Abstract:
A noise reducing apparatus and method for handling of fluid comprises a plurality of discs stacked on one another, each disc having a radially inner periphery and a radially outer periphery, and a plurality of fluid flow channels defined on at least some of the discs and extending from the inner periphery to the outer periphery. One or more sound reducing material elements are disposed to extend across at least some of the fluid flow channels so that fluid flowing through the channel passes through the sound absorbing material. Alternatively, a plurality of sound absorbing wafers are disposed in between adjacent discs and form a respective wall of the flow channels with respect to the flow channel of an adjacent disc.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to the field of fluid handling and acoustics, and more particularly pertains to devices and methods that can be used as a control valve and/or noise reducer that reduces fluid pressure, controls velocity of a fluid, and/or reduces noise that is generated by the fluid velocity in valve and fluid control operations. The present invention thus relates to noise control in valves, trims and/or flow controllers. 
   BACKGROUND OF THE INVENTION 
   There are a wide number of applications in industry and elsewhere where fluid is controlled within a gas or hydraulic system of some type. These fluid handling systems often involve valves which may regulate flow, not only from an on/off standpoint, but also provide intermittent flow modulation. In particular, flow control devices are known that are used in high pressure applications and typically include a valve trim which is a sort of flow restrictor. Valve trims can provide several advantages, particularly in the case of high pressures. 
   Typical valve trims are comprised of a single orifice, where the pressure is reduced in a single stage of pressure drop. Although the invention has applications with both compressible and non-compressible fluid flow, the major source of valve noise is aerodynamic noise in compressible fluid systems. Aerodynamic noise is noise generated from having Reynolds stresses or shear forces in a turbulent flow stream resulting from deceleration, expansion, or impingement. The principal area of noise generation in a control valve is the recovery region immediately downstream of the vena contracta, where the flow field is characterized by intense mixing and turbulence. 
   The best way to reduce valve generated noise is to reduce noise at the source, which is at the valve trim. Disc stack technology has provided several advantages over standard single stage valve trim with regard to noise reduction in a fluid handling system. One advantage that disc stack technology provides is the design uses multi-path flow geometry, where the flow stream is subdivided into many small paths. The fluid energy at the outlet of many small flow paths is much lower than at the outlet of a single large flow path of equivalent area. Multi-path trim designs are known to provide noise levels that are up to 15 dBA lower than standard trim. Another advantage is that the flow paths are configured to have a multistage pressure drop. This reduces the turbulence and energy release at each stage, reducing the overall generated noise. Disc stack valves also control fluid velocity, which is a noise generator in all fluid systems, and typically have an expanding flow path to reduce velocity and allow for fluid expansion. 
   The characteristic of disc stack trims for having a gradual pressure decrease is beneficial in permitting a valve to move between open, closed and intermediate flow positions without subjecting the entire system to excessive shocks. Another benefit of known valve trims is that they can provide noise attenuation within the fluid handling system. By gradually reducing the flow pressure in multiple stages over the valve trim area, the valve trims have proven very effective in reducing noise. 
   The geometry of the fluid path that is formed can take on a variety of configurations. The individual discs are assembled to create the so-called “disc stack” trims where a fluid restrictor is provided in connection with a valve. In one type of arrangement, a disc stack having a number of convoluted radial fluid paths is provided with a control element in the form of a fluid restriction or a plug centrally moveably provided within the disc stack. The fluid restrictor or plug is moved within the disc stack to expose a greater or smaller number of fluid paths thus controlling the amount of fluid flow. In addition to creating less valve-generated noise, such disc stacks are capable of providing a benefit of silencing existing noise in a flow stream as well. Besides the use of disc stacks in connection with the valve itself, the stacks have also been used as a silencer placed down stream of a control valve or at the end of a pipeline where it is desirable to reduce fluid pressure in a quiet manner. 
   There are many known arrangements of disc stack technology in industry. In general, in these devices, the convoluted flow path is formed as a series of radial grooves in a single disc that are torturous in nature. A number of multi-path, multistage discs are stacked on top of one another to form a cylindrical shaped disc stack. As mentioned above, the paths in the disc can be blocked or exposed by a plug moveably disposed in the center of the layer of discs. Because the paths are torturous, in that they provide a number of obstacles, right angle turns, expansion in the flow path, and a relative long overall flow path which creates frictional resistance, the pressure in the fluid as it travels through the path is reduced in a way that controls the velocity of the fluid. Because high velocity fluid can be a source of noise generation, reduction in velocity reduces noise, and the fluid also exits the valve trim at a much lower velocity compared to if a single orifice were used, thus allowing the valve trim to provide quiet operation compared to a single orifice. 
