Information
-
Patent Grant
-
6205808
-
Patent Number
6,205,808
-
Date Filed
Friday, September 3, 199925 years ago
-
Date Issued
Tuesday, March 27, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- McDermott; Corrine
- Jiang; Chen-Wen
Agents
- Beres; William J.
- O'Driscoll; William
- Ferguson; Peter D.
-
CPC
-
US Classifications
Field of Search
US
- 062 84
- 062 468
- 062 469
- 062 470
- 417 372
- 418 97
- 418 98
- 418 100
- 418 DIG 1
-
International Classifications
-
Abstract
A screw compressor in a refrigeration chiller includes one or more baffles disposed in the compressor housing so as to intercept and redirect oil which may flow and/or be blown, under certain operating conditions, in an upstream direction against the stream of suction gas that flows into the compressor from the evaporator. The baffles cause oil to be retained in the compressor rather than being blown back to the system evaporator to ensure that sufficient oil is available to the compressor under all operating conditions and eliminates the need for structure/apparatus in the evaporator dedicated to returning such oil to the compressor.
Description
BACKGROUND OF THE INVENTION
The present invention relates to screw compressors. More particularly, the present invention relates to screw compressors employed in refrigeration chillers. With still more particularity, the present invention relates to the prevention of oil backflow out of a screw compressor in a refrigeration chiller and the loss of oil to the system evaporator as a result thereof.
Screw compressors are compressors in which two or more screw rotors are disposed in an intermeshing relationship in a working chamber. The counter-rotation of the screw rotors draws gas into the working chamber at a first, relatively low pressure, causes the compression of such gas within the working chamber and causes the discharge of such gas at a higher, so-called discharge pressure therefrom.
In many screw compressor applications, including application in refrigeration chillers, oil may be injected directly into the compressor's working chamber for cooling and sealing purposes. Additionally, oil is used to lubricate the compressor bearings. Oil used for bearing lubrication in refrigeration chillers is typically vented/directed to a location within the compressor where refrigerant gas at a relatively low pressure is found. Such oil will, therefore, eventually make its way into the compressor's working chamber and become entrained in the refrigerant gas that flows through it. Such oil, together with any oil that was injected directly into the compressor's working chamber, is then carried out of the compressor entrained in the flow stream of gas discharged from the compressor.
Because the flow stream of refrigerant gas issuing from a screw compressor in a refrigerant chiller contains a relatively large amount of oil and because such oil needs to be returned to the compressor for the various purposes mentioned above, an oil separator is typically located in or immediately downstream of the compressor for the purpose of disentraining the oil from the discharge gas flow stream and gathering it for return to the compressor. In many chiller systems, it is the discharge pressure found in the oil separator that is used to drive the separated oil from the oil separator back to the compressor.
While the oil separates used in such systems are very highly efficient, typically disentraining 99% or more of the oil from the refrigerant gas flowing therethrough prior to the exit of the gas for delivering to the system condenser, it will be appreciated that over time the compressor's oil supply can come to be depleted. Any oil that makes its way past the system oil separator is typically carried into and through the system condenser and winds up in the system evaporator pooled on or in the liquid refrigerant that will be found at the bottom thereof. Provisions are typically made for regularly returning this relatively small amount of oil from the system evaporator back to the system compressor, such oil migration, once again, being typical in refrigeration chillers of all types and typically involving only a relatively very small amount of oil as a percentage of the chiller's oil supply.
Because there is a direct flow path from the chiller's evaporator to the chiller's compressor component through which suction gas is drawn into the compressor, the possibility does exist, under some conditions, for oil located within the compressor to flow out of the compressor, in a direction back toward and even into the evaporator. Such conditions are somewhat unique to and are exacerbated in refrigeration chillers that employ screw compressors due to the amount of oil which is used for various purposes within such compressors and due to the fact that the system evaporator is located below and generally in an open flow relationship with the suction area of the compressor in such systems. Oil flow directly into the system evaporator from the compressor, while atypical, can sometimes be in quantities greater than it is the capacity of the oil return apparatus associated with the evaporator to cope with and can result in chiller shutdown for lack of oil in sufficient quantity in the proper location to ensure that the compressor is continuously and adequately supplied with oil while in operation.
