AU2015208375B2

AU2015208375B2 - Ventilation louvre and associated naval vessel

Info

Publication number: AU2015208375B2
Application number: AU2015208375A
Authority: AU
Inventors: Yves BERNICOT; Frederic Fernand Pierre Renaud
Original assignee: DCNS SA
Current assignee: Naval Group SA
Priority date: 2014-01-21
Filing date: 2015-01-12
Publication date: 2018-09-27
Anticipated expiration: 2035-01-12
Also published as: MY189714A; FR3016604A1; CA2936132A1; WO2015110305A1; AU2015208375A1; CA2936132C; FR3016604B1

Abstract

The invention relates to a ventilation louvre (4), comprising: a front surface (10) intended for being visible and a rear surface (12) intended for being concealed; a grating (14), fins (24) attached to the grating substantially parallel to one another and defining ventilation passages between the front surface and the rear surface. Each fin has a substantially planar central surface that is substantially rectangular and defined by two side ends and two transverse ends, the transverse ends of the central portions of the fins being arranged parallel to the front plane and/or the rear plane, the side ends of the central portion of each fin having a length of 250 mm to 350 mm. The invention also relates to an associated naval vessel (2).

Description

Ventilation louvre and associated naval vessel

The present invention relates to the ventilation louvres in particular equipping naval vessels.

More particularly, the present invention relates to a ventilation louvre for a naval vessel, comprising: a front surface intended to be visible and a rear surface intended to be concealed, a frame, and fins attached to the frame substantially parallel to one another and defining ventilation passages between the front surface and the rear surface.

Louvres (or louvers) onboard a naval vessel are situated at the mouth of ventilation ducts used to supply certain pieces of equipment with air, for example to cool them, or to discharge tainted air generated by certain other pieces of equipment.

Because it is visible from the outside, this type of equipment is subject to radar and infrared discretion requirements. Indeed, it is important for the stealth of the naval vessel onboard which these louvers are installed for the latter to have a radar cross-section (RCS) that is as small as possible. Furthermore, it is important for their infrared signature, which is representative of their visibility in the infrared domain, to be as small as possible.

Consequently, in particular to decrease the radar cross-section of the louvers onboard vessels, it is known to equip the latter with a coating specifically designed to observe all or part of the incident radar waves, or to produce the louvers directly from materials having such properties.

However, the materials or coatings used to do this are generally complex to manufacture. For example, the coatings used assume the form of a superposition of layers, each of which seeks to absorb the electromagnetic waves in part of the spectrum or to modify the properties of the incidental electromagnetic waves, for example their frequency, such that the rays reflected by the corresponding louver will be difficult to detect by the incident wave source. Other known materials have a complex microscopic structure.

Due to this complexity, these materials are costly, such that their use to produce louvers results in a high cost for the latter. Consequently, one of the aims of the invention is to propose a louver having good stealth, in particular radar and infrared stealth, at a low cost.

To that end, the invention relates to a ventilation louver for a naval vessel, comprising a front surface intended to be visible and a rear surface intended to be concealed, a frame, fins attached to the frame substantially parallel to one another and defining ventilation passages between the front surface and the rear surface, wherein each fin has a substantially planar central surface, substantially rectangular and defined by two side ends and two front and rear ends, the side ends of the central part of each fin having a length comprised between 250 mm and 350 mm.

According to other advantageous aspects of the invention, the louver comprises one or more of the following technical features, considered alone or according to any technically possible combination(s): the distance between the respective central parts of two adjacent fins is comprised between 20 mm and 70 mm; the front surface extends substantially along the front plane; each fin is inclined upward from the front surface toward the rear surface of the louver, the incline angle formed between the front plane and the central surface of each fin being comprised between 140° and 160°; the frame comprises two transverse faces and two side faces, the ventilation louver further comprising a reinforcing bar extending between the two transverse faces of the frame, preferably substantially parallel to the side faces; each fin comprises, at each of its front and rear ends, a transverse rim extending toward an adjacent fin so as to partially close off a mouth of a ventilation passage defined between this louver and said adjacent fin; it has no coating or material designed to absorb the radar electromagnetic rays; the side ends of the central part of each fin form the physical side edges of said fin on at least part of their length; the frame and/or at least one fin is made from aluminum; the fins are all substantially identical, the arrangement of one fin relative to a fin adjacent to it being the same for all of the fins; an end fin and the frame define a cavity closed toward the rear, the cavity being at least partially closed off at the front face by one or more shields; and at least one shield has perforations, the frame having openings, the perforations and the openings defining an additional passage for fluid circulation between the front and rear faces of the ventilation louver.

