WO2020201087A1

WO2020201087A1 - Method for designing an air-oil separator

Info

Publication number: WO2020201087A1
Application number: PCT/EP2020/058715
Authority: WO
Inventors: Baptiste Joël Christian FEDI; Xavier Roger BETBEDER- LAÜQUE; Julie Denise QUEROIS
Original assignee: Safran
Priority date: 2019-03-29
Filing date: 2020-03-27
Publication date: 2020-10-08
Also published as: FR3094524A1; FR3094524B1

Abstract

The invention concerns a computer-implemented method for designing a three-dimensional modelled object of a mechanical part comprising a body, with a cell, and a lattice structure in the cell, which comprises the following steps: a) providing (E1) a representation by the edges of the body; b) providing (E2) a representation by the edges of an integration volume of the lattice structure; c) calculating (E3) a polygonal representation of the body and of the integration volume, from the representation by the edges of the body; d) providing (E4) a representation by the edges of an elementary pattern of the lattice structure; e) calculating (E5) a polygonal representation of an immediate lattice structure, from the representation by the edges of the elementary pattern; f) determining (E6), from the polygonal representation of the integration volume and of the intermediate volume, a polygonal representation of the lattice structure; g) assembling (E7) the polygonal representation of the body and of the lattice structure determined so as to obtain a three-dimensional modelled object of the sector.

Description

DESCRIPTION

TITLE: DESIGN METHOD OF AN AIR-OIL SEPARATOR

Technical field of the invention

Gas turbine aircraft engines have enclosures containing bearings and gears that are lubricated and cooled by oil. In order to prevent oil leaks to the outside of these enclosures, seals are arranged between the rotating parts and the fixed parts of the enclosures, or even between the rotating parts themselves. Among the seal technologies available, those offering the longest life are labyrinth seals and brush seals, the contact between the parts being non-existent in the first case and very limited in the second.

State of the prior art

To ensure perfect sealing of enclosures fitted with labyrinth seals or brush seals, on the other hand, it is necessary to pass a flow of air through the seals, this flow of air being generally taken from a stage of the engine compressor. . The use of such a method also involves providing devices separating the oil from the air to be evacuated outside the engine. Such devices - commonly called air-oil separator or also oil separator - are well known per se. Reference may for example be made to documents EP 1582703, US 4,981, 502 and US 6,033,450 which describe different types of centrifugal oil separators.

Such an air-oil separator, also called a degasser, is generally arranged and driven by a mechanical power take-off at the level of the accessories box or the reduction gear of the turbomachine.

In known manner, such a centrifugal degasser comprises one or more chamber (s) for centrifugal separation of the air / oil mixture arranged around a hollow shaft and delimited by an outer annular wall and an inner annular wall. The degasser further comprises an axial inlet for supplying the enclosure with the air / oil mixture, and a peripheral oil outlet provided in the outer wall. Thus, during the rotation of the degasser, generally obtained by means of a pinion of the accessory box or of the reducer, the oil is naturally driven by centrifugal force towards the oil outlet provided at the periphery. of the degasser. An oil-free air outlet is also provided in the internal wall and connected to the hollow shaft, which allows the air to be evacuated to the outside.

Thus, the flow of air and oil circulating in the air-oil separator is filtered through lattice structures. The term “lattice structure” is understood to mean a lattice structure corresponding to an assembly of metal segments crossed and held together so as to form a rigid and porous assembly. In the current art, the lattice structure is manufactured separately from the structural body of the air-oil separator, these two elements then being assembled. With the development of the use of additive manufacturing for the manufacture of turbomachine parts, the use of this technology can be envisaged for the manufacture of hybrid structures such as an air-oil separator.

For this, the oil separator must be modeled on a computer-aided design CAD platform, for example CATIA ® developed by Dassault Systems.

However, modeling complex repetitive structures such as lattices on CATIA, which is based on boundary representation (B-rep for boundary representation) requires the storage of a large amount of data, and therefore requires a lot of memory space. The objects modeled in this way can be difficult to handle (processing time and long calculations).

Problems encountered by CAD tools, such as CATIA, when modeling parameterized geometry such as that of lattices

are mainly linked to the quantity of data handled, making for example slow visualization and any time-consuming modification requiring significant computing time. Indeed, the large amount of data stored for the objects modeled by means of an edge representation, makes the modeling of such a lattice structure time-consuming, and results in a large file which is difficult to exploit and which is difficult to manipulate.

