Sound suppressing gas flow control device

Abstract

A co-axial stack of annular disks, each of which is preferably made of a sheet metal so thin as to be individually flexible, is held under axial compression to define an essentially rigid column. Each disk, on at least one surface thereof, is integrally formed with a plurality of radially extending depressions, preferably of non-circular cross-section, whose sidewalls diverge radially outwardly away from one another, each such depression defining a diffuser passage with a surface of an adjacent disk. The disks are formed with substantially identical patterns of depressions and the plurality of disks are substantially identically angularly oriented with respect to each other so that the land areas between depressions are directly superimposed on each other to sustain the axial compression of the stack without deformation of the individual thin disks. The compressed stack provides a very high density of inlet and outlet orifices on the inner and outer walls thereof whose interconnecting passageways are opened or closed by axial movement of a valve member through the central passage defined by the stack. The gradient of increase in cross-sectional area of the diffuser passages from inlet to outlet is calculated to maintain a substantially constant velocity of the gas flow therethrough, with a gradually increasing specific volume gradient from inlet to outlet.

Parent Case Text

This is a continuation of application Ser. No. 445,111, filed Feb. 25, 1974, which was a continuation of application Ser. No. 276,831, filed July 31, 1972, both now abandoned.

Description

The present invention relates to a high pressure reducing valve for gases that suppresses the generation of undesirable noise such as would otherwise be created by great pressure drops between the inlet and outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a valve incorporating the invention, with portions cut away to schematically show features of internal construction;

FIG. 2 is a plan view of one form of sound suppressing disk, superimposed on another identical disk;

FIG. 3 is a partial sectional view on the line 3--3 of FIG. 2; and

FIG. 4 is a partial plan view of another embodiment of sound suppressing disk.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As one illustration of the use of the invention, FIG. 1 schematically illustrates a valve configuration adapted to produce a variable flow rate with a high pressure differential, the flow rate being a function of downstream demand. As is schematically indicated, this exemplary pressure regulator valve assembly includes a hollow dome 10 mounted on a cup-like member 11 that is interiorly formed with a central guide sleeve 12. While not illustrated, it will be understood that the dome 10 houses a conventional regulator mechanism, such as a piston, drivingly connected to a poppet control rod 13 that is axially slidably mounted through the guide 12. The regulator assembly also includes conventional passages and controls (not shown) intercommunicating opposite sides of the piston to inlet and outlet pressures of the valve assembly in order to vary the flow rate through the valve assembly in accordance with downstream demand.

The poppet control rod 13 is formed with a circumferential groove 14 that retains an O-ring seal 15 to prevent leakage between the interior of the dome 10 and the gases passing through a valve body schematically indicated by the numeral 16. A cylindrical poppet body 17 may be integrally formed as a downward co-axial extension of the control rod 13, the poppet body being of cylindrical configuration and developing into a frusto-conically tapered poppet 18 that is matingly engageable with a frusto-conical seat 19 formed in the valve body 16. The valve body is also provided with a tubular guide sleeve 20, co-axially related to the valve seat 19 and poppet body 17, within which a reduced diameter guide rod 21, comprising a co-axial extension of the poppet body 17, is axially reciprocable. At its lower end, the rod 21 has a cylindrical guide member 22 rigidly secured thereto and formed with a circumferential groove 23 to retain a suitable O-ring 24 to seal the interior of the valve body 16 from the atmosphere.

The valve body 16 contains a co-axial stack 25 of sheet metal disks such as, for example, the disk 26 shown in FIG. 2. Each of the disks 26 is formed with a central circular opening 27 of a diameter to permit axial movement of the poppet body 17 therethrough with a very slight clearance, on the order 0.0005 inches. In addition, each disk 26 is formed with a plurality of circularly spaced apart perforations 28, all of the disks having the same pattern of holes 28 to define passages through the stack of disks to receive the unthreaded shanks of a plurality of bolts 29. As is shown in FIG. 1, the underside of the member 11 is formed with a circular recess 30 to receive a clamping ring 31 having internal and external diameters which are the same as the external and internal diameters of the disks 26. The clamping ring 31 is provided with a bolt hole pattern corresponding to the pattern of the disk opening 28, the bolt holes being countersunk to receive the heads of the bolts 29. The bottom of the valve body 16 is formed with a plurality of tapped bores 32 arranged in the same hole pattern as the bolt hole pattern of the clamping member 31. Accordingly, by torquing each of the bolts 29 to the same degree, the clamping ring 31 applies a uniform pressure to the stack of disks 25 to axially compress the disks between the clamping ring and the base of the valve body.