The invention further relates to a naval engine, characterized in that it comprises at least one ventilation louver as defined above.

The invention will be better understood upon reading the following detailed description, provided solely as an example and done in reference to the appended Figures, in which: - Figure 1 is a diagrammatic illustration of a naval vessel according to an embodiment of the invention; - Figure 2 is a diagrammatic illustration of a ventilation louver according to an embodiment of the invention; - Figure 3 is a longitudinal sectional view of the ventilation louver of Figure 2; and - Figure 4 is a diagrammatic illustration of a fin of the ventilation louver of Figures 2 and 3.

Figure 1 illustrates a naval vessel 2. The naval vessel 2 comprises one or more ventilation louvers 4, hereinafter referred to as louvers 4.

These louvers 4 are also known as baffle plates.

Each louver 4 is associated with one or more pieces of equipment 6 of the engine 2, to which it is fluidly connected, for example by a line 8. Each louver 4 is situated at the end of the line 8 and is in contact with the outside environment of the engine 2. Alternatively, at least one of the louvers is arranged through the wall of a room in which one or more pieces of equipment 6 are located, and is therefore not connected to these pieces of equipment by a line 8.

The louvers 4 each form an air inlet for supplying air to a piece of equipment 6, or an air outlet for discharging tainted air generated by a piece of equipment 6.

In reference to Figure 2, each louver 4 has a front surface 10 visible from the outside of the engine 2, and a concealed rear surface 12. The front surface 10 extends substantially along a front plane P1. The rear surface 12 extends substantially along a rear plane P2. In the example illustrated in the Figures, the planes P1 and P2 are parallel to one another. Each louver 4 is arranged on the engine 2 using a flush mount, i.e., such that its front plane P1 is substantially combined with the local plane of the surface of the engine 2 at which the louver 4 is installed.

In certain embodiments, at least one of the louvers 4 is arranged on the engine 2 in a configuration slightly tilted toward the rear, the front plane P1 having an incline comprised between 8° and 20° relative to the vertical. This results in minimizing the RCS of the louver 4 because the radar waves directly reflected by the louver 4 are not reflected toward the wave source.

Advantageously, each louver 4 has no coating or material specifically designed to absorb the electromagnetic rays, in particular the rays used by the radars. Thus, the cost of the louvers 4 is reduced.

The louver 4 comprises a frame 14. The frame 14 comprises two opposite transverse faces 16 and two opposite side faces 18. The transverse 16 and side 18 faces are attached to one another and are substantially orthogonal to the planes P1 and P2, each transverse face 16, side face 18, respectively, being attached to the two side faces 18, transverse faces 16, respectively. The frame 14 defines a generally parallelepiped cavity that emerges at the front 10 and rear 12 surfaces.

The frame 14 also comprises a fastening flange 20 extending substantially in the front plane P1 around the entire frame 14. The fastening flange 20 is provided with orifices 22 for the passage of fastening parts fastening the louver 4 to the engine 2. The fastening flange 20 is for example integral with the faces 16 and 18, or is alternatively attached to the faces 16 and 18.

The louver 4 further includes fins 24 and a reinforcing bar 26 configured to improve the mechanical strength of the louver 4. More specifically, the louver 4 comprises between ten and twenty fins 24, the exact number being conditioned by the use of the louver as a function of criteria known by those skilled in the art, for example the desired air flow rate.

In reference to Figures 2 to 4, the fins 24 are attached immovably to the frame 14. The fins 24 form a grid-type staged arrangement in the frame 14. The fins 24 conceal the opposite surface for a viewer looking at the louver 4 from normal or close to normal viewing angles at a given surface. Furthermore, the fins 24 define ventilation passages 25 between them for the fluid circulation between the front 10 and rear 12 surfaces of the louver 4.

As illustrated in Figure 4, each fin 24 has a central part 28 that is substantially planar and substantially rectangular. The central part 28 is defined by side ends 30 and front and rear ends 32.

Preferably, the side ends 30 correspond to the physical edges of the fin 24 over at least part of their length, advantageously over substantially all of their length. This makes it possible to simplify the shape of the fins, and therefore their manufacture.

