Processing

Please wait...

Settings

Settings

1. WO1979000043 - PRESSURE VARIATION ABSORBER

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

C L A I. M S
1. A diffuser (14) for use with compressible
fluids in a centrifugal compressor which is characterized by a plurality of walls having a fluid flow path
therebetween, one end of said path receiving the compressible fluid at relatively high speed and low static pressure and the other end of said path discharging the fluid at relatively low speed and high static pressure;
and a pressure variation absorber (10) being mounted -in direct acoustic and aerodynamic communication with
the fluid in the diffuser for absorbing both acoustic
and aerodynamic pressure variations.
2. The invention as set forth in claim 1, wherein the pressure variation absorber comprises a porous absorbing material (20) and a resonant cavity (18) , said
absorbing material being in communication with both the fluid in the diffuser and the fluid in the cavity.
3. The invention as set forth in claim 2, wherein the absorbing material is mounted to form a portion
of the walls having the fluid flowing therebetween.
4. The invention as set forth in claim 3, wherein the cavity is at least partially filled with damping
material.
5. The invention as set forth in claim 4, wherein the resonant cavity is divided into a plurality of
separate cavities each communicating with the absorbing material.
6. . The invention as set forth in claim 1, wherein the absorbing material has a flow resistance approximating the product of the fluid density times the speed
of sound in the fluid in the diffuser.
1 , In a centrifugal compressor or other dynamic head device for supplying a compressible fluid under
pressure and having a housing containing a fluid path
including an inlet port (42) and an impeller chamber
(46); an impeller (26) rotatably mounted within the
impeller chamber so that fluid enters into the impeller chamber and is accelerated by the impeller; a diffuser
(14) which receives the accelerated fluid from the _^-~. impeller; and a collector (12) for discharging fluid f O
Vtyxm, under pressure received from the diffuser, the improvement characterized by a pressure variation absorber
(10) being mounted in direct aerodynamic and acoustic communication with the fluid in the diffuser for
absorbing both acoustic and aerodynamic pressure variations.
8. The invention as set forth in claim 7 , wherein the pressure variation absorber comprises a porous
absorbing material (20) and a resonant cavity. (18) , said absorbing material being in communication with both the fluid in the diffuser and the fluid in the cavity.
9. The invention as set forth in claim 8, wherein the absorbing material is mounted to form a portion of the diffuser wall surface.
10. The invention as set forth in claim 9, wherein the resonant cavity is at least partially filled with an acoustic and aerodynamic damping material.
11. The invention set forth in claim 10, wherein the resonant cavity is divided into a plurality of
separate cavities each communicating with the absorbing material.
12. The invention as set -forth in claim 7, wherein the absorbing material has a flow resistance approximating the product of -the fluid density times the speed of sound in the fluid in the diffuser- 13. The invention as set forth in claim 10, wherein the resonant cavity is divided by a helical plate into a single helical cavity.
14. Apparatus for reducing aerodynamic and acoustic pressure variations within a moving stream of compressible fluid which is characterized by walls formed to provide a flow path for a stream of fluid, at least a portion of a wall of the flow path being constructed of porous material (10) permeable to the fluid in the flow path; and a resonant cavity (18) located adjacent the porous material on the side of the porous material away from the flow path, said porous material being capable of allowing fluid flow between the flow path and the resonant cavity.

15. The apparatus as set forth in claim 14, wherein the flow resistance of the

the product of the fluid density and the velocity of sound in .the fluid.
16. The apparatus as set forth in claim 15, wherein the depth of the resonant cavity is equal to one quarter of the wavelength of the lowest design frequency of pressure variations for which a coefficient of absorption of one is desired.
17. The apparatus of claim 14, wherein the resonant cavity includes means (22) to divide the cavity into a series of smaller cavities to reduce the fluid flow within the resonant cavity resulting from pressure variations within the fluid stream moving along the flow path.
18. The apparatus of claim 17, wherein the series of smaller cavities is at least partially filled with pressure variation damping material to further feduce pressure variations within the fluid stream.
19. A method for increasing the efficiency of a centrifugal compressor while reducing the audible noise emitted from the compressor and for providing a greater operational flow range of the compressor by reducing the flow volume at which surge occurs which is characterized by the steps of accelerating a compressible fluid with an impeller (16); receiving the accelerated fluid in a diffuser (14) wherein the fluid is slowed to
increase its static pressure; collecting the fluid in a collector (12) at high pressure; and absorbing both aerodynamic pressure variations and acoustic pressure variations within the diffuser.
20. The invention as set forth in claim 19,
wherein the step of absorbing pressure variations includes locating a porous absorbing material (20) in communication with the fluid; and providing a resonant cavity (18) in communication with the absorbing material whereby fluid flows between the cavity and the diffuser through the absorbing material.
21. The invention as set forth in claim 20, and further including the step of damping the aerodynamic and acoustic pressure variations within the cavity.
22. The invention as set forth in claim 21, and further including the step of dividing the resonant cavity to provide a plurality of smaller cavities each in communication with the absorbing material.
23. The invention as set forth in claim 22, wherein the step of locating a porous absorbing material includes the step of selecting a porous material so that its flow resistance approximates the density of the fluid multiplied by the speed of sound in the fluid.
24. A method for increasing the flow efficiency of a compressible fluid stream while reducing the audible noise emitted from the fluid and for providing a greater operational flow range by reducing acoustic aerodynamic pressure variations which is characterized by the steps of selecting an aerodynamic and acoustic pressure vari- ation absorbing material (20) having a flow resistance equal to the density of the fluid times the speed of sound of the fluid; locating the absorbing material in communication with the fluid; and providing a resonant cavity (18) in communication with the absorbing material so that fluid may flow through the absorbing material into the cavity.
25. The invention as set forth in claim 24 and further including the step of damping the aerodynamic and acoustic pressure variations within the cavity.
26. A method for increasing the flow efficiency of .a compressible fluid stream by reducing acoustic and aerodynamic pressure variations within the stream which is characterized by the steps of channelling the fluid stream along a flow path; interrupting fluid
flow along the flow path by mounting a resonant cavity (18) in direct communication therewith so that fluid may flow between the cavity and the flow path; and limiting the amount of fluid flow between the cavity and the flow path by locating a porous absorbing material (20) between the cavity and the flow path whereby
pressure variations within the fluid stream are absorbed without significantly reducing the fluid flow along the flow path.
27. The method of claim 26, wherein the step of limiting the fluid flow includes selecting an absorbing material

