HK1116236B - Compressor sound suppression - Google Patents

Description

Compressor noise suppression

Background

The present invention relates to a compressor. More particularly, the present invention relates to a compressor having a check valve.

Screw compressors are commonly used in air conditioning and refrigeration applications. In such compressors, intermeshed male and female lobed rotors or screws are rotated about their axes to draw the working fluid (refrigerant) from a low pressure inlet end to a high pressure outlet end. During rotation, successive lobes of the male rotor act as pistons pushing refrigerant downstream and compressing it within the space between a pair of adjacent female rotor lobes and the housing. Likewise successive lobes of the female rotor produce compression of refrigerant within the space between an adjacent pair of male rotor lobes and the housing. Compression occurs in the space between the lobes of the male and female rotors to form compression pockets (alternatively illustrated as male and female portions of a conventional compression pocket connected to the mesh zone). In one implementation, the male rotor is coaxial with the electric propulsion engine and is supported by bearings over the inlet and outlet sides of its impeller working portion. There may be multiple female rotors engaging a particular male rotor.

When one of the inter-impeller spaces is exposed to the inlet port, refrigerant enters the space substantially at suction pressure. As the rotor continues to rotate, at some point during rotation the space is no longer coupled with the inlet port and the flow of refrigerant to the space is cut off. After the inlet port is closed, the refrigerant is compressed as the rotor continues to rotate. At some point during rotation, each space intersects the associated outlet port and the closed compression process terminates. The inlet and outlet ports may each be radial, axial, or a hybrid combination of axial and radial ports. The compression pocket opening and closing (particularly the discharge port opening) is related to the pressure pulsations and the resulting noise. Noise suppression has therefore become an important consideration in compressor design. Many forms of compressor mufflers have been proposed.

Additionally, a wide variety of transient conditions may tend to cause reverse flow through the compressor. For example, upon a power failure or other uncontrolled shutdown, high pressure refrigerant will be left in the discharge plenum and downstream therein within the refrigerant flow path (e.g., within a muffler, oil separator, condenser, etc.). Such high pressure refrigerant will tend to flow backwards through the rotors, reversing their direction of rotation. If the rotation rate in the reverse direction is large, unpleasant noise is generated. Damage to mechanical components or internal surfaces of the housing can also occur with some screw compressors. Thus, a one-way valve (check valve) may be positioned along the flow path to prevent reverse flow. Other forms of compressors (e.g., scroll and reciprocating compressors) may include similar check valves.

Disclosure of Invention

A compressor device includes a housing having first and second ports along a flow path. One or more working elements cooperate with the housing to define a compression path along the flow path between the suction and discharge positions. The check valve includes a valve element having a first condition permitting downstream flow along the flowpath and a second condition blocking reverse flow. The noise dampening means at least partially surrounds the upstream flow path of the valve element.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

Brief description of the drawings

Fig. 1 is a longitudinal sectional view of a compressor.

Fig. 2 is a partial sectional view of a discharge casing of the compressor of fig. 1 including a first noise-abatement tool.

Fig. 3 is a partial sectional view of a discharge housing of the compressor of fig. 1 including a second noise-abatement tool.

Fig. 4 is a partial sectional view of a discharge casing of the compressor of fig. 1 including a third noise-abatement tool.

Like reference numbers and designations in the various drawings indicate like elements.

Detailed Description

FIG. 1 shows a compressor 20 having a housing assembly 22 housing an engine 24 that propels rotors 26 and 28 having respective central longitudinal axes 500 and 502. In the exemplary embodiment, rotor 26 has a male impeller body or working portion 30 that extends between a first end 31 and a second end 32. The working portion 30 meshes with a female lobed body or working portion 34 of the female rotor 28. The working portion 34 has a first end 35 and a second end 36. Each rotor includes a shaft portion (e.g., stubs 39, 40, 41, and 42 integrally formed with the associated working portion) extending from the first and second ends of the associated working portion. Each of these shaft stubs is mounted to the housing by one or more bearing assemblies 44 for rotation about the associated rotor axis.

