (1); making second slots (8) on a second side (4) of the ingot (1) opposite to the first side (3) to delimit a second half-block (9) into the ingot (1). The first slots (6) and the second slots (8) intersect each other so that the first and the second half-block (7, 9) define a single block (10) removable from the first side (3) and/or from the second side (4).

Description

"Method for the construction of stator and rotor elements of turbomachines"

DESCRIPTION

Field of the invention

The present invention relates to a method for the construction of rotor and stator elements of turbomachines.

Rotor and stator elements are typically bladed elements with more or less complex geometries that are usually machined from solid by removal of a high percentage of material with respect to the volume of the starting piece, up to 80%-90% of the volume of the starting piece.

The present invention applies both to motor turbomachinery (turbines) and operating turbomachinery (compressors).

Preferably but not exclusively, the present invention refers to turbomachines used in the aeronautical/aerospace field and/or in the energy field and/or in the engine field and/or in the marine field.

These elements are, for example but not exclusively, open or closed impellers, rotor and stator bladed rings or disks, preferably for radial turbines, inlet/outlet guide vanes, diaphragms, etc.

Preferably but not exclusively, the present invention refers to the expansion turbines used in apparatuses for the production of electricity which, preferably, exploit geothermal sources, for example by water Rankine vapour cycle or organic Rankine cycle (ORC).

Background of the invention

As is well known, the machining of stator and rotor elements from solid is carried out by mechanical machining processes on a solid starting piece (which can also be a cast or 3D printed piece) through operations that remove material progressively and a little at a time. Among the known technologies used, there are, for example, chip removal by means of mechanical milling machines, also robotised, or with Abrasive Water Jet (AWJ) and Electro Discharge Machining (EDM) or Electro Chemical Machining (ECM). These machining processes can reach, in the production of the complex rotor and stator elements of turbomachines of the present invention, removal rates of a few tens or a few hundreds of cubic centimetres per minute. For example, the roughing removal with a 40 mm milling machine can be carried out with a removal rate of approximately 80-100 cm³/min. Roughing removal with one or more AWJ heads can reach 300 - 350 cm³/min. There are also known methodologies that entail the removal of material in blocks by Abrasive Water Jet (AWJ). For example, the public document US2013/0171915 illustrates a manufacturing process for a vaned disc that comprises cutting a piece of material from a solid starting block by abrasive water jet. The abrasive water jet passes through the thickness of the solid starting piece, such that the cutout piece escapes from the block automatically by gravity.

The public documents US2013/0167359, US201 1/041334, US201 1/023300, US201 1/016716, US201 1/016714, US201 1/016712 also illustrate similar methodologies.

Summary

In this field, the Applicant has perceived the need to improve known construction methods for manufacturing complex rotor and stator elements of turbomachines, so as to assure a high quality of construction, to guarantee the reliability and efficiency of the turbomachines in which they are installed and, at the same time, to speed up their production and reduce the related costs.

The Applicant has indeed observed that traditional progressive material removal techniques entail long manufacturing times.

The Applicant has also observed that the faster methods like those described in the aforementioned documents allow, in some cases, to carry out only a coarse roughing and in other cases, for rotor and stator elements with complex shapes, cannot even be used because the through cut would intersect the geometries (typically the blades) of the rotor or stator elements to be obtained.

The term "complex geometry" typically means a geometry with (highly curved) action blades or a high number of blades, hence with little space between one and the other, or with blades that are highly twisted between inlet and outlet (used for example for compressors). Instead, the term "simple geometry" typically means a more reaction type geometry, or with fewer blades, or with untwisted blades.

Within this scope, the Applicant thus set itself the following objectives:

^■ to propose a method for the construction of rotor and stator elements of turbomachines that is fast and relatively simple, so as to reduce production cost, but at the same time that it allows to obtain complex geometries; ^■ to propose a method for the construction of rotor and stator elements of turbomachines that allows to improve their quality and constructive precision and hence the reliability and efficiency of the turbomachines in which they are installed.

More specifically, the Applicant set itself the following objectives:

^■ to reduce the machining times necessary to obtain the finished geometries of the blades;

^■ to reduce machining costs by reducing machining times;

^■ to reduce machining costs using machines with lower hourly costs and using fewer machining tools and/or machines that allow processing multiple slots in parallel;

^■ to allow machining any type of material in a more cost-efficient manner;

^■ to reduce investment costs pertaining to the machinery to be used;

^■ to allow reselling and/or re-using the removed scrap material.

