US20130136626A1 - Screw compressor with muffle structure and rotor seat thereof - Google Patents

Abstract

A rotor seat for a screw compressor with a muffle structure is provided. The rotor seat includes a seat body, a radial exhaust port arranged at the seat, a female rotor hole and a male rotor hole. The rotor seat further includes a plurality of axial blind holes arranged on a surface where the radial exhaust port is located.

Description

BACKGROUND
• The application generally relates to a compressor muffle structure. The application relates more specifically to a rotor seat for a screw compressor with a muffle structure.
• The working principle of compressors commonly used in cooling systems is to increase the pressure of a refrigerant gas from an evaporator to the pressure of the refrigerant gas in a condenser, so that under the increased pressure, the utilization of the refrigerant can be maximized to cool a medium to be cooled. In such compressor systems, a screw compressor can be a commonly used type of compressor. The screw compressor can be provided with a female rotor and a male rotor (also called a concave rotor and a convex rotor), which rotate in a compression cavity. When the rotors rotate, the suction port corresponding to the compression chamber is closed, and as the volume of the chamber decreases, a gas compression effect is achieved.
• A pair of female and male rotors in the screw compressor can incur strong fluid dynamic noise during high-speed rotation. The noise mainly includes periodic gas suction and exhaust noise, expansion and backflow noise of the over-compressed and under-compressed gas, and vortex noise in the tooth slot primitive volume. The fluid dynamic noise is always the main noise source of a screw compressor and a corresponding cooling system. Noise control targeting the fluid dynamic noise can be the most effective type but also has long been a technical problem to be solved in the art.
• In order to solve the problem of the exhaust noise, U.S. Pat. No. 5,051,077 entitled “SCREW COMPRESSOR” proposes to form different steps at a radial exhaust port under female and male rotor holes on a rotor seat body, so as to attenuate the exhaust noise. A drawback of this patent is that only when the volume ratio of the slots formed at the exhaust port reaches a certain value can noise attenuation be accomplished. However, the formation of the slots reduces the design VI (volume ratio or volume index) of the compressor, thereby deteriorating the performance of the compressor at designed working conditions.
• Therefore, what is needed is a solution which can effectively reduce the exhaust noise and suppress the exhaust noise energy at the source without deteriorating compressor performance.
SUMMARY
• The present invention is directed to a rotor seat for a screw compressor with a muffle structure. The rotor seat includes a seat body, a radial exhaust port arranged at the seat body, a female rotor hole and a male rotor hole and a plurality of axial blind holes arranged on an arc surface where the radial exhaust port is located.
• The present invention is also directed to a screw compressor with a muffle structure. The screw compressor includes a suction port, an exhaust port, and an operation cavity in communication with the suction port and the exhaust port. The screw compressor also includes female and male rotors arranged inside the operation cavity and a rotor seat to receive the female and male rotors. The rotor seat includes a seat body, a radial exhaust port arranged at the seat body, a female rotor hole and a male rotor hole and a plurality of axial blind holes arranged on a surface where the radial exhaust port is located.
• The present application provides a rotor seat for a screw compressor with a muffle structure. The rotor seat includes a seat body, a radial exhaust port arranged at the seat, and a female rotor hole and a male rotor hole. The rotor seat further includes a plurality of axial blind holes arranged on a surface where the radial exhaust port is located. In one embodiment, the axis of the blind hole is the normal line, at the hole, of the arc surface where the radial exhaust port is located. In another embodiment, the depths of the blind holes are in the range of ¼λ±15% of an interested sound frequency or an odd multiple of ¼λ±15% of the interested sound frequency, where λ is the wavelength of the interested sound frequency. In yet another embodiment, the diameters D of the blind holes are D≦0.586×c/f, where f is the interested sound frequency, and c is the sound speed in a medium. In still another embodiment, the blind holes are distributed in a uniform or non-uniform manner on the surface where the radial exhaust port is located. In a further embodiment, the quantity of the blind holes is at least two.
• The present application further provides a screw compressor with a muffle structure. The screw compressor includes a suction port, an exhaust port, an operation cavity in communication with the suction port and the exhaust port, and female and male rotors arranged inside the operation cavity. The screw compressor further includes a rotor seat as described above for receiving the female and male rotors.
• The muffle structure formed by the blind holes according to the present application can attenuate the acoustic energy in an outlet stream upon the discharging of a gas flow from a screw tooth slot primitive volume, thereby forming the muffle structure of the rotor seat for the screw compressor. When the unit operates with different loads, the muffle structure can attenuate the exhaust acoustic pulsation. Furthermore, since the blind holes are side branch holes and the gas flow can flow by the side of the opening of the blind holes rather than flow into the blind holes, a measurable pressure drop may not be caused. Thus, the additional loss of the outlet pressure can be ignored.
