Multiple Stage Restrictor

Abstract

A multiple stage restrictor is characterized by a plurality of stacked plates, the proximate surface of at least one of each pair of adjacent plates in the stack being provided with an arrangement of recesses such as to provide a plurality of alternate zones of relatively increased and relatively decreased velocity defining flow-restricting passages through which the fluid flows.

Parent Case Text

This is a continuation-in-part of my previous application Ser. No. 183,099, filed Sept. 23, 1971, now abandoned.

Description

This invention relates to fluid flow control and, more particularly, to a restrictor for dissipating energy when used to release a high pressure fluid.

Conventional flow control valves employ a single restriction to control the fluid flow rate. The velocity within this restriction is a function of the pressure differential on the upstream and downstream sides of the valve. Where the pressure differential is large, the high velocity created within the device can be detrimental. For example, in liquid systems the resulting high velocities can produce cavitation. This occurs when the pressure at the Vena Contracta falls below the vapor pressure of the liquid, producing vapor bubbles and subsequent collapse of the bubbles as they enter the relatively higher downstream pressure region. The collapse of these bubbles within the restriction device causes physical damage to the parts through errosion and thereby shortens the useful life of the device. In gas or vapor systems, the high velocities produced by a single-stage restriction cause a high degree of turbulence and the associated problems of noise. Where the pressure differential across the device is equal to or greater than the critical pressure ratio of the gas or vapor, sonic velocity occurs at the Vena Contracta and a shock wave is produced downstream of the restriction which causes additional turbulence and noise.

Flow-restricting devices have been proposed heretofore such, for example, as those disclosed in U.S. Pat. Nos. 3,197,483, 3,451,404, 3,485,474 and 3,513,864. In the first two of these patents, the restrictors in the valve comprise a bundle of small diameter conduits and control is obtained by exposing more or less of the number of these single-stage restrictive flow conduits to the path of fluid flow. In the third patent, the restriction takes place sidewise in a conical path where the spacing between each of the restriction steps is uniformly varied to control the total restriction and flow. In an emulsifier disclosed in U.S. Pat. No. 973,328, a stack of annular plates is assembled wherein each plate is provided with alternate sets of radial and circumferential grooves wherein the cross-sectional area of all grooves is identical in the path of fluid flow therethrough.

I have now devised a simple fluid flow restrictor that is characterized by a plurality of multiple stage restrictions which can be produced inexpensively and which can readily be replaced when necessary. The multiple stage restrictor of the present invention is adapted to be positioned in the path of flow of a fluid through a confining passage and comprises a stack of superimposed flow-restriction plates, each of the superimposed plates being provided in one surface thereof with a plurality of recesses which, in cooperation with the proximal surface of an adjacent superimposed plate, provides in the direction of said interface a plurality of communicating passages of alternately relatively small and relatively large cross-sectional areas so as to define a path of flow for fluid characterized by repeatedly alternate zones of relatively increased and relatively decreased velocity respectively. Baffle means are connected to both ends of the stack of plates and are adapted to close the confining passage except for flow of fluid through the stack of plates from one edge thereof to the other. In one specific embodiment of the invention, one of the superimposed plates is provided with at least one pair of spaced recesses in one surface thereof of which one of these recesses communicates with one edge of the plate and the other of said recesses communicates with the other edge of the plate, and another one of the superimposed plates is provided with at least one recess positioned intermediate its edges in the surface thereof adjacent the recess-provided surface of the first-mentioned plate. This intermediate recess in this embodiment of the invention extends a sufficient distance to partially overlap and thus communicate with the pair of recesses in the first-mentioned plate when the plates are positioned with these two surfaces in contact with one another. The resulting overlapping of the recesses of an adjacent pair of plates thus provides a communicataing series of offset recesses between the two edges of said pair of plates. In another specific embodiment of the invention, each of the superimposed plates is provided in one surface thereof with a plurality of communicating recesses arranged with one set of alternate recesses providing fluid flow in a direction normal to the direction of flow in the other set of alternate recesses, the cross-sectional area of each of one set of recesses being smaller than the cross-sectional area of each of the other set of recesses.