The length I of the side ends 30 of the central part 28 of each fin 24 is comprised between 250 mm and 350 mm. The front and rear ends 32 of the central part 28 of each fin 24 are positioned parallel to the front plane P1. The width of the fins 24, i.e., the dimensions of the front and rear ends 32 and therefore of the louver 4, is conditioned by the use of the louver 4 as a function of criteria known by those skilled in the art, for example the desired gas flow rate.

Each fin 24 is attached to the frame 14 in a position in which the central part 28 is orthogonal to the side faces 18 of the frame. The side ends 30 are fastened to the side faces 18. Furthermore, the front and rear ends 32 extend substantially parallel to the front plane P1. For example, the front end 32 of the fins 24 extends substantially in the front plane P1.

Furthermore, the fins 24 are inclined upward from the front surface 10 toward the rear surface 12. The incline angle i formed between the front plane P1 and the central surface 28 of each fin 4 is comprised between 140° and 160°. In light of the orientation of Figure 3, the fins are thus inclined by an angle comprised between 50° and 70° relative to the horizontal. Consequently, an observer looking at the front surface 10 of the louver 4 from an angle close to the normal to the front plane P1 can view part of the upper surfaces of the central parts 28 of the fins 24 through the mouths of the ventilation passages 25.

In reference to Figure 3, the central parts 28 of two consecutive fins 24 are substantially parallel to one another. These central parts 28 are at a distance e from one another whereof the value is preferably comprised between 20 mm and 70 mm.

Each fin 24 further comprises two transverse rims 34, including a front rim and a rear rim. The rims 34 are substantially planar and are respectively situated in the extension of both the front and rear ends 32 of the central part 28. Advantageously, the rims 34 extend over the entire length of the front and rear ends 32. The rims 34 each form a strip of material inclined relative to the central surface 28. The two rims 34 of a same fin 24 are positioned parallel to one another and are oriented in opposite directions. For example, in light of the orientation of Figures 3 and 4, the rim 34 oriented toward the front surface 10 of the louver 4 is oriented downward relative to the associated central surface 28, and the rim 34 oriented toward the rear surface 12 of the louver is oriented upward.

Each rim 34 extends toward an adjacent fin 24 so as to partially close off the mouth of a ventilation passage 25. Due to the relative orientation, the two rims of a fin 24 partially close off separate ventilation passage mouths 25. As will be seen below, the rims 34 result in increasing the number of reflections of the electromagnetic waves that penetrate inside the louver 4. The angle formed between the central surface 28 of a fin 24 and each rib 34 corresponds to the incline angle i. Thus, as illustrated in Figure 3, the rims 34 extend parallel to the front plane P1.

As illustrated in Figure 4, each fin 24 also comprises a slot 36 arranged in one of the rims 34 and in the central part 28. The slot 36 is provided to receive the reinforcing bar 26 and has dimensions complementary to the reinforcing bar 26.

Preferably, the fins 24 are all substantially identical to one another. Furthermore, the distance e between two adjacent fins 24 is substantially constant from one pair of fins 24 to the next. Furthermore, the incline angle between the central surface 28 of each fin and the front plane P1 is substantially the same for all of the fins.

In reference to Figure 2, the reinforcing bar 26 extends between the two transverse faces 16 of the frame 14 at the front face 10, preferably parallel to the side faces 18. For example, each end of the reinforcing bar 26 is welded to the corresponding transverse face 16. Furthermore, the reinforcing bar 26 is received by each of the fins 24 at the corresponding slot 36. For example, each fin 24 is welded to the reinforcing bar 26 over all or part of the contact zone between the edges of the slot 36 and the reinforcing bar 26.

Preferably, the louver 4 is made from aluminum. More specifically, the frame 14, the fins 24 and/or the reinforcing bar 26, and preferably each of them, are made from aluminum. This results in minimizing the galvanic interactions between the louver 4 and the surfaces of the vessel 2 with which the louver 4 is in contact. Furthermore, this results in favoring the proper corrosion resistance of the louver 4.

In reference to Figures 2 and 3, one of the end fins 24 of the louver 4, for example the highest fin 24 among all of the fins (within the orientation of Figures 2 and 3), defines, with the adjacent transverse face 16 and the side faces 18 of the frame 14, a cavity 38 closed toward the rear. This cavity 38 is partially closed off at the front face 10 by one or more shields 40, for example by two shields 40. Each shield 40 assumes the form of a metal plate, preferably made from aluminum, planar and solid, i.e., not perforated. Each shield 40 extends substantially in the front plane P1. Each shield 40 is attached to the reinforcing bar 26 and the frame 14, for example by welding. For example, the lower end of each shield 40 is situated at a distance from the fin 24 in question substantially equal to the distance of the front plane P1 between this fin 24 and the adjacent fin. This makes it possible to limit the negative impact of the cavity 38 on the RCS of the louver 4 resulting from the shape of the cavity 38, which causes only a limited number of reflections for the radar waves that penetrate it.

