HK1113058B - Compressor - Google Patents

Description

Compressor with a compressor housing having a plurality of compressor blades

Technical Field

The present invention relates to compressors, and more particularly to the suppression of noise and vibration in screw compressors.

Background

In a positive displacement compressor, discrete volumes of gas are collected at suction pressure, compressed, and discharged at discharge pressure. Both the pooling and venting processes may produce pressure pulsations and associated noise. Therefore, there has been a good development in the field of noise suppression of compressors.

One type of absorptive muffler involves passing the refrigerant flow discharged from the compressor working elements through an annular gap between inner and outer annular layers of noise absorbing material (e.g., fibrous wadding or foam). U.S. patent application publication No. 2004/0065504a1 discloses such a simplified muffler and modified versions thereof having helmholtz resonators formed integrally in the inner layer. The disclosure of the' 504 patent is incorporated by reference into this invention and is described in detail.

Disclosure of Invention

According to an aspect of the present invention, there is provided a compressor including a housing and one or more working elements. A muffler is disposed downstream of the discharge plenum. A centerbody is disposed in the exhaust plenum upstream of the muffler and spans a substantial length between the bearing housing and the muffler.

The cross-sectional area of the centerbody gradually expands downstream. The centerbody may be added to an existing compressor configuration that is redesigned or reconfigured and/or to a remanufacturing of an existing compressor that previously lacked such a resonator. During the redesign/reconfiguration process, the parameters of the centerbody may be optimized to provide a desired degree of minimization of the pressure drop across the discharge plenum.

The present invention provides a compressor, comprising: a first rotor having a first axis of rotation; a second rotor having a second axis of rotation and meshing with the first rotor; a third rotor having a third axis of rotation and meshing with the first rotor; a housing accommodating the first, second, and third rotors and having a bearing housing for supporting the first, second, and third rotors; a suction pressure chamber located within the housing; an outlet plenum within said housing, a flow path extending from downstream of said suction plenum to a discharge plenum; a muffler downstream of the outlet pressure chamber; a main body within the outlet pressure chamber, the main body spanning a substantial length between the bearing housing and the muffler.

Preferably, the downstream portion of the body has a cross-section at least 20% greater than the cross-section of the upstream portion of the body.

The present invention provides a compressor, comprising: a housing; one or more working elements located in the housing; a discharge plenum in the housing downstream of the working element and having a wall surface that tapers downstream; a muffler downstream of the discharge plenum; and means in said discharge pressure chamber upstream of said muffler for limiting the pressure drop between the outlet of said one or more working elements and the inlet of the muffler compared to the pressure drop that would be present without said means.

The present invention provides a compressor, comprising: a housing; one or more working elements; a discharge pressure chamber; a muffler downstream of the discharge plenum; and a central flow guide element located in the discharge plenum upstream of the muffler.

Drawings

One or more embodiments of the invention are set forth with reference to the following drawings and detailed description. Other features, objects, and advantages of the invention will be apparent from the description and claims, and from the drawings, in which:

FIG. 1 is a longitudinal sectional view of a compressor;

FIG. 2 is an enlarged view of the discharge pressure chamber of the compressor of FIG. 1;

FIG. 3 is a cross-sectional view of the compressor of FIG. 1 taken along line 3-3; and

fig. 4 is a cross-sectional view of the compressor of fig. 1 taken along line 4-4.

The same reference numbers and symbols in the various drawings indicate the same or similar elements.

Detailed Description

Fig. 1 shows a compressor 20 having a housing or casing assembly 22. The exemplary compressor is a three-rotor, screw hermetic compressor having rotors 26, 28, and 30 with respective central longitudinal axes 500, 502, and 504. In the exemplary embodiment, first rotor 26 is a lobed rotor driven by a coaxial motor 32, and meshes with lobed rotors 28 and 30 and drives lobed rotors 28 and 30. In the exemplary embodiment, male rotor axis 500 also forms a central longitudinal axis of compressor 20 as a whole. The rotor working portions are located in a rotor housing section 34 of the housing assembly 22 and may be supported by bearings 36 and closed by seals 38 engaging the rotor shaft at each end of the respective rotor working portion. Driven by the motor 32, the rotor pumps and compresses a working fluid (e.g., refrigerant) along a flow path from the suction plenum 40 to the discharge plenum 42. In the exemplary embodiment, a suction plenum 40 is disposed in an upstream end of rotor housing 34, and a discharge plenum is substantially disposed in a discharge housing 46 that is separated from the rotor housing by a bearing housing 48 and has an inner surface 49 that tapers substantially downstream. In the exemplary embodiment, a bearing cap/retainer plate 50 is disposed on a downstream end of bearing housing 48 for retaining a bearing cartridge. A muffler 52 in a muffler housing 54 is located downstream of the exhaust housing 46. An oil separator unit 60 is located downstream of the muffler 52, the oil separator unit 60 having a housing 62 holding a separator screen 64. An oil return tube 66 extends from the housing 62 to return oil blocked by the screen 64 to the lubrication system (not shown). An outlet pressure chamber 68 having an outlet port 69 is downstream of the screen 64.

The exemplary muffler 52 includes annular inner and outer elements 70 and 72 separated by a generally annular gap 74 (e.g., interrupted by support tabs for securing/positioning the inner element 70). These elements may be formed of noise absorbing material such as fiberglass filler encased in nylon and steel screens. In the exemplary embodiment, inner element 70 is secured and spaced from gap 74 by an inner foraminate sleeve 76 (e.g., nylon or wire mesh or perforated/expanded metal sheet), and outer element 72 is similarly spaced and secured by an outer foraminate sleeve 78. In the exemplary embodiment, the outer member 72 is encased within an outer sleeve 80 (e.g., similarly formed on the sleeves 76 and 78) that is telescopically received within the housing 54. The sleeves 80 and 78 are joined at upstream and downstream ends by annular plates 82 and 84. In the exemplary embodiment, an upstream end of sleeve 76 is closed by a disc 86 and a downstream end is closed by an annular plate 90. In the exemplary embodiment, an imperforate central core 94 (e.g., steel pipe) extends through inner member 70 and out the downstream end thereof.

