EP4291723A1

EP4291723A1 - Filtering device for collecting debris at the surface of bodies of water

Info

Publication number: EP4291723A1
Application number: EP22708203.9A
Authority: EP
Inventors: Guillaume Raymond; Pascal Crepet
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-02-10
Filing date: 2022-02-10
Publication date: 2023-12-20
Also published as: US20240093452A1; WO2022171962A1; CN116888326A; FR3119627A1; FR3119627B1

Abstract

The invention relates to a filtering device comprising: a pipe (11) intended to be submerged in a flow of fluid, the pipe comprising an inlet opening (12) receiving the flow of fluid, and an outlet opening (13), a filter (14) arranged in the pipe and extending over an entire cross-section of the pipe, the pipe comprising a downstream section (11b) conveying the flow of fluid exiting the filter towards the outlet opening, the outlet opening having a surface area smaller than a surface area of the inlet opening, the surface areas being viewed in a plane perpendicular to a longitudinal axis (X) of the pipe.

Description

Title: FILTERING DEVICE FOR COLLECTING DEBRIS AT THE

SURFACE OF WATER BODY

The present invention relates to the collection of floating solid waste on the surface or near the surface of bodies of water such as oceans, seas, rivers and lakes. Many solutions have been proposed. Generally, these solutions consist of an autonomous device dedicated to the collection of floating waste. Such a device has its own means of propulsion, which makes it expensive to manufacture, operate and maintain.

Devices capable of being towed by ships have also been proposed. Such a device is, for example, described in patent EP 2812498. This device comprises a channel arranged on the surface of the body of water in the direction of movement of the ship. The channel has a width increasing from the entrance of the channel to the entrance of a filter, in an attempt to reduce the drag of the filter and therefore limit the excess energy consumption of the ship due to the presence of the device dragged on the surface of the body of water. This device has the disadvantage of only being usable at low speed, less than 2 m/s, in particular to retain its ability to guide the fluid entering the filter. It is unsuitable for equipping ships generally moving at more than 2 m/s. Furthermore, at such speeds, the channel arranged around the filter introduces a drag which may be greater than that of the filter.

Indeed, it turns out that the more the speed of the water in the vicinity of the filter is reduced to lower the drag of the latter, the more the drag of the guide elements around the filter is increased. It is therefore desirable to provide a filtering device which is effective in collecting waste from the surface of a body of water, without requiring means of propulsion. It is also desirable to increase as much as possible the ratio between the flow rate of filtered water and the drag force generated by the filtering device when it is towed while submerged. It is also desirable for this filtering device to be able to equip any ship, and therefore can be driven at speeds greater than 2 m/s. With this in mind, this device must be able to withstand shocks from waves moving at high speed, and be protected against large debris that could obstruct the inlet of the filter.

Embodiments relate to a filtering device comprising: a conduit provided to be immersed in a flow of fluid, and a filter disposed in the conduit to filter the fluid entering the conduit, the conduit comprising: an inlet opening receiving the flow of fluid, an upstream section extending from the inlet opening and housing the filter, an outlet opening, and a downstream section extending from the filter to the outlet opening, to channel the flow of fluid leaving the filter towards the outlet opening, the downstream section having a length greater than or equal to the length of the upstream section, the outlet opening having a surface area smaller than a surface of the inlet opening, the surfaces being considered in a plane perpendicular to a longitudinal axis of the duct.

According to one embodiment, the upstream section has, in a plane passing through the longitudinal axis of the duct, an internal profile forming with the direction of the flow an angle of zero or between 0 and 16° towards the longitudinal axis of the duct.

According to one embodiment, the duct has a bulge on its outer face around the inlet opening, the bulge having at the inlet opening a tangent forming an angle greater than 45° with respect to the longitudinal axis of the duct.

According to one embodiment, the downstream section has, in a plane passing through the longitudinal axis of the conduit, a rectilinear or curved internal profile and forming with the direction of the flow an angle comprised between 0 and 20, and preferably comprised between 4 and 9 °.

According to one embodiment, the surface of the outlet opening is adjusted so that the speed of the fluid flow at the outlet of the conduit is between 80 and 110% of the speed of the fluid around the outlet opening. .

According to one embodiment, the surface of the outlet opening is between 0.1 and 5 times the total passage surface of the fluid through the filter. According to one embodiment, the duct has a section of circular, elliptical, trapezoidal, triangular, polygonal, square or rectangular shape, or a shape composed of these shapes.

According to one embodiment, the device comprises a grid arranged in front of the filter and having a passage surface for the fluid flow greater than the passage surface of the filter, the grid being placed in the duct, or else in front of the opening of the duct to perform a filter and/or breakwater function, the grid being associated or not with a cleaning or suction device to evacuate the debris retained by the grid.