It is therefore understood that the difficulty described above of representing and handling repetitive structures comprising lattices arises obviously in an air / oil separator but can also be considered for the design of other mechanical parts such as parts of structure (screeds, supports), power transmission (pinion, shaft), heat exchange, fire protection, sound insulation. The aim of the invention is in particular to provide a simple, effective and economical solution to the problems of the prior art described above.

Summary of the invention

To this end, a computer-implemented method is proposed for the design of a three-dimensional modeled object of a mechanical part, a sector of which comprises a body, comprising at least one cell, and a lattice structure housed in said cell, the method consists of the following steps:

a) Provide a representation by the edges (B-Rep) of the sector body;

b) Provide an edge representation (B-Rep) of an integration volume of the lattice structure;

c) Calculate a polygonal representation of the sector body and a representation polygonal of the integration volume of the lattice structure, from the representation by the edges (B-Rep) of the sector body;

d) Provide a representation by edges (B-Rep) of an elementary pattern of the lattice structure;

e) Calculate a polygonal representation of an intermediate lattice structure composed of a plurality of elementary patterns, from the representation by the edges (B-Rep) of the elementary pattern;

f) Determine, from the polygonal representation of the integration volume of the lattice structure and the polygonal representation of the intermediate volume, a polygonal representation of the lattice structure;

g) Assemble the polygonal representation of the sector body and the polygonal representation of the determined lattice structure so as to obtain a three-dimensional modeled object of the sector of said mechanical part.

Using the polygonal representation to model the lattice structure of a metal part does not require as much data as an edge representation. Consequently, a significant reduction in the data stored for the modeled object representing mechanical part is obtained, which makes the manipulation of the object easier, and modifications can be made without incurring significant calculation times. The use of two types of representation for the modeling of a hybrid structure of a mechanical part such as the air-oil separator, makes it possible to preserve for simple structures, such as the body of the separator, the wealth of data of a representation by edges, and to reduce this data for the modeling of complex structures of parameterized geometry. Modeling the body by an edge representation in CATIA® for example, allows both to have editable body geometry at any time and to easily access the history of body geometry modifications. Once the modeling of the body has been polygonalized, all information relating to the history of changes in the geometry of the body is lost, in fact introducing an element of approximation on the obtaining of the geometry.

This thus allows designers to be able to manipulate the modeled mechanical part: in other words, the reduction of the data stored for the hybrid structure, makes it possible to reduce the number of data to be processed for visualization or modification operations, and therefore to reduce the part generation time. In addition, the change of representation is compatible with the data format accepted by the preparation software of additive manufacturing platforms. At the end of the day, the modeled object can therefore be stored in a file that can be directly used for additive manufacturing. According to one characteristic, step d) can consist of:

Provide a skeleton including points and circles to define the segments and their intersections.

The elementary pattern is thus made up of segments, connected to each other. They are made from a skeleton, the points of which represent the ends of the segments and the circles the junction areas of these segments.

According to another characteristic of the invention, step e) can comprise the following steps:

Repeat in three mutually orthogonal directions the polygonal representation of the elementary pattern so as to form a first volume;

Determine the intermediate volume by geometric transformation of the first volume. The polygonal representation of the elementary pattern makes it possible to obtain the first volume simply and quickly, by repeating in the three directions of space of said elementary pattern. This reduces the amount of data in the first volume, allowing it to be manipulated digitally quickly. Consequently, the intermediate volume obtained by geometric transformation of the first volume is calculated almost instantaneously. In comparison, in the prior art relating to an air-oil separator, the generation time, corresponding to the calculation time at the various stages of design of an air-oil separator sector, was about 1 h 40 in the case of 'a lattice structure with 42 repetitions along x, 22 repetitions along y and 8 repetitions along z of the elementary pattern. For the same lattice structure, with the method proposed here, the generation time is approximately 25 s.

As this is a generally cylindrical shaped structure, the geometric transformation allowing the conversion of a straight line into a planar curve can be used. A spline can thus be used.