• One advantage of the present application is a muffle structure with a structure which is simple, compact and very reliable.
• Another advantage of the present application is that no additional structure is needed for noise control, which provides for a reduced cost.
• Other features and advantages of the present invention will be apparent from the following, more detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows an exemplary embodiment for a heating, ventilation and air conditioning system.
• FIG. 2 shows an isometric view of an exemplary vapor compression system.
• FIGS. 3 and 4 schematically show exemplary embodiments of a vapor compression system.
• FIG. 5 schematically shows an exemplary embodiment of a structure of a rotor seat for screw compressor.
DETAILED DESCRIPTION OF THE EMBODIMENTS
• FIG. 1 shows an exemplary environment for a heating, ventilation and air conditioning (HVAC)system10 in abuilding12 for a typical commercial setting.System10 can include avapor compression system14 that can supply a chilled liquid which may be used to coolbuilding12.System10 can include aboiler16 to supply heated liquid that may be used to heatbuilding12, and an air distribution system which circulates air throughbuilding12. The air distribution system can also include an air return duct18, anair supply duct20 and anair handler22.Air handler22 can include a heat exchanger that is connected toboiler16 andvapor compression system14 byconduits24. The heat exchanger inair handler22 may receive either heated liquid fromboiler16 or chilled liquid fromvapor compression system14, depending on the mode of operation ofsystem10.System10 is shown with a separate air handler on each floor ofbuilding12, but it is appreciated that the components may be shared between or among floors.
• FIGS. 2 and 3 show an exemplaryvapor compression system14 that can be used inHVAC system10.Vapor compression system14 can circulate a refrigerant through a circuit starting withcompressor32 and including acondenser34, expansion valve(s) or device(s)36, and an evaporator orliquid chiller38.Vapor compression system14 can also include acontrol panel40 that can include an analog to digital (A/D)converter42, amicroprocessor44, anon-volatile memory46, and aninterface board48. Some examples of fluids that may be used as refrigerants invapor compression system14 are hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, hydrofluoro olefin (HFO), “natural” refrigerants like ammonia (NH₃), R-717, carbon dioxide (CO₂), R-744, or hydrocarbon based refrigerants, water vapor or any other suitable type of refrigerant. In an exemplary embodiment,vapor compression system14 may use one or more of each of variable speed drives (VSDs)52,motors50,compressors32,condensers34,expansion valves36 and/orevaporators38.
• Motor50 used withcompressor32 can be powered by a variable speed drive (VSD)52 or can be powered directly from an alternating current (AC) or direct current (DC) power source.VSD52, if used, receives AC power having a particular fixed line voltage and fixed line frequency from the AC power source and provides power having a variable voltage and frequency tomotor50. Motor50 can include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source.Motor50 can be any other suitable motor type, for example, a switched reluctance motor, an induction motor, or an electronically commutated permanent magnet motor. In an alternate exemplary embodiment, other drive mechanisms such as steam or gas turbines or engines and associated components can be used to drivecompressor32.
• Compressor32 compresses a refrigerant vapor and delivers the vapor to condenser34 through a discharge passage.Compressor32 can be a screw compressor in one exemplary embodiment. The refrigerant vapor delivered bycompressor32 tocondenser34 transfers heat to a fluid, for example, water or air. The refrigerant vapor condenses to a refrigerant liquid incondenser34 as a result of the heat transfer with the fluid. The liquid refrigerant fromcondenser34 flows throughexpansion device36 toevaporator38. In the exemplary embodiment shown inFIG. 3,condenser34 is water cooled and includes atube bundle54 connected to acooling tower56.
• The liquid refrigerant delivered toevaporator38 absorbs heat from another fluid, which may or may not be the same type of fluid used forcondenser34, and undergoes a phase change to a refrigerant vapor. In the exemplary embodiment shown inFIG. 3,evaporator38 includes a tube bundle having asupply line60S and areturn line60R connected to acooling load62. A process fluid, for example, water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable liquid, entersevaporator38 viareturn line60R and exitsevaporator38 viasupply line60S.Evaporator38 chills the temperature of the process fluid in the tubes. The tube bundle inevaporator38 can include a plurality of tubes and a plurality of tube bundles. The vapor refrigerant exitsevaporator38 and returns tocompressor32 by a suction line to complete the cycle.