According to one embodiment, the device comprises at least one filter having one of the following characteristics: the filter has a conical or pyramidal shape, the filter has a conical or pyramidal shape and a debris evacuation opening at the top of the conical or pyramidal shape, the filter is flat and arranged perpendicular to the longitudinal axis of the conduit, the filter is flat and inclined relative to the longitudinal axis of the conduit, the filter has a plurality of juxtaposed grooves with a cross-section in the shape of V, each face of the filter has a convex part and a concave part, the filter is formed of parallel rods, and the filter has profiled rods or meshes in order to reduce the drag of the filter.

According to one embodiment, the filter is associated with a cleaning device or a suction device, to evacuate debris retained by the filter.

According to one embodiment, the device comprises a member configured to push the device upwards when the device is completely submerged in the body of water, and a member configured to push the device downwards when the device is not completely submerged in the body of water.

Embodiments may also relate to a method for collecting solid debris near the surface of a body of water, the method comprising steps consisting of: providing a filtering device as defined above, and associating the filtering device to a structure keeping the conduit of the filtering device submerged at the surface of the body of water in a flow of water, or else associating the filtering device with a vessel in such a way as to keep the conduit of the filtering device submerged at the surface of the body of water, and put the vessel in motion at a cruising speed in order to generate a flow of water in and around the conduit of the filtering device.

According to one embodiment, the method comprises a step of collecting debris in a reservoir. According to one embodiment, the flow of water has a speed of between 1 and 15 m/s.

Examples of embodiments of the invention will be described in the following, on a non-limiting basis in relation to the attached figures, among which: [Fig. 1] Figure 1 shows in longitudinal section along a vertical plane, a filtering device according to one embodiment,

[Fig. 2] figure 2 is a perspective view of a filtering device, according to another embodiment,

[Fig. 3] Figure 3 is a longitudinal sectional view along a vertical plane of the filter device of Figure 2, according to one embodiment,

[Fig. 4] Figure 4 is a longitudinal sectional view of a filter of the filtering device, according to one embodiment, and Figure 4A is a detailed sectional view of part of the filter shown in Figure 4,

[Fig. 5] Figure 5 is a perspective view of the filtering device, according to another embodiment,

[Fig. 6] Figure 6 is a longitudinal sectional view along a vertical plane of the filter device of Figure 5, according to one embodiment,

[Fig. 7] FIG. 7 is a view in longitudinal section along a vertical plane of the filtering device, according to another embodiment, [Fig. 8] Figure 8 is a perspective view of the filtering device, according to another embodiment,

[Fig. 9] FIGS. 9A, 9B are views in longitudinal section along a vertical plane and along a horizontal plane of the filtering device of FIG. 8, according to one embodiment, [Fig. 10] figure 10 is a perspective view of a filter of the filtering device, according to another embodiment,

[Fig. 11] FIGS. 11 A and 11 B are views from above and in longitudinal section, respectively in a horizontal plane and in a vertical plane, of a filtering device, according to another embodiment, [Fig. 12] [Fig. 13] [Fig. 14] Figures 12 to 14 are views in longitudinal section along a vertical plane of filtering devices, according to various other embodiments,

[Fig. 15] [Fig. 16] Figures 15 and 16 are views in longitudinal section along a vertical plane of filtering devices, according to the prior art.

FIG. 1 represents a filtering device 10 according to one embodiment. The device 10 comprises a filter 14 disposed in a tubular conduit 11 comprising an upstream section 11a channeling a flow of fluid to be filtered having entered through an inlet opening 12 of the conduit, and a downstream section 11b channeling a flow of filtered fluid towards a outlet opening 13 of the duct. The filter 14 is arranged in the conduit between the upstream and downstream sections, so as to receive the flow of fluid to be filtered.

The filtering device 10 can be used by being immersed in a flow of fluid, for example pulled or pushed under the surface 1 of a body of water, or kept fixed under the surface of a watercourse. It can be observed that only the inlet opening 12 of the device can be submerged, the longitudinal axis X of the device 10 being maintained at an angle of less than 25° with respect to the surface 1 of the water.

According to an embodiment illustrated by FIG. 1, the upstream section 11a delimits an internal volume of cylindrical shape having a constant surface section between the inlet opening 12 and the inlet of the filter 14. Thus the total surface of the filter may be identical to the surface of the inlet opening 12. The downstream section 11b delimits an internal volume of frustoconical shape with an internal section narrowing from the outlet of the filter 14 to the outlet opening 13. The internal volume of the downstream section may have other shapes such as that of a hyperboloid of revolution.