The tubular portion 20 of the valve is provided with an inlet 35 that is in communication with a high pressure source of a gas, while the valve body 16 is provided with an outlet 36 to supply downstream demand. As is shown in FIGS. 2 and 3, one face of each disk 26 is formed with a plurality of grooves 37 separated by land areas 39 so that each pair of disks defines a plurality of radially extending passageways 40 through which gas may flow upon actuation of the poppet 17. An annular area 41 is defined between the outer periphery of the stack 25 of disks and the surrounding wall of the valve body 16. Accordingly, upon downstream demand being sensed by the regulator assembly the poppet 17 is raised from the fully closed position shown in FIG. 1, whereby gas flows radially outwardly through the stack of disks into the annulus 41, thence to supply the downstream demand through the outlet 36.

In the exemplary disk 26, there are four quadrants of the grooves 37, each quadrant in this case containing ten of the diffuser grooves, the quadrants being separated by relatively broad land areas 39a in which the bolt hole perforations 28 are formed. FIG. 4 is a partial plan view of another exemplary form of disk 42, formed on one surface with another configuration of radially extending diffuser grooves 43 separated by land portions 44. While not fully shown, it is to be understood that the disk 42 is also divided into sectors or quadrants, each containing a plurality of the passages 43, each of the sectors or quadrants being separated by relatively large land areas adapted to accommodate a desired hole pattern of perforations for receiving the corresponding bolts utilized in the compression of a stack of such disks.

The disks 26 and 42 are specifically adapted for use in a valve designed for handling of high pressure air or nitrogen or the like. As such, they are preferably made by a chemical milling process with a desired number of grooves being etched out of one surface of a thin sheet of metal as for example, stainless steel on the order of 0.002 inch in thickness and with a depth of etch of the grooves on the order of 30 microns. It will also be understood that, depending on the desired characteristics of the valve, with respect to flow rate and inlet and outlet pressures, each disk may be made in any desired pattern of sectors or quadrants of grooves, each containing a desired number of the grooves, with each quadrant or sector being divided by an appropriate number of land areas within which the bolt hole perforations may be formed in a desired hole pattern. Additionally, while it is preferred that each groove be formed to define a substantially rectangular cross-sectional area, other cross-sectional areas may be employed so that each groove defines a passageway of non-polygonal cross-sectional configuration when placed on a stack of similar disks, with each groove being closed by an unetched area of another disk thereon, or with each groove in registration with a similar groove of another disk thereon. Furthermore, while in the case of the disks 26 and 42 the grooves 37 and 43, respectively are symmetrically formed with radii of the disk as their axes of symmetry, the grooves may be sinuous or tortuous in form. In any event, for optimum sound suppression in accordance with the invention it is desired that each groove increase in cross-sectional area, from the inlet end to the outlet end thereof, at a rate which will effect a substantially constant velocity of the gas therethrough, with a desired gradual rate of increase of the specific volume of the gas from the inlet to the outlet, and with a desired gradual rate of reduction of pressure from the inlet to the outlet.

By way of example, let it be assumed that the regulator valve of FIG. 1 contains a compressed stack of the disks 26 of FIG. 2, having grooves 37 etched in one face only thereof, the grooves of each disk being closed by the unetched continuously planar underface of an adjacent disk to define the passages 40. As illustrated in FIG. 2, each groove 37 has sidewalls constituting radii of the disk 26 with an inlet having a width on the order of 1/4 or 1/5 of the width of the outlet end of the groove. Accordingly, when placed in a compressed stack 25, the disks 26 define radial diffuser passages 40 with a cross-sectional area expansion ratio on the order of 4 or 5 to 1, at a uniform rate of expansion, geometrically.

