US20240093452A1

US20240093452A1 - Filtering device for collecting debris at the surface of bodies of water

Info

Publication number: US20240093452A1
Application number: US18/276,445
Authority: US
Inventors: Pascal CREPET; Guillaume Raymond
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-02-10
Filing date: 2022-02-10
Publication date: 2024-03-21
Also published as: FR3119627B1; CN116888326A; EP4291723A1; WO2022171962A1; FR3119627A1

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

The present invention relates to the collection of solid debris floating at the surface or near the surface of bodies of water such as oceans, seas, rivers and lakes.
Numerous solutions have been proposed. In general, these solutions consist of an autonomous device dedicated to collecting floating waste. Such a device comprises its own means of propulsion, making it costly to manufacture, to operate and to maintain.
Devices able to be towed by ships have also been proposed. Such a device is, for example, described in patent EP 2 812 498. That device comprises a duct positioned at the surface of the body of water in the direction of travel of the ship. The duct has a width that increases from the inlet of the duct to the inlet of a filter, in an attempt to reduce the drag of the filter and thus limit the excess energy consumption of the ship as caused by the presence of the device towed on the surface of the body of water. That device has the disadvantage of being able to be used only at low speed, less than 2 m/s, notably in order to maintain its ability to guide the incoming fluid toward the filter. It proves unsuitable for equipping ships generally travelling at more than 2 m/s. Further, at such speeds, the duct arranged around the filter introduces drag that may exceed that of the filter.
Specifically, it is found that the greater the extent to which the velocity of the water surrounding the fluid is reduced in an attempt to reduce the drag of this filter, the more the drag of the guide elements around the filter increases.
It is therefore desirable to propose a filtering device that is effective at collecting waste at the surface of a body of water, without requiring propulsion means. It is also desirable to increase as far as possible the ratio between the flow rate of filtered water and the force of drag generated by the filtering device when it is towed in the immersed state. It is also desirable for the filtering device to be able to equip any ship, and therefore be able to be driven at speeds greater than 2 m/s. To this end, the device needs to be able to withstand the impact of waves travelling at high speed, and be protected against large waste items that may obstruct the filter inlet.
Some embodiments relate to a filtering device comprising: a pipe intended to be immersed in a flow of fluid, and a filter arranged in the pipe to filter the fluid that enters the pipe, the pipe 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 as far as the outlet opening in order to convey the flow of fluid leaving the filter toward 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 less than a surface area of the inlet opening, the surface areas being considered in a plane perpendicular to a longitudinal axis of the pipe.
According to one embodiment, the upstream section has, in a plane passing through the longitudinal axis of the pipe, an internal profile which, with the direction of the flow, makes a zero angle or angle comprised between 0 and 16° toward the longitudinal axis of the pipe.
According to one embodiment, the pipe has a bulge on its exterior face around the inlet opening, the bulge having, at the inlet opening, a tangent that makes an angle greater than 45° with respect to the longitudinal axis of the pipe.
According to one embodiment, the downstream section has, in a plane passing through the longitudinal axis of the pipe, an internal profile that is rectilinear or curved and that, with the direction of the flow, makes an angle of between 0 and 20° and preferably of between 4 and 9°.
According to one embodiment, the surface area of the outlet opening is tailored such that the velocity of the flow of fluid at the pipe outlet is comprised between 80 and 110% of the velocity of the fluid around the outlet opening.
According to one embodiment, the surface area of the outlet opening is comprised between 0.1 and 5 times the total surface area for the passage of the fluid through the filter.
According to one embodiment, the pipe has a cross section of circular, elliptical, trapezoidal, triangular, polygonal, square or rectangular shape or of a shape made up of these shapes.
According to one embodiment, the device comprises a grating positioned in front of the filter and having a surface area for the passage of the flow of liquid that is greater than the passage surface area of the filter, the grating being positioned in the pipe, or else in front of the opening of the pipe so as to act as a filter and/or a breakwater, the grating potentially being associated with a cleaning or suction device for removing the debris caught by the grating.
According to one embodiment, the device comprises at least a filter exhibiting one of the following features: the filter has a cone or pyramid shape, the filter has a cone or pyramid shape and a debris discharge opening at the vertex of the cone or pyramid shape, the filter is planar and arranged perpendicular to the longitudinal axis of the pipe, the filter is planar and arranged inclined with respect to the longitudinal axis of the pipe, the filter exhibits a plurality of juxtaposed grooves of V-shaped normal cross section, each face of the filter exhibits a convex part and a concave part, the filter is made up of parallel rods, and the filter comprises rods or meshes that are profiled so as to reduce the drag of the filter.
According to one embodiment, the filter is associated with a cleaning device or with a suction device, to remove the debris caught by the filter.
According to one embodiment, the device comprises a member configured to push the device upward when the device is fully immersed in the body of water, and a member configured to push the device downward when the device is not fully immersed in the body of water.
Some embodiments may also relate to a method for collecting solid debris near the surface of a body of water, the method comprising steps consisting in: providing a filtering device as described hereinabove, and associating the filtering device with a structure that keeps the pipe of the filtering device immersed at the surface of the body of water in a flow of water, or else associating the filtering device with a ship so as to keep the pipe of the filtering device immersed at the surface of the body of water, and moving the ship at a cruising speed so as to generate a flow of water in and around the pipe 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 velocity of between 1 and 15 m/s.