The Applicant has found that the above objectives and others besides can be achieved by making first slots on a first side of an ingot from which the rotor or stator elements are to be obtained so as to delimit/obtain, on the first side and partially through a thickness of the ingot, a first half-block of material that has a face still joined to the ingot. Subsequently, second slots are made on a second side of the ingot to delimit a second half-block of material joined to the first half- block and separated from the rest of the ingot.

In particular, the indicated objectives and others besides are substantially achieved by a method for the construction of rotor and stator elements of turbomachines according to one or more of the appended claims and/or in accordance with one or more of the following aspects.

More specifically, according to one aspect, the present invention relates to a method for the construction of rotor and stator elements of turbomachines.

The method comprises: providing an ingot of material to be machined; performing cuts in the ingot so as to delimit blocks of material interposed between portions of material intended to form blades of the rotor or stator element; removing said blocks freeing passages between the portions of material; finishing said portions of material until the final shape is given to said blades and to said passages.

In one aspect, making cuts comprises: making first slots on a first side of the ingot, wherein the first slots penetrate only partially through a thickness of the ingot to delimit in said ingot a first half-block of material joined to the ingot; making second slots on a second side of the ingot opposite to the first side to delimit in said ingot a second half-block of material; wherein the first slots and the second slots are mutually incident so that the first and the second half-block define a single block extractable from the first side and/or from the second side.

The Applicant has verified that the method according to the invention allows first of all to produce such complex rotor and stator element as to allow for greater design freedom.

The Applicant has verified that the method according to the invention allows to remove blocks of greater size and to immediately approach the final shape of the required geometry even when said geometry is highly complex.

The Applicant has also verified that the method according to the invention allows to considerably reduce the machining times and costs necessary to obtain said complex geometries.

The Applicant has also verified that making slots on both sides allows to maximise the ratio between the total volume removed after taking away the block and the volume of material removed while making the slots or between the total volume removed after taking away the block and the total volume to be removed to have the final bladed geometry.

The Applicant has also verified that, thanks to machining on both sides, the method according to the invention allows to cut high thicknesses of material even using already available cutting tools and/or techniques.

In one aspect, the ingot is metallic, preferably forged.

In one aspect, the first slots and the second slots are obtained in sequence or simultaneously.

In one aspect, the single block can be extracted indifferently from the first side and from the second side.

In one aspect, the single block can be extracted only from the first side or only from the second side. Preferably, the shape of the block obtained is such as to allow its extraction only from one of the two sides. Preferably, the extraction from the other side is prevented.

In one aspect, after the removal of the single block, additional cuts are made, preferably to remove additional blocks and to increase the removed volume before finishing the piece. In one aspect, the first slots on the first side of the ingot and the second slots on the second side of the ingot opposite to the first side define a plurality of single blocks that can be extracted from the first side and/or from the second side.

In one aspect, the blocks of said plurality can be extracted along mutually different directions, preferably from a same side.

In one aspect, the blocks of said plurality can be extracted along the same directions.

The creation and extraction of multiple blocks allows to generate even highly twisted blades and to optimise the volume of removed material.

In one aspect, taking as a reference a direction entering the ingot from the first side, the first slots are mutually diverging.

In one aspect, taking as a reference a direction entering the ingot from the first side, the second slots are mutually converging.

In one aspect, taking as a reference a direction entering the ingot from the first side, the first slots are mutually converging.

In one aspect, taking as a reference a direction entering the ingot from the first side, the second slots are mutually diverging.

In one aspect, the first slots are mutually parallel.

In one aspect, the second slots are mutually parallel.

In one aspect, each of the first and/or second slots lies in a plane.

In one aspect, each of the first and/or second slots lies defines at least one curved surface inside the ingot.

In one aspect, the first half-block and/or the second half-block have a tapered shape.

In one aspect, the first half-block and/or the second half-block curved and/or wavy surfaces.

In one aspect, said shape tapers proceeding towards the interior of the ingot.

In one aspect, said shape diverges proceeding towards the interior of the ingot. In one aspect, the first half-block and/or the second half-block have a constant cross section along a direction through a thickness of the ingot.

In one aspect, the first half-block and/or the second half-block have a variable cross section along a direction through a thickness of the ingot.