The disk 42 of FIG. 4 is formed with grooves 43, providing a changing rate of cross-sectional area expansion, in which the sidewalls of each groove 43 diverge from the inlet to the outlet ends thereof at a rate which increases with increase in radius of the cross-sectional area from the center of disk 42. For example, it being understood that the representation of FIG. 4 is schematic, let it be assumed that the disk 42 has an inner diameter of .875 inches and an outer diameter of 3.50 inches. In this instance, where it was desired to maintain a constant velocity of air, of dew point -50.degree.F., through each diffuser passage at approximately 300 feet per second, with each passage delivering approximately 0.3 scfm, to achieve a pressure drop of about 3,800 psig, the grooves 43 were sized as follows. Each groove was etched to a depth of 30 microns with the width increasing at an increasing rate proportional to its radius from the geometric center of the disk. In view of the desired substantially constant velocity and the specified pressure reduction of the particular gas, the width of the passage 43 was determined at radius increments R' 0.437 inches, R" 0.650 inches and R'" 1.750 inches as widths a 0.017, b 0.025 and c 0.041 inches, respectively, with intermediate points interpolated and joined by plotting a curve. As a result, there was a decrease in pressure gradient from the inlet to the outlet from 4,500 to 735 psig and an increase in specific volume gradient of the air from inlet to outlet from 0.0458 to 0.248 ft. 3/lb. The gas velocity through each passageway was thus maintained substantially constant at 300 feet per second, decreasing to no less than 280 feet per second at the exit, and the temperature of the air flowing through each passageway remained at substantially 32.degree.F. As the velocity of the gas flow was maintained substantially constant, the noise generated was radically less than the noise which would otherwise have been generated in a comparable valve in which the pressure differential was a function only of the clearance of the poppet with respect to the valve seat, or by dividing the gas for passage through small orifices of uniform cross-section throughout their length. In addition, freezing of air in the flow channels was prevented, the temperature having been maintained on the order of 80.degree.F. above the dew point of the air being passed, in view of the elimination of abrupt expansion of cross-sectional area throughout the length of each flow passage.

As is shown in FIG. 1, the valve seat 19 is located immediately beneath the stack 25 of disks and when the seat is closed by the poppet 18 the inlet ends of all of the disks of the stack are closed by the poppet body 17. As will be apparent, the amount of exposure of the inlets to the stack of disks is proportional to the linear displacement of the poppet 18 from the seat 19. Under conditions of partial flow, a portion of the poppet body 17 continues to close the inlets to a corresponding axial length of the stack 25. In this connection, it is desirable to minimize, as greatly as possible, the flow of gas between the poppet body 17 and the inlets to that length of the stack desired to be closed. Accordingly, the clearance between the poppet body 17 and the inner peripheries 27 of the stack of disks should be held to a minimum and, under conditions of partial flow, the poppet body 17 must be maintained in precise co-axial alignment with the inner edges or peripheries 27 of the stack of disks. As the poppet control rod 13 and the poppet body 17 have a close sliding fit in the central opening of the member 39 and in the guide cylinder 12, at one end, and at the other end is interconnected to the rod extension 21 whose lower end is supported by the guide member 22 having a close sliding fit with the tubular extension 20, the desired precise co-axial alignment of the poppet body 17 in the stack 25 can be maintained in all conditions of flow, the poppet being balanced.