Exemplary embodiments of the invention will be described in what follows, nonlimitingly and in connection with the attached figures among which:

FIG. 1 depicts, in longitudinal section on a vertical plane, a filtering device according to one embodiment,

FIG. 2 is a perspective view of a filtering device according to another embodiment,

FIG. 3 is a view in longitudinal section, on a vertical plane, of the filtering device of FIG. 2 , according to one embodiment,

FIG. 4 is a view in longitudinal section of a filter of the filtering device, according to one embodiment, and FIG. 4A is a detailed sectional view of part of the filter shown in FIG. 4 ,

FIG. 5 is a perspective view of the filtering device according to another embodiment,

FIG. 6 is a view in longitudinal section, on a vertical plane, of the filtering device of FIG. 5 , according to one embodiment,

FIG. 7 is a view in longitudinal section, on a vertical plane, of the filtering device according to another embodiment,

FIG. 8 is a perspective view of the filtering device according to another embodiment,

FIGS. 9A and 9B are views in longitudinal section, on a vertical plane and on a horizontal plane, of the filtering device of FIG. 8 according to one embodiment,

FIG. 10 is a perspective view of a filter of the filtering device according to another embodiment,

FIGS. 11A and 11B are views, from above and in longitudinal section, on a horizontal plane and on a vertical plane respectively, of a filtering device according to another embodiment,

FIG. 14 FIGS. 12 to 14 are views in longitudinal section, on a vertical plane, of filtering devices according to various other embodiments,

FIGS. 15 and 16 are views in longitudinal section, on a vertical plane, of filtering devices according to the prior art.

