Flow regulating device

A flow regulating device 2 comprising a plurality of coaxial vortex chambers 16, 116, 216, 316 disposed in flow series. Each vortex chamber 16, 116, 216, 316 has an inlet 22, 122, 222, 322 disposed to promote rotational flow within the vortex chamber 16, 116, 216, 316, and an outlet 24, 124, 224, 324. A diffusion chamber 12, 112, 212 is disposed between adjacent vortex chambers 16, 116, 216, 316, and the outlet 24, 124, 224, 324 of one and the inlet 22, 122, 222, 322 of the other of the adjacent vortex chambers 16, 116, 216, 316 open into the diffusion chamber 12, 112, 212.

FIELD OF THE INVENTION

This invention relates to a flow regulating device, and particularly, although not exclusively, relates to a device for regulating stormwater flow in a stormwater system.

BACKGROUND OF THE INVENTION AND PRIOR ART

It is known that vortex valves can be used to regulate stormwater flow. For example, WO99/43899 discloses a vortex valve for regulating stormwater flow comprising a vortex chamber defined by a circular cylindrical wall and two axial end walls. The vortex chamber has an outlet through one end wall and an inlet arranged to cause swirl in the chamber when a certain critical flow has been attained.

At low flow rates, water entering through the inlet of a vortex valve passes through the vortex chamber to the outlet with substantially no pressure drop, and the valve can be considered to be open. At high flow rates, water enters through the inlet with enough energy to create a vortex in the vortex chamber which results in a significant pressure drop between the inlet and the outlet. The pressure drop generates an air-filled core at the center of the vortex which restricts flow through the outlet, and can even substantially cut it off altogether. The valve thus limits the rate of flow through the valve automatically. Vortex valves can be used, for example, to control the flow of stormwater in sewers so that equipment downstream of the valve is not overloaded during periods of heavy rainfall.

The performance of a vortex valve under particular flow conditions is dictated by the geometry of the vortex valve, for example the size of the inlet or outlet, or the diameter of the vortex chamber.

An important characteristic of a vortex valve is the relationship between the pressure head across the valve and the flow rate through the valve. The required characteristic is commonly specified by the customer. If a fixed geometry vortex valve is to be provided, the customer's requirement can sometimes call for the outlet of the vortex valve to have a relatively small diameter, which may be subject to blockage by debris entrained in the flow through the vortex valve. An increase in the diameter of the outlet to reduce the risk of blockage will increase the flow rate through the valve under storm conditions, and this may not be acceptable.

Also where a vortex valve is installed with standard pipe fittings, or retrofitted into an existing drainage system, the inlet/outlet of the valve must be sized to accommodate the diameter of the pipes to which the valve is connected. Consequently, in order to deliver the required performance, the geometry of the vortex chamber other than the inlet/outlet diameter, for example the diameter of the vortex chamber, must be designed to meet performance requirements. Vortex valves are thus often designed on an ad hoc basis for specific applications.

Furthermore, where the geometry of the valve is constrained by the inlet and outlet diameter requirements, the space in which the valve is fitted often has to be adapted to accommodate the valve. This is both costly and time consuming.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a flow regulating device comprising a plurality of coaxial vortex chambers disposed in flow series, each vortex chamber having an inlet disposed to promote rotational flow within the vortex chamber, and an outlet, a respective diffusion chamber being disposed between each two adjacent vortex chambers, whereby the outlet of one and the inlet of the other of the two adjacent vortex chambers open into the diffusion chamber.

The vortex chambers may be disposed in a common duct, wherein each vortex chamber may comprise a housing having a circumferential outer wall and first and second end walls, one of the end walls comprising a partition which extends across the duct, the outlet of the respective vortex chamber being formed in the partition.

Adjacent ones of the partitions may define the respective diffusion chambers.