Exemplary of previous arrangements by which such oil is caught and trapped for return to the compressor in a refrigeration chiller after backflowing thereoutof are those found in U.S. Pat. Nos. 5,086,621 and 5,396,784. The '621 patent addresses the oil backflow problem by positioning a tray within the evaporator beneath the piping through which suction gas is drawn from the evaporator to the compressor. That tray catches and accumulates any backflowing oil. Such oil is then returned on a continuing basis to the system compressor by use of the eductor apparatus.
The '784 patent likewise teaches the positioning of a tray beneath the evaporator outlet in a refrigeration chiller to catch and return backflowing oil. In the '784 patent, however, when the level of oil in the tray becomes sufficiently high, gas flow from the evaporator to the compressor comes to be restricted with the result that gas flow velocity is caused to increase. The increased flow velocity of the gas flowing out of the evaporator to the compressor causes the entrainment of oil located in the tray in the gas stream flowing out of the evaporator back to the compressor.
As will be appreciated, both such arrangements require the fabrication and installation of parts/components which are assembled into the system evaporator to address the oil backflow problem. Such parts/components, their fabrication and installation come at significant expense and their operation comes at some expense in terms of the overall power consumed by the chiller system.
The need continues to exist for an arrangement by which to prevent the backflow of oil from a screw compressor to the evaporator in a refrigeration chiller system which does not add significantly to the expense of the compressor or chiller system and which does not penalize chiller efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to limit and/or prevent the backflow of oil from a compressor in a refrigeration chiller to the chiller system evaporator.
It is another object of the present invention to prevent the backflow of oil from the compressor to the evaporator in a refrigeration chiller system by intercepting and re-directing backflowing oil within the compressor, prior to its escape therefrom.
It is a still further object of the present invention to prevent the backflow of essentially all oil from the compressor to the evaporator in a refrigeration chiller system in a manner which is passive and which adds relatively very little expense to the cost of the chiller system in terms of its fabrication, in terms of the parts/components employed for the oil backflow prevention purpose and in terms of its effect on chiller operating efficiency.
These and other objects of the present invention, which will be appreciated when the following Description of the Preferred Embodiment and the attached Drawing Figures are considered, are accomplished in a refrigeration chiller system that employs a screw compressor in which one or more oil backflow baffles are strategically placed upstream of the compressor's working chamber and/or suction area to intercept backflowing oil and to re-direct it back to the compressor without permitting its escape from the compressor housing in the first instance. In the preferred embodiment, such baffles are disposed in the portion of the compressor housing in which the compressor's drive motor is disposed. The drive motor, in the preferred embodiment, is cooled by the flow of refrigerant gas from the system evaporator enroute to the working chamber of the compressor. Under those relatively infrequent chiller operating conditions during which oil backflow from the compressor to the evaporator might otherwise occur, the baffles act to block the backflow of oil from the compressor housing and to re-direct it in an upstream direction for use in the compressor.
DESCRIPTION OF THE DRAWING FIGURES
FIG. 1
schematically illustrates the refrigeration chiller of the present invention.
FIG. 2
is a cross-sectional view of the compressor portion of the refrigeration chiller of FIG.
1
.
FIG. 3
is an end view of the motor housing of the compressor illustrated in FIG.
2
and taken along line
3
—
3
therein.
FIG. 4
is a perspective cross-sectional view of the motor housing of
FIG. 3
taken along line
4
—
4
therein.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to Drawing
FIG. 1
, refrigeration chiller
10
, in its most basic form, includes a compressor portion
12
, a condenser
14
, an expansion device
16
and an evaporator
18
all of which are connected for flow to form a refrigeration circuit. Generally speaking, refrigerant gas is compressed in compressor
12
and is discharged therefrom at relatively high pressure and temperature. Such gas is delivered to condenser
14
where it is cooled and condensed in a heat exchange relationship with a relatively cooler medium, such as water, flowing through tube bundle
20
.
The now condensed refrigerant flows from condenser
14
to expansion device
16
where, by its passage therethrough, the pressure and temperature of the refrigerant is reduced. A portion of the liquid refrigerant flowing through device
16
vaporizes in the expansion process. The now two-phase refrigerant flows from expansion device
16
into evaporator
18
where it is brought into heat exchange contact with a medium flowing through tube bundle
22
.