The outer surface of the duct 11 may have, around the inlet opening 12, a curved profile widening from the inlet opening 12. The curved profile has a tangent T1 at the edge of the opening 12 approaching of the plane of the opening, that is to say forming an angle Q with the longitudinal axis X, greater than 45°, and preferably greater than 65°. At the junction of the upstream 11a and downstream 11b sections, the profiles of the latter have the same tangent. It can be observed that such a profile generates a drag opposite to the direction of the flow 2, that is to say favoring the movement of the device in the flow. In the example of figure 1, this curved profile widening to about half the length of the upstream section 11a, then narrowing to the outlet opening 13. According to one embodiment, the ratio between the length of the inner profile and the length of the outer profile of the upstream section 11a is between 0.7 and 1.0. The bulge thus produced increases the length of the path traveled by the fluid and therefore increases the speed of the latter around the upstream section 11a. This results in a decrease in the pressure around the upstream section 11a, which creates a positive drag. A better hydrodynamic performance of the tubular conduit 11 is thus obtained, regardless of the speed of the fluid in and around the conduit.

According to one embodiment, the upstream section 11 has, in a plane passing through the longitudinal axis X of the duct, a curved or rectilinear internal profile, and forming with the direction of the flow an angle comprised between 0° and 16°, and preferably between 4 and 9°. These features help reduce drag acting in the direction of flow 2.

According to one embodiment, the downstream section 11b has, in a plane passing through the longitudinal axis X of the duct 11, a rectilinear or curved internal profile and forming with the direction of the flow an angle a of between 0 and 20°.

According to one embodiment, the downstream section 11b comprises a section 11c having a circular internal section, the downstream end of which delimits the opening 13. The size of the internal section of the section 11c is such that the edge of the opening 13 is tapered. The transition zone between the frustoconical internal part and the cylindrical internal part 11c of the downstream section 11b may have a rounded external profile, in order to delay the possible detachment of the fluid from the external wall of the conduit 11 in this zone.

According to one embodiment, the surface of the outlet opening 13 is defined so that the speed of the fluid leaving the conduit 11 is between 80 and 110%, and preferably equal to 100% of the speed of the fluid around the outlet opening 13. In this way, the shear appearing at the interface between the fluid leaving through the outlet opening 13 and the fluid outside the duct is reduced, which makes it possible to reduce the drag s exerting on the conduit 11 . The surface of the outlet opening 13 can be adjusted by acting on the length of the downstream section 11b and on the angle a. Furthermore, the flow velocity in the duct depends on the characteristics of the filter and in particular its drag coefficient. The lower this coefficient, the more the length of the downstream duct 11b can be reduced, which also reduces the drag of the downstream duct. Furthermore, the lower the drag coefficient of the filter, the higher the fluid velocity through the filter can be. Thus, the outlet opening 13 can be larger.

Filter 14 includes pores or mesh through which fluid can flow. In what follows, the “passage area” of the filter designates the sum of the surfaces of the pores or meshes of the filter. According to one embodiment, the outlet opening 13 has a lower surface than the passage surface of the filter 14, in order to reduce the difference between the speed of the fluid at the outlet 13 of the conduit 11 and the speed of the fluid around the conduit outlet.

Outlet opening 13 may have a surface area of between 0.1 times and five times the fluid passage surface through filter 14, depending on the characteristics of the filter.

The meshes of the filter can be delimited by a wire of circular section. According to one embodiment, the wire delimiting the meshes of the filter has a hydrodynamic profile (lower drag coefficient) oriented in the direction of the flow of fluid 2, as illustrated by FIG. 4A.

According to an embodiment illustrated by FIGS. 2 and 3, the filtering device 10 comprises a grid 17 (or several) arranged in front of the filter 14 to prevent excessively large debris from entering the conduit 11 as far as the filter, and to channel them towards a tank 22 for storing these debris which can be fixed above the pipe 11. The grid 17 comprises parallel rods inclined at the top towards the rear of the pipe 11 as far as an inlet of the tank 22 so that the debris can be drawn towards the reservoir 22 under the effect of the flow of fluid 2. For this purpose, the conduit 11 has an upper opening 26 through which the rods of the grid 17 pass. The grid 17 may have a flow passage surface of fluid greater than the passage surface of the filter 14. According to one embodiment, the rods forming the grid 17 have a hydrodynamic profile in order to minimize their drag under the effect of the flow of fluid 2.

