Patent Application
20230340743
This patent application claims priority from Australian patent application no. 2022901063, filed on Apr. 22, 2022, the entire disclosure of which is incorporated herein by reference.
The present invention relates to filters and screens, in particular, but not exclusively, to filters and screens for use with systems which abstract water from lakes, rivers or ponds.
Screens or filters (collectively referred to herein as “filters”) which take water from a natural source, for example a pond or river, become clogged over time and need to be cleaned. Many such filters are provided with a self-cleaning mechanism which periodically cleans the filter media.
Typically, in the filters of the prior art, the filter or screen medium closest to the filter outlet pipe accumulates particulates faster than the rest of the filter media. This reduces the surface area available for water flow through the filter media, which consequently increases the velocity of the water flowing through the remainder of the filter media. This may cause higher “head loss” (pressure drop) over the filter, which may increase the cost of operating an associated pump. Furthermore, particles which are embedded into the filter media at a high velocity may be more difficult to remove with a self-cleaning mechanism.
Some filters, for example filters which take water from sources which are habitats for living creatures (e.g. fish), may also be required to meet certain parameters regarding maximum allowable water velocity perpendicular to the filter media (e.g. to reduce the risk of harm to the wildlife). For example, in some cases the velocity of the water in a direction perpendicular to the filter media (e.g. the approach velocity) may be required to remain less than 0.1 m/s.
Some filters of the prior art may meet the required parameters when clean (e.g. immediately after a cleaning cycle), but may cause velocities above the required parameters when part of the filter media is blocked.
Use of such filters in lotic (flowing) water may also result in failure to meet design parameters regarding water velocities.
It is an object of the technology to provide a filter or screen comprising a filter media, which creates even flow rates through the filter media. Alternatively, it is an object of the technology to provide a filter or screen which creates lower head loss.
Alternatively, it is an object of the technology to overcome or ameliorate problems with filters or screens of the prior art, or to at least provide the public with a useful choice.
According to one aspect of the technology there is provided a filter or intake screen (“filter”) for removing particles from a fluid,
Preferably, the interior volume is shaped such that the velocity of the water flowing through the interior volume is substantially constant.
Preferably, the filter further comprises a flow guide provided on a downstream side of the vanes, the flow guide defining a boundary of the interior volume, wherein a clearance distance between the downstream end of each respective vane and the flow guide decreases with increasing distance from the first end of the filter media.
Preferably, the clearance distance between the downstream end of each respective vane and the flow guide is such that the velocity of the water flowing between each downstream end and the flow guide is substantially constant.
Preferably, the vanes are configured to accelerate the flow between the upstream end and the downstream end of each vane.
Preferably, filter comprises an outer housing on the first side of the filter media.
Preferably the outer housing defines an inlet at one end of the filter and a bypass outlet at the opposite end.
Preferably, the outer housing inlet is provided at an opposite end of the filter to the discharge port.
Preferably, the outer housing bypass outlet is provided at the same end of the filter as the discharge port.
Preferably, a clearance distance between the outer housing and the first side of the filter media decreases with increasing distance from the outer housing inlet.
Preferably, the filter media is shaped as a surface of revolution, and the filter is configured to rotate the filter media about its central axis.
Preferably, the filter media comprises one or more of woven mesh, perforated plate, circumferential wedge-wire, longitudinal wedge-wire and multi layered sintered media.
According to another aspect of the present technology there is provided filter or intake screen (“filter”) for removing particles from a fluid, the filter comprising a filter media having a first side and an opposite second side, wherein the fluid flows, in use, from the first side to the second side, the filter further comprising an outlet port, wherein the filter is configured such that a velocity of fluid flowing through the filter media is substantially constant across the entire filter media.
Preferably, the filter comprises a plurality of vanes configured to direct the fluid flow from the filter media towards the outlet port.
In examples, the filter is configured as a fish protection or fish exclusion screen.
Further aspects of the technology, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the technology.
