WO 2006/096179 PCT/US2005/007597
COMPRESSOR SOUND SUPPRESSION
BACKGROUND OF THE INVENTION
[0001] The invention relates to compressors. More
particularly, the invention relates to compressors having
check valves.
[0002] Screw-type compressors are commonly used in air
conditioning and refrigeration applications. In such a
compressor, intermeshed male and female lobed rotors or screws
are rotated about their axes to pump the working fluid
(refrigerant) from a low pressure inlet end to a high pressure
outlet end. During rotation, sequential lobes of the male
rotor serve as pistons driving refrigerant downstream and
compressing it within the space between an adjacent pair of
female rotor lobes and the housing. Likewise sequential lobes
of the female rotor produce compression of refrigerant within
a space between an adjacent pair of male rotor lobes and the
housing. The interlobe spaces of the male and female rotors in
which compression occurs form compression pockets
(alternatively described as male and female portions of a
common compression pocket joined at a mesh zone). In one
implementation, the male rotor is coaxial with an electric
driving motor and is supported by bearings on inlet and outlet
sides of its lobed working portion. There may be multiple
female rotors engaged to a given male rotor.
[0003] When one of the interlobe spaces is exposed to an inlet
port, the refrigerant enters the space essentially at suction
pressure. As the rotors continue to rotate, at some point
during the rotation the space is no longer in communication
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 rotors continue to rotate. At some point
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during the rotation, each space intersects the associated
outlet port and the closed compression process terminates. The
inlet port and the outlet port may each be radial, axial, or a
hybrid combination of an axial port and a radial port. The
compression pocket opening and closing (particularly discharge
port opening) are associated with pressure pulsations and
resulting sound. Sound suppression has thus been an important
consideration in compressor design. Many forms of compressor
mufflers have been proposed.
[0004] Additionally, various 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 thereof in the refrigerant flowpath (e.g., in the
muffler, oil separator, condenser, and the like). Such high
pressure refrigerant will tend to flow backward through the
rotors, reversing their direction of rotation. If rotation
speed in the reverse direction is substantial, undesirable
sound is generated. For some screw compressors, damage to
mechanical components or internal housing surfaces can also
occur. Accordingly, a one-way valve (a check valve) may be
positioned along the flowpath to prevent the reverse flow.
Other forms of compressor (e.g., scroll and reciprocating
compressors) may include similar check valves.
SUMMARY OF THE INVENTION
[0005] A compressor apparatus has a housing having first and
second ports along a flowpath. One or more working elements
cooperate with the housing to define a compression path
between suction and discharge locations along the flowpath. A
check valve has a valve element having a first condition
permitting downstream flow along the flowpath and a second
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condition blocking a reverse flow. The valve element includes
a resonator.
[0006] 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.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a longitudinal sectional view of a
compressor.
[0008] FIG. 2 is a partial sectional view of a discharge
housing check valve of the compressor of FIG. 1 in a first
condition.
[0009] FIG. 3 is a partial sectional view of the discharge
housing check valve of the compressor of FIG. 1 in a second
condition.
[0010] FIG. 4 is a partial sectional view of a second check
valve.
[0011] FIG. 5 is a partial sectional view of a third check
valve.
[0012] FIG. 6 is an end view of the check valve of FIG. 5.
[0013] Like reference numbers and designations in the various
drawings indicate like elements.
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DETAILED DESCRIPTION
[0014] FIG. 1 shows a compressor 20 having a housing assembly
2 2 containing a motor 24 driving rotors 2 6 and 2 8 having
respective central longitudinal axes 500 and 502. In the
exemplary embodiment, the rotor 2 6 has a male lobed body or
working portion 30 extending between a first end 31 and a
second end 32. The working portion 3 0 is enmeshed 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 shaft portions (e.g., stubs 39, 40,
41, and 42 unitarily 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.
[0015] 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 motor's
rotor so as to permit the motor to drive that rotor about its
axis. When so driven in an operative first direction about the
axis, the rotor drives 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 motor length and a downstream/discharge end
face 50 essentially coplanar with the rotor body ends 32 and
36. Many other configurations are possible.
[0016] The exemplary housing assembly 22 further comprises a
motor/inlet housing 52 having a compressor inlet/suction port
53 at an upstream end and having a downstream face 54 mounted
to the rotor housing downstream face (e.g., by bolts through
both housing pieces). The assembly 22 further includes an
outlet/discharge housing 56 having an upstream face 57 mounted
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to the rotor housing downstream face and having an
outlet/discharge port 58. The exemplary rotor housing,
motor/inlet housing, and outlet housing 56 may each be formed
as castings subject to further finish machining.