As will now be apparent, when the poppet 18 is open, the flow resistance through the valve is greater than merely the resistance created by the linear displacement of the poppet 18 from the seat 19, and comprises the sum of the flow resistances of the exposed radial diffuser passageways through the stack 25 of disks. The velocity of the gas through the valve is not a function of the linear displacement of the poppet 18 from its seat 19 but is, instead, a function of the configuration of the divergent diffuser passages, such as the passages 37. As the diffuser passages maintain a substantially constant velocity of the gas flowing therethrough, at a desired rate which is less than the sonic range for the pressure differential of the particular valve under consideration, the creation of noise due to the pressure reduction between inlet and outlet, which may be very great, is minimized. In this connection, the use of non-circular diffuser passageways is preferred to induce turbulence in the flow of the gas therethrough, to both increase the frictional resistance to the flow and to inhibit any tendency to increase the pressure of the gas in its passage from the inlet to the outlet ends thereof.

While specific presently preferred embodiments of the invention have been disclosed and described, it will be appreciated that variations from the specific geometry and relationship of the parts may be made, all within the purview of the invention.

Claims

We claim:

1. A constant velocity gas flow control device comprising:

a housing having an inlet and an outlet intercommunicated by a gas flow passage;

a rigid gas flow velocity control means rigidly mounted in said housing and having sufficient cross-sectional area to fully occupy the cross-sectional area of that portion of said flow passage in which said rigid means is mounted;

said rigid means comprising a compressively loaded stack of planar members of abutting surface shape characteristics defining a plurality of rigidly inflexibly defined, clear unobstructed flow passageways therethrough, between adjacent pairs of said planar members, oriented to intercommunicate inlet and outlet portions of said flow passage, each of said passageways having an exit, opening into the outlet portion of said passage, that is of larger cross-sectional area than the cross-sectional area of the entrance of said passageway,

each of said passageways increasing in cross-sectional area from its entrance to its exit along a predetermined gradual gradient of increase of cross-sectional area for maintaining the velocity of the gas substantially constant during passage through each of said passageways.

2. A device as in claim 1 in which each of said passageways is formed about a straight line axis of the passageway.

3. A device as in claim 1 in which said predetermined gradient of increase in cross-sectional area of each passageway is at a non-uniform gradually increasing rate.

4. A device as in claim 1 in which said device includes a valve member having a surface of shape characteristics matingly complementary to that end of said rigid gas flow control means in which said entrances of said passageways are formed, said valve member being mounted for movement in a direction to vary the number of said entrances that are obstructed by said valve member.

5. A sound suppressing valve comprising:

a valve housing having an inlet and an outlet intercommunicated by a flow passage;

a stack of planar laminae, each of which comprises a thin flexible sheet that is formed with a plurality of individual lands on at least one surface thereof for abutment with a confronting surface of an adjacent one of said sheets, all of said sheets having some lands arranged for superimposition when said stack is under compression, the voids between said lands providing a plurality of rigidly inflexibly defined, clear unobstructed passageways through said stack between each adjacent pair of said sheets when said stack is held under compression imposed on said superimposed lands, each of said passageways being gradually divergent with an exit orifice, opening into the outlet portion of said flow passage, that is of larger cross-sectional area than the cross-sectional area of the inlet orifice of said passageway, each of said passageways increasing in cross-sectional area from its inlet to its exit along a predetermined gradual gradient of increase of cross-sectional area to maintain a substantially constant velocity during gas flow from the inlet to the exit of said passageway;

a means in said valve housing for supporting said stack, under compression, across an outlet portion of said flow passage whereby said stack is rigidified and defines a high density of inlet and outlet orifices of said flow passageways on opposite sides of said stack comprising the sum of the pluralities of said passageways defined between each pair of adjacent sheets in the compressed stack;

and a valve member having a surface of shape characteristics matingly complementary to that end of said compressed stack in which said inlet orifices of said passageways are defined, said valve member being mounted for movement in a direction to vary the number of said inlet orifices that are obstructed by said valve member.

6. A valve as in claim 5 in which each of said sheets comprises a sheet of metal that is etched on at least one surface thereof to define said lands, with the etch-roughened surfaces of said sheet of metal comprising part of said passageways to induce frictional drag in the gas passing therethrough.

7. A valve as in claim 6 in which said stack is comprised of annular sheets and each of said lands extends from the inlet side to the outlet side of said stack to define one of said plurality of passageways between adjacent ones of said plurality of lands.