   While the above described noise reducing systems have proven to be very successful, it would be desirable to have even lower noise generation performance than is provided by the known disc stacks. Accordingly, there is a need in the art for sound attenuation devices and methods that can provide enhanced performance and/or convenience of manufacture and use in some applications. 
   SUMMARY OF THE INVENTION 
   The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments provides enhanced noise reduction and/or pressure drop or other benefits. 
   In accordance with one embodiment of the present invention, a pressure reducing apparatus for handling of fluid comprises a plurality of discs stacked upon one another, each disc having a radially inner periphery and a radially outer periphery, and a plurality of fluid flow channels defined on at least some of the discs and extending from the inner periphery to the outer periphery; and one or more sound reducing material elements disposed in the disc stack to extend across at least some of the fluid flow channels so that fluid flowing through the channel passes through the sound absorbing material. 
   In accordance with another embodiment of the present invention, a pressure reducing apparatus for handling of fluid comprises a plurality of adjacent discs stacked upon one another, each disc having a radially inner periphery and a radially outer periphery, and a plurality of fluid flow channels defined on at least some of the discs and extending from the inner periphery to the outer periphery; and a plurality of sound absorbing wafers disposed in between at least some adjacent discs and forming a respective wall of at least a portion of the flow channels with respect to the flow channel of an adjacent disc. 
   In accordance with still another embodiment of the present invention, a pressure reducing apparatus for handling of fluid comprises a plurality of discs stacked upon one another, each disc having a radially inner periphery and a radially outer periphery, and a plurality of fluid flow channels defined on at least some of the discs and extending from the inner periphery to the outer periphery; and sound reducing means disposed in the disc stack to extend across at least some of the fluid flow channels so that fluid flowing through the channel passes through the sound absorbing material. 
   In accordance with yet another embodiment of the present invention, a pressure reducing apparatus for handling of a fluid comprises a plurality of adjacent discs stacked upon one another, each disc having a radially inner periphery and a radially outer periphery, and a plurality of fluid flow channels defined on at least some of the discs and extending from the inner periphery to the outer periphery; and sound absorbing means disposed in between at least some adjacent discs and forming a respective wall of at least a portion of the flow channels with respect to the flow channel of an adjacent disc. 
   In accordance with another embodiment of the present invention, a method of pressure reduction for handling of fluid comprises providing a plurality of discs stacked upon one another, each disc having a radially inner periphery and a radially outer periphery, and a plurality of fluid flow channels defined on at least some of the discs and extending from the inner periphery to the outer periphery; and inserting one or more sound reducing material elements into the disc stack disposed to extend across at least some of the fluid flow channels so that fluid flowing through the channel passes through the sound absorbing material. 
   In accordance with another embodiment of the present invention, a method of pressure reduction for handling of a fluid, comprises providing a plurality of adjacent discs stacked upon one another, each disc having an radially inner periphery and a radially outer periphery, and a plurality of fluid flow channels defined on at least some of the discs and extending from the inner periphery to the outer periphery; and inserting a plurality of sound absorbing wafers in between adjacent discs and forming a respective wall of at least a portion of the flow channels with respect to the flow channel of an adjacent disc. 
   There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
   In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
   As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cut-away plan view of a disc stack according to a first preferred embodiment of the present invention. 
       FIG. 2  is a cross-sectional view taken through lines  2 — 2  in  FIG. 1 , also showing a valve plug as well as a top plate not seen in  FIG. 1 . 
       FIG. 3  is a perspective cut-away view of a second embodiment of the invention. 
       FIG. 4  is a cross-sectional view of a valve using the disc stack. 
   

   DETAILED DESCRIPTION 
   The present invention provides improved apparatuses and methods for reducing noise and/or providing pressure drop in a fluid handling system, which may be used with or without an associated valve plug arrangement. Preferred embodiments of the invention will now be described with references to the drawing figures, in which like reference numbers refer to like parts throughout. 
   In a first embodiment illustrated in  FIGS. 1 and 2 , a disc stack type fluid handling valve and/or trim  10  is shown.  FIG. 1  is a top cut-away plan view showing a first disc  12 . The disc  12  has torturous flow passages, also referred to as torturous flow paths, labeled  14 ,  16  or  18  as illustrated. The paths  14 ,  16 , or  18  illustrate alternative examples of typical flow paths. In a preferred embodiment, one or the other types of torturous paths  14 ,  16  or  18  would usually be utilized all around the circumference of the disc. Another example of a suitable torturous path stage is shown in U.S. Pat. No. 6,161,584, titled “HIGH ENERGY LOSS FLUID CONTROL DEVICE”, issued Dec. 19, 2000, the disclosure of which is hereby incorporated by reference in its entirety. 