[0017] Surfaces of the housing assembly 22 combine with the
enmeshed rotor bodies 3 0 and 34 to define inlet and outlet
ports to compression pockets compressing and driving a
refrigerant flow 504 from a suction (inlet) plenum 60 to a
discharge (outlet) plenum 62 (FIG.2). A series of pairs of
male and female compression pockets are formed by the housing
assembly 22, male rotor body 30 and female rotor body 34. Each
compression pocket is bounded by external surfaces of enmeshed
rotors, by portions of cylindrical surfaces of male and female
rotor bore surfaces in the rotor case and continuations
thereof along a slide valve, and portions of face 57.
[0018] FIG. 2 shows further details of the exemplary flowpath
at the outlet/discharge port 58. A check valve 70 is provided
having a valve element 72 mounted within a boss portion 74 of
the outlet housing 56. The exemplary valve element 72 is a
front sealing poppet having a stem/shaft 76 unitarily formed
with and extending downstream from a head 78 along a valve
axis 520. The head has a back/underside surface 80 engaging an
upstream end of a compression bias spring 82 (e.g., a metallic
coil). The downstream end of the spring engages an
upstream-facing shoulder 84 of a bushing/guide 86. The
bushing/guide 8 6 may be unitarily formed with or mounted
relative to the housing and has a central bore 88 slidingly
accommodating the stem for reciprocal movement between an open
condition of FIG. 2 and a closed condition of FIG. 3. The
spring 82 biases the element 72 upstream toward the closed
condition. In the closed condition, an annular peripheral
seating portion 90 of the head upstream surface seats against
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an annular seat 92 at a downstream end of a port 94 from the
discharge plenum 62.
[0019] The opening and closing of the compression pockets at
suction and discharge ports produce pressure pulsations. As
the pulsations propagate into the gas in the discharge plenum
and downstream thereof, they cause vibration and associated
radiated sound which are undesirable. This pulsation may be at
least partially addressed by modifications involving the check
valve. Exemplary modifications involve modifications to the
valve head to incorporate one or more resonators tuned to
suppress/attenuate one or more sound/vibration frequencies.
Exemplary modifications make use of existing manufacturing
techniques and their artifacts. Exemplary modifications may be
made in a remanufacturing of an existing compressor or a
reengineering of an existing compressor configuration. An
iterative optimization process may be used to tune the
resonator(s).
[0020] FIG. 2 shows one exemplary modification of a basic
valve element. This modification involves providing the head
78 with an upstream extending annular wall 100 inboard of the
seating portion 90. The wall has inboard and outboard surfaces
102 and 104. The exemplary wall 100 extends upstream from a
proximal downstream end 106 (joining a remaining portion of
the head) to a distal upstream end formed by a rim 108. The
surface 102 of the wall 100 and an upstream-facing surface 109
of a central web portion 110 of the head form a
forwardly/upstream open blind compartment/cavity 112 having an
upstream port/opening 114 encircled by the rim 108. Along the
compartment 112, the inboard surface has an essentially
constant radius R along a length L. The compartment 112 forms
a side branch resonator. Geometric properties of the
compartment 112 (e.g., the length and volume) may be tuned to
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suppress/attenuate one or more sound/vibration frequencies at
one or more conditions. An exemplary frequency is that of the
compression pockets opening/closing at the designed compressor
operating speed and at the designed refrigeration system
operating condition. Thus examples of otherwise identical
compressors may feature differently-tuned resonators for use
in different systems or conditions thereof. Exemplary
modifications make use of existing manufacturing techniques
and their artifacts. Exemplary modifications may be made in a
remanufacturing of an existing compressor or a reengineering
of an existing compressor configuration. An iterative
optimization process may be used to tune the resonator(s).
[0021] FIG. 4 shows an alternate check valve 170 which may be
generally similar to the check valve 70. Like features of
these two valves are shown with like reference numerals. The
valve 170 has a valve element 172 wherein the resonator blind
compartment/cavity 174 extends downstream into the stem 178
from a port 180 in the head 176 and has a length L1 and a
radius R1. These may, respectively be larger and smaller than
corresponding parameters of the valve 70 if required to tune
the resonator for a corresponding frequency.
[0022] FIGS. 5 and 6 show an alternate check valve 270 which
may be generally similar to the check valves 70 and 170. Like
features of these three valves are shown with like reference
numerals. The valve 270 has a valve element 272 wherein the
resonator compartment/cavity 274 extends upstream within the
stem 276 from a port 280 at a stem downstream rim/end 278
toward the head 282(and potentially into the head). The cavity
has a length L2 and a radius R2. These may be similar to
corresponding parameters of the valve 170.
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[0023] The relative proximity of the resonator to the
discharge plenum is believed advantageous for several reasons.