FIG. 1 depicts a filtering device 10 according to one embodiment. The device 10 comprises a filter 14 arranged in a tubular pipe 11 comprising an upstream section 11 a conveying a flow of fluid that is to be filtered and that has entered via an inlet opening 12 of the pipe, and a downstream section 11 b conveying a flow of filtered fluid toward an outlet opening 13 of the pipe. The filter 14 is arranged in the pipe between the upstream and downstream sections, so as to receive the flow of fluid that is to be filtered.
The filtering device 10 may be used immersed in a flow of fluid, for example towed or pushed along beneath the surface 1 of a body of water, or held fixed beneath the surface of a water course. It may be noted that it is possible for only the inlet opening 12 of the device to be immersed, the longitudinal axis X of the device 10 being kept at an angle less than 25° with respect to the surface 1 of the water.
According to one embodiment illustrated in FIG. 1 , the upstream section 11 a delimits an internal volume of cylindrical shape having a cross-sectional area that remains constant between the inlet opening 12 and the inlet of the filter 14. Thus, the total surface area of the filter may be identical to the surface area of the inlet opening 12. The downstream section 11 b delimits an internal volume of frustoconical shape with an internal cross section that narrows from the outlet of the filter 14 to the outlet opening 13. The internal volume of the downstream section may exhibit other shapes such as that of a hyperboloid of revolution.
The exterior surface of the pipe 11 may exhibit, around the inlet opening 12, a bulging profile that widens from the inlet opening 12. The bulging profile has a tangent T1 to the edge of the opening 12 that converges toward the plane of the opening, which is to say that forms an angle θ with the longitudinal axis X that is greater than 45° and preferably greater than 65°. At the junction between the upstream section 11 a and downstream section lib, the profiles of these sections have the same tangent. It may be noted that such a profile generates drag in the opposite direction to the direction of the flow 2, which is to say that encourages the device to move through the flow. In the example of FIG. 1 , this bulging profile widens as far as approximately mid-way along the length of the upstream section 11 a and then narrows as far as the outlet opening 13. According to one embodiment, the ratio between the length of the interior profile and the length of the exterior profile of the upstream section 11 a is comprised between 0.7 and 1.0. The bulge thus created increases the length of the path taken by the fluid and therefore increases the velocity of this fluid around the upstream section 11 a. The result of this is that the pressure around the upstream section 11 a decreases, creating positive drag. This then gives the tubular pipe 11 better hydrodynamic performance, this being true regardless of the velocity of the fluid in and around the pipe.
According to one embodiment, the upstream section 11 a exhibits, in a plane passing through the longitudinal axis X of the pipe, an internal profile that is curved or rectilinear and that, with the direction of the flow, makes an angle of between 0° and 16° and preferably between 4 and 9°. These features contribute to reducing the drag acting in the direction of the flow 2.
According to one embodiment, the downstream section 11 b exhibits, in a plane passing through the longitudinal axis X of the pipe 11, an internal profile which is rectilinear or curved and that, with the direction of the flow, makes an angle α of between 0 and 20°.
According to one embodiment, the downstream section 11 b comprises a section 11 c that has a circular internal cross section the downstream end of which delimits the opening 13. The size of the internal cross section of the section 11 c is such that the edge of the opening 13 is tapered. The zone of transition between the frustoconical internal part and the cylindrical internal part 11 c of the downstream section 11 b may have a rounded external profile, so as to delay the possible separation of the fluid from the external wall of the pipe 11 in this zone.
According to one embodiment, the surface area of the outlet opening 13 is defined in such a way that the velocity of the fluid at the outlet of the pipe 11 is comprised between 80 and 110%, and preferably equal to 100%, of the velocity of the fluid around the outlet opening 13. In this way, the shear that appears at the interface between the fluid leaving via the outlet opening 13 and the fluid external to the pipe is reduced, making it possible to reduce the drag exerted on the pipe 11. The surface area of the outlet opening 13 may be tailored by altering the length of the downstream section 11 b and altering the angle α. Moreover, the velocity of the flow in the pipe is dependent on characteristics of the filter and particularly dependent on the drag coefficient thereof. The lower this coefficient, the more the length of the downstream pipe 11 b can be reduced, and this likewise reduces the drag of the downstream pipe. Moreover, the lower the coefficient of drag of the filter, the higher the velocity of the fluid through the filter can be. Thus, the outlet opening 13 can be larger.
The filter 14 has pores or meshes through which the fluid can flow. In what follows, the “passage surface area” of the filter refers to the sum of the surface areas of the pores or meshes of the filter. According to one embodiment, the outlet opening 13 has a surface area smaller than the passage surface area of the filter 14, so as to reduce the difference between the velocity of the fluid at the outlet 13 of the pipe 11 and the velocity of the fluid around the pipe outlet.
The outlet opening 13 may have a surface area of between 0.1 times and 5 times the surface area for passage of the fluid through the filter 14, depending on the characteristics of the filter.
The meshes of the filter may be delimited by a wire of circular cross section. According to one embodiment, the wire delimiting the meshes of the filter has a hydrodynamic profile (lower coefficient of drag) facing into the direction of flow of the fluid 2, as illustrated by FIG. 4A.