The medium flowing through tube bundle
22
within evaporator
18
carries with it heat from the heat load which it is the purpose of chiller
10
to cool. Such heat will be rejected from that medium to the relatively cooler, low pressure refrigerant that is delivered into evaporator
18
which, in turn, causes the vaporization of the majority of the liquid portion thereof. The now cooled medium flowing within tube bundle
22
is delivered back to the heat load in order to further cool it. At the same time, the vaporized refrigerant in evaporator
18
is drawn thereoutof back to compressor
12
where it is recompressed for delivery to the condenser in an ongoing process.
In the preferred embodiment of the chiller system of the present invention, compressor
12
is a compressor of the screw type. In that regard, compressor
12
has a housing
24
which generally includes a rotor housing
26
and a motor housing
28
. Rotor housing
26
defines a working chamber
30
in which a first screw rotor
32
and a second screw rotor
34
are disposed in a counter-rotating, intermeshed relationship. Compressor drive motor
36
is disposed in motor housing
28
and is connected to one of rotors
32
and
34
so as to drive it.
In the chiller of the preferred embodiment, suction gas is drawn out of evaporator
18
through suction line
38
which opens into the motor housing portion
28
of compressor housing
24
. The suction gas flows through motor housing
28
, around motor
36
and cools motor
36
in the process. The suction gas is then drawn into working chamber
30
, where it is compressed by the counter rotation of the motor-driven screw rotors, and is discharged through discharge line
40
to an oil separator
42
prior to flowing downstream to condenser
14
as was earlier described.
As is the case with most compressors, including screw compressor
12
of the preferred embodiment, one or more components thereof will be a rotating part and, as such, will typically be mounted in bearings. As is also typical, such bearings require lubrication. In the chiller system of the preferred embodiment, screw rotors
32
and
34
are mounted for rotation in bearings, such as bearings
44
and
46
, which require lubrication. Because compressor
12
is a screw compressor, there is also a need to use oil for additional purposes. These additional purposes can include the cooling of refrigerant gas undergoing compression and/or the cooling of the screw rotors within the working chamber as well as the sealing of the interfaces between the rotating screw rotors themselves and between the rotors and the walls of working chamber
30
.
With the above in mind and referring additionally now to
FIG. 2
, chiller
10
requires the use of a significant amount of oil, such oil being delivered, for example, to bearings
44
and
46
through supply lines
48
and
50
. Oil is also injected into working chamber
30
of compressor
12
through supply line
52
which opens into working chamber
30
at a location where the pressure of the refrigerant gas undergoing compression is less than discharge pressure.
Such oil is sourced from sump
54
of oil separator
42
and flows through line
56
to supply lines
48
,
50
and
52
under the impetus of the disclosure pressure found in oil separator
42
. That pressure will be greater than the pressure found at the locations of oil use and/or the locations to which such oil is directed/vented/drained after being used in the compressor for its intended purpose. While oil separator
42
is highly efficient, a relatively very small portion of the oil that issues from compressor
12
entrained within the discharged refrigerant gas will make its way, with the refrigerant gas, past the oil separator and will settle in evaporator
22
. Such oil, which is, once again, relatively small in quantity, is returned for use in the compressor by apparatus
200
, shown in phantom in
FIG. 1
, which directs such oil back to compressor
12
through line
202
.
Among the locations to which oil will make its way after use within the compressor is suction area
58
of the compressor. Under normal operating conditions, the flow of gas to and through compressor
12
is sufficiently high to ensure that oil located within and in the vicinity of suction area
58
is drawn into, passes through and passes out of the compressor's working chamber to oil separator
42
entrained in that gas. When load conditions are such that the amount of gas flowing into the compressor from the evaporator is significantly reduced, the dynamics of drive motor and screw rotor rotation within the compressor housing, together with pressure pulsations that can come to exist under such conditions, can act to blow oil out of suction area
58
of the compressor, back through the motor housing and into the system evaporator, against the significantly reduced resistance offered by the relatively anemic stream of gas flowing to the compressor from the evaporator. Under certain of such conditions, oil blowback can be sufficiently forceful and sustained to cause a relatively large portion of the compressor's oil supply to be blow out of the compressor to the system evaporator. It is generally beyond the capacity of oil return apparatus
200
to return this amount of oil to the compressor in a timely fashion and if such circumstances are not otherwise addressed, compressor shutdown and/or damage for lack of oil can result.