The flow regulating device may further comprise a common duct provided with spaced apart partitions extending across the duct, alternate partitions having vortex chamber inlets and vortex chamber outlets whereby each vortex chamber is defined between an upstream partition having a vortex chamber inlet and a downstream partition having a vortex chamber outlet, and each diffusion chamber is defined between an upstream partition having a vortex chamber outlet and a downstream partition having a vortex chamber inlet.

The duct may comprise a circumferential outer wall and the vortex chamber inlets are adjacent the circumferential outer wall.

Each vortex chamber inlet may comprise a notch at the periphery of the upstream partition.

The upstream partition of each vortex chamber may be inclined in the downstream direction in the region of the inlet aperture so as to promote rotational flow within the vortex chamber.

The plurality of coaxial vortex chambers may comprise at least three vortex chambers.

According to a second aspect of the invention there is provided a stormwater system including a device for regulating stormwater flow in the system, the device comprising a flow regulating device comprising a plurality of coaxial vortex chambers disposed in flow series, each vortex chamber having an inlet disposed to promote rotational flow within the vortex chamber, and an outlet, a respective diffusion chamber being disposed between each two adjacent vortex chambers, whereby the outlet of one and the inlet of the other of the two adjacent vortex chambers open into the diffusion chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1shows a first embodiment of a flow regulating device2for regulating stormwater flow through a stormwater system. The device2comprises a duct in the form of a cylindrical casing4, the inside of which cylinder is of uniform cross-section which is open at each end. The open ends respectively define a device inlet6and a device outlet8. In use, the general direction of flow from the inlet6towards the outlet8defines the downstream direction.

Circular partition discs10,110,210,310are spaced equally along the length of the casing4and partition the casing4into diffusion chambers12,112,212. The diffusion chambers12,112,212are thus defined between adjacent partition discs10,110,210,310and the casing4. In the embodiment shown inFIG. 1, there are four partition discs10,110,210,310which define three diffusion chambers12,112,212between adjacent discs10,110,210,310.

A vortex chamber16,116,216,316is disposed at the upstream surface of each partition disc10,110,210,310. Each vortex chamber16,116,216,316is defined by an end wall, also referred to as a top wall,18,118,218,318and a circumferential outer wall20,120,220,320which extends about the periphery of the end wall18,118,218,318, and joins the end wall18,118,218,318to the upstream surface of the corresponding partition disc10,110,210,310. Each partition disc10,110,210,310thus forms an opposite end wall of a vortex chamber16,116,216,316. Each vortex chamber16,116,216,316is substantially cylindrical and has a longitudinal axis which is coaxial with the axes of the other vortex chambers and coaxial with the longitudinal axis of the cylindrical casing4.

A vortex chamber inlet22,122,222,322is provided through the circumferential outer wall20,120,220,320. A portion of the outer wall20,120,220,320extends tangentially with respect to the vortex chamber16,116,216,316adjacent the inlet22,122,222,322so as to guide flow in a tangential direction through the inlet22,122,222,322. A vortex chamber outlet24,124,224,324is provided through the center of each partition disc10,110,210,310.

The internal diameter of each vortex chamber16,116,216,316is smaller than the internal diameter of the cylindrical casing4in the region within which the vortex chamber16,116,216,316is disposed. The vortex chambers16,116,216,316are connected in series by the respective diffusion chambers12,112,212.

In use, water enters the flow regulating device2through the device inlet6and flows through the successive vortex chambers16,116,216,316and corresponding diffusion chambers12,112,212before being discharged through the device outlet8.

At low flow rates, the level of water rises in the region between the device inlet6and the first partition disc10, and in the first vortex chamber16, until the water overflows the edge of the vortex chamber outlet24into the diffusion chamber12. Continued flow causes successive overflow of the water through the vortex chamber outlets124,224,324so that the water reaches the device outlet8. The water thus flows through each of the successive vortex chambers16,116,216,316and diffusion chambers12,112,212with substantially no pressure drop.