According to an embodiment illustrated in FIGS. 2 and 3 , the filtering device 10 comprises a grating 17 (or several gratings 17) positioned in front of the filter 14 to prevent excessively bulky debris from entering the pipe 11 and reaching the filter, and to direct this debris toward a debris storage reservoir 22 which may be fixed above the pipe 11. The grating 17 comprises parallel rods that are inclined at the top toward the rear of the pipe 11 up to an inlet of the reservoir 22 so that the debris can be driven toward the reservoir 22 under the effect of the flow of fluid 2. For this purpose, the pipe 11 has an upper opening 26 through which the rods of the grating 17 pass. The grating 17 may have a surface area for the passage of the flow of liquid that is greater than the passage surface area of the filter 14. According to one embodiment, the rods that form the grating 17 have a hydrodynamic profile so as to minimize the drag they induce under the effect of the flow of fluid 2.
According to one embodiment, a profiled element 27 intended to act as a breakwater and a deflector to divert the large debris is held across the inlet opening 12 by rods 23. The profiled element 27 may have a hydrodynamic profile so as to limit its drag.
According to one embodiment illustrated by FIGS. 3 and 4 , the filter 14 has the shape of a cone the axis of which substantially coincides with the axis X of the pipe 11. The filter 14 has an opening at the vertex of its cone shape, this opening being positioned downstream in the pipe 11 and opening into a pipe 24. The shape of the filter 14 allows the collected debris to be ducted toward the pipe 24 under the effect of the flow of fluid passing through the filter. According to one embodiment, the discharge pipe 24 opens into a debris collecting reservoir 21, which may be fixed above the pipe 11. The pipe 24 may be arranged in such a way that the flow of fluid entering the pipe 11 and then the pipe 24 carries the debris into the reservoir 21 or into the reservoir 22 that forms a single reservoir positioned or fixed above the pipe 11.
According to one embodiment illustrated by FIGS. 1 to 3 , the inlet opening 12 is centered on the longitudinal axis of the pipe 11. In the example of FIG. 1 , the pipe 11 exhibits symmetry of revolution about its longitudinal axis X (if the opening 26 is disregarded).
Moreover, when considering the bulging shape of the profile of the upstream section 11 a and the frustoconical shape of the downstream section 11 b, each angular sector (about the longitudinal axis X of the pipe) of the pipe 11 has a tendency to exert thrust toward the outside of the pipe in a direction perpendicular to the internal surface of the pipe. When the pipe 11 is fully immersed in the fluid, the thrusts exerted by the various sectors of the pipe are in equilibrium with one another. By contrast, when for example the upper part of the pipe 11 emerges from the fluid, this equilibrium disappears because the upper sector of the pipe is no longer exerting upward thrust. The result of this is that the lower sector of the pipe has a tendency to drive the pipe 11 downward, to a fully immersed position.
According to one embodiment, the upper part of the pipe 11 is longer than the lower part thereof. Thus, the pipe has a tendency to rise above the surface of the water, because of the fact that the thrust exerted by the upper part of the pipe is greater than the thrust exerted by the lower part of the pipe. When the pipe is partially emerged, it has a tendency to drop back beneath the surface of the water because of the fact that the thrust exerted by the lower part of the pipe is greater than the thrust exerted by the emerged upper part of the pipe. Thus, the pipe is automatically kept near the surface of the water. This effect may also be obtained by adjusting the bulge of the upper part of the upstream section 11 a. This effect may also be obtained using fins fixed on the external face of the pipe, on the top, at the front or at the rear of the pipe, or on each side of the pipe 11 (fins 19 in FIG. 2 ) so as to remain immersed, and oriented in such a way as to exert an upward thrust that is less than or equal to the downward thrust exerted by the pipe when it is only partially immersed.
FIG. 4 depicts the filter 14 according to one embodiment. The filter 14, in the shape of a cone, is associated with a cleaning device 15 comprising a brush configured to brush the meshes of the filter 14, and to rotate on itself about the longitudinal axis of the filter 14, the debris being driven toward the vertex of the cone shape so that they can be removed by the pipe 24 under the effect of the flow of fluid. The thrusting force of the flow of fluid passing through the filter can be used to drive the rotation of the brush.
According to another embodiment, the cleaning device is fixed and the filter 14 rotates about its longitudinal axis. The removal of debris toward the pipe 24 may be achieved or facilitated by applying vibration to the filter.
According to another embodiment, the filter exhibits, on an opposite side to the direction of the flow, a convex part formed in a concave part. Thus, the filter may exhibit a frustoconical part with a large base and a small base coupled to an end part of conical shape, the vertex of the cone shape extending toward the large base of the frustoconical shape. Thus, in a plane perpendicular to the plane that contains the large base of the frustoconical part and that passes through the vertex of the cone shape, the filter exhibits a W-shaped cross section.
FIGS. 5 and 6 depict a filtering device 30 according to another embodiment. The filtering device 30 differs from that of FIG. 2 in that it comprises a pipe 31 of rectangular cross section with inlet and outlet openings 32 and 33 of rectangular shape. The filter 14 is replaced by a filter 34. The filter 34 may be associated with a cleaning device 35 in the form of a roller brush moving between the lower and upper parts of the filter 34 to drive the debris on the filter toward a reservoir 21′.
The filtering device 30 may also comprise a set of parallel rods 37, which is fixed in the pipe 31 between the inlet opening 32 and the filter 34. The rods 37 are able to remove the large debris toward a reservoir 22′ positioned above the pipe 31. To do that, each of the rods 37 has an inclined part in front of the opening 32 of the pipe 31 so that the upper part of the rod is further downstream relative to the pipe 31 than a lower part of the inclined part of the rod. Thus, debris caught by the rods 37 can be diverted upward into the reservoir 22′ under the effect of the flow of fluid. For that purpose, the pipe 31 has an upper opening 26′ through which the rods 37 pass. The rods 37 may exhibit a surface area for the passage of the flow of fluid that is greater than the passage surface area of the filter. The rods 37 may for example exhibit a surface area for the passage of the flow of fluid that is greater than 70% of the normal cross sectional area of the pipe. According to one embodiment, the rods 37 are profiled so as to minimize the drag they induce under the effect of the flow of fluid 2.