   That is, the illustrated embodiment  12  shows three different exemplary types of paths  14 ,  16  or  18  for convenience. Some embodiments use different types of paths such as shown, while other embodiments would simply use one of the illustrated types of paths, or any other torturous path. By way of example, the type of path  14  is a relatively straight radial passage having an expanding cross-section moving radially outwardly. The type of path  16  provides for four fluid turns or pressure drop stages leading in a single collection point that then splits into two further paths that then meet at a single outlet. The type of path  18  each has a first radial portion which moves around a central block, and then extends outward to a diverting path leading to an outlet, also providing for four fluid turns. 
   The paths such as  14 ,  16  or  18  may be provided in various ways. In one embodiment, the paths are cut part way into the depth of the disc, so that a plurality of discs can be stacked on top of each other with the paths formed in between. 
   The paths  14 ,  16  and  18  lead from a central hole or bore  20  forming a radially inward edge of the stack, (which can be blocked by a movable plug  22  (see FIG.  2 )), to the radially outer circumference  24  of the disc. 
   A feature of some preferred embodiments of the invention is the addition of a sound absorbing material insert  50  into the disc stack. In the example shown in  FIGS. 1 and 2 , a plurality of noise reducing valve inserts  50  have been placed into the structure as shown. The inserts  50  are disposed in axially extending curved slots in the disc stack in such a way so that all the fluid has to pass through one of the inserts  50  on its travel through the disc. Examples of appropriate sound absorbing material for the insert  50  include for example, knitted wire mesh or metal foam. Another example of material is sintered metal. Other porous materials are also suitable. 
   It will be appreciated that by virtue of the placement of the sound absorbing material  50 , the fluid is subjected not only to a torturous, convoluted, or otherwise specially designed path via the passages  14 ,  16  or  18 , for example, but also moves through the sound absorbing material  50  as well. The sound absorbing material  50  also in some embodiments interconnects to some extent some adjacent paths within one disc, and also in some embodiments axially connects to some extent a number of the paths between different disc stacks. This provides a further degree of complexity to the flow path, and/or pressure equalization between paths, which further can reduce noise. 
   In the embodiment illustrated in  FIG. 1 , it is seen that a number of generally C-shaped cylindrical cutout sound reducing material regions  50  are provided. The number and spacing of these regions can be modified in any desirable fashion. For example, a continuous cylindrical ring of sound absorbing material might be provided, located radially in between two metal path discs having different and inner diameters and outer diameters. On the other hand a larger number of concentric individual sound-reducing material rings, or partial rings, might be provided. Further, while in the embodiment illustrated in  FIG. 1 , each torturous path intersects with only one sound reducing layer  50 , it will be appreciated that a greater number of sound reducing layers could be used along each torturous path. Also in some embodiments, there may be paths that do not interact with a sound-reducing plug  50 . 
     FIG. 3  illustrates an alternative embodiment of the invention.  FIG. 3  illustrates two discs  112  each having torturous paths  114  carved partially through their depths. A ring of sound absorbing material  150  resides in the channel of the bottom surface of each disc  112  as shown. It will be appreciated that each torturous path  114  thus has as part of its top enclosed surface the sound absorbing material  150 . The sound absorbing material  150  can be selected from any of the materials that have been identified as suitable for use as the sound absorbing material  50  in the first embodiment. 
   In other words, in the embodiment of  FIG. 3 , one wall of at least part of the torturous path is provided by the sound absorbing material  150 . In this embodiment, the fluid does not necessarily pass through the sound absorbing material as in the first embodiment, however it flows along the sound absorbing material and thus noise is suppressed when the sound energy is dissipated within and through the material. For example, in the case of knitted wire mesh used as the material  150 , the sound energy causes the wires to vibrate, converting acoustical energy to thermal energy and thus reducing sound. 
   In the embodiment of  FIG. 3 , the sound absorbing material  150  is in the form of wafers inserted into a groove formed on the bottom surface of each disc, opposite of the side with the flow pattern in order to be trapped between the discs. Alternatively, the sound absorbing discs  150  could have the full diameter of the discs  112 , and thus the discs  150  can be alternated with the discs  112  without residing in a channel therein. 