As the pressure head of the water at the device inlet6increases, the flow rate through the first vortex chamber inlet22correspondingly increases. At a predetermined pressure head determined by the design of the first vortex chamber16, the flow rate through the first vortex chamber inlet22will be sufficient to generate a circulating flow, or vortex, around the outer wall20of the first vortex chamber16. This is assisted by the tangential arrangement of the vortex chamber inlet22, which promotes rotational flow within the vortex chamber16. The high velocities of the vortex reduce the static pressure at the center of the vortex thereby creating an air core at the center of the vortex. The center of the vortex forms at the vortex chamber outlet24and so creates a pressure drop between the inlet22and the outlet24. The presence of an air core reduces the effective flow area of the vortex chamber outlet24and so restricts flow of water through the vortex chamber outlet24. This significantly reduces the flow rate through the vortex chamber outlet24into the diffusion chamber12, and increases the pressure drop across the first vortex chamber16.

The water is discharged through the vortex chamber outlet24at a reduced pressure into the diffusion chamber12immediately downstream of the vortex chamber outlet24. As the water disperses within the diffusion chamber12, the rotational and axial flow velocities reduce. When the vortex in the first vortex chamber16first initiates, the resulting flow rate into the first diffusion chamber12, and thence through the inlet122of the second vortex chamber116may not be sufficient to generate a vortex in the second vortex chamber116. Consequently, the pressure drop across the second vortex chamber116, and the subsequent vortex chambers216,316may remain low.

A further increase in pressure head at the device inlet6will increase flow through the first vortex chamber16, and into the first diffusion chamber12, sufficiently to cause a vortex to be generated in the second vortex chamber116, so providing a further flow rate reduction and overall pressure drop. Further increases in pressure head will likewise cause vortices to be generated successively in the third and fourth vortex chamber216,316. The reduction in pressure at each outlet124,224,324further inhibits flow through the device2. Thus, the vortex generated in each successive vortex chamber16,216,316contributes to a reduction in the flow rate through the device2. The resultant flow rate and pressure drop through the flow regulating device2is dependent on the number of vortex chambers16,116,216,316constituting the device2.

A desired pressure drop characteristic or flow restriction through the flow regulating device2can be achieved by varying the number of vortex chambers16,116,216,316which constitute the device2without having to vary the diameter of the cylindrical casing4or the diameter of device inlet6or device outlet8. A graphical illustration of pressure drop across the flow regulating device2(vertical axis) against flow rate through the flow regulating device2(horizontal axis) is shown inFIG. 3for a flow regulating device2provided with a different number of vortex chambers16,116,216,316. It can be seen that, for a particular flow rate, increasing the number of vortex chambers16,116,216,316increases the pressure drop across the flow regulating device2.

The flow regulating device2shown inFIG. 1achieves an overall flow rate reduction at higher inlet pressure heads comparable to that of a single chamber vortex valve having an outlet smaller than any of the vortex chamber outlets24,124,224,324. The vortex valve outlets24,124,224,324are each larger than the single outlet of a comparable single chamber vortex valve and so are less likely to be blocked by debris passing through the flow regulating device2.

A second embodiment of the flow regulating device2is shown inFIG. 2. Those aspects of the device2which differ from that shown inFIG. 1will be described.

Control discs26,126,226,326are interposed between the partition discs10,110,210,310. The control discs further partition the cylindrical casing4along its length. The vortex chambers16,116,216,316are defined between each control disc26,126,226,326and a partition disc10,110,210,310which is downstream of, and adjacent to, the control disc26,126,226,326. Thus, instead of a separately defined vortex chamber as described in the first embodiment, the second embodiment has vortex chambers16,116,216,316defined between respective control discs26,126,226,326, partition discs10,110,210and the cylindrical casing4.

Each vortex chamber inlet22,122,222,322comprises a notch28,128,228,328in the periphery of the control disc26,126,226,326. The notch28may, for example, be a cut-out segment at the periphery of the control disc26,126,226,326having orthogonal edges which extend along respective chords of each control disc26,126,226,326. The major part of the area of each control disc26,126,226,326lies in a plane transverse to the axis of the casing4. However, the upstream surface of each control disc26,126,226,326adjacent the notch28,128,228,328is inclined with respect to that transverse plane so as to promote rotational flow in the vortex chamber16,116,216,316. For example, the region of each control disc near the notch28,128,228,328may be deflected in the downstream direction.