Alternatively, one or more shields 40, for example each shield 40, has perforations 42 (in dotted lines in Figure 2) over all or part of its surface. The number, locations and dimensions of the perforations are determined in a manner known by those skilled in the art in order to minimize the contributions of the perforations and shields to the RCS of the louver 4. Furthermore, the upper transverse face 16 is provided with openings 44 (shown in Figure 3). The perforations 42 and the openings 44 define an additional fluid circulation passage between the front 10 and rear 12 surfaces, the presence of which makes it possible to improve the aspiration performance of the louver 4 compared to an embodiment without perforations 42 and/or without openings 44. Preferably, the louver 4 is then arranged on the engine 2 such that play exists between the transverse face 16 provided with openings 44 and the associated edge of the opening arranged in the engine 2 in which the louver 4 is received, which allows the effective circulation of gas by this additional passage.

Preferably, the lower end fin, i.e., the lowest fin 24, is arranged in the frame 14 such that the free edge of its rim 34 visible from the front face is in contact with the lower transverse face 16. As a result, the louver 4 does not have a lower cavity having a geometry that is difficult to control.

The manufacture of a louver 4 according to the invention will now be described in reference to the Figures.

First, the fins 24 are manufactured, for example by machining or cutting. In particular, the ribs 34 are inclined relative to the central surface 28, and the slot 36 is arranged in a rim 34 of the fin 24. In parallel, the transverse 16 and side 18 faces are fastened to one another, for example by welding. The flange 20 is also produced.

The reinforcing bar 26 is next fastened to the frame 14. The fins are then successively installed in the frame 14. Each fin 24 is engaged by the rear surface 12 and placed in the provided position such that the rim 34 visible from the front face 10 extends substantially in the plane P1. The fin 24 is next attached in the frame 14 by welding at the reinforcing bar 26 and at weld zones situated on the inner surface and/or the outer surface of the side faces 18. The shields 40 are next installed.

The operation of a louver 4 according to the invention will now be described in reference to the Figures.

During operation, gases, for example air, become engaged in the ventilation passages 25 defined by the fins 24 and circulate between the front surface 10 and the rear surface 12 of the louver 4, for example under the effect of suction or an overpressure generated by a piece of equipment 6. The precise circulation direction of the gases within the louver 4 results from the use of the louver as a ventilation or discharge louver.

In the case of an attempt to detect the engine 2 by a remote radar device, electromagnetic waves are emitted toward the louver 4. Part of these waves are directly reflected in a direction other than that of the transmitting radar by the front face 10 of the louver 4, in particular by the front ribs 34, the flange 20 and the reinforcing bar 26. Another part of the radar waves penetrates the louver 4 through the mouth of the ventilation passages 25.

Once the waves have penetrated the ventilation passages 25, they are then successively reflected by both of the central surfaces 28 of the fins defining the corresponding ventilation passage 25. Due to the incline angle between the central surfaces 28 and the plane P1 on the one hand, and the ribs 34 at the ends of the fins 24 on the other hand, the waves then undergo a very large number of reflections in the corresponding ventilation space 25, each of which leads to the dissipation of part of the energy of these waves. In particular, they travel through the ventilation passages 25 in both directions and are reflected at the ends of these passages by the rims 34. As a result, the waves that end up leaving the louver 4 through the front surface 10 of the louver 4 have both a decreased energy level and different directions from one another and that of the raider device having emitted the radar waves, which contributes to greatly decreasing the RCS of the louver 4.

The louver 4 according to the invention has several advantages.

First of all, the dimensions of the central parts 28 of the fins 24, and in particular the length of the side ends 32, result in increasing the number of reflections of radar waves that may enter the louver 4, and thus decreasing the radar cross-section of the louver 4 as explained above.