Such a transformation makes it possible to produce an intermediate volume with a curved lattice structure such as present in the air-oil separator. The reduction in the number of data stored by the polygonal representation of the lattice structure makes it possible to facilitate and make faster the calculation of the geometric transformation of the first volume.

Furthermore, according to an additional characteristic, step f) can include the following step:

Calculate the intersection between the polygonal representation of the integrating volume of the lattice structure and the polygonal representation of the intermediate volume to obtain the polygonal representation of the lattice structure of the sector of said mechanical part.

In this way, the polygonal representation of the lattice of the mechanical part is obtained, with an outer shape delimited by the outer shape of the integration volume. Of this way, the representation of the lattice structure has a complementary shape with an empty volume of the sector body.

Also, step g) can include the following step:

calculating the polygonal representation union of the sector body and the polygonal representation of the sector lattice structure to obtain the polygonal representation of a sector of said mechanical part.

A polygonal representation of a sector of the mechanical part is then obtained, this representation being readable by the software of the additive manufacturing platforms. Thus, due to the small size of the data in this representation, it can easily be transmitted, and the mechanical part can be manufactured using an additive manufacturing platform or facility. According to another characteristic, step g) can be followed by the following step:

repeat the polygonal representation of the sector of said mechanical part obtained around an axis of revolution of said mechanical part so as to obtain a three-dimensional modeled object of said mechanical part.

Thus, the entire mechanical part can easily be modeled by exploiting its form of revolution.

In particular, according to another characteristic, said mechanical part can be an air / oil separator.

The invention further relates to an additive manufacturing process, comprising a step of using said three-dimensional modeled object of the mechanical part obtained at the end of step h). The modeled object can be manufactured by additive manufacturing.

Therefore, at the end of the process presented above, the modeled object obtained from the mechanical part can be used so that it can be transmitted to an additive manufacturing platform or installation.

The invention also relates to a three-dimensional modeled object of an air-oil separator obtained by the process as described above.

The invention also relates to the data file storing the three-dimensional modeled object of an air-oil separator as described above.

The file thus comprises less data than the file comprising a three-dimensional modeled object entirely designed with CAD tools based on the representation by edges, and therefore can be more easily manipulated, or even transmitted.

The invention also relates to a computer program comprising instructions for implementing the method as described above, when it is executed on a processor.

The invention also relates to a data storage medium on which the program as described above is recorded. Finally, the invention relates to a CAD system comprising a processor coupled to a memory and a graphical user interface and able to communicate with an additive manufacturing platform, such as the program as detailed above.

Such a system then makes it possible to manufacture the air-oil separator modeled by additive manufacturing, making it possible in particular to design a hybrid structure without having a welding operation.

The invention will be better understood and other details, characteristics and advantages of the invention will become apparent on reading the following description given by way of non-limiting example with reference to the accompanying drawings.

Brief description of the figures

[Fig. 1] is a flowchart representing steps of the process according to the invention;

[Fig. 2] is a perspective view of an air-oil separator;

[Fig. 3] is a front view of a sector of the air-oil separator of Figure 2;

[Fig. 4] is a perspective view of the integration volume of the lattice structure;

[Fig. 5] illustrates several examples of elementary patterns;

[Fig. 6] is an example of a skeleton used for the design of elementary patterns;

[Fig. 7] part A illustrates the structure of the first volume of the lattice obtained in step e) and part B illustrates the intermediate volume of the lattice obtained at the end of step e);

[Fig. 8] Part A illustrates part of the modeled object obtained at the end of the process according to the invention and part B illustrates the modeled object at the end of the process according to the invention.

Detailed description of the invention

Figure 1 is a flowchart showing the course of the method according to the invention. A first step E0 prior to the process corresponds to the supply of the mechanical part to be modeled. Here, the method aims to provide a method for designing a mechanical part which will be referred to here as a hybrid. By hybrid, we therefore mean that the part comprises at least a portion of the lattice and at least a non-lattice (that is to say dense) part. An example of this type of part is the centrifugal air-oil separator 2, a view of which is shown in Figure 2.

The air-oil separator 2 comprises a first shell surrounded by a second shell which defines the body of the air-oil separator. The space between these two shells forms a vein 4 of revolution around the axis of revolution X of the air-oil separator 2, intended to circulate the air-oil mixture to be separated.