According to one embodiment, a profiled element 27′ intended to divert the 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 that moves along the rods in order to drive the debris toward the reservoir 22′.
According to one embodiment, the rods have a hydrodynamic profile facing into the direction of the flow 2 of fluid.
According to one embodiment, the pipe 31 is associated with lateral fins 39 arranged in such a way as to keep the pipe 31 immersed just below the surface 1 of the fluid, as illustrated in FIG. 5 . Fins may also be placed on the top, front, rear or underside of the pipe 31.
According to various embodiments, the filter 44 is planar and arranged in the pipe 41 like the filter 34 in the pipe 31, in a position that is inclined toward an opening provided in an upper part of the pipe 41, or in a space formed between the external and internal faces of the pipe 31. The filter 44 may also have the form of the filter 14 coupled to a pipe for discharging debris to a reservoir.
According to another embodiment illustrated in FIG. 7 , the pipe 31′ and in particular the upper external face of the pipe is configured in such a way as to house the set of rods 37 and the reservoirs 21″, 22″. Thus, the upper external face of the pipe may for example be bulged to accommodate this. In such a case, the opening 26 is unnecessary and may be omitted.
FIGS. 8, 9A and 9B depict a filtering device 40 according to another embodiment. The filtering device differs from that of FIG. 2 in that it comprises a pipe 41 of rectangular cross section with inlet and outlet openings 42 and 43 of rectangular shape. The filter 14 is replaced by a filter 44. The filter 44 may 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 may also comprise a set of parallel rods 47 which is fixed on the outside of the pipe 41 facing the inlet opening 42. The rods 47 act as a breakwater and are able to remove large debris to a reservoir 48 positioned above the pipe 41. For that purpose, each of the rods 47 has a part that is inclined in front of the opening 42 of the pipe 41 so that the upper part of the rod is further downstream relative to the pipe 41 than a lower part of the inclined part of the rod. Thus, debris caught by the rods 47 can be diverted upward 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 downstream and slightly inclined with respect to the horizontal.
According to one embodiment, the gratings 47 are also associated with a cleaning device 46 moving along the rods to drive the debris caught by the gratings toward the reservoir 48.
According to one embodiment, the rods 47 have a hydrodynamic profile facing into the direction of the flow 2 of fluid.
According to one embodiment, the pipe 41 is associated with lateral fins 49 arranged as illustrated in FIGS. 8 and 9B in order to keep the pipe 41 immersed just below the surface 1 of the fluid.
According to various embodiments, the filter 44 is planar and arranged in the pipe 41 like the grating 17 in the pipe 11, in a position inclined toward an opening made in an upper part of the pipe 41. The filter 44 may also have the form of the filter 14 coupled to a pipe for discharging the debris to a reservoir.
According to one embodiment, the filter 44 and the rods are substantially parallel and inclined with respect to the longitudinal direction X of the pipe, and the pipe is configured in such a way that the plane of the inlet opening 42 is parallel to the filter. Thus, if the filter and the rods are inclined upward, the lower part of the pipe extends further in the upstream direction than the upper part of the pipe.
FIG. 10 depicts a filter 44′ according to another embodiment. The filter 44′ exhibits a plurality of juxtaposed grooves of V-shaped normal cross section. The filter 44′ may be arranged in the pipe 41 in such a way that its grooves are oriented in a vertical longitudinal plane of the pipe and inclined at the top toward the rear of the pipe 44. The filter 44′ may be associated with a cleaning brush arranged horizontally and having a shape that conforms to the cross-sectional shape of the filter in a horizontal plane. The filter 44′ may be cleaned by moving the brush between the lower and upper parts of the filter 44′.
According to other embodiments, the filter has the shape of a pyramid of square or rectangular cross section, with a pointed or rectilinear-edge vertex. Thus, in order to be made to suit the filtering device 40, the filter may be of pyramid shape with a rectangular cross section and a vertex in the form of a straight-line segment.
According to one embodiment, the filter is cleaned by a suction system coupled to a reservoir (for example 21, 21′ or 48) and comprising a pump connected to a hose the end of which is moved along the surface of the filter. The reservoir that collects the debris may also be connected by piping to a more capacious reservoir.
According to one embodiment, the filter has no meshes but is made up of parallel rods, for example arranged vertically. It has been found that such a filter is easier to clean and generates less drag. The rods or the meshes that form the filter may be profiled in order to reduce the filter drag.
FIGS. 11A and 11B depict a filtering device according to another embodiment. The filtering device comprises the pipe 41 described with reference to FIGS. 8, 9A and 9B, and a set of parallel rods 47′ which are held in front of the upstream opening of the pipe 41 by two floats 9, the pipe 41 being anchored to the floats 9 for example by cables 8. The rods 47′ are able to remove large debris to a reservoir 48′ fixed above the floats 9. For this purpose, the rods 47′ are inclined in front of the opening 42 of the pipe 41 so that the upper part of the rods is further downstream relative to the pipe 41 than a lower part of the rods. Thus, the debris caught by the rods 47′ can be deflected upward 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 that moves along the rods to drive the debris toward the reservoir 48′.
The rods 47′ may exhibit a hydrodynamic profile so as to minimize their drag. Further, the rods 47′ may be hollow so as to be buoyant thus minimizing the volume of the floats 9 and therefore the drag thereof.
According to one embodiment, the filter present in the embodiments described hereinabove may be flexible and rolled around rollers at the top and bottom of the pipe 11, 31, 41. A fixed rotary brush is able to clean the filter as it moves upwards or downwards wound onto one of the rollers.
The filter may also be cleaned using a delivery pump emitting a jet of water in the opposite direction to the direction of flow 2 of the fluid.