Furthermore, the distance values e between the central parts 28 of the fins 24 result in allowing the louver 4 to retain high suction and discharge capabilities while minimizing the risks of icing of the ventilation passages 25 under rigorous environmental conditions. This in particular makes it possible to exempt the louver 4 from having a deicing system, such a system being expensive and contributing to increasing the infrared signature of the louver 4. Furthermore, this range of distance values e results in preventing network effects, by which a structure having a repetitive geometry and in which incident waves penetrate can amplify the waves before they are retransmitted and thus have a large RCS.

Furthermore, the range of values of the incline angle i of the central parts 28 of the fins 24 simultaneously results in contributing to the increase in the reflection number of the waves in the louver 4 and minimizing the bulk of the louver: indeed, with a fixed fin 24 length, these incline values make it possible to decrease the depth of the louver 4.

Furthermore, the presence of the reinforcing bar 26 results in substantially increasing the mechanical strength of the louver 4 in general. In particular, the mechanical strength of the louver 4 with respect to green seas is substantially improved for a low cost. In a known manner, the green seas correspond to large masses of water placed in suspension, in particular by a choppy sea, and which are a significant factor in the deterioration of physical structures of the engine 2.

Furthermore, as previously indicated, the presence of the rims 34 at the front and rear ends of the fins 24 results in contributing to increasing the number of reflections of the radar waves in the louver 4. The radar stealth performance of the louver 4 is improved accordingly.

Furthermore, the feature according to which the side ends 32 of the central part 28 of the fins form the physical longitudinal edges of the corresponding fin 24 makes it possible to simplify the shape of the fins and therefore the manufacture of the fins themselves. nowever, in some emooaimems, me siae enas ot me cemrai pans are exienaea over all or part of their length by complementary attachment structures, for example tongues intended to be inserted in the side faces 18 of the frame 14.

Furthermore, as previously indicated, producing the louver 4 from aluminum results in minimizing the galvanic interactions at the interface between the louver 4 and the engine 2. Furthermore, due to the lightness of this material, the mass of the louver 4 is thus decreased, which facilitates handling, in particular for its installation.

Furthermore, due to their arrangement, the fins 24 obstruct the vision when the louver is viewed from normal or close to normal viewing angles. Indeed, the louver 4 has good concealing properties for hotspots situated at the pieces of equipment 6 to which the louvers 4 are coupled, and thus has a low infrared signature.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A ventilation louver for a naval vessel, comprising: a front surface intended to be visible and a rear surface intended to be concealed, a frame, fins attached to the frame substantially parallel to one another and defining ventilation passages between the front surface and the rear surface, wherein each fin has a substantially planar central surface, substantially rectangular and defined by two side ends and two front and rear ends, the side ends of the central part of each fin having a length comprised between 250 mm and 350 mm.
2. The ventilation louver according to claim 1, wherein the distance between the respective central parts of two adjacent fins is comprised between 20 mm and 70 mm.
3. The ventilation louver according to claim 1 or 2, wherein the front surface extends substantially along the front plane.
4. The ventilation louver according to claim 3, wherein each fin is inclined upward from the front surface toward the rear surface of the louver, the incline angle formed between the front plane and the central surface of each fin being comprised between 140° and 160°.
5. The ventilation louver according to any one of the preceding claims, wherein the frame comprises two transverse faces and two side faces, the ventilation further comprising a reinforcing bar extending between the two transverse faces of the frame.
6. The ventilation louver according to any one of the preceding claims, wherein each fin comprises, at each of its front and rear ends, a transverse rim extending toward an adjacent fin so as to partially close off a mouth of a ventilation passage defined between this louver and said adjacent fin.
7. The ventilation louver according to any one of the preceding claims, wherein it has no coating or material designed to absorb the radar electromagnetic rays.
8. The ventilation louver according to any one of the preceding claims, wherein the side ends of the central part of each fin form the physical side edges of said fin on at least part of their length.
9. The ventilation louver according to any one of the preceding claims, wherein the frame and/or at least one fin is made from aluminum.
10. The ventilation louver according to any one of the preceding claims, wherein the fins are all substantially identical, the arrangement of one fin relative to a fin adjacent to it being the same for all of the fins.
11. The ventilation louver according to any one of the preceding claims, wherein an end fin and the frame define a cavity closed toward the rear, the cavity being at least partially closed off at the front surface by one or more shields.
12. The ventilation louver according to claim 11, wherein at least one shield has perforations, the frame having openings, the perforations and the openings defining an additional passage for fluid circulation between the front and rear surfaces of the ventilation louver.
13. A naval vessel, wherein it includes at least one ventilation louver according to any one of claims 1 to 12.