According to one embodiment, a profiled element 27 provided to perform the function of breakwater and deflector to repel very large debris, is held in front of the inlet opening 12 by rods 23. The profiled element 27 can present a hydrodynamic profile in order to limit its drag According to one embodiment illustrated by Figures 3 and 4, the filter 14 has a conical shape whose axis substantially coincides with the axis X of the conduit 11. The filter 14 has an opening at the top of its conical shape, arranged in downstream in the conduit 11 and opening into a conduit 24. The shape of the filter 14 makes it possible to channel the debris collected towards the conduit 24 under the effect of the flow of fluid passing through the filter. According to one embodiment, the evacuation duct 24 opens into a tank 21 for collecting debris, which can be fixed above the duct 11 . The conduit 24 can be arranged so that the flow of fluid penetrating into the conduit 11, then into the conduit 24, carries the debris into the reservoir 21 or into the reservoir 22 forming a single reservoir disposed or fixed above the led 11 .

According to one embodiment illustrated by Figures 1 to 3, the inlet opening 12 is centered on the longitudinal axis of the conduit 11. According to the example of Figure 1, the conduit 11 has a symmetry of revolution around its longitudinal axis X (disregarding the opening 26).

Furthermore, if we consider the rounded shape of the profile of the upstream section 11a and the tapered shape of the downstream section 11b, each angular sector (around the longitudinal axis X of the duct) of the duct 11 tends to exert a pushed out of the conduit in a direction perpendicular to the inner surface of the conduit. When the conduit 11 is totally immersed in the fluid, the thrusts exerted by the different sectors of the conduit are balanced. On the other hand, when for example the upper part of the duct 11 comes out of the fluid, this balance disappears because the upper sector of the duct no longer exerts upward thrust. As a result, the lower sector of the duct tends to drag the duct 11 downwards, in a position of complete immersion.

According to one embodiment, the upper part of the duct 11 is longer than the lower part of the latter. In this way, the duct tends to rise above the surface of the water, because the thrust exerted by the upper part of the duct is greater than the thrust exerted by the lower part of the duct. When the conduit is partly emerged, it tends to descend below the surface of the water because the thrust exerted by the lower part of the conduit is greater than the thrust exerted by the emerged upper part of the conduit. Thus, the conduit is automatically maintained in the vicinity of the surface of the water. This effect can also be obtained by adjusting the crowning of the upper part of the upstream section 11a. This effect can also be obtained using fins fixed to the external face of the duct, on the top, at the front or at the rear of the duct, or on each side of the duct 11 (fins 19 in the figure 2), so as to remain submerged, and oriented so as to exert an upward thrust less than or equal to the downward thrust exerted by the conduit when it is only partially immersed.

Figure 4 shows the filter 14 according to one embodiment. The filter 14, of conical shape, is associated with a cleaning device 15 comprising a brush configured to brush the meshes of the filter 14, and to turn on itself and around the longitudinal axis of the filter 14, the debris being driven towards the top of the conical shape to be evacuated through conduit 24, under the effect of the fluid flow. The rotational drive of the brush can exploit the pushing force of the fluid flow passing through the filter.

According to another embodiment, the cleaning device is fixed and the filter 14 rotates around its longitudinal axis. Evacuation of debris to conduit 24 can be effected or facilitated by the application of vibrations to the filter.

According to another embodiment, the filter has, on a side opposite to the direction of the flow, a convex part formed in a concave part. Thus, the filter may have a frustoconical part with a large base and a small base coupled to a bottom part of conical shape, the top of the conical shape extending in the direction of the large base of the frustoconical shape. Thus, the filter has a W-shaped section in a plane perpendicular to the plane containing the large base of the frustoconical part and passing through the top of the conical shape.

Figures 5, 6 show a filter device 30 according to another embodiment. The filtering device 30 differs from that of FIG. 2 in that it comprises a duct 31 of rectangular section with inlet 32 and outlet 33 openings of rectangular shape. The filter 14 is replaced by a filter 34. The filter 34 can be associated with a cleaning device 35 in the form of a roller brush which moves between the lower and upper parts of the filter 34 to sweep debris onto the filter to a 21' tank. The filtering device 30 can also comprise a set of parallel rods 37, fixed in the duct 31 between the inlet opening 32 and the filter 34. The rods 37 make it possible to evacuate the large debris towards a tank 22 ′ arranged at the above conduit 31 . To this end, each of the rods 37 has an inclined part in front of the opening 32 of the duct 31, so that the upper part of the rod is further downstream with respect to the duct 31 than a lower part of the inclined part of the stem. Thus, the debris retained by the rods 37 can be pushed upwards into the reservoir 22' under the effect of the flow of fluid. For this purpose, the duct 31 has an upper opening 26' through which the rods 37 pass. The rods 37 may have a passage surface for the flow of fluid greater than the passage surface of the filter. The rods 37 can for example have a fluid flow passage surface greater than 70% of the surface of the cross section of the duct. According to one embodiment, the rods 37 are profiled in order to minimize their drag under the effect of the flow of fluid 2.