In operation, a flow of compressed gas exits the compression pockets of the screw rotors 26, 28, 30 and flows into the discharge plenum 42. As the gas flow exits the compressor discharge plenum, it enters the muffler housing 54 and flows to the annular gap 74. The gas stream exiting the muffler is typically entrained with oil droplets and flows through the oil separating screen 64. The screen 64 collects any oil entrained in the gas and returns it to the oil treatment system via conduit 66. The gas exits the oil separation screen and enters the pressure chamber 68 and exits the outlet 69 toward a condenser (not shown).

As described above, the compressor may be of an existing structure, and the principles of the present invention may be applied to different structures.

In accordance with the present invention, a centerbody 120 is positioned in the flow path between the rotors and the muffler. Fig. 2 shows the centerbody 120 having a substantially frustoconical outer surface 122 extending from a circular upstream end/face 124 to a circular downstream face 126.

Fig. 3 shows discharge ports 200 and 202 for discharging compressed refrigerant, which open into the outlet plenum 42. The exhaust ports 200 and 202 are oriented to direct the flow of air exiting the rotor to the exhaust plenum 42. The ports are positioned at the ends of the compression chambers formed by the meshing between the male and female rotors. In a two rotor configuration, only one exhaust port is required. The ports direct flow around the cavities present in the exhaust bearing 36 and seal 38. The cavity is closed by a bearing cap 50.

Various materials and techniques may be used to fabricate the centerbody. The central body may be constructed substantially of at least one of molded plastic (e.g., non-foamed polypropylene or glass-filled nylon) or of polymeric foam or of expanded particulate material (e.g., molded in one or more parts or cut from one or more parts).

In the exemplary embodiment, the overall size and shape of the centerbody is selected so as to provide a smooth transition from the exhaust port to the muffler. Thus, the upstream/forward face 124 is sized to conform to the inside contour of the ports 200 and 202 defined by the plate 50. This may be: substantially equal to the root radius of the working components of rotor 26 at the radius. Similarly, the downstream/aft face 126 is sized to conform to the inner element of the muffler (e.g., having a similar outer radius).

Engineering configuration and/or optimization of resonators can take various levels of measures from basic to detailed and can include various theoretical/simulated and/or empirical/experimental steps. The pressure differential may be calculated and/or measured (e.g., between the upstream and downstream ends of the discharge plenum, between the upstream end of the discharge plenum and a location along or downstream of the muffler, etc.). Sound can be measured (both inside and outside the venting pressure chamber for one or more discrete target frequency ranges).

For example, a first approximation of the centerbody size and shape may be selected based solely on geometry (e.g., muffler inner element diameter and clearance between bearing housing ports) and a prototype built. With the prototype, one or more parameters of pressure difference and/or noise at a target speed may be measured. At least one of the size and shape of the central body may be selected/changed and the one or more parameters measured again in an iterative process may obtain the desired level of these parameters.

The centerbody may be incorporated into a remanufacturing of a compressor or a reconfiguration process of a compressor structure. Various existing elements may be substantially retained in reconfiguration or remanufacturing.

One or more embodiments of the present invention have been described above. 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 reconfiguration or remanufacturing situation, details of the existing system may significantly affect or dictate details of the implementation. Accordingly, other embodiments are within the scope of the following claims.

Claims (12)

1. A compressor, comprising:

a first rotor having a first axis of rotation;

a second rotor having a second axis of rotation and meshing with the first rotor;

a third rotor having a third axis of rotation and meshing with the first rotor;

a housing accommodating the first, second, and third rotors and having a bearing housing for supporting the first, second, and third rotors;

a suction pressure chamber located within the housing;

an outlet plenum within said housing, a flow path extending from downstream of said suction plenum to a discharge plenum;

a muffler downstream of the outlet pressure chamber;

a centerbody within the outlet pressure chamber extending generally from the bearing housing to the muffler.

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

the central body is coaxial with the first rotor.

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

the central body outer surface is generally frusto-conical in shape.

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

the central body has a substantially continuously increasing cross-section downstream.

5. The compressor as set forth in claim 1, wherein: the downstream portion of the centerbody has a cross-section at least 20% greater than the cross-section of the upstream portion of the centerbody.

6. The compressor as set forth in claim 1, wherein: the centerbody outer surface is substantially divergent toward the muffler.

7. The compressor as set forth in claim 1, wherein: the central body is constructed substantially from at least one of molded plastic, polymer foam, and expanded particulate material.

8. A compressor, comprising:

a housing;

one or more working elements located in the housing;

a discharge plenum in the housing downstream of the working element and having a wall surface that tapers downstream;

a muffler downstream of the discharge plenum; and

a centerbody located in the discharge plenum upstream of the muffler for limiting a pressure drop between an outlet of the one or more working elements and an inlet of the muffler from a pressure drop that would be present without the centerbody.

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

the one or more working elements comprise:

a convex screw rotor; and

a concave screw rotor engaged with the convex screw rotor.

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

the central body includes a generally frustoconical shape.

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

the centerbody is affixed to a downstream tapered inner surface of the discharge plenum,

the centerbody smoothes the flow transition from the exhaust port to the muffler.

12. A compressor, comprising:

a housing;

one or more working elements;

a discharge pressure chamber;

a muffler downstream of the discharge plenum; and

a central flow guide element located in the discharge plenum upstream of the muffler.