   Accordingly, some embodiments of the invention reduce sound by taking advantage of two different structural and operative features. A first feature is the provision of multi-path multi-pressure drop, velocity control flow paths, inherent with many disc stack designs which have the effect of reducing noise. Since each flow path and pressure drop can be considered a noise source, this is done by creating many lower energy noise sources in place of one high energy noise source resulting in less turbulence and noise. Using many small flow passages also has the effect of creating a frequency shift in the fluid generated noise, or valve generated noise which has the benefit of higher frequency transmission loss through the pipe wall. 
   Preferred embodiments of the invention also take advantage of the second feature of using a noise suppressing material such as for example a mesh material, a fibrous material, a foam material, or other porous materials to suppress noise. A material such as for example knitted wire mesh or metal foam can effectively reduce noise acting as a sound barrier when the fluid must pass through it or along it. The fluid is broken up into small flow streams producing greater restriction and velocity reduction than might be provided by a disc stack flow path without the additional sound absorbing material. 
   In the examples shown in  FIGS. 1 and 2 , one or more sound absorbing elements  50  are inserted into the stack formed by the discs  12 . Each disc  12  has a flow pattern  14 ,  16  or  18  formed partially into one portion of the disc  12  and also has a central hole  20  through the disc so that when the discs are stacked together an element of sound absorbing material  50  can be inserted through all the discs  12 , essentially along the length of the disc stack. With compressible fluids, the flow will generally be in the direction from the inside periphery  20  of the disc stack to the outside periphery  24 . In the case of a valve trim, as the plug  22  is withdrawn and the disc is exposed, the fluid will be subdivided into a number of flow passages  14 ,  16  or  18 . Before the fluid reaches the outside periphery  24 , it will be forced to pass though the sound absorbing element  50 . Because only a predetermined number of holes are exposed on the inside periphery  24  of the disc  12 , the fluid can exit the trim through any number of holes around the outside of the trim as the fluid can pass axially, radially, and or circumferentially through the element  50  ensuring that fluid velocities are low. In some embodiments, noise is significantly reduced using noise reduction qualities that exist with both the disc stack and sound absorption techniques. 
   The disc stack has end caps  30  and  32  (see  FIG. 2 ) to prevent the fluid from passing out the ends. In one preferred optional feature of this embodiment, the disc stack can be constructed so that the sound absorbing elements  50  are removable for cleaning or replacement should they become clogged with debris. That is, one or both of the end caps  30  and  32  can be removed and the sound absorbing elements  50  can be slid out for cleaning or replacement. This can provide advantages in some applications, because the sound absorbing elements  50  can also provide some degree of filtration, particle removal, or debris removal if desired. 
   Although the sound absorbing material  50  can be selected to reduce sound, the material could alternatively be selected for its filtration or other properties such as merely for pressure drop. 
   Another benefit of the removable type of sound absorbing elements  50  is that different materials or types of sound absorbing elements can be substituted for different applications. That is, the overall pressure drop and noise reducing characteristics, as well as filtration ability, clogging resistance, material compatibility, useful life, etc., of a given disc stack can be adjusted by selecting an appropriate mesh size, porosity, and the like of the sound absorbing material. 
   Turning to the embodiment of the  FIG. 3 , it will be appreciated that a number of wafers of sound absorbing material  150  are trapped with each one respectively being trapped between a pair of adjacent discs  112 . The fluid passes through the passages  114  that are formed in the disc  112  surface, and the noise is reduced using the velocity control methods provided by the disc stack flow path. Further, the noise is also additionally reduced by having the sound absorbing material  150  on one surface of at least part of the flow path. The incident sound energy waves are absorbed at least to some extent by the wafer material  150  which provides a damping effect on any noise that is generated in the pressure reduction process of passing through the paths in the disc stack. The surface of the sound absorbing material may also be rough at least to some extent and in such a case will add frictional resistance to the flow path helping control the velocity of the fluid. 
     FIG. 4  is a cross-sectional view of a valve system  100  including a valve body  102  having an inlet  104  leading to a flow channel  106 . An inlet region  108  at the lower part of the disc stacks leads upward into a plurality of stacked discs  12 . To the left of the center line of this drawing the plug  22  is shown in a lowered or closed position and so fluid is not able to reach the paths in the discs  12 . In this position the valve  100  is closed. To the right of the center line of  FIG. 4 , the plug  22  is shown in a fully raised position and the inner periphery of the disc  12  is visible. Fluid flows up through the inlet  108  and through the tortuous paths in each of the discs  12  and is thus able to exit into a flow region  110  and out an outlet  112 . A stem  114  is shown for moving plug  22  up and down between open and closed position. 
   The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.