According to one embodiment, a profiled element 27' designed to repel very large debris is held in front of the inlet opening 32 by rods 23'.

According to one embodiment, the rods 37 are also associated with a cleaning device 36 moving along the rods to carry the debris towards the tank 22'.

According to one embodiment, the rods have a hydrodynamic profile oriented in the direction of the flow 2 of fluid.

According to one embodiment, the duct 31 is associated with lateral fins 39 arranged to keep the duct 31 submerged just below the surface 1 of the fluid, as illustrated in FIG. 5. Fins can also be placed on top, in front, behind or below conduit 31.

According to various embodiments, the filter 44 is flat and arranged in the duct 41 like the filter 34 in the duct 31, in an inclined position towards an opening provided in an upper part of the duct 41, or in a space provided between the faces external and internal of the conduit 31. The filter 44 can also have the form of the filter 14 coupled to a conduit for the evacuation of the debris towards a reservoir. According to another embodiment illustrated by FIG. 7, the conduit 31' and in particular the upper external face of the conduit is shaped so as to house all the rods 37 and the reservoirs 21", 22". Thus, the upper outer face of the duct may for example have an extended bulge for this purpose. In this case, the opening 26 is not necessary and can be omitted.

Figures 8, 9A and 9B show a filter device 40 according to another embodiment. The filtering device 40 differs from that of FIG. 2 in that it comprises a duct 41 of rectangular section with inlet 42 and outlet 43 openings of rectangular shape. The filter 14 is replaced by a filter 44. The filter 44 can be associated with a cleaning device 45 in the form of a roller brush moving between the lower and upper parts of the filter 44.

The filtering device 40 can also comprise a set of parallel rods 47, fixed to the outside of the duct 41 opposite the inlet opening 42. The rods 47 act as a breakwater and allow large debris to be evacuated. to a tank 48 arranged above the conduit 41. For this purpose, each of the rods 47 has a portion inclined in front of the opening 42 of the conduit 41, so that the upper part of the rod is further downstream with respect to the conduit 41 than a lower part of the inclined part of the rod. Thus, the debris retained by the rods 47 can be pushed upwards into the reservoir 48 under the effect of the flow of fluid. The lower part of the inclined part of the rods is connected to a lower part of the edge of the opening 42 by a part directed towards the downstream, slightly inclined with respect to the horizontal.

According to one embodiment, the grids 47 are also associated with a cleaning device 46 moving along the rods to drive the debris retained by the grids towards the tank 48.

According to one embodiment, the rods 47 have a hydrodynamic profile oriented in the direction of the flow 2 of fluid.

According to one embodiment, the duct 41 is associated with lateral fins 49 arranged as illustrated in FIGS. 8, 9B, to keep the duct 41 submerged just below the surface 1 of the fluid.

According to various embodiments, the filter 44 is flat and arranged in the duct 41 like the grid 17 in the duct 11, in an inclined position towards an opening provided in an upper part of the duct 41 . The filter 44 can also take the form of the filter 14 coupled to a conduit for the evacuation of debris to a reservoir.

According to one embodiment, the filter 44 and the rods are substantially parallel and inclined relative to the longitudinal direction X of the duct, and the duct is shaped so that the plane of the inlet opening 42 is parallel to the filter. Thus, if the filter and the rods are angled upwards, the lower part of the pipe extends upstream more than the upper part of the pipe.

Figure 10 shows a filter 44' according to another embodiment. The filter 44' has a plurality of juxtaposed grooves with a V-shaped cross section. The filter 44' can be arranged in the conduit 41 so that its grooves are oriented in a vertical longitudinal plane of the conduit and inclined at the top the rear of the duct 44. The filter 44' can be associated with a cleaning brush arranged horizontally and having a shape matching the shape of the section of the filter in a horizontal plane. The cleaning of the 44' filter can be carried out by moving the brush between the lower and upper parts of the 44' filter.

According to other embodiments, the filter has a pyramidal shape with a square or rectangular section, with a pointed or straight apex. Thus, in order to be able to be adapted to the filtering device 40, the filter can be pyramidal in shape with a rectangular section and apex in the form of a straight segment.

According to one embodiment, the cleaning of the filter is carried out by a suction system coupled to a reservoir (for example 21, 21' or 48), and comprising a pump connected to a pipe whose end is moved along the filter surface. The tank receiving the debris can also be connected by a pipe to a larger tank.