The geometry of the slots and hence the geometry of each of the two half-blocks generated are such that the single block can be extracted from the ingot, preferably, without carrying out additional machining processes. The two half- blocks, therefore, cannot be both tapered towards each other.

In one aspect, the first and second slots are obtained by water jet under high or very high pressure, preferably abrasive (Abrasive Water Jet, AWJ) or electro discharge, preferably by means of EDM (Electro Discharge Machining) machines, or by mechanical chip removal, by milling or by means of a laser device or a plasma torch.

In one aspect, the first and second slots are obtained by a hybrid machining process resulting from the combination of two or more of the aforementioned techniques.

In one aspect, the first and second slots are made by successive steps, i.e. making cuts in succession with ever greater depths. This solution allows better control of the final depth of the cut and better evacuation of the water, in case of use of the water jet, and of the removed material.

In one aspect, the first and second slots are made moving a water jet according to a non-linear path, for example spiral, zig-zagging, but always along the cut, to obtain a greater width of the cut than that of the water jet, i.e. a cut by erosion. In one aspect, the first and second slots are made keeping the water jet inclined with respect to a surface of the ingot.

In one aspect, the water jet forms with a cut segment already made at an angle greater than 90° or, in other words, a head of the device that emits the jet is inclined towards the surface of the ingot that has not yet been cut. This position allows an easier exit of the water from the cut just made and of the removed material.

In one aspect, the water jet forms with a cut segment already made at an angle smaller than 90° or, in other words, the head of the device that emits the jet is inclined towards the surface of the ingot that has already been cut.

In one aspect, each of the first and/or second slots has a substantially planar development.

In one aspect, each of the first and/or second slots has a substantially constant thickness.

In one aspect, each of the first and/or second slots has a wedge shape.

In one aspect, each of the first and/or second slots has variable thickness. In one aspect, the first slots and/or the second slots are made by cutting and removing blocks, preferably but not exclusively wedge shaped. Preferably, said blocks have triangular section. Preferably, said blocks are removed before extracting the single block.

In one aspect, the ingot of material to be machined is a disk having a main axis or axis of rotation, two axially opposite sides and a radially external peripheral surface.

In one aspect, the ingot of material to be machined is a ring having a main axis or axis of rotation, axially opposite sides, a radially external peripheral surface and a radially internal peripheral surface.

Preferably, the two axially opposite sides are defined by planar surfaces.

In one aspect, the first side and the second side are the axially opposite sides of the disk or of the ring.

In one aspect, the single block is extracted along an axial or substantially axial direction.

In one aspect, the first side and the second side are the radially external peripheral surface and the radially internal peripheral surface.

In one aspect, the single block is extracted along a radial or substantially radial direction.

In one aspect, the extraction takes place by gravity.

In one aspect, the method is used to build at least one of the following elements of turbomachines: an axial diaphragm, an axial bladed disk, a radial diaphragm, a radial bladed disk or ring, an impeller, a rotor or a Pelton turbine.

In one aspect, the method for building the rotor of the Pelton turbine comprises providing an ingot comprising an outer toroidal portion, intended to form the blades of the Pelton turbine, and a radially inner portion with smaller axial thickness with respect to the outer toroidal portion.

In one aspect, the method for building the rotor of the Pelton turbine comprises turning the ingot until obtaining the outer toroidal portion and the radially inner portion with smaller axial thickness, preferably by turning.

In one aspect, the first and the second slots are made in the outer toroidal portion, preferably after turning. Further features and advantages shall be more readily apparent from the detailed description of methods for the construction of rotor and stator elements of turbomachines according to the present invention. Description of the drawings

Such description will be made herein below with reference to the accompanying drawings, provided for indicative purposes only and therefore not limiting, in which:

^■ Figure 1 shows a three-dimensional view in x, y, z of a portion of a bladed disk for axial turbines during its fabrication carried out with the method according to the present invention;

^■ Figures 2A, 2B and 2C show a schematic section view along z of a portion of the bladed disk of Figure 1 in a sequence of machining steps;

^■ Figures 3A, 3B and 3C show a schematic section view along z of the portion of Figures 2A and 2B according to a variant of the method;

■ Figure 4 shows a three-dimensional view of a portion of a closed impeller during its fabrication carried out with the method according to the present invention;

^■ Figure 4A shows a block extracted from the portion of impeller of Figure 4;

■ Figures 5A, 5B and 5C show a schematic view of a portion of the closed impeller of Figure 4 in a sequence of machining steps;