These and other novel features of the invention will be more readily understood from the following description taken in conjunction with the accompanying drawing in which:

FIG. 1 is a sectional side elevation of a fluid restrictor embodying the invention installed in a pipe system;

FIG. 2 is a top plan view of one of the flow restriction plates in the embodiment shown in FIG. 1;

FIG. 3 is a partial top plan view of two of the flow restriction plates of the embodiment shown in FIG. 1 and arranged in operative position;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is a perspective view of a stack of the restriction plates of FIGS. 2-4 progressively more rotated about their common axis;

FIG. 6 is a partial plane view of another modification of the flow restriction plate designed to restrict the flow of a liquid;

FIG. 7 is a side elevation, partly in section, of a conventional fluid control valve provided with a restrictor pursuant to FIGS. 1-5;

FIG. 8 is a partial elevation, partly in section, of a valve having a simple cylindrical outlet port and provided with restriction plates of the type shown in FIGS. 1-5;

FIG. 9 is a top plan view of another embodiment of flow restriction plate pursuant to the invention;

FIG. 10 is a sectional view taken along line 10--10 in FIG. 9; and

FIG. 11 is a sectional side elevation of a fluid restrictor embodying the plates shown in FIGS. 9 and 10 and installed in a pipe system.

In FIG. 1, the restrictor 10 is shown mounted between adjacent flanged ends 11 and 11a of fluid flow conduits 12 and 12a. The restrictor comprises a stack of superimposed flow-restriction plates 13 provided with end baffles 14 and 15. One of the end baffles 14 is annular in form and advantageously has an outer diameter greater than the internal diameter of the conduits 12 and 12a so that it can be clamped between the flanged ends 11 and 11a of the conduit in order to hold the restrictor in place. The other restrictor baffle plate 15 is in the form of a plate. Thus, the flow of fluid through the conduits 12 and 12a must pass through restriction orifices 16 formed between the restriction plates 13. The restriction plates and their end baffle plates 14 and 15 are held together as an assembly by bolts or the like.

The restriction plates 13 shown in detail in FIG. 2 are particularly designed for restriction of the flow of a gas or vapor through a conduit or valve. The plate is characterized by a specific arrangement of recesses in its surface. This arrangement includes a pair of recesses 17a and 17b formed in one surface 18 of the plate and radially spaced from one another along the line of flow of fluid through the stack of plates in the valve. The inner recess 17a opens into the open core 13a of the annular plate 13 and increases in width in an outward radial direction. The outer recess 17b opens into the peripheral edge 13b of the plate and similarly increases in width in an outwardly radial direction. The arrangement of recesses further includes another recess 19 in the opposite surface 20 of the plate. The recess 19 is displaced arcuately from the position of the pair of spaced recesses 17a and 17b and is radially placed along the line of flow of fluid through the stack so that its inner radial extremity 19' is positioned inwardly of the outermost extremity 17a" of the recess 17a and so that its outer radial extremity 19" is positioned outwardly of the innermost extremity 17b' of the recess 17b. Thus, when two such plates 13 are brought into axially aligned juxtaposition with one plate rotated with respect to the other in order that the recesses 17a, 19 and 17b are in radial alignment as shown in FIG. 3, the radially outermost end portion 17a" of the recess 17a in the surface 18 of one plate overlaps and communicates with the innermost end portion 19' of the recess 19 in the adjacent surface 20 of the other plate 13 to define a restriction flow orifice A, and similarly the outermost end portion 19" of the recess 19 overlaps and communicates with the innermost end portion 17b' of the recess 17b in the adjacent plate surface 20 to define another restriction flow orifice B. The resulting communication of the aligned recesses provides, as shown in FIG. 4, a passage for the fluid from the core 13a radially outwardly through the recess 17a of increasing width, thence through restriction orifice A in a direction perpendicular to the plane of the plate 13 into the recess 19, again outwardly through the recess 19 of increasing width until it again changes to a direction perpendicular to the plane of the plate 13 as it passes through restriction orifice B into the recess 17b, and finally flows radially outwardly through the recess 17b of increasing width to the outermost end portion 17b" at the periphery 13b of the assembled plates. The radially outwardly increasing width of each recess permits progressive expansion of the fluid when it is a gas or vapor, and the abrupt change in direction of flow as the fluid moves from one recess to the next provides effective restriction of the flow in addition to that caused by the friction of the fluid flowing through the relatively shallow channels defined by the cooperating recesses and overlying adjacent plate surface. The effectiveness of the communicating recesses in offering restriction of the flow of fluid through the orifices A and B can also be influenced by the depth of the recesses formed in the plates 13, but in all cases it will be apparent that the arrangement of recesses defines a path of flow of fluid characterized by repeatedly alternate zones of relatively decreased and relatively increased flow velocity.