According to one embodiment, the filter does not include meshes, but consists of parallel rods, for example arranged vertically. It turns out that such a filter is easier to clean and generates less drag. The rods or the meshes forming the filter can be profiled in order to reduce the drag of the latter.

Figures 11A, 11B represent a filtering device according to another embodiment. The filtering device comprises the conduit 41 described with reference to FIGS. 8, 9A and 9B, and a set of parallel rods 47' held in front of the upstream opening of conduit 41 by two floats 9, conduit 41 being secured to floats 9, for example by cables 8. rods 47' make it possible to evacuate the large debris towards a tank 48' fixed above the floats 9. For this purpose, the rods 47' are inclined in front of the opening 42 of the conduit 41, so that the upper part of the rods either further downstream with respect to conduit 41 than a lower part of the rods. Thus, the debris retained by the rods 47' can be pushed upwards into the reservoir 48' under the effect of the flow 2 of fluid.

According to one embodiment, the rods 47' are associated with a cleaning device moving along the rods to carry the debris towards the tank 48'.

The 47' rods can have a hydrodynamic profile to minimize their drag. In addition, the rods 47' can be hollow in order to be able to float and therefore to minimize the volume of the floats 9 and therefore the drag of the latter.

According to one embodiment, the filter present in the previously described embodiments can be flexible and wound around rollers in high and low positions in the conduit 11, 31, 41. A stationary rotating brush cleans the filter when it is moved up or down and rolled onto one of the rollers.

The filter can also be cleaned using a pressure pump emitting a jet of water opposite to the flow direction 2 of the fluid.

According to one embodiment, the floats 9 are replaced by one or more fins connected to the grid formed by the rods 47' in order to provide lift and to maintain the grid at the desired height, with a submerged part and an emerged part. .

FIGS. 12 to 16 represent different profiles of ducts of the filtering device, according to various embodiments. FIG. 12 represents a filtering device 50 comprising a conduit 51 and a filter 54. The conduit 51 comprises an upstream section 51a and a downstream section 51b having a length comprised between 7 and 9 times the length of the upstream section 51a. The interior volume of the upstream section 51 has, in a horizontal longitudinal plane, a trapezoidal section symmetrical with respect to the longitudinal axis X of the duct 50, and widening downstream as far as the filter 54 at an angle a1 . Volume interior of the downstream section 51b has, in the horizontal longitudinal plane, a trapezoidal section symmetrical with respect to the longitudinal axis X, and widening upstream as far as the filter 54 at an angle a2 with respect to the longitudinal axis X. On the outside, the longitudinal section of the upstream section 51a has a rounded shape widening out to the location of the filter 54. The external shape of the longitudinal section of the downstream section 51b is substantially rectilinear or slightly curved outwards. The outlet opening 53 has a surface area smaller than the area of the inlet opening 52, and the area of the inlet opening 52 is smaller than the area of the cross section of the conduit 50 at the location of the filter 54.

FIG. 13 represents a filtering device 60 comprising a pipe 61 and a filter 64. According to one embodiment, the pipe 61 only comprises a downstream section 61b. The interior volume of the downstream section 61b has, in the horizontal longitudinal plane, a trapezoidal section symmetrical with respect to the longitudinal axis X, and widening upstream as far as the filter 64 from the angle a2 with respect to the longitudinal axis X. The outer shape of the longitudinal section of the downstream section 61b widens following a rounded contour, then becomes substantially rectilinear. The outlet opening 63 has a surface smaller than the surface of the inlet opening 62 corresponding to the size of the filter 64. The inlet opening 62 may have the bulge described

FIG. 14 represents a filtering device 70 comprising a pipe 71 and a filter 74. The pipe 71 comprises an upstream section 71a and a downstream section 71b having a length equal to that of the upstream section 71a. The interior volume of the upstream section 71a has, in the horizontal longitudinal plane, a trapezoidal section symmetrical with respect to the longitudinal axis X of the duct 70, and widening downstream as far as the filter 74 of the angle a1. The interior volume of the downstream section 71b has, in the horizontal longitudinal plane, a trapezoidal section symmetrical with respect to the longitudinal axis X, and widening upstream as far as the filter 74 at an angle a2 with respect to the longitudinal axis X. On the outside, the longitudinal section of the upstream section 71 has a domed shape, tapering at the inlet opening 72 and at the level of the filter 74, and thicker near the middle of the upstream section . The outer shape of the longitudinal section of the downstream section 71b is substantially rectilinear with a thickness which may be substantially constant. The outlet opening 73 has a surface area smaller than the surface area of the inlet opening 72, and the area of the inlet opening 72 is smaller than the surface area of the cross section of the duct 71 at the location of the filter 74.

