EP2306134B1 - Method for manufacturing a heat exchanger element and exchanger obtained using the method - Google Patents

Description

Object of the invention

The present invention relates to a method of manufacturing a surface heat exchanger air / fluid. It relates more particularly but not exclusively to a method of manufacturing a surface heat exchanger air / oil used in a turbomachine.

The present invention also relates to the heat exchanger obtained by the process.

State of the art

In the case of a turbomachine, various members and equipment must be lubricated and / or cooled, the heat generated being generally transported by oil systems and discharged by fuel-oil and / or air-oil exchangers. In the latter, also called ACOC (Air Cooled Oil Cooler), a forced air flow is brought on a solid exchange surface of the oil circuit. A surface exchanger is preferred to a compact block exchanger, the first disturbing minus the flow of air and the operation of the turbomachine. The exchange surface may consist of a plate with fins or similar elements for exchanging heat with a cold air flow flowing parallel to the plate.

In the state of the art, there are several methods of manufacturing air-oil surface exchangers. These methods pose problems of manufacture and cost or problems of thermal efficiency.

On the air circuit side, there may be mentioned a first method of manufacture which consists of molding, extruding or machining a plate having fins parallel to the air flow, the fins being interruptable and of any shape. Such an embodiment is illustrated in the figure 1a where the oil circuit is also shown below the plate. The air circuit is parallel, perpendicular or any direction with respect to the oil circuit. Such achievements are massive and lead to thicknesses unfavorable to a good heat exchange, or they require machining techniques or foundry long, complex and expensive to minimize this disadvantage, but without eliminating it. This phenomenon is even more marked in the case of curved heat exchangers. Starting from a thick plate, the bending is carried out by a 5-axis machining which requires a large costly machine, and a very important material removal, long and expensive material. Starting from a thinner plate, the machining (3 axes) generates less chips but the curvature is made by deformation of the plate which can be critical.

Another known embodiment is shown in figure 1b and consists of a smooth plate having fins of any shape reported by welding or brazing. Such embodiments are complex to make and pose problems of reliability and quality of the exchange to the oil.

Yet another embodiment according to the state of the art consists of a smooth plate having air channels obtained by a folded (or corrugated) sheet brazed or welded, with or without a closing plate of said air channels (see fig.lc). These exchangers are less complex to manufacture but have a high resistance to air circulation, particularly the covered variant, and are therefore not very effective, especially if a large dimension in the direction of the air flow is desired. They are also fragile, especially the uncovered variant.

Finally, we can also mention as known embodiment the spiky plates as shown in Figure ld, obtained by deep forging or special machining. This type of embodiment is also relatively fragile and / or complex to manufacture.

Regarding the oil circuit, it is integrated or reported below the plate. In the first case, it is partially machined. For example, grooves are cut or molded in the mass and an insert plate is welded or brazed below the grooves. However, it is difficult to manufacture the oil channels by machining because of their large number and the small dimensions thereof. In the second case, the oil circuit is in the form of channels reported by various technologies. For example, tubes are welded or brazed or a plate is brazed underneath a corrugated sheet, etc.

Goals of the invention

The present invention aims to provide a solution that makes it possible to overcome the disadvantages of the state of the art.

In particular, the invention aims to provide an air cooling system for a fluid, made by industrial methods with little complexity, and in a minimum of operations, while ensuring optimal heat exchange and sufficient strength.

The present invention also aims to allow a common realization of the fluid and air circuits without mass or foundry machining operation.

Main characteristic elements of the invention

1. a) on forme sur une première tôle une pluralité de plis serrés sur eux-mêmes, lesdits plis faisant office d'ailettes,
   ou, alternativement, la première tôle comportant une première partie et une seconde partie, on forme uniquement sur la première partie des plis serrés sur eux-mêmes ;
   ladite première tôle ou ladite première partie constituant une tôle en position supérieure ;
2. b) on ouvre les plis serrés sur une partie de leur hauteur ;
3. c) on pose la première tôle obtenue à l'étape b) sur une seconde tôle, ladite seconde tôle constituant une tôle en position inférieure,
   ou, alternativement, on rabat la première partie obtenue à l'étape b) sur la seconde partie ; ladite seconde partie constituant une tôle en position inférieure ;
4. d) on brase la partie serrée des plis et on brase la première tôle sur la seconde tôle,
   ou, alternativement, on brase la partie serrée des plis et on brase la première partie sur la seconde partie ;
5. e) optionnellement, on place et on brase en dessous de la tôle en position inférieure une troisième tôle ; ladite troisième tôle constituant alors la tôle en position inférieure.