In the exemplary embodiment, the motor is an electric motor having a rotor and a stator. One of the shaft stubs of one of the rotors 26 and 28 may be coupled to the rotor of the engine so as to permit the engine to push that rotor about its axis. When such urging is in a first operative direction about the axis, the rotor urges the other rotor in an opposite second direction. The exemplary housing assembly 22 includes a rotor housing 48 having an upstream/inlet end face 49 approximately midway along the length of the engine and a downstream/discharge end face 50 substantially coplanar with the rotor body ends 32 and 36.

The exemplary housing assembly 22 further includes an engine/inlet housing 52 having a compressor inlet/suction port 53 at an upstream end and having a downstream face 54 that fits to a downstream face of the rotor housing (e.g., by screws passing through both housing pieces). The assembly 22 further includes an outlet housing 56 (shown as an assembly) having an upstream face 57 mounted to the rotor housing downstream face and having an outlet/discharge port 58. The exemplary rotor housing, engine/inlet housing, and outlet housing 56 may each be formed as castings subject to further finishing.

Surfaces of the housing assembly 22 in combination with the enmeshed rotor bodies 30 and 34 define inlet and outlet ports to compression pockets compressing and urging refrigerant flow 504 from a suction (inlet) plenum 60 to a discharge (outlet) plenum 62. A pair of male and female compression pockets are formed by the housing assembly 22, the male rotor body 30, and the female rotor body 34. In this pair, one such pocket is positioned between a pair of adjacent impellers of each associated rotor.

Fig. 2 shows further details of an exemplary flow path at the outlet/discharge port 58. A check valve 70 is provided having a valve element 72 that fits within a barrel portion 74(boss portion) of the outlet housing 56. The exemplary valve element 72 is a front closure poppet having a stem/shaft 76 integrally formed with the top 78 and extending downstream therefrom along a valve axis 520. The top has a rear/underside surface 80 that engages the upstream end of a compression biasing spring 82 (e.g., a coil of metal). The downstream end of the spring engages an upstream-facing shoulder 84 of a bushing/guide sleeve 86. The bushing/guide 86 may be integrally formed with or assembled relative to the housing and has a central bore 88 that slidingly engages the stem for relative movement between an open condition (not shown) and the closed condition of fig. 3. The spring 82 biases the element 72 upstream toward the closed state. In the closed condition, the annular peripheral seat portion 90 of the top upstream surface seats against the annular seat 92 from the exhaust plenum at the downstream end of the port 94.

To control/unload the volume, the compressor includes a slide valve 100 having a valve element 102. The valve element 102 has a portion 104 along the mesh region between the rotors. An exemplary valve element has a first portion located at the discharge plenum and a second portion located at the suction plenum. The valve element is movable to control compressor capacity to provide unloading. The exemplary valve moves via linear translation parallel to the rotor axis.

The opening and closing of the compression pockets at the suction and discharge ports creates pressure pulsations. As the pulsations propagate into the gas in and downstream of the exhaust plenum, they cause vibrations and associated radiated noise that is undesirable. This pulsation may be at least partially addressed by modifying the exhaust plenum upstream including the check valve. Exemplary modifications include modifying the exhaust plenum at port 94 to incorporate one or more resonators tuned to suppress/attenuate one or more noise/vibration frequencies at one or more conditions. Exemplary frequencies are compression pockets open/closed at designed compressor operating rates and at designed cooling system operating conditions. Thus an example of an otherwise identical compressor features the use of resonators that can be tuned differently in different systems or states thereof. Exemplary modifications utilize existing manufacturing techniques and their products. Exemplary modifications may be obtained in the remanufacturing of an existing compressor or the reengineering of an existing compressor configuration. An iterative optimization process may be used to tune the resonator.

Figure 2 shows an exemplary modification of the basic compressor. This modification includes providing an outlet conduit 120 having an upstream projection 122 extending into the exhaust plenum to the end of a rim 126. In an exemplary implementation, the outlet conduit is separately formed from the remainder of the outlet housing (e.g., as a cylindrical steel tube with a proximal/downstream portion 127 press-fit within 2cm of the top 78 in the cast iron housing member 56 in the second (closed) state). An annular channel 128 is defined within the exhaust plenum surrounding the projecting portion 122 to form an annular resonance cavity that functions as a side branch resonator. The exemplary cavity has an annular opening/port 130. When implemented in the remanufacturing of an existing compressor or the reengineering of an existing configuration, the cavity may be related to a change in the local discharge plenum surface 132 (e.g., from an initial/baseline surface 132'). In an exemplary implementation, the surface is relieved so as to deepen and widen the cavity. The cavity is shown as having a length L, an interior radius R, and a radius span ar. These parameters may be selected to provide the desired adjustment. The annular base portion of the surface 132 forms the back wall of the cavity from which the pressure wave reflects to exit. The length L may be selected to provide cancellation out of phase with respect to (incident) pulsations that tend to occur at the plane of the port 130 and the edge 126. This cancellation reduces the magnitude of pulsations at the catheter port and, in turn, downstream through the catheter. By changing the curved cross-section of the baseline surface 132' to a more right-angled cross-section of the surface 132, a flat radial back wall/foundation is formed that provides a more coherent reflection, allowing for advantageous cancellation characteristics.