product of the fluid density times the velocity of sand in the fluid.
28. The method of claim 26, and further including the step of damping pressure variations within the
resonant cavity by at least partially filling said
cavity with a damping material so that the pressure variations in the fluid stream are further reduced.

IJURE

OMPI AMENDED CLAIMS
(received by the International Bureau on 12 July 1978 (12.07.78))

1. In a centrifugal compressor or other dynamic head, device for supplying a compressible fluid under pressure
and having a housing containing a fluid path including an
inlet port (42) and an impeller chamber (46); an impeller
(26) rotatably mounted within the impeller chamber so that
fluid enters into the impeller chamber and is accelerated by ' the impeller; a diffuser (14) which receives the accelerated fluid from the impeller; and a collector (12) for discharging fluid under pressure received from the diffuser, the improvement characterized by a pressure variation absorber
(10) being mounted in direct aerodynamic and acoustic communication with the fluid in the diffuser for absorbing both acoustic and aerodynamic pressure variations.
2. The invention as set forth in claim 1, wherein the pressure variation absorber comprises a porous absorbing
material (20) and a resonant cavity (18) , said absorbing
material being in communication wit both the fluid in the
diffuser and the fluid in the cavity.
3. The invention as set forth in claim 2, wherein the absorbing material is mounted to form a portion of the diffuser wall surface.
4. The invention as set forth in claim 3, wherein the resonant cavity is at least partially filled with an
acoustic and aerodynamic damping material.
5. The invention set forth in claim 4, wherein the
resonant cavity is divided into a plurality of separate
cavities each communicating with the absorbing material.
6. The invention as set forth in claim 1, wherein the absorbing material has a flow resistance approximating the
product of the fluid density times the speed of sound in the fluid in the diffuser.
7. The invention as set forth in claim 4, wherein the resonant cavity is divided by a helical plate into a single helical cavity. - _ _^yQ~

8. A method for increasing the efficiency of a
centrifugal compressor while reducing the audible noise emitted from the compressor and for providing a greater operational flow range of the compressor by reducing the flow volume at which surge occurs which is characterized by the steps of accelerating a compressible fluid with an impeller (16); receiving the accelerated fluid in a diffuser (14) wherein the fluid is slowed to increase its static pressure; collecting the fluid in a collector (12) at high pressure; and absorbing both aerodynamic pressure variations and acoustic pressure variations within the diffuser.
9. The invention as set forth in claim 8, wherein the step of absorbing pressure variations includes locating a porous absorbing material (20) in communication with the fluid; and providing a resonant cavity (18) in communication with the absorbing material whereby fluid flows between the cavity and the diffuser through the absorbing material.
10. The invention as set forth in claim 9, and further including the step of damping the aerodynamic and acoustic pressure variations within the cavity.
11. The invention as set forth in claim 10, and
further including the step of dividing the resonant
cavity to provide a plurality of smaller cavities each in communication with the absorbing material.
12. The invention as set forth in claim 11, wherein the step of locating a porous absorbing material includes the step of selecting a porous material so that its flow resistance approximates the density of the fluid multiplied by the speed of sound in the fluid.

-^RE
O P STATEMENTUNDERARTICLE 19

1. Enclosed is a placement sheet for pages 10, 11, 12, and 13 of the International Application. Page 14 of the original application is' hereby cancelled. The amendment involves the* cancellation of originally filed claims 1 to 6, 14 to 18 and 24 to 28 together with the renumbering of original claims 7 to 13 and 19 to 23 and the associated changes in the dependences- set forth in these claims. The language of the claims maintained in the application has not changed. .
2. The amendments have been made to reduce the number of independent claims in the application to those independent claims, together with their dependent claims, which most clearly expressed the inventive advance provided by the present invention.