The present invention relates to a method for manufacturing an air / fluid heat exchanger, said method comprising at least the following steps:

1. a) forming on a first sheet a plurality of folds tight on themselves, said folds acting as fins,
   or, alternatively, the first sheet having a first portion and a second portion, forming only on the first portion folds tight on themselves;
   said first sheet or said first portion constituting a sheet in the upper position;
2. b) open the folds tight on part of their height;
3. c) installing the first sheet obtained in step b) on a second sheet, said second sheet constituting a sheet in the lower position,
   or, alternatively, the first part obtained in step b) is folded onto the second part; said second portion constituting a sheet in the lower position;
4. d) the tight part of the plies is brazed and the first sheet is bristled on the second sheet,
   or, alternatively, the tight part of the plies is bristled and the first part is bristled on the second part;
5. e) optionally, a third sheet is placed and brazed below the sheet in the lower position; said third sheet then constituting the sheet in the lower position.

• la première tôle, la seconde tôle et la troisième tôle sont respectivement planes ou ondulées ;
• lorsque la seconde tôle ou, alternativement, la seconde partie de la première tôle est plane, la troisième tôle est ondulée ;
• lorsque la seconde tôle ou, alternativement, la seconde partie de la première tôle est ondulée, la troisième tôle est ondulée ou plane ;
• les tôles ondulées ont un espacement de crête à crête égal à l'espacement entre les plis de la première tôle ou de la première partie de la première tôle ;
• les creux de la seconde tôle ondulée ou, alternativement, les creux de la seconde partie de la première tôle ondulée sont placés en regard des plis serrés de la première tôle ou de la première partie de la première tôle respectivement ;
• les creux de la troisième tôle ondulée sont placés en regard des reliefs de la seconde tôle ondulée ou, alternativement, en regard des reliefs de la seconde partie de la première tôle ondulée ;
• dans l'étape c) et dans la direction transverse aux ailettes, les extrémités de la seconde tôle sont repliées sur les extrémités de la première tôle ou, alternativement, une extrémité de la seconde partie rabattue sur la première partie à une première extrémité est repliée sur la seconde extrémité de la première partie ;
• dans l'étape d), on applique une pression de direction respectivement parallèle et perpendiculaire par rapport à l'axe des plis serrés ;
• la pression de direction perpendiculaire est appliquée avant la pression de direction parallèle ;
• dans l'étape d) ou e), on place, dans le sens longitudinal des ailettes, des pièces d'étanchéité aux extrémités de l'échangeur air/fluide ;
• il comporte après l'étape d) ou après l'étape e), une étape additionnelle e') d'apport de matière par soudage entre la tôle en position supérieure et les pièces d'étanchéité ;
• on ménage des ouvertures dans la tôle en position inférieure ;
• lesdites ouvertures se trouvent à côté des pièces d'étanchéité ;
• une boîte à huile est fixée au niveau desdites ouvertures soit directement sur la tôle en position inférieure, soit sur une pièce de renfort placée dans l'étape d) ou e) ;
• le fluide est de l'huile.