One or more embodiments of the technology will be described below by way of example only, and without intending to be limiting, with reference to the following drawings, in which:
Referring first to
The filter 100 comprises a filter or screen media 110. A range of filter/screen media 110 may be used, for example woven mesh, perforated plate, circumferential wedge-wire, longitudinal wedge-wire or multi layered sintered media. In the examples shown in the figures, the filter media 110 is configured as a relatively thin walled cylinder. In use, a fluid F (typically water) flows from a first side 120 of the filter media 110 to a second side 130, as shown in
The filter 100 comprises a plurality of vanes 140 on the downstream side of the filter media 110, adjacent or in contact with the second side 130 of the filter media 110. Water flows from the vanes 140 into an interior volume 150 which is in fluid communication with a discharge port 160 provided at a first end 162 of the filter media 110. The vanes 140 are configured to direct the flow of water from the filter media 110 towards the discharge port 160, as is explained further below.
The cross-sectional area of the interior volume 150 decreases with increasing distance from the discharge port 160. Put another way, the cross-sectional area of the interior volume 150 increases in the direction of fluid flow towards the discharge port 160. This increase of cross-sectional area means that although additional flow is added to the stream of water moving towards the discharge port 160, the velocity of the water in the interior volume 150 remains substantially constant. This, in turn, means that the flow conditions at the downstream end 170 of each vane 140 are the same, and so the flow rate of water flowing between each pair of vanes 140 is substantially the same along the length of the filter media 110.
Referring next to
The shape of the vanes 140, including the spacing between the vanes 140, is configured to increase the velocity of the water as it flows from the upstream end 180 of each vane to the downstream end 170. Water flows through the filter media 110 at a relatively low velocity due to the resistance caused by the filter media 110. Once the flow has passed through the filter media 110 it must be accelerated to the speed of the flow in the discharge port 160. This acceleration is done in a way that continues the uniformity of flow through the filter media 110. The vanes 140 split the flow and allow it to continue at this lower velocity for a short distance in a first zone 190. In the first zone 190, the cross-sectional area between the adjacent vanes 140 remains constant. The flow then flows through a second zone 200 in which it is steadily accelerated and its direction is changed such that it is flowing towards the discharge port 160. The cross-sectional area between adjacent vanes 140 decreases in the second zone 200 in order to cause the acceleration.
Once the flow has effectively reached the same velocity and direction as the bulk flow in the interior volume 150, it leaves the area between the vanes 140 and enters the interior volume 150. This ensures that the flow rate through the filter media 110 is substantially constant across the entire length of the filter media 110, rather than the flow rate being greater adjacent the discharge port 160 (when the filter media is clean), as is the case with many prior art filters.
The exact geometry of the vanes 140 may vary depending on the type of filter/screen media used and the velocity and angle of the water flow exiting the filter/screen media.
Referring next to
In examples, the clearance space between the flow guide 210 and the downstream end 170 of each vane 140 decreases with increasing distance from the first end 162 of the filter media 110. That is, the clearance space C1 between the flow guide 210 and the downstream end 170 of the vane closest to the first end 162 of the filter media 110 (and the discharge port 160) is greater than the clearance space C2 between the flow guide 210 and the downstream end 170 of the vane which is furthest away from the first end 162, such that the cross-sectional area of the interior volume 150 increases in the direction of fluid flow towards the discharge port 160.
The vanes 140 and the flow guide 210 work together to ensure that substantially the same flow rate of fluid flows through the volume between each pair of vanes 140.
In examples, the upstream end 230 of the flow guide 210 may extend beyond the filter media 110 and may have a rounded shape to reduce turbulence in the water flowing over the filter media 110. The surface of the flow guide 210 may be undulating to control the flow between flow guide 210 and the end of the vanes 140, as best seen in
By providing a flow guide 210 as described, it may be possible to configure all of the vanes 140 to be substantially the same size and shape, thereby decreasing manufacturing costs. By contrast, the vanes 140 of the example shown in
In some examples shown the filter 100 also comprises an outer housing 240. The outer housing 240 may have a bypass outlet 250 and an inlet 260, as seen in
In examples, the fluid in the space between the outer housing 240 and the filter media 110 flows in the same direction as the fluid flowing in the interior volume 150. In examples the inlet 260 is provided at an opposite end of the filter to the discharge port 160.