According to an exemplary embodiment, the angle a1 is between 0 and 20° and the angle a2 is between 7 and 20°. In the example of Figure 14, the angles a1 and a2 are between 4 and 9°, for example equal to 6°.

FIG. 15 represents a filtering device 80 comprising a conduit 81 and a filter 84. The conduit 81 comprises only an upstream section 81a. The interior volume of the upstream section 81a has, in the horizontal longitudinal plane, a trapezoidal section symmetrical with respect to the longitudinal axis X, and widening downstream to the filter 84 of the angle a1. On the outside, the longitudinal section of the upstream section 81 has a rounded shape, tapered at the inlet 82 and outlet 83 openings, and thicker between the openings 82, 83. The outlet opening 83 corresponding to the size of the filter 84 has a surface greater than the surface of the inlet opening 82.

FIG. 16 represents a filtering device 90 comprising a conduit 91 and a filter 94. The conduit 91 differs from the conduit 71 in that it has an outlet opening 93 having a surface greater than the surface of the inlet opening. 92.

To assess the effectiveness of the filtration devices described above, comprising a filter arranged in a pipe, it is necessary to consider the drag of the filter device when it is dragged through the water, for example by a ship. The drag results from four additive components, namely the filter pressure drag and viscous drag, and the duct pressure drag and viscous drag. Generally speaking, drag is related to the velocity of the fluid along the walls of the conduit and through the filter. Filter pressure drag is related to the shape of the filter, the aggregate filter mesh area and the cross-sectional area of the filter. The viscous drag of the filter is caused by the friction of the water on the walls formed by the meshes of the filter. It is therefore low because the friction surface is low. The viscous drag of the pipe depends on the friction surface of the fluid on the inner and outer walls of the pipe. The pressure drag depends on the shape and cross-sectional area of the duct. Various simulations were carried out to evaluate the performance of the various profiles presented with reference to figures 1 and 12 to 16, by fixing the speed of the fluid around the pipe at 11 m/s, i.e. 21.38 knots, and by fixing the cumulative surface meshes of the filter to 50% of the total surface of the filter, these surfaces being considered in a transverse plane. The results collated in Table 1 below were obtained with a flat filter placed in the circular section duct, in an inclined position, the upstream face of the filter being oriented upwards. The results collated in Table 2 below were obtained with a flat filter placed perpendicular to the longitudinal axis X of the duct.

[Table 1]

[Table 2

The first column of tables 1 and 2 contains the references of the filtering devices as used in FIGS. 1 and 12 to 16. Columns 2 and 3 of tables 1 and 2 bring together the pressure and viscous drag values of the filter. Columns 4 and 5 of tables 1 and 2 bring together the pressure and viscous drag values of the duct. Column 6 contains the sum of the drag values indicated in the columns 2 to 5. It should be noted that the negative drag values correspond to a force contributing to the advancement of the device in the fluid, and are obtained thanks to the bulge formed by the outer surface of the upstream section of the duct. Column 7 gathers the fluid flow rate values at the conduit outlet. Finally, the last column indicates the values of the airflow to total drag ratio allowing the efficiency of the different profiles to be compared.

It emerges from Tables 1 and 2 that the inclined arrangement of the filter is generally more favourable, and that the profiles of the filtering devices 10, 50 and 60 perform better than the profiles of the filtering devices 70, 80, 90. should also be observed that the profile of the filtering device 80 aimed at limiting the pressure of the fluid at the level of the filter, is the least effective. Furthermore, if we compare the performance of the profiles of the filtering devices 70 and 90, the provision of an outlet opening with a smaller surface than the inlet opening makes it possible to increase the performance of the profile.

It will clearly appear to those skilled in the art that the present invention is capable of various variant embodiments and various applications. In particular, the invention is not limited to a device towed or pushed by a ship. Indeed, the device can be fixed relative to a structure channeling the flow of fluid, for example fixed to a fixed structure holding the device in a watercourse.

Furthermore, the internal section of the duct can be of any shape, for example circular, elliptical, square, rectangular, trapezoidal, triangular, polygonal or a shape combining these shapes.

In addition, the filter can have meshes of different sizes, for example a larger mesh to allow the passage of plankton. The filter also does not necessarily cover the entire surface of the duct section. Also, several filters can be arranged in series in the duct, spaced along the longitudinal axis X.