According to one embodiment, the floats 9 are replaced by one or more fins connected to the grating formed by the rods 47′ so as to create lift and to keep the grating at the desired height, with one part immersed and one part emerged.
FIGS. 12 to 16 depict various profiles of pipes of the filtering device, according to various embodiments. FIG. 12 depicts a filtering device 50 comprising a pipe 51 and a filter 54. The pipe 51 comprises an upstream section 51 a and a downstream section 51 b having a length comprised between 7 and 9 times the length of the upstream section 51 a. The interior volume of the upstream section 51 a exhibits, in a horizontal longitudinal plane, a trapezoidal cross section that is symmetrical about the longitudinal axis X of the pipe 50, widening in the downstream direction as far as the filter 54 of an angle α1. The interior volume of the downstream section 51 b exhibits, in the horizontal longitudinal plane, a trapezoidal cross section that is symmetrical about the longitudinal axis X and that widens in the upstream direction as far as the filter 54 by an angle α2 with respect to the longitudinal axis X. On the outside, the longitudinal section of the upstream section 51 a exhibits a rounded shape widening as far as the location of the filter 54. The exterior shape of the longitudinal cross section of the downstream section 51 b is substantially rectilinear or slightly outwardly curved. The outlet opening 53 has a surface area smaller than the surface area of the inlet opening 52 and the surface area of the inlet opening 52 is smaller than the normal cross sectional area of the pipe 50 at the location of the filter 54.
FIG. 13 depicts a filtering device 60 comprising a pipe 61 and a filter 64. According to one embodiment, the pipe 61 comprises only a downstream section 61 b. The interior volume of the downstream section 61 b exhibits, in the horizontal longitudinal plane, a trapezoidal cross section that is symmetrical about the longitudinal axis X, widening in the upstream direction as far as the filter 64 by the angle α2 with respect to the longitudinal axis X. The exterior shape of the longitudinal section of the downstream section 61 b widens, following a curved contour, then becomes substantially rectilinear again. The outlet opening 63 exhibits a surface area smaller than the surface area of the inlet opening 62 corresponding to the size of the filter 64. The inlet opening 62 may exhibit the bulge described.
FIG. 14 depicts a filtering device 70 comprising a pipe 71 and a filter 74. The pipe 71 comprises an upstream section 71 a and a downstream section 71 b having a length equal to that of the upstream section 71 a. The interior volume of the upstream section 71 a exhibits, in the horizontal longitudinal plane, a trapezoidal cross section that is symmetrical about the longitudinal axis X of the pipe 70 and that widens in the downstream direction as far as the filter 74 by the angle α1. The interior volume of the downstream section 71 b exhibits, in the horizontal longitudinal plane, a trapezoidal cross section that is symmetrical about the longitudinal axis X and widens in the upstream direction as far as the filter 74 by an angle α2 with respect to the longitudinal axis X. On the outside, the longitudinal section of the upstream section 71 a exhibits a bulging shape, tapered at the inlet opening 72 and at the filter 74, and thicker near the middle of the upstream section. The exterior shape of the longitudinal section of the downstream section 71 b is substantially rectilinear with a thickness that may be substantially constant.
The outlet opening 73 has a surface area smaller than the surface area of the inlet opening 72, and the surface area of the inlet opening 72 is less than the normal cross sectional area of the pipe 71 at the location of the filter 74.
According to one exemplary embodiment, the angle α1 is comprised between 0 and 20° and the angle α2 is comprised between 7 and 20°. In the example of FIG. 14 , the angles α1 and α2 are comprised between 4 and 9°, for example equal to 6°.
FIG. 15 depicts a filtering device 80 comprising a pipe 81 and a filter 84. The pipe 81 comprises only an upstream section 81 a. The interior volume of the upstream section 81 a exhibits, in the horizontal longitudinal plane, a trapezoidal cross section that is symmetrical about the longitudinal axis X and that widens in the downstream direction as far as the filter 84 by the angle α1. On the outside, the longitudinal section of the upstream section 81 a has a rounded shape, tapered at the inlet and outlet openings 82 and 83 and thicker between the openings 82, 83. The outlet opening 83 which corresponds to the size of the filter 84 has a surface area greater than the surface area of the inlet opening 82.
FIG. 16 depicts a filtering device 90 comprising a pipe 91 and a filter 94. The pipe 91 differs from the pipe 71 in that it has an outlet opening 93 having a surface area greater than the surface area of the inlet opening 92.
In order to evaluate the effectiveness of the filtration devices described hereinabove, comprising a filter arranged in a pipe, it is necessary to consider the drag of the filtering device when it is driven through the water for example by a ship. The drag is the result of four components that are summed with one another, namely the pressure drag and the viscous drag of the filter, and the pressure drag and the viscous drag of the pipe. In general, drag is associated with the velocity of the fluid along the walls of the pipe and through the filter. The pressure drag of the filter is associated with the shape of the filter, the combined surface area of the meshes of the filter, 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 area is small. The viscous drag of the pipe is dependent on the area over which the fluid rubs with friction over the interior and exterior walls of the pipe. The pressure drag is dependent on the shape and cross sectional area of the pipe.
Various simulations were conducted in order to evaluate the performance of the various profiles set out with reference to FIGS. 1 and 12 to 16 , fixing the velocity of the fluid around the pipe at 11 m/s, namely 21.38 knots, and setting the cumulative surface area of the meshes of the filter at 50% of the total surface area of the filter, these areas being considered in a transverse plane. The results collated in table 1 below were obtained with a planar filter placed in the circular-section pipe in an inclined position with the upstream face of the filter being directed upward. The results collated in table 2 below were obtained with a planar filter placed perpendicular to the longitudinal axis X of the pipe.