Referring additionally now to
FIGS. 3 and 4
, the flow of suction gas from evaporator
18
through line
38
, in the preferred embodiment, is into motor housing
28
, as is indicated by arrows
100
. Once in the motor housing, the suction gas flows through, over and around motor
36
, cooling it in the process. While some of the flow of suction gas is through the relatively small rotor-stator gap of the motor (not shown), it is much more so around and over motor
36
through suction gas passages
60
A,
60
B and
60
C which are defined, in the preferred embodiment, by the interior walls of the motor housing. Once past the driver motor, the suction gas flows into suction area
58
, which is generally located and defined at the interface of the rotor housing and motor housing portions of compressor housing
24
. From there, the gas is drawn into the compressor's working chamber.
When compressor
12
is fully loaded, slide valve
62
abuts slide stop
64
, as is illustrated in Drawing
FIG. 2
, with the result that all of the suction gas that enters suction area
58
comes to be directed and drawn into suction subarea
58
A. Suction subarea
58
A is the location of the compressor's suction port, the suction port being the location where gas exists the suction area of the compressor and is drawn into the working chamber. Suction gas flows into the compressor's working chamber through the suction port, is compressed therein and is delivered out of the compressor to oil separator
42
through discharge line
40
. Suction gas flow under full load conditions is most typically in relatively large quantity and at relatively high velocity and will, as will further be described, tend to pick up and carry oil that has made its way into subarea
58
B of suction area
58
, such as the oil in pool
66
.
When chiller
10
operates less than fully loaded, slide valve
62
is retracted from slide stop
64
by a distance appropriate to the load on the chiller, thereby exposing a portion of the working chamber
30
and the screw rotors therein back to suction area
58
in a manner which effectively short circuits a portion of the refrigerant gas flow through the working chamber. The effect of slide valve retraction is to reduce the effective length of the screw rotors, thereby reducing the capacity of the compressor. In the case of compressor
12
the intermeshed, counter-rotating screw rotors are exposed, when slide valve
62
is retracted, to subarea
58
B of the compressor's suction area
58
. Suction subarea
58
B is generally located at the bottom of the compressor, opposite suction subarea
58
A, and is, as indicated, a location where oil tends to collect after being used in the compressor for various purposes.
The retraction of slide valve
62
away from slide stop
64
is a typical and normal occurrence but its effect is to set up some disruption in the suction gas flow pattern within the suction area compressor. Further, the retraction of slide valve
62
away from slide stop
64
exposes the screw rotors, which are rotating at high speed, to the pool of oil
66
that collects in suction subarea
58
B. The amount of such oil can be fairly significant and will vary depending on system operating conditions. Under most conditions, oil is continuously drawn off of and out of pool
66
by suction gas flow and is carried therewith into and through the working chamber and into the system oil separator, even when the slide valve is retracted.
As has been mentioned, however, under some chiller operating conditions, particularly when slide valve
62
is fully or near fully retracted, oil in suction area
58
, including the oil in pool
66
, can be blown out of compressor
12
, against suction gas flow, back to the system evaporator. Whereas previous arrangements have relied upon the trapping and/or collection of such oil in the system evaporator and on apparatus configured to accomplish the return of such oil from the system evaporator to the compressor, the chiller of preferred embodiment of the present invention seeks to prevent the backflow of oil out of the compressor housing in the first instance.
In that regard, one or more baffles are strategically disposed upstream of working chamber
30
in compressor housing
24
at a location or locations which prevent and/or result in the physical interception and/or re-direction of the majority of any oil backflowing therein. Such baffles do not, however, adversely affect or disrupt the normal flow of gas to the compressor's working chamber to any significant degree. First baffle
68
, in the preferred embodiment, is positioned generally at the end of motor housing
28
which is closest to suction line
38
and includes a generally planar wall
70
which faces in the downstream gas flow direction into suction gas passage
60
A. Wall
70
, while not being impinged upon by or otherwise inhibiting suction gas flow in its normal downstream flow direction through compressor housing
24
, presents directly into the face of any oil which is blown upstream through passes
60
A back toward suction line
38
.