Claims

1. Filtering device comprising a conduit (11, 31, 41, 51, 61, 71) intended to be immersed in a flow of fluid, and a filter (14, 34, 44, 44 ', 54, 64, 74) arranged in the duct to filter the fluid entering the duct, the duct comprising: an inlet opening (12, 32, 42, 52, 62, 72) receiving the flow of fluid, an upstream section (11a, 31a, 41a, 51a, 71a) extending from the inlet opening and housing the filter, an outlet opening (13, 33, 43, 53, 63, 73), and a downstream section (11b, 31 b, 41 b, 51 b, 61 b, 71 b) extending from the filter to the outlet opening, to channel the flow of fluid leaving the filter towards the outlet opening, the downstream section having a length greater than or equal to the length of the upstream section, the outlet opening having a surface smaller than a surface of the inlet opening, the surfaces being considered in a plane perpendicular to a longitudinal axis (X) of the duct .

2. Device according to claim 1, wherein the upstream section (11a, 31a, 41a, 51a, 71a) has in a plane passing through the longitudinal axis (X) of the conduit an internal profile forming with the flow direction an angle of zero or between 0 and 16° towards the longitudinal axis of the duct.

3. Device according to one of claims 1 and 2, wherein the conduit (11, 31, 41, 51) has a bulge on its outer face around the inlet opening (12, 32, 42, 52) , the bulge having at the inlet opening a tangent (T1) forming an angle greater than 45° with respect to the longitudinal axis (X) of the duct (11, 31, 41, 51).

4. Device according to one of claims 1 to 3, wherein the downstream section (11b, 31b, 41b, 51b, 61b, 71b) has in a plane passing through the longitudinal axis (X) of the duct a straight or curved internal profile and forming with the direction of the flow an angle comprised between 0 and 20, and preferably comprised between 4 and 9°.

5. Device according to one of claims 1 to 4, wherein the surface of the outlet opening (13, 33, 43, 53, 63, 73) is adjusted so that the speed of the fluid flow in conduit outlet is between 80 and 110% of the fluid velocity around the outlet opening.

6. Device according to claim 5, in which the surface of the outlet opening (13, 33, 43, 53, 63, 73) is between 0.1 and 5 times the total passage surface of the fluid through the filter (14, 34, 44, 44', 54,

64, 74).

7. Device according to one of claims 1 to 6, wherein the conduit (11, 31, 41, 51, 61, 71) has a section of circular, elliptical, trapezoidal, triangular, polygonal, square or rectangular shape, or a form composed of these forms.

8. Device according to one of claims 1 to 7, comprising a grid (23, 17, 47) arranged in front of the filter (14, 34, 44, 44 ', 54, 64, 74) and having a passage surface of the flow of fluid greater than the passage surface of the filter, the grid being arranged in the duct, or else in front of the opening of the duct to provide a filter and/or breakwater function, the grid being associated or not with a cleaning or suction device (16, 36, 46) for removing debris retained by the screen.

9. Device according to one of claims 1 to 8, comprising at least one filter having one of the following characteristics: the filter (14) has a conical or pyramidal shape, the filter (14) has a conical or pyramidal shape and a debris evacuation opening (24) at the top of the conical or pyramidal shape, the filter (34) is flat and arranged perpendicular to the longitudinal axis (X) of the duct (31), the filter (34) is flat and disposed inclined with respect to the longitudinal axis of the duct, the filter (44') has a plurality of juxtaposed grooves with a V-shaped cross section, each face of the filter has a convex part and a concave part, the filter is formed of parallel rods, and the filter has profiled rods or meshes in order to reduce the drag of the filter.

10. Device according to one of claims 1 to 9, wherein the filter (14, 34, 44, 44 ') is associated with a cleaning device (15, 35) or a suction device, to evacuate debris retained by the filter.

11. Device according to one of claims 1 to 10, comprising a member (19, 39, 49) configured to push the device upwards when the device is completely submerged in the body of water, and a member configured to push the device down when the device is not completely submerged in the body of water.

12. Method for collecting solid debris in the vicinity of the surface of a body of water, the method comprising steps consisting in: providing a filtering device according to one of claims 1 to 11, and associating the filtering device to a structure maintaining the conduit (11, 31, 41, 51) of the filtering device immersed on the surface of the body of water in a flow of water, or else associating the filtering device with a ship so as to maintain the conduit (11, 31, 41, 51) of the submerged filtering device on the surface of the body of water, and setting the vessel in motion at cruising speed in order to generate a flow of water in and around the conduit of the device of filtering.

13. Method according to claim 12, comprising a step of collecting debris in a reservoir (21, 22, 21', 22', 21", 22", 48, 48').

14. Method according to claim 12 or 13, in which the flow of water has a speed of between 1 and 15 m/s.