Fig. 3 shows an alternative modification in which the outlet conduit 220 has an upstream end wall 222 and a side wall 224. The end wall 222 includes an array of apertures 226. The side wall 224 includes an array of apertures 228. The apertures 226 and 228 serve to break up the effluent stream into many sub-streams that pass through the apertures and recombine within the interior of the conduit 220. This helps to attenuate the downstream impact of the upstream pulsations. The size, density and distribution of the apertures may be selected to provide a desired degree of attenuation. Optionally, there may be some adjustment of the volume of the plenum surrounding the conduit 220 to also provide additional pulsation reduction within the conduit 220.

FIG. 4 shows an additional alternative modification in which the outlet conduit assembly 320 has a main conduit 322 extending downstream from an edge 324. Although optionally similar to the build conduit 120, the conduit 322 has an arrangement of apertures 326 similar to the apertures 228 of the conduit 220. However, rather than passing through a net flow, the orifice 328 acts as a port to the resonator volume 330 surrounding the conduit. Volume 330 is otherwise sealed and bounded longitudinally as well as laterally by an inwardly opening C-section member 332 (e.g., having a pair of upstream and downstream flanges 333 and 334 welded to the outside surface of conduit 322). Thus, although similar to being positioned in the resonator volume 128, the resonator volume 330 has a longitudinal and circumferential arrangement of discrete radial ports provided by the apertures 326 rather than a single annular longitudinal port 130. Optionally, volume 330 may be filled with a noise dissipating substance. The presence of the dissipating substance may reduce the effectiveness of the cancellation at a single target frequency but makes the accuracy of the adjustment less critical by providing some additional wide frequency range of cancellation compensation.

The relative proximity of the resonator to the discharge plenum is considered advantageous for several reasons. First, the flow turbulence may tend to increase downstream. Turbulent conditions make tuning difficult. The relatively low turbulence at the upstream location (e.g., within the compressor housing) helps facilitate proper tuning. Second, proximity to the source of pulsation can improve noise/vibration cancellation.

Many known or yet to be developed resonator configurations and optimization techniques may be applied. Previously included, for example, Helmholtz (Helmholtz) resonators.

One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, in a rebuild or remanufacture scenario, details of the existing compressor may significantly affect or dictate details of the implementation. Implementations may include check valves for other locations in the flow line. The principles may be applied to compressors having working elements other than helical rotors (e.g., reciprocating and scroll compressors). Accordingly, other embodiments are within the scope of the following claims.

Claims (25)

1. A compressor device (20) comprising:

an outer shell (22) assembly having first (53) and second (58) ports along a flow path and including a cast exhaust housing (56);

one or more working elements (26, 28) cooperating with the housing (22) to define a compression path between intake (60) and exhaust (62) air chambers along the flow path, wherein the one or more working elements comprise:

a helical male impeller rotor (26) having a first axis of rotation (500); and

a helical female lobed rotor (28) having a second axis of rotation (502) and meshing with the male lobed rotor;

a check valve (70) within the discharge housing and having a valve element (72) with a first condition permitting downstream flow along the flowpath and a second condition blocking reverse flow; and

a noise dampening means (120, 220, 320) at least partially surrounding the flow path upstream of the valve element.

2. The compressor as set forth in claim 1, wherein:

the noise dampening means includes a rigid conduit (120, 220, 322) having a first portion (127) secured to the discharge housing and a second portion (122) extending away from the check valve.

3. A compressor as set forth in claim 2, wherein:

the conduit (120, 322) has a fully open upstream end.