According to particular embodiments of the invention, the method comprises at least one or a suitable combination of the following characteristics:

• the first sheet, the second sheet and the third sheet are respectively flat or corrugated;
• when the second sheet or, alternatively, the second part of the first sheet is flat, the third sheet is corrugated;
• when the second sheet or, alternatively, the second part of the first sheet is corrugated, the third sheet is corrugated or flat;
• the corrugated sheets have a peak-to-peak spacing equal to the spacing between the folds of the first sheet or part of the first sheet;
• the depressions of the second corrugated sheet or, alternatively, the recesses of the second part of the first corrugated sheet are placed opposite the tight folds of the first sheet or the first part of the first sheet respectively;
• the recesses of the third corrugated sheet are placed facing the reliefs of the second corrugated sheet or, alternatively, facing the reliefs of the second part of the first corrugated sheet;
• in step c) and in the direction transverse to the fins, the ends of the second sheet are folded over the ends of the first sheet or, alternatively, an end of the second part folded on the first part at a first end is folded back on the second end of the first part;
• in step d), applying a steering pressure respectively parallel and perpendicular to the axis of the tight folds;
• the perpendicular direction pressure is applied before the parallel direction pressure;
• in step d) or e), sealing pieces are placed in the longitudinal direction of the fins at the ends of the air / fluid exchanger;
• it comprises after step d) or after step e), an additional step e ') of material supply by welding between the sheet in the upper position and the sealing pieces;
• openings are made in the sheet in the lower position;
• said openings are next to the sealing pieces;
• an oil box is fixed at said openings either directly on the sheet in the lower position, or on a reinforcement piece placed in step d) or e);
• the fluid is oil.

The present invention also relates to an air / fluid exchanger obtained by means of the method as described above.

Brief description of the figures

FIGS. 1a to 1d, already mentioned, show schematically ACOC type cooling systems according to the state of the art.

The figure 2 schematically represents a sectional view of an air cooling system according to the invention, said cooling system comprising two sheets.

The figure 3 schematically represents a sectional view of the press-in principle during the soldering step.

The figure 4 schematically represents a sectional view of a variant of the cooling system according to the invention and the associated variant of the press tooling during the brazing step.

The Figures 5, 6 and 7 schematically represent respective sectional views of other variants of the cooling system according to the invention comprising two sheets or three sheets in the case of the variant of the figure 7 .

The figure 8 schematically represents a sectional view of another embodiment of the cooling system according to the invention comprising a single sheet.

The figure 9 schematically represents the placement of a sealing piece at one end of the cooling system according to the invention.

Legend:

1. (1) Air / fluid heat exchanger
2. (2) First sheet metal
   • (2a) First part of the first sheet (2)
   • (2b) Second part of the first sheet (2)
3. (3) Tight folds forming the fins
4. (4) Fluid passage channel
5. (5) Solder
6. (6) Second sheet
7. (7) Third sheet
8. (8) Sealing piece
9. (9) Weld
10. (10) Reinforcement bar
11. (11) Opening
12. (12) Staple fold

Description of preferred embodiment of the invention

The invention generally relates to a method of manufacturing an air exchanger for cooling a heat transfer fluid, the exchanger according to the invention can be used in any application where a large surface is swept by air. More particularly, the method described below relates to a surface ACOC exchanger that can be installed in a turbomachine.

According to the invention, a first sheet 2 is folded, in a step a), with folds tight on themselves so as to make fins 3 (see FIG. fig.2 ). In a step b), the two faces of each fold are separated at the foot of the fold over a greater or lesser height so as to provide an opening subsequently to form a channel 4 for the passage of the fluid as described below.

In a step c), the first sheet 2 thus folded, also called sheet in the upper position, is then deposited on a second sheet 6, flat or corrugated of to close the openings and thus form the fluid passage channels 4. In the example illustrated in FIG. figure 2 the second sheet is flat and constitutes the sheet in the lower position.

To increase the rigidity and improve the sealing of the fins in case of impact, particularly at the ends, the tight portion of the fold can advantageously be brazed (solder 5). Similarly, the second sheet 6 is brazed to the first sheet 2. Brazing is an assembly by means of a filler metal whose melting point is lower than that of the metal parts to be assembled and wetting the surfaces of the contact. In a step d), the brazing of both the second sheet and the folds in a single heating is made possible by the orthogonal direction of the two sets of joints, allowing the easy realization of tools to apply the pressure necessary for brazing as that represented at the figure 3 . According to the invention, it is preferable to apply the horizontal pressure F1 before the vertical pressure F2. The solder does not seal the bottom plate but the cohesion of the device.