The air-oil separator 2 comprises cells 6 regularly distributed around the X axis. In each of these cells 6 are housed lattice structures 8, also called “foam”, making it possible to filter the finest droplets during the setting. rotation of the air-oil separator 2. With regard to the symmetry of revolution of this part 2 around the axis of revolution X, the design of a three-dimensional modeled object of the mechanical part 2 is made from an angular sector 10 of this part 2 with respect to the axis of revolution X.

As can be seen in FIG. 2, the air-oil separator 2 is composed of an angular sector 10 which is repeated around the axis of revolution X. Thus, initially, only this angular sector 10 is modeled. .

An example of angular sector 10 to be modeled of the air-oil separator is shown in Figure 2.

The angular sector thus comprises a body 12, a dense one-piece part, comprising a honeycomb structure. The honeycomb structure is composed of a 6 honeycomb and an 8 lattice structure.

The cell 6 has a curved shape according to an arc of a circle having a median radius with respect to the axis of revolution X of the oil separator. As can be seen in Figure 2, a lattice structure 8 is housed in this cell 6. It is a lattice structure corresponding to an assembly of metal segments intersecting and held to each other so as to form a rigid assembly.

The first step E1 of the process for designing a three-dimensional modeled object of the oil separator 2 consists in providing a representation by the edges (B-Rep) of the body 12 of sector 10.

This involves modeling, using conventional computer-aided design (CAD) tools, such as CATIA, the body 12 of sector 10 while respecting its geometry and its dimensions, which are defined and parameterized.

An example of visualization of a body 12 of sector 10 modeled by the representation by the edges is illustrated in FIG. 3. As can be seen, the body 12 is modeled with a cell 6, able to receive a lattice structure 8, arranged in a radially upper part with respect to the axis of revolution X.

The shape of the cell 6 is characterized by the following three dimensions: a minimum radius Rmin, a maximum radius Rmax, and a median radius Rmédian, shown in Figure 3.

The second step E2 consists in providing a representation by the edges (B-Rep) of an integration volume 14 of the lattice structure 8.

The integration volume 14 of the lattice structure corresponds to a full volume designed to materialize the volume in which the lattice structure 8 must be integrated. An example of visualization of an integration volume 14 is illustrated in FIG. 4. As can be seen, this integration volume 14 has a shape complementary to the cell, and therefore therefore has the same characterizing dimensions of the alveoli 6, in particular the same median radius Rmédian. To ensure a good intersection of the lattice structure 8 with the body of the sector 12 during the subsequent assembly of these two elements, it is advisable to design the integration volume 14 so that it intersects the internal surface 16 of the sector body delimiting the cell 6.

The integration volume 14, modeled by a representation by edges, can be produced using CATIA for example, or any other suitable CAD software using the representation by edges.

Steps E1 and E2 can be performed so that the geometries of the body and of the sector's integration volume remain configurable.

The third step E3 consists in calculating a polygonal representation of the sector body 12 and a polygonal representation of the integration volume 14 of the lattice structure, from the representation by the edges (B-Rep) of the sector body 12.

This step consists in calculating and recording the data related to the surfaces of the modeled body and the modeled integration volume. Thus the modeled body and the modeled integration volume are saved in separate files in two formats: the native format of the CAD software used and in an stl data format used in stereolithography.

The stl format allows you to save only the three-dimensional area of the modeled objects. Unlike the native recording format of conventional CAD software, material information, texture information or other common parameters. Consequently, this type of format is lighter than the native formats of classic CAD software.

The fourth step E4 consists in providing a representation by the edges (B-Rep) of an elementary pattern 18 of the lattice structure 8.

The lattice structure 8 consists of an elementary pattern 18 which repeats in three directions in space, thus forming a three-dimensional network.

An elementary pattern 18 can be chosen from an infinite number of possible patterns, examples of which are illustrated in FIG. 5. As can be seen in FIG. 5, the width, the section, the length of each of the segments 20 constituting the pattern. Elementary 18 may vary. For example, the segments 20 can delimit a volume, can also include openings 22 or else can be of variable section. The segments 20 are generally metallic.

Such elementary patterns 18 are designed on CATIA or using any CAD software allowing a representation by the edges, from a skeleton 24. This is a diagram from which the elementary pattern 18 is designed. .