By repeating the pattern of the foregoing arrangement of recesses around both surfaces of each plate, a number of such restriction passages can be provided by each adjoining pair of plates. If each plate is provided with four alignment holes 21 through which each of the four alignment bolts 22 extend, then each plate is provided with a second set of alignment holes 23 angularly displaced the same as the angular displacement of the radial axis of the pair of recesses 17a and 17b with respect to the radial axis of the recess 19. By then positioning alternate plates on the bolts 22 using the alignment holes 21 for one plate and the alignment holes 23 for the next adjacent plate, the recesses 17a, 19 and 17b will be aligned for the entire stack of plates as for the single pair referred to in the preceding discussion.

It should be understood that the recesses 17a and 17b can be formed in the surface 18 of one disc and that the cooperating recess 19 need not be formed in the other surface of the same disc but can be formed only in that surface of an adjoining disc which faces the surface 18 of the first disc. In such an arrangement, one disc will be provided with the recesses 17a and 17b in its surface 18 and the adjoining disc will be provided with a recess 19 in its surface 20. As a result, a pair of discs will provide an arrangement of communicating recesses only along the adjoining faces of that pair of discs. On the other hand, where the recesses 17a and 17b are formed in the surface 18 of each disc and the cooperating recess 19 is formed in the other surface 20 of each disc, there will be a restriction path for the flow of fluid between each adjoining pair of surfaces of discs in the stack.

As shown in FIG. 5, a further variation in the degree of flow restriction provided by each pair of adjoining plates can be obtained by rotating alternate plates 13 less than the arcuate distance between the centerline radius of the recesses 17a and 17b and the centerline radius of the recess 19. In this way, the overlap of the recesses can be altered from maximum to minimum extent. To obtain such lesser amounts of relative rotation of alternate plates, it is advantageous to establish and maintain the relative positions of the plates not by the bolts 22 extending through the holes 21 and 23 in the plates 13 but by positioning notches 24 in the peripheries 13b of the plates so that the notch in each plate in sequence is further around the periphery of that plate. These notches can then be aligned with a single post 25 mounted adjacent the peripheral portions of the stacked plates.

When the restriction plates are to be used for control of a liquid, which is relatively inexpandible, the recesses 17a, 17b and 19, as shown in FIG. 6, can be of uniform width radially of the plates. The overlapping portions of the recesses are, however, smaller in cross-sectional area than the body of the recesses so as to provide the aforementioned arrangement of alternate zones of relatively increased and relatively decreased flow velocity.

In FIG. 7, the restrictor is shown mounted in a conventional valve comprising a valve body 26 having an inlet port 27 and an outlet port 28. Within the valve body is a valve member 29 mounted on a valve stem 30 and cooperating with a valve seat 31 (if tight shut-off is required) to control flow of a fluid through the valve. The valve seat 31 is mounted in a seat ring 32 positioned at the opening 33 between the inlet port passageway 34 and the hollow interior of the valve body.

Positioned immediately above the seat ring 31, and axially located within an annular outlet port passageway 35 in the interior of the valve body, is the stack of superimposed flow restriction plates 13. In the embodiment of the valve shown in FIG. 7, the restriction plates 13, as shown in detail in FIG. 2, are annular in shape with a central open core 13a of sufficient diameter to permit the valve member 29 to be moved axially therethrough as the valve stem 30 is raised or lowered. The plates 13 are held in fixed position by at least one alignment bolt 22 mounted in the seat ring 32 and extending through the entire stack of plates, and the plates are held in firm face-to-face contact by a spacer ring 36 forced against the opposite end of the stack of plates by the valve body cover plate 37.