It is to be noted that while some oil may escape baffle
68
and flow to the evaporator from the compressor in the upstream direction, the amount thereof is, under most circumstances, manageable. Further, that relatively small amount of oil is capable of being returned to the compressor, under typical operating conditions, by apparatus
200
the primary purpose of which is to return the relatively small amount of oil that makes its way to the evaporator in a downstream flow direction during the normal course of chiller operation.
Oil impinging upon wall
70
of baffle
68
will drain theredown, by force of gravity, to sloped wall
72
and then to the bottom of the motor housing such as to location
74
. Like wall
30
, wall
72
is generally unexposed to, is generally unaffected by and does not generally effect the normal downstream flow of gas into and through the motor housing to suction area
58
. Oil making its way into location
74
flows into oil return passages
76
and
78
, which are defined the bottom of the motor housing. Passages
76
and
78
, in turn, deliver such oil back to pool
66
in suction subarea
58
B of the compressor housing from where it will be drawn into the compressor's working chamber when chiller operating conditions normalize.
A second baffle
80
is disposed in compressor housing
24
of the preferred embodiment between lubricator pool
66
and the location at which suction gas flows out of suction gas passage
60
A and into suction area
58
in the downstream flow direction. The physical makeup of the compressor of the preferred embodiment is such that the counter-rotation of the screw rotors in the compressor's working chamber, the relative location and disposition of the suction gas passage in the motor housing, the relative location and disposition of the compressor's drive motor and the drive motor's direction of rotation
82
all cooperate to result in a tendency for lubricant in pool
66
to be carried/blow upward along surface
84
of motor housing
28
toward the exit of passage
60
A.
Under normal operating conditions and in the absence of baffle
80
, lubricant travelling upward along surface
84
would become entrained in the suction gas exiting suction gas passage
60
A and would be delivered into the working chamber of the component therewith. Under the light load/extreme ambient temperature conditions referred to earlier, however, when gas flow through passage
60
A is in relatively small quantity and/or at relatively low velocity, oil travelling upward along surface
84
can, in the absence of baffle
80
, be blown back through suction gas passage
60
A, against the weak suction gas stream flowing downstream therethrough.
By positioning second baffle
80
immediately below the exit of passage
60
A in the motor housing, the majority of any oil flowing upward along surface
84
out of pool
66
is, as is indicated by arrow
86
in
FIG. 4
, intercepted, deflected and redirected and is effectively blocked from entering the vicinity of the exit of passage
60
A. As such, second baffle
80
effectively prevents, in the first instance, the delivery of a majority of the oil in pool
66
to a location in suction area
58
, where it is likely to be blown back out of the compressor housing. Baffle
68
, on the other hand, is positioned to intercept the oil which is, in fact, blown back through suction gas passage
60
A and is configured to direct such lubricant downward, at the upstream end of the motor housing, into passages that return such oil to pool
66
.
As will be noted and appreciated, the compressor in the chiller of the present invention makes use of two baffles and is a screw compressor in which suction gas flows around and cools the compressor drive motor prior to entering the compressor's working chamber. It is to be understood that the present invention has application not only to screw compressors where the compressor drive motor is upstream of the compressor and is cooled by suction gas, but to compressors in which suction gas is drawn directly through a suction area and into the compressor's working chamber without interacting with a drive motor, such as to cool it.
Further, in the compressor of the chiller of the present invention, oil found in suction area
58
will tend to be moved by the dynamics of gas flow and rotor rotation in a direction and into a location within a suction area
58
where, if low load/extreme ambient temperature conditions exist, it is likely to be blown back out of the compressor housing through suction gas passage
60
A as opposed to the other suction gas passage defined in the motor housing. That is, in the compressor of the chiller of the present invention, oil will not tend to accumulate in a location where it is likely to be blown back of suction gas passage
60
B or
60
C, even when low load/extreme ambient conditions exist. As such, baffles
68
and
80
are located and configured with respect to suction passage
60
A to take into account the configuration and oil backflow tendencies of the compressor of the preferred embodiment. In other compressors, more or one fewer baffle might be required to intercept and/or prevent oil backflow and the locations of such baffles might be different from those in the compressor of the chiller of the preferred embodiment. Such arrangements do, as will be appreciated, fall within the scope of the present invention.