In some examples of the invention an outer housing 240 is not required.
In another example, shown in
Flow enters the volume between the outer flow guide 410 and the filter media 110 via a course screen 420. A diffuser formation 430 is provided between the course screen 420 and the volume V2 between the filter media 110 and the outer flow guide 410 which reduces the speed of the flow before entering the space V2 between the outer flow guide 410 and the filter media 110. In examples, the diffuser 430 is provided with flow straightening formations 470.
A portion of the flow through the inlet 260 does not pass through the filter media 110, but instead follows a bypass path B between the outer flow guide 410 and the outer housing 400. This bypass flow is drawn back into the space V2 between the outer flow guide 410 and the filter media 110 once more by the higher speed flow (relative to the bypass flow velocity) coming out of the diffuser formation 430. In examples, the filter is configured to reduce mixing of the bypass flow and the fresh inlet flow.
The bypass flow may carry dirt from the upstream side of the filter media 110. The outer housing 400 may be provided with an outlet 440 through which the flow within the housing 400 is drained periodically, in order to remove the dirt which has accumulated in the bypass flow. An instrument port 450 may also be provided in the outer housing 400. Instrument ports may also be provided at the inlet and/or outlet.
In the example shown in
In examples, the filter 100 may be provided with a cleaning mechanism for continuously or periodically cleaning (e.g. by backflushing, brushing etc) the filter media 110. However, in some forms of the technology the flow between the outer housing 240, 400 and the first side of the filter media 110 may draw the filtered particulates away from the filter media 110, meaning that no additional cleaning mechanism is required. The filter 100 may also be provided with a trash rack (not shown) upstream of the inlet 260, in order to prevent large objects from entering the filter 100.
Referring next to
In some forms of the technology, a curved blade 280 may be provided adjacent the outlet of each nozzle. The blade 280 may be shaped to direct the jet of water J flowing from the nozzle in an arcuate path, first towards the filter media 110, then away from the filter media 110. The water jet J from each nozzle 270 may entrain debris from the surface of the filter media 110, thereby cleaning it. In examples the water jet J remains attached to the surface of the blade 280 due to the Coanda effect.
In examples, the nozzles 270 are arranged in a single row, for example, connected to a common manifold 272.
In other examples (not shown) a cleaning mechanism (e.g. nozzles, a brush etc) may be provided on an internal side of the filter media, e.g. between the filter media and vanes. In such examples the vanes may be spaced apart from the filter media to allow space for the cleaning mechanism.
The filter media 110 may be arranged to rotate about its central axis A (e.g by means of a water turbine, an electric gearmotor or hydraulic motor or similar) such that a single row of nozzles (e.g nozzles 270), a brush, or any other suitable cleaning mechanism, can clean the entire filter media 110. In such examples, the filter media 110 may be configured as a surface of revolution, such that distance between the cleaning mechanism (e.g. nozzles 270) and the filter media 110 remains constant over the entire revolution of the filter media 110.
In other examples of the invention (not shown) which are configured for use with pre-filtered or pre-screened water, the outer housing 240, inlet 260 and bypass outlet 250 may be configured to generate a smaller bypass flow than would be used for examples which take water directly from a lake, river or pond. In such examples, the bypass flow may be carried through to a secondary filter. The secondary filter may be periodically backflushed and the dirty water discharged from the system.
In examples (not shown) the bypass outlet 250 (if provided) may be fluidly connected to a bypass conduit which has an outlet which is at a lower pressure than the pressure at the housing inlet 260, in order to drive flow through the bypass outlet 250. In examples, the bypass conduit outlet may be provided downstream of a weir or similar.
Referring next to
Referring next to
As shown in
While the examples shown above show the inlet 260 to the outer housing 240 as circular, in other examples a non-circular inlet 260 may be provided, as show in
Referring next to
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of “including, but not limited to”.
The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference.
Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.
The technology may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.
Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.
It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the technology and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present technology.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022901063 | Apr 2022 | AU | national |
