WO2008047236A2

WO2008047236A2 - Fluid pressure reducing device

Info

Publication number: WO2008047236A2
Application number: PCT/IB2007/003942
Authority: WO
Inventors: Peter Connan
Original assignee: Actuators & Controls (Pty) Ltd Trading As Mitech
Priority date: 2006-10-16
Filing date: 2007-10-16
Publication date: 2008-04-24
Also published as: GB0620518D0; WO2008047236A3; GB2456485A

Abstract

A fluid pressure reducing device 10 comprises a stack 14 of annular discs 12. Each disc 12 includes a circumferential array of arcuate elements 16 and a plurality of fluid flow paths, each fluid flow path being at least partly defined between adjacent arcuate elements of each annular disc and extending from the interior of the stack 14 to the exterior of the stack 14.

Description

FLUID PRESSURE REDUCING DEVICE

The present invention relates to a fluid pressure reducing device and particularly, although not exclusively, to a new method of construction of a disc-type flow restrictor for use in a valve or other assembly for controlling fluid pressure. The device can also be used to control other fluid flow parameters, for example, flow rate, temperature, energy and velocity.

It is known to use a disc-type flow restrictor to create a large pressure reduction in a valve or piping system for fluids. A disc-type restrictor typically comprises an axial stack of annular discs, each disc being a one-piece component having cut-away portions, slots, and/or apertures, which communicate with the cut-away portions, slots and/or apertures of adjacent discs in the stack. High-pressure fluid flow typically enters the interior of the stack, defined by central openings in the discs, and passes radially and axially through the cut-away portions, slots and/or apertures of adjacent discs, which create tortuous three-dimensional fluid flow paths through the discs. The flow emerges from these tortuous paths at the exterior of the stack. The flow direction can also be arranged to flow from the exterior to the interior of the stack, as required.

The numerous changes in direction of the fluid flow create a multi-stage pressure reducer. An advantage of this type of restrictor is that the flow restriction is caused with a minimum of noise, vibration, cavitation and abrasion, as explained, for example in WO 01/31322 (KWON KAB JU). However, the discs are complicated to manufacture.

According to a first aspect of the present invention there is provided a fluid pressure reducing device comprising a stack of annular discs, each disc comprising a circumferential array of arcuate elements and a plurality of fluid flow paths, each fluid flow path being at least partly defined between adjacent arcuate elements of each annular disc and extending from the interior of the stack to the exterior of the stack.

The arcuate elements of each annular disc may be spaced apart from one another to define the flow paths.

The fluid flow paths may be sinuous.

The fluid flow paths may each comprise at least three changes in direction. The changes in direction provide a tortuous fluid flow path for creating a pressure reduction in a fluid flowing in the flow path. Each change in direction creates a pressure drop, and hence the multiple changes in direction of the flow path create multi-stage pressure reduction.

The arcuate elements may each comprise inner and outer edges and first and second profiled edges, extending between the inner and outer arcuate edges. The first and second profiled edges of each element are preferably of complementary shape to each other, so that the first edge of one element can cooperate with the second edge of an adjacent element to form one of the flow paths.

Adjacent discs in the stack may be attached to one another, for example, with adhesive.

The arcuate elements may be made from any suitable material, such as a ceramic, metal or metal alloy.

The arcuate elements may be manufactured by powder metallurgy.

The fluid flow paths of adjacent annular discs in the stack may be rotationally offset relative to one another.

By rotationally offsetting adjacent discs relative to one another, fluid is prevented from flowing out of the flow paths of one disc into the flow paths of an adjacent disc. The flow restriction achieved is then dependent on the shape of the first and second profiled radial edges of each element.

According to a second aspect of the present invention there is provided a valve comprising a fluid pressure reduction device according to the first aspect of the invention.

The present invention also provides an arcuate element for use in the assembly of a fluid pressure reduction device according to the first aspect of the invention. For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way__pf_exaiπpJS-,_toJha accompanying drawings, in which:-

Fig 1 is a perspective view of a fluid pressure reduction device;

Fig 2A is a perspective view of an arcuate element in accordance with the first aspect of the invention;

Fig 2B is a plan view of the arcuate element of Fig 2A;

Fig 2C is a side view of the arcuate element of Fig 2A and 2B; and

Fig 3 is a plan view of three arcuate elements arranged adjacent one-another.

Referring firstly to Fig 1 , a fluid pressure reduction device is indicated at 10. The fluid pressure reduction device 10 comprises a plurality of annular discs 12 arranged in a stack 14. Each disc 12 is made up of twelve arcuate elements 16, and fifteen discs 12 are shown in the stack. The number of arcuate elements 16 and/or discs 12 may be varied as required.

Referring also to Figs 2A to 2C, each arcuate element 16 is planar and has a thickness, indicated at 18 in Fig 2C. The elements 16 have a shape defined by an inner arcuate edge 20, an outer arcuate edge 22, a first profiled edge 24, and a second profiled edge 26. The profiled edges 24,26 extend between the respective ends of the inner and outer arcuate edges 20,22.

The first and second profiled edges 24,26 of the element 12 are of complementary shape with one another. In the embodiment shown, the first and second profiled edges 24,26 are sinuous, with substantially male and female wave-like profiles including peaks 29 and troughs 30. The troughs 30 are curved, to avoid creating areas of high stress in the manufacture of the element. Each profiled edge 24,26 includes three peaks 29 and three troughs 30. The peaks 29 each have a concave portion 28 at their tips. A rib 32 is provided at substantially the centre of the inner arcuate edge 20. The elements16 can be made from ceramic, metal or metal alloy, and are preferably manufactured using powder metallurgy. This enables the elements to be-made~from very hard and brittle materials, which have high wear resistance when subjected to a high pressure fluid flow. The shape of the elements 16 lends itself to manufacture in this way, and so the elements 16 can be made relatively inexpensively.