An example of a skeleton 24 is illustrated in FIG. 6. It is composed of points 26, connected to each other by segments 28, as well as of circles 30, having these points 26 as their center. The segments 28 represent the metal segments 20. constituting the elementary pattern 18. The circles 30 represent the section either of a junction of two segments 20, or of a free end of segments 20. The design of an elementary pattern 18 on the CAD software can be carried out by making certain dimensions configurable, so as to make it adjustable according to needs. The designed elementary pattern 18 must meet the following two requirements:

The manufacturability of the elementary pattern 18 as a function of the manufacturing process envisaged, for example by 3D printing;

The coincidence of elementary patterns 18 repeated in the lattice structure 8 so as to ensure the continuity of the latter.

The fifth step of the method E5 of the method consists in calculating a polygonal representation of an intermediate lattice structure 32 composed of a plurality of elementary patterns 18, from the representation by the edges (B-Rep) of the elementary pattern 18. As detailed above with reference to the third step E3, from the representation by the edges of the elementary pattern 18, a polygonal representation is calculated. Thus, only the modeling of the elementary pattern volume surface 18 is saved in a file in stl format.

Subsequently, the modeling of the intermediate lattice 32 structure is carried out using software, usually dedicated to animation modeling, Blender. Any other software that supports stl format support can be used as long as it has the necessary solid deformation and pattern repeating tools.

In Blender, a first step consists in repeating in three mutually orthogonal directions the polygonal representation of the elementary pattern 18 so as to form a first volume. As can be seen in part A of FIG. 7, the repetition is carried out in the three directions x, y and z of the frame of reference 34. The repetition of the elementary pattern 18 can be of a number distinct from one direction to the other. other, so as to obtain a paving stone.

A second step aims to determine the intermediate volume 32 by geometric transformation of the first volume. An example of an intermediate volume lattice 32 is illustrated by part A of FIG. 7. In order to ensure that the lattice structure 8 has the same curvature as the cell 6 in the x direction, the image of the first volume by the geometric transformation allowing the conversion of a rectilinear line into a planar curve is calculated. A spline is for example used.

Thus, as can be seen in part A of FIG. 7, the repetition along x corresponds to the repetition according to the median curvature of radius Rmedian. The repetition along y corresponds to the maximum radius Rmax and the minimum radius Rmin. The repetition according to corresponds to the height of the intermediate structure.

The sixth step E6 of the method consists in determining, from the polygonal representation of the integration volume 14 of the lattice structure and from the polygonal representation of the intermediate volume 32, the polygonal representation of the lattice structure 34. From this step, operations are performed using any software capable of reading stl formats. Preferably, with a view to subsequently manufacturing the part by an additive manufacturing platform, the operations can be carried out using additive manufacturing platform preparation software so as to obtain the part in this software capable of communicating with the additive manufacturing platform. The Magic software can for example be used. The latter presents a particularly efficient anomaly detection and automatic repair module, suitable for complex structures such as lattices.

Step E6 consists in calculating the intersection between the polygonal representation of the integration volume 14 of the lattice structure and the polygonal representation of the intermediate volume 32 to obtain the polygonal representation of the lattice structure 8 of the sector of said mechanical part 2 .

It is therefore a matter of calculating the result of the operation of Boolean intersection between the respective polygonal representations of the integration volume 14 and of the intermediate lattice structure 32. The polygonal representation of the lattice structure 8 thus obtained, visible on the part B of FIG. 7, has an external surface identical to the surface of the integration volume 14, visible in FIG. 4.

The seventh step E7 aims to assemble the polygonal representation of the sector body 12 and the polygonal representation of the lattice structure 8 determined so as to obtain a three-dimensional modeled object of the sector 10 of said mechanical part 2. This involves calculating the union of polygonal representation of the body 12 of the sector and the polygonal representation of the lattice structure 8 of the sector to obtain the polygonal representation of a sector 10 of said mechanical part 2. The lattice structure 8 is then included in the cell 6 of the sector so these ends intersect the internal surface walls 16 of the cell 6. By crossing the internal surface walls 16 delimiting the cell 6, the connection between the body 12 of sector 10 and the lattice structure 8 is ensured.

Two views of the sector 10 obtained by means of this process are visible in parts A and B of FIG. 8.