It will be appreciated that the restrictor 10 need not be positioned within the valve body as shown in FIG. 7 and that it can be positioned at either the inlet 27 or outlet 28 of the valve in the same manner that it was positioned between the adjacent conduits or pipes 12 and 12a in FIG. 1.

When the valve member 29 is a simple plate, as in a conventional valve, and the valve is opened by axial movement of the stem 30, the fluid is free to distribute itself throughout the core 13a of the stack of plates and its flow will be distributed substantially equally between all of the plates in the stack. However, by providing the valve member with a cylindrical body portion 29a of diameter such as to fit closely within the core of the stack of plates, the position of the valve member 29 at the bottom edge of the cylinder 29a will determine how many of the cooperating plates 13 will be available for permitting the restrictive flow of the fluid. In this way, control of the flow rate through the valve can be achieved. Further variety in the extent of flow control can be obtained by using such a number of plates 13 as to fill only a portion of the outlet port passageway 35, with the result that when the valve member cylinder 29a is raised above the top end plate of the stack, the passageway 35 becomes open to unrestricted flow of fluid through the valve.

The annular restriction plate 38 shown in detail in FIGS. 9 and 10 is similarly characterized by a specific arrangement of recesses in its surface. In this embodiment of the invention the recesses include outer or peripheral radial channels 39 communicating inwardly with an annular channel 40. Extending further inwardly from the annular channel 40 are additional radial channels 39' communicating with an inner annular channel 40' which in turn communicates with the inner open core 13a through inner radial channels 39". The transverse cross-sectional area of the individual channels 39, 39' and 39" is relatively small compared to that of the annular channels 40 and 40' and that of the inner core 13a. Thus, each adjacent pair of restriction plates in a stack thereof, as shown in FIG. 11, defines in the path of flow of fluid repeatedly alternate zones of relatively decreased and relatively increased flow velocity. The resulting restrictor structure 10a, as also in the case of the restrictor embodiment of the invention shown in FIGS. 1 through 9, is analagous to a conduit provided with a series of flow-restrictive orifices each separated axially of the conduit by an intervening expansion chamber.

Claims

I claim:

1. A multiple stage fluid restrictor adapted to be positioned in the path of flow of a fluid through a confining passage which includes an inlet and an outlet port and comprising a stack of superimposed flow-restriction plates, one plate of said stack of superimposed plates being provided with at least one plurality of spaced recesses in one surface thereof of which one of said recesses communicates with one edge of said plate and another of said recesses communicates with the other edge of said plate, and another one of said plates of said stack of superimposed plates being provided with at least one recess positioned between its edges in the surface thereof adjacent the recess-provided surface of the first-mentioned plate, each recess in the other plate extending a sufficient distance across said other plate to partially overlap and thus communicate with successive ones of said plurality of spaced recesses in the first-mentioned plate when the plates are positioned with these two surfaces in contact with one another, the resulting overlapping of the recesses of an adjacent pair of plates thus providing a communicating series of restriction orifices of relatively small cross-sectional area connecting the offset recesses of relatively large cross-sectional area extending between the two edges of said adjacent pair of plates so as to define a path of flow for fluid characterized by repeatedly alternate zones of relatively increased and relatively decreased flow velocity respectively, and baffle means connected to both ends of the stack of plates adapted to close said confining passage except for flow of fluid through the stack of plates from one edge thereof to the other.

2. A multiple stage fluid restrictor according to claim 1 in which each of said plates is provided with the first-mentioned plurality of recesses in one surface of the plate and is provided on the opposite surface thereof with each secondmentioned overlapping recess arcuately offset from the firstmentioned plurality of recesses, alternate plates being so positioned in axial alignment that successive recesses in one surface of one plate are overlapped by each recess in the proximate surface of the adjacent plate.

3. A multiple stage fluid restrictor according to claim 1 in which the entire outlet port is filled with an assembly of said superimposed flow-restriction plates.

4. A multiple stage fluid restrictor according to claim 1 in which the outlet port is annular in shape and the plates are of substantially the same annular shape.

5. A multiple stage fluid restrictor according to claim 1 in which said one plate of said stack of superimposed plates includes two spaced recesses communicating with the edges of said one plate.