TABLE 1

	Filter drag	Pipe drag	Total	Flow	Flow
Dev.	(kN)	(kN)	drag	rate	rate/drag

Ref.	Press.	Visc.	Press.	Visc.	(kN)	m³/s	(m³/s/kN)

10	2.941	0.061	−0.670	2.794	5.126	2.55	0.497
50	2.895	0.062	−0.535	2.317	4.739	2.48	0.523
60	2.682	0.053	−0.258	2.110	4.587	2.47	0.538
70	1.827	0.041	−0.535	3.359	4.692	1.88	0.401
80	9.508	0.231	16.216	1.696	27.651	3.76	0.136
90	3.582	0.096	2.495	3.220	9.393	1.98	0.211

TABLE 2

	Filter drag	Pipe drag	Total	Flow	Flow
Dev.	(kN)	(kN)	drag	rate	rate/drag

Ref.	Press.	Visc.	Press.	Visc.	(kN)	m³/s	(m³/s/kN)

10	3.481	0.064	−1.094	2.786	5.237	2.54	0.485
50	3.332	0.062	−0.847	2.314	4.861	2.45	0.504
60	3.527	0.067	−0.588	2.089	5.095	2.4	0.471
70	2.045	0.041	−0.729	3.347	4.704	1.89	0.402
80	10.414	0.229	14.865	1.698	27.206	3.75	0.138
90	3.648	0.089	2.559	3.204	9.5	1.99	0.209

The first column of tables 1 and 2 contain the references of the filtering devices as used in FIGS. 1 and 12 to 16 . Columns 2 and 3 of tables 1 and 2 collate the values for the pressure drag and viscous drag of the filter. Columns 4 and 5 of tables 1 and 2 collate the values for the pressure drag and viscous drag of the pipe. Column 6 contains the sum of the drag values indicated in columns 2 to 5. It should be noted that the negative drag values correspond to a force that contributes to the forward motion of the device through the fluid, and are obtained thanks to the bulge formed by the exterior surface of the upstream section of the pipe. Column 7 collates the values of fluid flow rate at the pipe outlet. Finally, the last column indicates the values of the ratio of flow rate to total drag, enabling a comparison of the effectiveness of the various profiles.
It is apparent from tables 1 and 2 that the inclined position of the filter is generally more favorable, and that the profiles of the filtering devices 10, 50 and 60 perform better than the profiles of the filtering devices 70, 80 and 90. It should also be noted that the profile of the filtering device 80 aimed at limiting the pressure of the fluid at the filter has the poorest performance. Moreover, if the performance of the profiles of the filtering devices 70 and 90 are compared, the provision of an outlet opening of smaller surface area than the inlet opening makes it possible to improve the performance of the profile.
It will be clearly apparent to the person skilled in the art that the present invention is suitable for various embodiment variants and various applications. In particular, the invention is not restricted to a device towed or pushed by a ship. Specifically, the device may be fixed relative to a structure that ducts the flow of fluid, for example fixed to a stationary structure that holds the device in a water course.
Moreover, the internal cross section of the pipe may be of any shape, for example circular, elliptical, square, rectangular, trapezoidal, triangular, polygonal or a shape combining the shapes.
Further, the filter may have meshes of different sizes, for example a coarser mesh to allow the passage of plankton. The filter does not necessarily cover the entire cross sectional area of the pipe. Also, several filters may be arranged in series in the pipe, spaced apart along the longitudinal axis X.