• FIG. 4, which is similar toFIG. 3, shows thevapor compression system14 with anintermediate circuit64 incorporated betweencondenser34 andexpansion device36.Intermediate circuit64 has aninlet line68 that can be either connected directly to or can be in fluid communication withcondenser34. As shown,inlet line68 includes anexpansion device66 positioned upstream of anintermediate vessel70.Intermediate vessel70 can be a flash tank, also referred to as a flash intercooler, in an exemplary embodiment. In an alternate exemplary embodiment,intermediate vessel70 can be configured as a heat exchanger or a “surface economizer.” In the configuration shown inFIG. 4, i.e., theintermediate vessel70 is used as a flash tank, afirst expansion device66 operates to lower the pressure of the liquid received fromcondenser34. During the expansion process, a portion of the liquid vaporizes.Intermediate vessel70 may be used to separate the vapor from the liquid received fromfirst expansion device66 and may also permit further expansion of the liquid. The vapor may be drawn bycompressor32 fromintermediate vessel70 through aline74 to the suction inlet, a port at a pressure intermediate between suction and discharge or an intermediate stage of compression. The liquid that collects in theintermediate vessel70 is at a lower enthalpy from the expansion process. The liquid fromintermediate vessel70 flows inline72 through asecond expansion device36 toevaporator38.
• In an exemplary embodiment,compressor32 can include a compressor housing that contains the working parts ofcompressor32. Vapor fromevaporator38 can be directed to an intake passage ofcompressor32.Compressor32 compresses the vapor with a compression mechanism and delivers the compressed vapor to condenser34 through a discharge passage.Motor50 may be connected to the compression mechanism ofcompressor32 by a drive shaft.
• Vapor flows from the intake passage ofcompressor32 and enters a compression pocket of the compression mechanism. The compression pocket is reduced in size by the operation of the compression mechanism to compress the vapor. The compressed vapor can be discharged into the discharge passage. For example, for a screw compressor, the compression pocket is defined between the surfaces of the rotors of the compressor. As the rotors of the compressor engage one another, the compression pockets between the rotors of the compressor, also referred to as lobes, are reduced in size and are axially displaced to a discharge side of the compressor.
• An exemplary embodiment of a rotor seat for a screw compressor is shown inFIG. 5. As shown inFIG. 5, arotor seat100 for a screw compressor includes: aseat body104, aradial exhaust port101 arranged, located or positioned in theseat body104, and a female rotor hole102aand a male rotor hole102bfor receiving a female rotor and a male rotor of the screw compressor, respectively. A plurality of axialblind holes103 having certain or predetermined diameters and/or certain or predetermined depths can be arranged, located or positioned on a surface where theradial exhaust port101 is located or discharges. In an exemplary embodiment, an axis of eachblind hole103 can be the normal line, at theblind hole103, of the surface where theradial exhaust port101 is located.
• In another exemplary embodiment, the depths of theblind holes103 can be in the range of ¼λ±15% of an interested sound frequency, e.g., a sound frequency to be attenuated, or an odd multiple of ¼λ±15% of the interested sound frequency, where λ is the wavelength of the interested sound frequency. For example, if the interested sound frequency is 750 Hz, and the sound speed is 150 m/s, the values of the depths of theblind holes103 can be in the range of 50 mm±15% or an odd multiple of ¼λ±15% (for example, 150 mm±15%).
• In a further exemplary embodiment, the diameters D of theblind holes103 can be defined by D≦0.586×c/f (where f is the interested sound frequency, and c is the sound speed in a medium).
• Theblind holes103 may be distributed in a uniform or non-uniform manner on the surface where theradial exhaust port101 is located, and the quantity of theblind holes103 can be at least two.
• One exemplary embodiment provides a screw compressor with the muffle structure or muffler. The screw compressor can include a suction port, an exhaust port, an operation cavity in communication with the suction port and the exhaust port, and female and male rotors arranged, located or positioned inside the operation cavity. The screw compressor can further include therotor seat100 as shown inFIG. 5. In other words, therotor seat100 can include a plurality of axialblind holes103 having certain or preselected diameters and certain or preselected depths located or positioned on the surface where theradial exhaust port101 of therotor seat100 is located, to serve as the muffle structure. Therotor seat100 can be for receiving the female rotor and the male rotor.
• The muffle structure formed by theblind holes103 can attenuate the acoustic energy in an outlet stream upon the discharging of a gas flow from a screw tooth slot primitive volume, thereby forming the muffle structure of therotor seat101 for the screw compressor. When the unit operates with different loads, the muffle structure can always attenuate the exhaust acoustic pulsation. Furthermore, since theblind holes103 are side branch holes and the gas flow can flow by the side of the opening of theblind holes103 rather than flow into theblind holes103, a measurable pressure fall or pressure drop may not be caused. Thus, the additional loss of the outlet pressure can be ignored. In addition, the muffle structure has a structure which is simple, compact and very reliable, and no additional structure is needed, which will not bring additional costs.
• It is important to note that the construction and arrangement of the present application as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this application, those who review this application will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described in the application. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present application. Accordingly, the present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims.
• Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