^■ Figure 6 shows a three-dimensional view of a portion of a rotor of a Pelton turbine during its fabrication carried out with the method according to the present invention;

■ Figure 7 shows a three-dimensional view of the portion of Figure 6 during its fabrication carried out with the method according to the present invention;

^■ Figure 8 shows a three-dimensional view of the portion of Figure 6 during its fabrication carried out with an additional variant of the method according to the present invention;

^■ Figure 9 shows a three-dimensional and partially sectioned view of an additional machining step of the Pelton turbine of Figures 6, 7 and 8; Figure 10 shows a three-dimensional view in x, y, z of a portion of a bladed disk with twisted blades during its fabrication carried out with the method according to the present invention;

Figure 1 1 shows a block removed from the portion of Figure 10;

Figure 12 shows a three-dimensional view in x, y, z of a portion of an additional bladed disk with twisted blades during its fabrication carried out with the method according to the present invention;

Figures 13 and 14 show a block removed from the portion of Figure 12. Detailed description

With reference to the aforementioned figures, the reference numeral 1 designates in its entirety an ingot of material to be machined from which is obtained a rotor element or a stator element of a turbomachine, for example but not exclusively, an open or closed impeller, a rotor or stator bladed ring or disk, an inlet/outlet guide vane, a diaphragm, a closed impeller etc.

Figure 1 shows a portion of a bladed disk for axial turbines during its fabrication carried out with the method according to the present invention. The bladed disk comprises a plurality of blades 2 (drawn in dashed lines because they are not yet physically manufactured) with their own leading edge that develops substantially along a radial direction with respect to an axis of rotation "X" of the bladed disk 1 . The bladed disk is also circled, i.e. it has a ring that connects the radial ends of the blades 2.

The bladed disk is built starting from the ingot 1 of material to be machined, for example of metal, for example forged, which has a disk shape with a main axis that, when the bladed disk is finished and installed, coincides with its own axis of rotation "X". The disk-shaped ingot 1 thus has a first side 3 and a second side 4, orthogonal to the axis of rotation "X" and axially opposite to each other, and a radially outer peripheral surface 5. The disk-shaped ingot 1 has a thickness "t" measured along an axial direction.

The method according to the present invention comprises making in the ingot 1 first slots 6 on the first side 3 of the ingot. The first slots 6 penetrate only partially through the thickness "t" of the ingot so as to delimit in said ingot a first half-block 7 of material still joined to the ingot 1 . For example, a depth "p1 " of said first slots 6 can be approximately half of the thickness "t" (Figure 2A). These first slots 6 are for example made with a water jet device configured to make cuts with water jets under very high pressure with abrasive (Abrasive Water Jet - AWJ). For example, the water jet is emitted at a pressure of 5000 bar and the abrasive comprises a grain of dimensions 400 pm and a mesh of 60 pm.

These first slots 6 are, for example, obtained with a single and continuous movement of a head Ή" of the water jet device that describes a first closed path "C1 " on the first side 3, like the one shown in Figure 1 . The first path "C1 " delimits a visible face of the first half-block 7.

In the embodiment shown in Figures 1 , 2A-2C, the first slots 6 comprise two slots lying on respective planes, radial or substantially parallel to each other, wherein said planes are circumferentially distanced from each other. The first slots 6 further comprise two slots lying on respective planes substantially perpendicular to radial directions and radially distanced from each other. Thus the first half-block 7 has, in addition to the visible face, four planar or substantially planar faces. The sixth face is joined to the ingot 1.

The method comprises making in the ingot 1 second slots 8 on the second side 4 of the ingot 1 itself. The second slots 8 also penetrate only partially through the thickness "t" of the ingot 1 , for example by a depth "p2", to delimit a second half- block 9 in said ingot 1 . The second slots 8 penetrate until joining the first slots 6 so that the first and the second half-block 7, 9 define a single block 10 that can be extracted from the ingot along a direction of extraction Έ".

The second slots 8 too are, for example, obtained with a single and continuous movement of a head Ή" of the water jet device that describes a second closed path "C2" on the first side 4, like the of the shown in Figure 1 . This second path "C2" delimits a visible face of the second half-block 9.