Claims

1. A filtering device comprising:

a pipe intended to be immersed in a flow of fluid, and a filter arranged in the pipe to filter the fluid that enters the pipe, the pipe having:

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 as far as the outlet opening in order to convey the flow of fluid leaving the filter toward 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 less than a surface area of the inlet opening, the surface areas being considered in a plane perpendicular to a longitudinal axis of the pipe.

2. The filtering device as claimed in claim 1, wherein the upstream section has, in a plane passing through the longitudinal axis of the pipe, an internal profile which, with the direction of the flow, makes a zero angle or angle comprised between 0 and 16° toward the longitudinal axis of the pipe.

3. The filtering device as claimed in claim 1, wherein the pipe has a bulge on its exterior face around the inlet opening, the bulge having, at the inlet opening, a tangent that makes an angle greater than 45° with respect to the longitudinal axis of the pipe.

4. The filtering device as claimed in claim 1, wherein the downstream section has, in a plane passing through the longitudinal axis of the pipe, an internal profile that is rectilinear or curved and that, with the direction of the flow, makes an angle of between 0 and 20°.

5. The filtering device as claimed in claim 1, wherein the surface area of the outlet opening is tailored such that the velocity of the flow of fluid at the pipe outlet is comprised between 80 and 110% of the velocity of the fluid around the outlet opening.

6. The filtering device as claimed in claim 5, wherein the surface area of the outlet opening is comprised between 0.1 and 5 times the total surface area for the passage of the fluid through the filter.

7. The filtering device as claimed in claim 1, wherein the pipe has a cross section of circular, elliptical, trapezoidal, triangular, polygonal, square or rectangular shape or of a shape made up of these shapes.

8. The filtering device as claimed in claim 1, comprising a grating positioned in front of the filter and having a surface area for the passage of the flow of fluid that is greater than the passage surface area of the filter, the grating being positioned in the pipe, or else in front of the opening of the pipe so as to act as a filter and/or a breakwater, the grating optionally being associated with a cleaning or suction device for removing the debris caught by the grating.

9. The filtering device as claimed in claim 1, comprising at least a filter exhibiting one of the following features:

the filter has a cone or pyramid shape,

the filter has a cone or pyramid shape and a debris discharge opening at the vertex of the cone or pyramid shape,

the filter is planar and arranged perpendicular to the longitudinal axis (X) of the pipe,

the filter is planar and arranged inclined with respect to the longitudinal axis of the pipe,

the filter exhibits a plurality of juxtaposed grooves of V-shaped normal cross section,

each face of the filter exhibits a convex part and a concave part,

the filter is made up of parallel rods, and

the filter comprises rods or meshes that are profiled so as to reduce the drag of the filter.

10. The filtering device as claimed in claim 1, wherein the filter is associated with a cleaning device or with a suction device, to remove the debris caught by the filter.

11. The filtering device as claimed in claim 1, comprising a member configured to push the device upward when the device is fully immersed in the body of water, and a member configured to push the device downward when the device is not fully immersed in the body of water.

12. A method for collecting solid debris near the surface of a body of water, the method comprising the steps of:

providing a filtering device as claimed in claim 1, and

associating the filtering device with a structure that keeps the pipe of the filtering device immersed at the surface of the body of water in a flow of water, or else

associating the filtering device with a ship so as to keep the pipe of the filtering device immersed at the surface of the body of water, and moving the ship at a cruising speed so as to generate a flow of water in and around the pipe of the filtering device.

13. The method as claimed in claim 12, comprising a step of collecting debris in a reservoir.

14. The method as claimed in claim 12, wherein the flow of water has a velocity of between 1 and 15 m/s.

15. The filtering device as claimed in claim 4, wherein the downstream section has, in a plane passing through the longitudinal axis of the pipe, an internal profile that is rectilinear or curved and that, with the direction of the flow, makes an angle of between 4 and 9°.