First, the check valve is upstream of components like piping
and oil separator that radiate sound due to internal
pulsations. Locating a resonator in the check valve therefore
cancels pulsations upstream of such components. Second,
locating a resonator in the check valve is an effective use of
space. Alternative locations might require adding additional
material to housing walls.
[0024] Many known or yet-developed resonator configurations
and optimization techniques may be applied. The former
include, for example, Helmholtz resonators.
[0025] 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
reengineering or remanufacturing situation, details of the
existing compressor may particularly influence or dictate
details of the implementation. Implementations may involve
check valves used in other locations in the fluid circuit. The
principles may be applied to compressors having working
elements other than screw-type rotors (e.g., reciprocating and
scroll compressors). Accordingly, other embodiments are within
the scope of the following claims.
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CLAIMS
What is claimed is:
1. A compressor apparatus (20) comprising:
a housing (22) having first (53) and second (58) ports
along a flow path;
one or more working elements (26; 28) cooperating with
the housing (22) to define a compression path between suction
(60) and discharge (62) locations along the flow path; and
a check valve (70; 170; 270) having a valve element (72;
172; 272) having a first condition permitting downstream flow
along the flow path and a second condition blocking a reverse
flow,
wherein, the valve element includes a resonator (112; 174;
274) .
2. The compressor of claim 1 wherein:
the check valve (70; 170; 270) is within the housing (22)
immediately downstream of the discharge location (62).
3. The compressor of claim 1 wherein:
the valve element (72; 172) has an upstream head (78;
176) and a downstream stem (76; 178) ; and
the resonator (112; 174) is at least partially within the
head.
4. The compressor of claim 3 wherein:
the resonator (112; 174) has a port (114; 180) in an
upstream face of the head (78; 176) .
5. The compressor of claim 1 wherein:
the valve element (172; 272) has an upstream head (176;
282) and a downstream stem (178; 276); and
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the resonator (174; 274) is.at least partially within the
stem.
6. The compressor of claim 5 wherein:
the resonator (274) has a port (280) in a downstream end
of the stem.
7. The compressor of claim 1 wherein:
the resonator (112; 174; 274) is a branch resonator.
8. The compressor of claim 1 wherein the one or more working
elements include:
a male-lobed rotor (26) having a first rotational axis
(500); and
a female-lobed rotor (28) having a second rotational axis
(502) and enmeshed with the male-lobed rotor.
9. A compressor system (20) comprising:
a compressor having first (53) and second (58) ports
along a flow path; and
a check valve (70; 170; 270) having a valve element (72;
172; 272) having a first condition permitting flow in a first
direction along the flowpath and a second condition blocking
flow opposite the first direction; and
means (112; 174; 274) at least partially in the check
valve (70; 170; 270) for limiting sound caused by pressure
pulsations.
10. The system of claim 9 wherein the means is at least
partially in the valve element (72; 172; 272).
11. The system of claim 9 wherein the means comprises a
branch resonator.
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12. The system of claim 9 wherein the means (112) comprises a
branch resonator in a head (78) of the valve element.
13. The system of claim 9 wherein the means (274) comprises a
branch resonator in a stem (276) of the valve element.
14. An apparatus (20) comprising:
a housing (22) having first (53) and second (58) ports
along a flow path;
one or more working elements (26; 28) cooperating with
the housing (22) to define a compression path between suction
(60) and discharge (62) plenums along the flow path; and
a check valve (70; 170; 270) having a valve element (72;
172; 272) having a first condition permitting downstream flow
from the discharge plenum and a second condition blocking
upstream flow into the discharge plenum; and
means (112; 174; 274) at least partially in the check
valve (70; 170; 270) for limiting sound caused by pressure
pulsations.
15. The apparatus of claim 14 wherein the compressor is a
screw compressor.
16. A method for remanufacturing a compressor or
reengineering a configuration of the compressor comprising:
providing an initial such compressor or configuration
having:
a housing having a flow path between first and
second ports;
a one or more working elements cooperating with the
housing to define a compression path between suction and
discharge locations along the flowpath; and
a check valve along the flow path and having a valve
element; and
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selecting at least one geometric parameter of a
compartment in the valve element to provide a desired control
of a pressure pulsation parameter.
17. The method of claim 16 wherein:
the selecting locates the compartment at least partially
in a head of the valve element.
18. The method of claim 16 wherein the selecting comprises an
iterative :
varying of said at least one geometric parameter; and
directly or indirectly determining the pressure pulsation
parameter.
19. The method of claim 18 wherein:
the determining comprises measuring a sound intensity at
a target frequency for pulsation.
20. The method of claim 16 wherein:
the initial such compressor or configuration lacks said
compartment.
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A compressor
apparatus having a check valve (70)
having a first condition permitting
downstream flow along the flowpath
and a second condition blocking
a reverse flow. The valve element
includes a resonatoer, (112).