Still further, it is to be noted that in some compressor configurations oil return passages
76
and
78
can be dispensed with. For instance and with reference to
FIG. 3
, if the height of surface
300
in motor housing
28
, which cooperates in the definition of suction gas passage
60
C, were lowered, such as to the height indicated by dashed line
302
which is at or below the lowermost point of aperture
304
through which suction gas enters motor housing
28
, oil at the upstream end of the motor housing would return to suction area
58
through passage
60
C without the need for passages
76
and
78
. In that regard, it will be remembered that passage
60
C is not one through which oil tends to be blown back out of the compressor. Therefore, while the use of oil return passages
76
and
78
is mandatory in some instances, their use in other instances and compressor configurations may not be.
While the present invention has been described in terms of a preferred embodiment, other modifications, additions, alterations and the like thereto will be apparent to those skilled in the art. As such, the scope of the present invention is not limited to the configuration of the preferred embodiment described herein.
Claims
- 1. A refrigeration chiller comprising:a condenser; an expansion device; an evaporator; a compressor, said compressor, said condenser, said expansion device and said evaporator being serially connected for refrigerant flow and forming a refrigeration circuit, and compressor having a housing, at least one baffle, a working chamber and a location, upstream of said working chamber, where oil tends to collect, said at least one baffle being disposed upstream of said working chamber in said housing and being positioned to prevent the flow of oil out of said housing against refrigerant gas flowing in a downstream flow direction through said housing from said evaporator to said working chamber.
- 2. A refrigeration chiller according to claim 1 wherein said at least one baffle is positioned to both intercept and redirect oil which backflows from said location where oil tends to collect in said compressor housing.
- 3. The refrigeration chiller according to claim 1 wherein oil redirected by said baffle is redirected into said location where oil tends to collect.
- 4. The refrigeration chiller according to claim 3 further comprising a compressor drive motor, said compressor drive motor being disposed in said compressor housing upstream of said working chamber and upstream said location where oil tends to collect and downstream of the location at which refrigerant gas flows into said compressor housing from said evaporator.
- 5. The refrigeration chiller according to claim 4 wherein said at least one baffle is disposed upstream of said compressor drive motor.
- 6. The refrigeration chiller according to claim 5 wherein said compressor housing defines one or more suction gas flow passages running along the length and exterior of said compressor drive motor, the majority of the suction gas flowing into said compressor housing flowing through said one or more suction gas passages enroute to said working chamber, said at least one baffle having a face disposed so as to face downstream into at least one of said suction gas passages so that oil flowing in an upstream direction therethrough will tend to impact said face and to drain theredown.
- 7. The refrigeration chiller according to claim 6 wherein said compressor housing defines one or more oil-return passages, said one or more oil return passages communicating between a location upstream of said motor, into which oil draining down said face of said at least one baffle is deposited, and a location downstream of said motor where oil flowing out of said at least one oil return passage flows into said location where oil tends to collect.
- 8. The refrigeration chiller according to claim 7 wherein said compressor has two baffles, a first of said two baffles being said baffle which is positioned upstream of said motor to intercept and redirect oil that backflows within said compressor housing and a second of said baffles being disposed so as to prevent the backflow oil from said location where oil collects in the first instance.
- 9. The refrigeration chiller according to claim 8 wherein said second baffle is downstream of said motor.
- 10. The refrigeration chiller according to claim 9 further comprising a first screw rotor; a second screw rotor; and, a capacity control valve, said first and said second rotors being disposed for rotation in said working chamber and said capacity control valve being positionable to vary the capacity of said compressor, the positioning of said capacity control valve to reduce the capacity of said compressor exposing said first and said second rotors to said location in said compressor housing where oil tends to collect.
- 11. The refrigeration chiller according to claim 9 wherein said second baffle is positioned to intercept and redirect the flow of oil away from the downstream exit of one of said suction passages.
- 12. The refrigeration chiller according to claim 2 wherein said at least one baffle is positioned to prevent oil from backflowing out of said location where oil tends to collect against the downstream flow of gas from said evaporator to said working chamber of said compressor.
- 13. The refrigeration chiller according to claim 12 further comprising a compressor drive motor disposed in said housing upstream of said working chamber and wherein said compressor housing defines at least one suction gas passage, said passage running exterior and along the length of said motor and opening into a location in said compressor housing at a location upstream and above the oil in said location where oil tends to collect, said at least one baffle being disposed so as to prevent the flow of oil from said location where oil tends to collect into said location into which said at least one suction gas passage opens.