In the embodiment shown in Figures 1 , 2A-2C, the second slots 8 comprise two slots lying on respective planes diverging from each other, taking as a reference a direction going into the ingot 1 from the second side 4. These second diverging slots are joined to the two first slots lying on the radial planes. The second slots 8 comprise two slots lying on respective planes substantially perpendicular to radial directions and radially distanced from each other. The second slots 8 lying on respective planes substantially perpendicular to radial directions are joined to the two first slots lying on respective planes substantially perpendicular to radial directions. The first and second slots 6, 8 of this embodiment have a substantially constant thickness as a function of an average diameter of the water jet under very high pressure.

Thus the second half-block 9 has, in addition to the visible faces, four planar or substantially planar faces, two mutually parallel and two mutually diverging. The second half-block 9 therefore has a tapered shape that diverges proceeding towards the interior of the ingot 1. The sixth face is joined to the first half-block 7 so as to delimit the single block 10.

As can be noted, if some of slots were extended beyond approximately half of the thickness of the ingot 1 , they would cross the blades 2 still to be manufactured.

The method then comprises extracting the single block 10 from the first side 3 along the direction of extraction Έ" that is substantially parallel to the axis of rotation "X". The extraction from the second side is prevented by the tapered shape of the second half-block 9.

The extraction frees a respective passage 1 1 substantially axial that lies between two portions of material of the ingot 1 destined to form two blades 2 of the bladed disk 1 (Figure 2C). These portions of material are then finished, for example by material removal, until the final shape is given to said blades 2 and to said passages 1 1 . In an embodiment not illustrated herein, in the two portions of material of the ingot 1 , before finishing, additional supplementary cuts are made to remove supplementary blocks.

Figures 3A, 3B and 3C show a variant of the steps 2A and 2B directed at obtaining the same passage 1 1 of Figure 2C.

The first and the second slots 6, 8 have a wedge shape and are obtained by cutting and removing wedge shaped blocks 12 (Figure 3C). For this purpose, first notches 13 and second notches 14 are made in the first and in the second side 3, 4 to delimit the wedge shaped blocks 12. The blocks 12 are then removed (Figure 3C) and then the resulting single block 10 is removed.

Figure 4 shows a three-dimensional view of a portion of a closed impeller during its fabrication carried out with the method according to the present invention. The closed impeller, known in itself, comprises a plurality of substantially radial passages 15 delimited between two plate-shaped elements 16 and by walls 17 shaped as blades interposed between said two plate-shaped elements 16. The substantially radial passages 15 have a radially inner opening and a radially outer opening.

The closed impeller is built starting from an ingot 1 of material to be machined, for example of forged metal, which has a ring shape with a main axis that, when the closed impeller is finished and installed, coincides with the axis of rotation "X".

The ring-shaped ingot 1 thus has two axially opposite sides, a radially external peripheral surface and a radially internal peripheral surface. The radially external peripheral surface constitutes a first side 3, the radially internal peripheral surface defines a second side 4. The ring-shaped ingot 1 has a thickness "t" measured along a radial direction and constituting the distance between the first side 3 and the second side 4 (Figures 5A, 5B, 5C).

As shown in Figures 5A, 5B, 5C, the method is similar to the one described above and the numbers used in the drawings are the same for the corresponding elements. The extracted single block 10 too (better visible in Figure 4A) is similar, aside from the dimensions and the ratios between the dimensions. In this case, the method comprises extracting the single block 10 from the first side 3 along the direction of extraction Έ" that is radial (not axial as in the embodiment described above).

Figure 6 shows a three-dimensional view of a portion of a rotor of a Pelton turbine during its fabrication carried out with the method according to the present invention.

The Pelton turbine, long known in itself, comprises a plurality of radial blades. Each blade has the shape of two paired buckets, between which is a splitter configured to split the water jet in half.

The Pelton turbine is built starting from an ingot 1 of material to be machined, for example of forged metal, which has a disk shape with a main axis that, when the turbine is finished and installed, coincides with its own axis of rotation "X". The disk-shaped ingot 1 thus has a first side 3 and a second side 4, orthogonal to the axis of rotation "X" and axially opposite to each other, and a radially outer peripheral surface 5. The disk-shaped ingot 1 has a thickness "t" measured along an axial direction.

The method comprises making the first slots 6 on the first side 3 of the ingot (upper side of Figure 6) through the water jet device. The first slots 6 penetrate partially through the thickness "t" of the ingot 1 by a depth "p1 ". The head "H" is moved along a first path "C1 " on the first side 3 that begins and ends at the radially outer peripheral surface 5 and has substantially triangular shape. The first slots 6 are mutually parallel and substantially parallel to the axis of rotation "X".