Claims (20)

What is claimed is:

1. A rotor seat for a screw compressor with a muffle structure, the rotor seat comprising:

a seat body;

a radial exhaust port arranged at the seat body;

a female rotor hole and a male rotor hole; and

a plurality of axial blind holes arranged on an arc surface where the radial exhaust port is located.

2. The rotor seat according toclaim 1, wherein the axis of a blind hole of the plurality of blind holes is the normal line, at the blind hole, of the arc surface where the radial exhaust port is located.

3. The rotor seat according toclaim 2, wherein the depths of the plurality of blind holes are in the range of ¼λ±15% of an interested sound frequency or an odd multiple of ¼λ±15% of the interested sound frequency, and λ is a wavelength of the interested sound frequency.

4. The rotor seat according toclaim 2, wherein the diameters D of the plurality of blind holes are less than or equal to 0.586×c/f, where f is an interested sound frequency, and c is a sound speed in a medium.

5. The rotor seat according toclaim 1, wherein the depths of the plurality of blind holes are in the range of ¼λ±15% of an interested sound frequency or an odd multiple of ¼λ±15% of the interested sound frequency, and λ is a wavelength of the interested sound frequency.

6. The rotor seat according toclaim 5, wherein the diameters D of the plurality of blind holes are less than or equal to 0.586×c/f, where f is an interested sound frequency, and c is a sound speed in a medium.

7. The rotor seat according toclaim 1, wherein the diameters D of the plurality of blind holes are less than or equal to 0.586×c/f, where f is an interested sound frequency, and c is a sound speed in a medium.

8. The rotor seat according toclaim 7, wherein the depths of the plurality of blind holes are in the range of ¼λ±15% of an interested sound frequency or an odd multiple of ¼λ±15% of the interested sound frequency, and λ is a wavelength of the interested sound frequency.

9. The rotor seat according toclaim 1, wherein the plurality of blind holes are distributed in one of a uniform or non-uniform manner on the arc surface where the radial exhaust port is located.

10. The rotor seat according toclaim 1, wherein the plurality of the blind holes is at least two blind holes.

11. A screw compressor with a muffle structure, the screw compressor comprising:

a suction port;

an exhaust port;

an operation cavity in communication with the suction port and the exhaust port;

female and male rotors arranged inside the operation cavity; and

a rotor seat to receive the female and male rotors, the rotor seat comprising:

a seat body;

a radial exhaust port arranged at the seat body;

a female rotor hole and a male rotor hole; and

a plurality of axial blind holes arranged on a surface where the radial exhaust port is located.

12. The screw compressor according toclaim 11, wherein the axis of a blind hole of the plurality of blind holes is the normal line, at the blind hole, of the surface where the radial exhaust port is located.

13. The screw compressor according toclaim 12, wherein the depths of the plurality of blind holes are in the range of ¼λ±15% of an interested sound frequency or an odd multiple of ¼λ±15% of the interested sound frequency, and λ is a wavelength of the interested sound frequency.

14. The screw compressor according toclaim 12, wherein the diameters D of the plurality of blind holes are less than or equal to 0.586×c/f, where f is an interested sound frequency, and c is a sound speed in a medium.

15. The screw compressor according toclaim 11, wherein the depths of the plurality of blind holes are in the range of ¼λ±15% of an interested sound frequency or an odd multiple of ¼λ±15% of the interested sound frequency, and λ is a wavelength of the interested sound frequency.

16. The screw compressor according toclaim 15, wherein the diameters D of the plurality of blind holes are less than or equal to 0.586×c/f, where f is an interested sound frequency, and c is a sound speed in a medium.

17. The screw compressor according toclaim 11, wherein the diameters D of the plurality of blind holes are less than or equal to 0.586×c/f, where f is an interested sound frequency, and c is a sound speed in a medium.

18. The screw compressor according toclaim 17, wherein the depths of the plurality of blind holes are in the range of ¼λ×15% of an interested sound frequency or an odd multiple of ¼λ±15% of the interested sound frequency, and λ is a wavelength of the interested sound frequency.

19. The screw compressor according toclaim 11, wherein the plurality of blind holes are distributed in one of a uniform or non-uniform manner on the surface where the radial exhaust port is located.

20. The screw compressor according toclaim 11, wherein the plurality of the blind holes is at least two blind holes.

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