- 14. A refrigeration chiller according to claim 1 further comprising a baffle disposed upstream of said motor and being disposed to redirect oil blown upstream through said at least one suction gas passage back to said location where oil tends to collect.
- 15. A screw compressor comprising:a housing, said housing defining a working chamber, a suction area in which oil tends to collect and a location at which suction gas enters said housing; a first screw rotor; a second screw rotor, said first and said second screw rotors being disposed in intermeshing relationship in said working chamber, said suction area being defined intermediate said working chamber and said location at which suction gas enters said housing and being a location where oil tends to collect; and a baffle, said baffle being disposed in said housing, upstream of said working chamber but downstream of said location at which suction gas enters said housing, said baffle being positioned to prevent the backflow of oil from said suction area back to and through said location at which suction gas enters said compressor housing.
- 16. The screw compressor according to claim 15 further comprising a motor, said motor being connected to at least one of said first and said second rotors, said motor being disposed upstream of said suction area and downstream of said location at which suction gas enters said compressor housing.
- 17. The screw compressor according to claim 16 wherein said compressor housing defines a suction gas passage communication between said suction area and said location at which suction gas enters said housing, oil tending to be blown out of said suction area through said suction gas passage against suction gas that flows downstream through said suction gas passage under certain compressor operating conditions.
- 18. The screw compressor according to claim 16 wherein said baffle is disposed upstream of said motor and downstream of said location at which suction gas enters said compressor housing.
- 19. The screw compressor according to claim 18 wherein said baffle is disposed so as to intercept and redirect oil blown back through said suction gas passage to the location in said suction area where oil tends to collect.
- 20. The screw compressor according to claim 17 wherein said baffle is disposed downstream of said motor and in said suction area.
- 21. The screw compressor according to claim 20 wherein said baffle is disposed at the exit of said suction gas passage and is positioned so as to intercept and redirect oil which makes its way into the vicinity of the exit of said passage away therefrom, said baffle thereby preventing at least some oil from entering a location in said suction area from where it is susceptible to being blown back through said suction passage.
- 22. The screw compressor according to claim 17 wherein said baffle is disposed upstream of said motor and downstream of said location at which suction gas enters said compressor housing and further comprising a second baffle, said second baffle being disposed downstream of said motor and in said suction area.
- 23. The screw compressor according to claim 22 wherein said first baffle is configured and positioned to intercept oil which is blown back through said suction gas passage and to redirect such oil back to the location in said suction area where oil tends to collect and wherein said second baffle is configured to prevent the flow of oil to a location in said suction area where it is prone to being blown back through said suction gas passage in the first instance.
- 24. The screw compressor according to claim 23 wherein said motor housing defines at least one oil return passage through which oil intercepted and redirected by said first baffle is redirected into said suction area.
- 25. A method for preventing the backflow of oil from the compressor in a refrigeration chiller system to the refrigeration system evaporator comprising:delivering refrigerant gas from said evaporator to said compressor in a downstream direction; flowing said refrigerant gas delivered to said compressor in said delivering step in said downstream direction through said compressor and to a working chamber in said compressor; flowing oil to said compressor for use therein, a portion of said oil collecting, after being used, in a location in said compressor which is upstream of said working chamber; and disposing at least one baffle in said compressor to intercept oil which flows out of said location where oil tends to collect in a direction which is opposite said downstream direction.
- 26. The method according to claim 25 comprising the further step of redirecting oil intercepted in said disposing step back to said location where oil collects in said compressor.
- 27. The method according to claim 26 wherein said compressor has a drive motor disposed upstream of said location where oil collects after its use and wherein said flowing step includes the step of flowing refrigerant gas around said motor in said downstream direction so as to cool said motor prior to the entry of said gas into said working chamber.
- 28. The method according to claim 27 wherein said disposing step includes the step of disposing said baffle upstream of said motor with respect to said downstream direction.
- 29. The method according to claim 27 wherein said disposing step includes the step of positioning said baffle downstream of said motor and upstream of said working chamber in said compressor.
- 30. The method according to claim 27 wherein said disposing step includes the steps of disposing a first baffle upstream of said motor and of disposing a second baffle downstream of said motor.
US Referenced Citations (10)