The method comprises making the second slots 8 on the second side 4 of the ingot 1 (lower side not visible in Figure 6).

The second slots 8 also penetrate only partially through the thickness "t" of the ingot 1 by a depth "p2". The second slots 8 penetrate until joining the first slots 6 so that the first and the second half-block 7, 9 define a single block 10 that can be extracted from the ingot 1 along an axial direction of extraction Έ". The second slot 8 mutually diverge, taking as a reference a direction entering the ingot 1 from the second side 4. The single block 10 can be extracted from the first side 3 along the direction of extraction Έ" which in Figure 6 is vertical and directed upwards. In this case, the extraction can also be radial.

Figure 7 shows a variant of the manufacturing method of the Pelton turbine, which is differentiated from the method of Figure 6 because the second slots 8 converge with each other, taking as a reference a direction entering the ingot 1 from the second side 4. The single block 10 can therefore be extracted from the second side 4 along the direction of extraction Έ" which in Figure 7 is vertical and directed downwards.

Figure 8 shows an additional variant of the embodiment of the Pelton turbine, which is differentiated from the method of Figure 6 because both the first slots 6 and the second slots 8 are mutually parallel and substantially parallel to the axis of rotation "X". Therefore, the first half-block 7, the second half-block 9 and thus the single block 10 have a constant cross section along an axial direction that passes through the thickness "t" of the ingot 1 . The single block 10 can therefore be extracted from the first or from the second side 3, 4 or also radially.

Figure 9 shows a variant of the ingot 1 of material to be machined to obtain the Pelton turbine. Before making the slots 6, 8 and extracting the blocks 10 (according to the method shown in Figures 6, 7 and 8) the disk-shaped ingot is turned until obtaining the shape of Figure 9 whish has an outer annular or toroidal portion 18, intended to form the blades of the Pelton turbine, and a radially inner portion 19 with reduced axial thickness with respect to the outer annular or toroidal portion. Figure 9 also shows a block 10 cut by the head "H". The methods for obtaining the rotor elements illustrated in detail above and represented in the accompanying figures can use, instead of the water jet under very high pressure with abrasive (Abrasive Water Jet, AWJ), other cutting techniques, for example electro discharge, preferably by means of EDM (Electro Discharge Machining) machines, or by mechanical chip removal, by milling or by means of a laser device or a plasma torch, or hybrid machining obtained from the combination of two or more of the aforementioned techniques.

Moreover, the extracted single blocks 10 can have several shapes, some of which are shown in Figures 1 1 , 13 and 14 for highly twisted blades.

Figure 10 shows a three-dimensional view of a portion of a rotor of an axial turbine with twisted blades and of a single block 10 generated between two blades 2 with the method according to the invention. The single block 10 can be extracted along the direction of extraction Έ" or radially.

Figure 12 shows a three-dimensional view of a portion of a rotor similar to that of Figure 10, in which there are two generated blocks 10 (shown in Figures 13 and 14), extracted from the same side (the first side 3) but along different directions, Έ1 ", Έ2".

The following Tables 1 and 2 (one relating to small thicknesses, i.e. between 0 mm and 150 mm, and the other to large thicknesses, i.e. between 150 mm and 800 mm) show the characteristic values of the percentage ratio "Vb/Vtot" between the volume removed after removal of the blocks "Vb" (Vb = Vbl + Vt) and total volume "Vtot" (Vtot = Vbl + Vt + Vfin) of material removed from the ingot after finishing, obtained with the machining process according to the invention (for different types of rotor and stator elements) compared with the same ratio obtained by removal of blocks with through cuts carried out by AWJ - Abrasive Water Jet.

The same Tables also show the values of the ratio "Vt/Vbl" between the volume of material removed by the cuts "Vt" and the volume "Vbl" of the cut blocks in the method according to the invention.

It should be recalled that the term "complex geometry" typically means a geometry with (highly curved) action blades or a high number of blades (hence with little space between one and the other, or with blades that are highly twisted between inlet and outlet (used for example for compressors)). Instead, the term "simple geometry" typically means a more reaction type geometry, or with fewer blades, or with untwisted blades. Table 1

Simple geometry n.a. 95% 2%

As is readily apparent, with regard to the components with small thicknesses, some geometries, such as complex ones with circled/closed blades (in particular, those that have a high number of blades), cannot be obtained (in Table 1 they are indicated as "n.a.") with the through cuts nor can they be obtained with the method according to the invention.