Referring now to Fig 3, three identical arcuate elements designated 16,116 and 216 are shown arranged adjacent one another, to form part of an annular disc 12. The first profiled edge 24 of the element 216 is adjacent the second profiled edge 26 of adjacent element 116, and the first profiled edge 24 of the element 116 is adjacent the second profiled edge 26 of adjacent element 16. Although there is a space 34 between adjacent elements, the peaks 29 of adjacent elements 16,116,216 overlap one another. Consequently, each space 34 provides a tortuous fluid flow path. In use, this creates a pressure reduction in a fluid flowing in the flow path. The peaks 29 and troughs 30 of adjacent elements change the direction of the flow path in a zigzag manner. The multiple changes in direction of the flow path create a multi-stage pressure reducer.

As can be appreciated from Fig 3, each flow path comprises a series of chambers 36 defined between the concave portions 28 and the adjacent troughs 30. The chambers 36 are interconnected by generally straight passages 38 defined between opposing flanks of the peaks 28 and troughs 30 of the elements 16. (Only some of the concave portions 28, chambers 36 and straight passages 38 are referenced in Fig 3 for the sake of clarity).

Adjacent annular discs 12 in the stack are rotationally offset relative to one another, so that the spaces 34 between the elements 16 of one disc 12 are out of alignment with the spaces 34 between the elements 16 of the or each adjacent disc 12. By rotationally offsetting adjacent discs 12, each flow path between adjacent elements 16 is closed by the planar faces of the elements 16 of the discs 12 immediately above and below. Consequently, in use, fluid is prevented from flowing out of the flow paths of one disc into the flow paths of an adjacent disc, but is instead constrained to flow to the outer face of the stack. The ribs 32, which are axially disposed in the stack 14, enable visual and mechanical alignment of the elements relative to one another.

The flow restriction achieved by the device 10 is dependent on the shape of the first and second profiled radial edges 24,26 of each element 16. In use, the fluid pressure reduction device 10 is mounted in a valve or other assembly and fluid can flow though the spaces 34 to or from a central axial passage 40 formed by the stacking -of-the discs 12 in the stack 14.

The shape of the profiled edges 24,26 can be changed to provide the fluid flow path required. The arcuate elements 16 of each disc 12 are substantially identical with one another and therefore are simpler to manufacture than other unitary discs, which are often of a different specification to other discs in a stack. The elements 16 are also smaller components than unitary discs and do not generally require machine finishing, enabling them to be made from harder materials than known fluid control discs. When assembled into a stack 14, the arcuate elements 16 are attached to one another by bonding with adhesive, or by mechanical fastenings or locating arrangements.

Claims

1. A fluid pressure reducing device comprising a stack of annular discs, each disc comprising a circumferential array of arcuate elements and a plurality of fluid flow paths, each fluid flow path being at least partly defined between adjacent arcuate elements of each annular disc and extending from the interior of the stack to the exterior of the stack.

2. A fluid pressure reducing device as claimed in claim 1 in which the arcuate elements of each annular disc are spaced apart from one another to define the flow paths.

3. A fluid pressure reducing device as claimed in claim 1 or claim 2 in which the fluid flow paths are sinuous.

4. A fluid pressure reducing device as claimed in any preceding claim in which the fluid flow paths each comprise at least three changes in direction.

5. A fluid pressure reducing device as claimed in any preceding claim in which the arcuate elements each comprise inner and outer arcuate edges and and first and second profiled edges, extending between the inner and outer arcuate edges.

6. A fluid pressure reducing device as claimed in claim 5 in which the first and second profiled edges of each element are of complementary shape to each other.

7. A fluid pressure reducing device as claimed in any preceding claim in which adjacent discs in the stack are attached to one another.

8. A fluid pressure reducing device as claimed in claim 7 in which adjacent discs in the stack are bonded to one another with adhesive.

9. A fluid pressure reducing device as claimed in any preceding claim in which the arcuate elements are made from ceramic.

10. A fluid pressure reducing device as claimed in any one of claims 1 to 9 in which the arcuate elements are made from metal or metal alloy.

11. A fluid control device as claimed in any preceding clairrπn whicb_the_ar.cuate elements are manufactured by powder metallurgy.

12. A fluid pressure reduction device as claimed in any preceding claim in which the fluid flow paths of adjacent annular discs in the stack are rotationally offset relative to one another.

13. A fluid pressure reduction device substantially as described herein with reference to and as illustrated in Fig 1 of the accompanying drawings.

14. A valve comprising a fluid pressure reduction device as claimed in any preceding claim.

15. An arcuate element for use in the manufacture of a fluid pressure reducing device in accordance with any one of claims 1 to 13.

16. An arcuate element as claimed in claim 15, which comprises inner and outer arcuate edges and first and second profiled edges extending between the inner and outer arcuate edges, the first and second profiled edges having shapes which are complementary to each other.

17. An arcuate element for use in the manufacture of a fluid pressure reducing device, the element being substantially as described herein with reference to, and as shown in, Figures 2A, 2B, 2C and 3 of the accompanying drawings.