The figure 4 presents a variant where the second sheet 6 is corrugated and where the press tool is modified accordingly. The term "corrugated sheet" refers to any sheet that has a regular alternation of reliefs and depressions. According to the present invention, the hollow portions of the second sheet 6 are placed opposite the tight folds 3 of the first sheet 2 and the peak-to-peak distance is equal to the spacing between the tight folds.

According to yet another embodiment of the present invention shown in figure 5 the first sheet 2 is corrugated and the second sheet 6 is flat thus making it possible to modify the shape of the fluid passage channels 4.

Still according to the present invention, all combinations of lower and upper plate variants can be used to modify the shape of the channels.

Similarly, the tight fold can be opened to a greater or lesser height to also modulate the shape and size of the fluid passage channel 4 as shown in FIG. figure 6 .

According to yet another embodiment of the present invention, illustrated in FIG. figure 7 a third sheet 7 is added and brazed in a step e) in order to split the number of oil channels 4. In this variant, it is the third sheet 7 which constitutes the sheet in the lower position. When the latter is undulated and placed below a second sheet 6 also corrugated, the recesses of the third sheet are placed opposite the reliefs of the second sheet to form the additional channels.

The lateral ends of the exchanger 1, that is to say in the direction transverse to the fins, are closed only by the brazing of the two (or three) sheets as shown in FIGS. Figures 2-7 or by further using a staple fold (not shown).

According to yet another variant of the present invention, it is also possible to produce the exchange plate from only the first sheet 2. In this variant, a first portion 2a of this first sheet 2 is folded in step a ) to form the fins 3 and a second part 2b of this first sheet 2 is folded over the first part 2a in step b) with a stapling fold 12 to form the fluid passage channels 4 (see fig.8 ). In this form of embodiment of the invention, the second part 2b constitutes the sheet in the lower position. An additional plate may also be placed below the second portion 2b to double the number of channels. In this case, the additional plate, also called third sheet, is the sheet in the lower position.

The sealing of the front and rear ends of the exchanger, that is to say in the longitudinal direction of the fins, can be achieved in various ways. By way of example, use may be made of sealing pieces 8 machined or formed in any way to fill the passages of the fluid, and placed in the tooling in step d) or e) . The local deformations of the sheets make it possible to close the passages during soldering, or to bring the edges sufficiently close together so that a conventional solder 9 performed after the brazing step d) or e) in an additional step e ') makes it possible to guarantee the sealing.

The connection to oil boxes can be made by drilling the bottom plate 6, 7 or 2b or interrupting it at the points of entry and exit. The boxes (not shown) are then reported by welding or any other means, to the right of these openings 11, either directly on the constituent plates 6, 7 or 2b, or on reinforcing pieces or bars 10 placed during the brazing of the whole as represented in figure 9 .

Advantages of the process according to the invention

• Facilité de fabrication sans usinage, procédés industriels rapides et simples ;
• Economie de matière (pas d'enlèvement de matière, copeaux) puisqu'on part d'une tôle ;
• Proximité entre les ailettes se trouvant dans le flux d'air et les canaux d'huile, ce qui améliore l'échange thermique ;
• Bonne résistance aux diverses sollicitations (flux d'huile à une pression de quelques bars, vibrations du moteur, impacts derrière le fan).

The exchanger according to the present invention has the following advantages in particular:

• Ease of manufacturing without machining, fast and simple industrial processes;
• Saving material (no removal of material, chips) since we start from a sheet;
• Proximity between the fins in the airflow and the oil channels, which improves the heat exchange;
• Good resistance to various stresses (oil flow at a pressure of a few bars, engine vibration, impacts behind the fan).