The variant shown inFIG. 2is simple to manufacture, assemble and/or modify. For example, a prefabricated casing4can be adapted so that control discs26,126,226,326and partition discs10,110,210,310can be added or removed to modify the performance characteristics of the flow regulating device2.

In use, the upstream static pressure of water entering the inlet6may, for example, be between 7000 and 8500 Pa. When vortices have initiated within all of the vortex chambers16,116,216,316, the pressure in the first diffusion chamber12is between 5000 Pa and 6000 Pa. The pressure in the second diffusion chamber112is between 3000 Pa and 4500 Pa. The pressure in the third diffusion chamber212is between 1100 Pa and 2500 Pa. The pressure at the device outlet8is between 100 Pa and 700 Pa. It will be appreciated that the absolute static pressures within the diffusion chambers12,112,212and pressure drops across each vortex chamber16,116,216,316are dependent on the pressure of the in flowing water and the performance characteristics of the individual vortex chambers16,116,216,316.

In the embodiments ofFIGS. 1 and 2, each partition and the vortex chamber disposed at its upstream surface may be referred to as an assembly. Each diffusion chamber extends completely across the interior of the duct so as to form a free space which physically separates each assembly from its adjacent upstream assembly. For example, inFIG. 1each assembly comprises a partition10,110, etc. and a vortex chamber formed by16,116, etc., the vortex chamber having a circumferential outer wall formed by20,120, etc., a top wall18,118, etc., and a bottom wall which is a portion of the partition10,110located within the boundary of the circumferential outer wall20,120, etc. InFIG. 2, each assembly comprises a partition10,110, etc. and a vortex chamber, the vortex chamber having a circumferential outer wall formed by the inside wall of duct4, a top wall formed by an upstream control disc26,126, etc. and a bottom wall which is the entire portion of the partition10,110, etc. located within the boundary of the outer wall duct4.

Each of the variants described above can be modular; that is, vortex chambers and diffusion chambers can be constructed as modular components which can be added or removed to change the flow characteristics of the flow regulator. For example, the flow regulating device can be configured to deliver a required performance by the addition or removal of vortex chambers. The performance characteristics of a flow regulating device comprising two, three, four or more modular components can be calibrated. Referring for example toFIG. 3, line “a” shows pressure drop versus flow rate for four valves, line “b” shows the same for three valves, line “c” shows the same for two valves and “d shows the same for one valve. Line “e” shows the pressure drop versus flow rate at the orifice. Flow regulating devices having a particular number of modular devices can therefore be assembled to satisfy particular performance requirements.

The partition discs shown inFIG. 1and/or the control discs shown inFIG. 2may be spaced from each other at different distances to define vortex chambers and/or diffusion chambers which differ in volume from other vortex chambers/diffusion chambers of the flow regulating device.

The flow areas of the outlets of the vortex chambers may be the same. However, the flow area of the outlet of each successive vortex chamber may be less than, or greater than, the flow area of the outlet, or outlets, of at least one, or all, of the upstream vortex chambers. For example, the flow areas of the outlets of the vortex chambers may be sized so that they decrease from the device inlet towards the device inlet such that the most downstream vortex chamber is the first to initiate, the remaining vortex chambers initiating successively in the upstream direction. The initiation sequence may also be determined by varying the coefficient of drag (Cd) of each of the vortex chambers.

A flow regulating device as described above is particularly suitable for use in regulating relatively low flow rate stormwater flows. For instance, such a device would be suitable for flow systems in which the size of a single valve which would achieve an equivalent flow restriction would be unfeasible due to the likelihood of blockage. By assembling the device from appropriate components, the flow characteristic of the device can be tailored to specific circumstances.