The eighth step E8 of the process makes it possible to finalize the design and therefore to obtain a three-dimensional modeled object of the mechanical part having a symmetry of revolution, here the air-oil separator. This step consists in repeating the polygonal representation of the sector obtained around the axis of revolution X of the ai-oil separator so as to obtain a three-dimensional modeled object of the separator.

Thus, the three-dimensional modeled object of the air-oil separator is saved in a data file from Magies. This data file then groups together all geometry information that can be used for additive manufacturing. A step subsequent to the progress of the process according to the invention consists of using the modeled object of the air-oil separator. In particular, the method can be followed by an additive manufacturing method comprising a step of using said three-dimensional modeled object of the mechanical part obtained at the end of step E8.

In order to optimize the digital design process of the three-dimensional modeled object of the mechanical part, a computer program including instructions for carrying out the process when executed on a processor can also be realized. This program can be recorded on a data storage medium.

In order to optimize the manufacturing process by additive manufacturing of the mechanical part, a CAD system can be designed. This CAD system comprises a processor coupled to a memory and a graphical user interface and is able to communicate with an additive manufacturing platform. The previously presented program can be saved to memory.

Claims

1. Computer-implemented method for the design of a three-dimensional modeled object of a mechanical part (2), a sector (10) of which comprises a body (12), comprising at least one cell (6), and a lattice structure ( 8) housed in said cell (6), the method comprises the following steps:

a) Provide a representation by the edges (B-Rep) of the sector body (12);

b) Provide a representation by the edges (B-Rep) of an integration volume (14) of the lattice structure;

c) Calculate a polygonal representation of the sector body (12) and a polygonal representation of the integration volume (14) of the lattice structure, from the representation by edges (B-Rep) of the sector body (12) ;

d) Provide a representation by the edges (B-Rep) of an elementary pattern (18) of the lattice structure;

e) Calculate a polygonal representation of an intermediate lattice structure (32) composed of a plurality of elementary patterns (18), from the representation by the edges (B-Rep) of the elementary pattern (18);

f) Determine, from the polygonal representation of the integration volume of the lattice structure and the polygonal representation of the intermediate volume, a polygonal representation of the lattice structure (8);

g) Assemble the polygonal representation of the sector body (12) and the polygonal representation of the lattice structure (8) determined so as to obtain a three-dimensional modeled object of the sector (10) of said mechanical part (2).

2. The method of claim 1, wherein step e) comprises the following steps:

Repeat in three mutually orthogonal directions the polygonal representation of the elementary pattern (18) so as to form a first volume;

Determine the intermediate volume (32) by geometric transformation of the first volume.

3. Method according to one of the preceding claims, wherein step f) comprises the following step:

Calculate the intersection between the polygonal representation of the integration volume (14) of the lattice structure and the polygonal representation of the intermediate volume (32) to obtain the polygonal representation of the lattice structure (8) of the sector (10) of said mechanical part (2).

4. Method according to one of the preceding claims, in which step g) comprises the following step: Calculate the polygonal representation union of the sector body (12) and the polygonal representation of the lattice structure (8) of the sector to obtain the polygonal representation of a sector (10) of said mechanical part (2).

5. Method according to one of the preceding claims, wherein step g) is followed by the following step:

h) Repeat the polygonal representation of the sector (10) of said mechanical part (2) obtained around an axis of revolution X of said mechanical part (2) so as to obtain a three-dimensional modeled object of said mechanical part (2).

6. Method according to one of claims 1 to 5, wherein said mechanical part (2) is an air / oil separator.

7. Manufacturing process, characterized in that it comprises a use of the three-dimensional modeled object of the mechanical part (2) obtained at the end of step h), the modeled object being manufactured by additive manufacturing.

8. Three-dimensional modeled object of a mechanical part (2) obtained by the method according to one of claims 1 to 6.

9. Data file storing the three-dimensional modeled object of an air-oil separator according to claim 8.

10. A computer program comprising instructions for carrying out the method according to any one of claims 1 to 6, when executed on a processor.

11. Data storage medium on which the program of claim 10 is recorded.

12. CAD system comprising a processor coupled to a memory and a graphical user interface and able to communicate with an additive manufacturing platform, such that the program according to claim 10 is recorded on the memory.