Claims (17)

1. Method for manufacturing an air/fluid heat exchanger (1), the said method including at least the following steps:

   a) on a first sheet metal plate (2), a plurality of tight folds is shaped, those folds acting as fins (3);
   or, alternatively, the first sheet metal plate (2) comprising a first part (2a) and a second part (2b), tight folds (3) are formed only on the first part (2a);
   the said first sheet metal plate (2) or the said first part (2a) constituting a sheet metal plate in the upper position;

   b) the tight folds (3) are opened on a part across their height to form first openings;

   c) the first sheet metal plate (2) obtained in step b) is placed on a second sheet metal plate (6) so as to close the said first openings and thus form fluid flow channels (4), the said second sheet metal plate (6) constituting a sheet metal plate in the lower position,
   or, alternatively, the first part (2a) obtained in step b) is folded over the second part (2b) to form the fluid flow channels (4); the said second part (2b) constituting a sheet metal plate in the lower position;

   d) the tight part of the folds (3) is brazed and the first sheet metal plate (2) is brazed on the second sheet metal plate (6), or, alternatively, the tight part of the folds (3) is brazed and the first part (2a) is brazed on the second part (2b);

   e) optionally, a third sheet metal plate (7) is placed and brazed under the sheet metal plate in the lower position; the said third sheet metal plate thus constituting the sheet metal plate in the lower position.
2. Manufacturing method as in claim 1, distinguished by the fact that the first sheet metal plate (2), the second sheet metal plate (6) and the third sheet metal plate (7) are respectively flat or corrugated.
3. Manufacturing method as in claim 2, distinguished by the fact that, when the second sheet metal plate (6) or, alternatively, the second part (2b) of the first sheet metal plate (2) is flat, the third sheet metal plate (7) is corrugated.
4. Manufacturing method as in claim 2, distinguished by the fact that, when the second sheet metal plate (6) or, alternatively, the second part (2b) of the first sheet metal plate (2) is corrugated, the third sheet metal plate (7) is corrugated or flat.
5. Method as in any of the preceding claims, distinguished by the fact that the corrugated sheet metal plates have a peak-to-peak distance equal to the distance between the folds (3) of the first sheet metal plate (2) or the first part (2a) of the first sheet metal plate (2).
6. Manufacturing method as in any of the preceding claims, distinguished by the fact that the hollows of the second corrugated sheet metal plate (6) or, alternatively, the hollows of the second part (2b) of the first corrugated sheet metal plate (2), are placed opposite to the tight folds of the first sheet metal plate (2) or the first part (2a) of the first sheet metal plate (2) respectively.
7. Manufacturing method as in claim 4, distinguished by the fact that the hollows of the third corrugated sheet metal plate (7) are placed opposite to the reliefs of the second corrugated sheet metal plate (6) or, alternatively, opposite to the reliefs of the second part (2b) of the first corrugated sheet metal plate (2).
8. Manufacturing method as in claim 1, distinguished by the fact that, in step c) and in the direction transverse to the fins (3), the ends of the second sheet metal plate (6) are folded over the ends of the first sheet metal plate (2) or, alternatively, an end of the second part (2b) folded over the first part (2a) at a first end is folded over the second end of the first part (2a).
9. Manufacturing method as in claim 1, distinguished by the fact that in step d), pressure is applied in a direction parallel and perpendicular, respectively, to the axis of the tight folds (3).
10. Method as in claim 9, distinguished by the fact that the perpendicular pressure is applied before the parallel pressure.
11. Method as in claim 1, distinguished by the fact that in step d) or e), sealing parts (8) are placed, in the longitudinal direction of the fins (3), at the ends of the air/fluid exchanger (1).
12. Method as in claim 11, distinguished by the fact that it includes, after step d) or after step e), an additional step e') for welding filler material (9) between the sheet metal plate in the upper position and the sealing parts (8).
13. Method as in claim 1, distinguished by the fact that second openings (11) are cut in the sheet metal plate in the lower position.
14. Method as in claim 13, distinguished by the fact that the said second openings (11) are located next to the sealing parts (8).
15. Method as in claims 13 or 14, distinguished by the fact that an oil can is fixed at the said second openings (11) either directly on the sheet metal plate in the lower position or on a reinforcement part (10) placed in step d) or e).
16. Method as in any of the preceding claims, distinguished by the fact that the fluid is oil.
17. An air/fluid exchanger (1) obtained using the method as in any of the preceding claims.

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