4. A compressor as set forth in claim 2, wherein:

the catheter (220) has:

a partially closed upstream end (222) having a plurality of ports (226); and

a sidewall (224) having a plurality of longitudinally and circumferentially spaced ports (228).

5. A compressor as set forth in claim 2, wherein:

the conduit (120, 220, 322) has an upstanding cylindrical sidewall (120, 224, 322).

6. A compressor as set forth in claim 2, wherein:

a volume (128, 330) surrounding the conduit (120, 220, 322) forms a resonator.

7. The compressor as set forth in claim 6, wherein:

the resonator has a port (130) surrounding the end of the conduit.

8. The compressor as set forth in claim 6, wherein:

the resonator has a plurality of ports spaced longitudinally and circumferentially along the conduit.

9. The compressor as set forth in claim 1, wherein:

the valve element (72) has an upstream tip (78) and a downstream stem (76).

10. A compressor as set forth in claim 9, wherein:

the noise dampening means comprises a conduit (120, 220, 322) that is interference fit within 2cm of the top portion (78) within the exhaust housing (56) in the second state.

11. The compressor as set forth in claim 1, wherein:

the noise suppression means comprises a branch resonator.

12. A compressor includes:

a housing having first and second ports along a flow path; and

a noise-dampening element having a conduit (120, 220, 322) with a first portion interference-fit within an exhaust housing member of the outer shell and a second portion extending upstream from the first portion.

13. A compressor according to claim 12, wherein said conduit comprises a metal right circular cylindrical tube.

14. The compressor of claim 12, wherein said conduit cooperates with a portion of said discharge housing member to define a resonator.

15. The compressor of claim 12 being a screw compressor.

16. A method for remanufacturing a compressor or reengineering a configuration of a compressor comprising:

providing an initial compressor or configuration having:

a housing having a flow path between first and second ports; and

one or more working elements cooperating with the housing to define a compression path along the flow path between the suction plenum and the discharge plenum;

a check valve along the flow path and having a valve element; and

noise suppression means are added to the exhaust plenum and include a rigid conduit extending upstream from a portion mounted to the housing.

17. The method of claim 16 further comprising:

at least one geometric parameter of the conduit is selected to provide a desired pressure pulsation parameter control.

18. The method of claim 17, wherein:

the selecting includes tuning the resonator.

19. The method of claim 17, wherein said selecting comprises iteratively:

changing the at least one geometric parameter; and

determining the pressure pulsation parameter.

20. The method of claim 19, wherein:

the determining includes measuring noise intensity at a target frequency of the pulsation.

21. The method of claim 16, wherein:

such initial compressors or configurations lack such conduits.

22. The method of claim 16 applied to the remanufacturing of a screw compressor or the reengineering of a screw compressor configuration.

23. A compressor device (20) comprising:

a housing (22) assembly having first (53) and second (58) ports along a flow path and including a cast exhaust housing;

one or more working elements (26, 28) cooperating with the housing (22) to define a compression path along the flow path between a suction (60) plenum and a discharge (62) plenum; and

a check valve (70) within the discharge housing and having a valve element (72) with a first condition permitting downstream flow along the flowpath and a second condition blocking reverse flow; and

a noise dampening means (120, 220, 320) at least partially surrounding the flow path upstream of the valve element and having a conduit (120, 220, 322), wherein a volume (128, 330) surrounding the conduit (120, 220, 322) forms a resonator having a plurality of ports (228, 326) spaced longitudinally and circumferentially along the conduit.

24. A compressor device (20) comprising:

a housing (22) assembly having first (53) and second (58) ports along a flow path and including a cast exhaust housing;

one or more working elements (26, 28) cooperating with the housing (22) to define a compression path along the flow path between a suction (60) plenum and a discharge (62) plenum; and

a check valve (70) within the discharge housing and having a valve element (72) with an upstream tip (78) and a downstream stem (76) and having a first condition permitting downstream flow along the flowpath and a second condition blocking reverse flow; and

a noise dampening means (120, 220, 320) at least partially surrounding the flow path upstream of the valve element.

25. A compressor as set forth in claim 24, wherein:

the noise dampening means comprises a conduit (120, 220, 322) that in the second state is interference fit within 2cm of the top portion (78) within the exhaust housing.