The same complex geometries but with open blades can instead be obtained with the method of the invention and not with through cuts.

Simple geometries instead can be obtained with both methods, but the method of the invention optimises the removable volume.

With regard to components with large thickness (Table 2), they cannot be obtained with through cuts, while the invention allows to machine them, apart from a few cases, i.e. closed complex geometries.

This means that the method according to the invention allows to obtain a broader range of components of various dimensions, in a simpler and faster manner and hence with savings in terms of times and costs. In addition, as can be noted from the third column, it is sufficient to remove little material by means of the cuts to remove blocks of significant volume.

List of elements

1 ingot of material to be machined

2 blades

3 first side of the ingot

4 second side of the ingot

5 radially outer peripheral surface of the ingot

6 first slots

7 first half-block

8 second slots

9 second half-block

10 single block

1 1 passage

12 wedge-shaped blocks

13 first notches

14 second notches

15 substantially radial passages

16 plate-shaped elements

17 walls

18 outer annular or toroidal portion

19 radially inner portion

Claims

1 . Method for the construction of rotor and stator elements of turbomachines, comprising:

■ providing an ingot (1 ) of material to be machined;

^■ performing cuts in the ingot (1 ) so as to delimit blocks (10) of material interposed between portions of material intended to form blades (2) of the rotor or stator element;

^■ removing said blocks (10) by clearing passages (1 1 ) between the portions of the material;

^■ finishing said portions of material until the final shape is provided to said blades (2) and to said passages (1 1 );

wherein performing cuts comprises:

making first slots (6) on a first side (3) of the ingot (1 ), wherein the first slots (6) penetrate only partially through a thickness (t) of the ingot (1 ) to delimit into said ingot (1 ) a first half-block (7) of material joined to the ingot (1 ); making second slots (8) on a second side (4) of the ingot (1 ) opposed to the first side (3) to delimit a second half-block (9) of material in said ingot (1 ); wherein the first slots (6) and the second slots (8) intersect each other so that the first and second half-blocks (7, 9) define a single block (10) removable from the first side (3) and/or from the second side (4).

2. Method according to claim 1 , wherein the single block (10) can be removed only from the first side (3) or only from the second side (4).

3. Method according to claim 1 , wherein, taking as reference a direction entering the ingot through the first side (3), the first slots (6) diverge from one another and, taking as reference a direction entering the ingot through the second side (4), the second slots (8) converge with each other, or, taking as reference a direction entering the ingot through the first side (3), the first slots (6) converge with each other and, taking as reference a direction entering the ingot through the second side (4), the second slots (8) diverge from one another.

4. Method according to claim 1 , wherein the first slots (6) are parallel to each other and, taking as reference a direction entering the ingot through the second side (4), the second slots (8) are mutually converging, diverging or parallel or the second slots (8) are parallel to each other and, taking as reference a direction entering the ingot through the first side (3), the first slots (6) are mutually converging, diverging or parallel.

5. Method according to claim 1 , wherein the first half-block (7) and/or the second half-block (9) have a tapered shape.

6. Method according to claim 1 , wherein the first slots (6) and the second slots (8) are made by mechanical chip removal and/or laser and/or electro-erosion and/or plasma jet and/or high pressure water-jet.

7. Method according to claim 1 , wherein the first slots (6) and/or the second slots (8) each have a wedge shape.

8. Method according to claim 1 , wherein the first slots (6) and/or the second slots (8) are made by cutting and removing wedge shaped blocks (12).

9. Method according to claim 1 , wherein the ingot (1 ) of material to be machined is a disc or ring having a rotation axis (X); wherein the first side (3) and the second side (4) are axially opposite sides of the disc or ring; or wherein the ingot (1 ) of material to be machined is a ring having a radially inner surface and a radially outer surface; wherein the first side (3) is constituted by the radially inner surface and the second side (4) is constituted by the radially outer surface.

10. Method according to claim 1 , wherein the first slots (6) on the first side (3) of the ingot (1 ) and the second slots (8) on the second side (4) of the ingot (1 ) opposite the first side (3) delimit a plurality of single blocks (10), wherein the blocks (10) of said plurality are extractable along directions (E1 , E2) different from each other from a same side (3, 4).