Abstract:
An apparatus for separating an oil from a refrigerant has a housing, an inlet conduit for receiving a refrigerant/oil mixture, a separator medium, a refrigerant outlet conduit, and an oil outlet conduit. The inlet conduit has an inlet external to the housing and an outlet within the housing and provides means for limiting external sounds transmitted by the housing.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to compressor systems. More particularly, the invention relates to systems having refrigerant/oil separators.  
         [0002]     Refrigerant compressors come in a wide variety of configurations and are used in a wide variety of applications. Exemplary configurations include various screw-type compressors, scroll-type compressors, and reciprocating compressors. Exemplary applications include use in refrigeration systems, air conditioning systems, heat pump systems, chiller systems, and the like. Typical applications involve closed-loop systems.  
         [0003]     Compressor lubrication may be important to control heating and wear. The lubricant (oil) may also help seal the compressor working element(s) relative to the housing and/or each other. There is a tendency for oil to become entrained in the refrigerant as the refrigerant passes through the compressor. For system efficiency, it is desirable to separate this oil from the compressed refrigerant before the compressed refrigerant is passed to downstream system components (e.g., condensers, expansion devices, evaporators, and the like).  
         [0004]     A variety of refrigerant/oil separator systems exist. Exemplary systems return separated oil to the compressor. Exemplary systems are pressure driven, returning the oil to suction or near-suction conditions or up to near-discharge conditions.  
         [0005]     Sound suppression has also been an important consideration in compressor design. Many forms of compressor mufflers have been proposed.  
       SUMMARY OF THE INVENTION  
       [0006]     One aspect of the invention involves an apparatus for separating an oil from a refrigerant. The apparatus has a housing, an inlet conduit for receiving a refrigerant/oil mixture, a separator medium, a refrigerant outlet conduit, and an oil outlet conduit. The inlet conduit has an inlet external to the housing and an outlet within the housing and provides means for limiting external sounds transmitted by the housing.  
         [0007]     In various implementations the separator medium may comprise wire batting. The inlet conduit inlet may be external to the housing. The housing may comprise a longitudinally-extending sidewall of essentially annular section and first and second domed ends. The inlet conduit outlet may be positioned to direct a refrigerant/oil inlet flow to impact the first domed end off-center. The apparatus may be in combination with a compressor, the compressor having a discharge port coupled to the inlet conduit inlet. The inlet conduit may be a single inlet conduit and the inlet conduit outlet may be a single outlet.  
         [0008]     Another aspect of the invention involves a method for remanufacturing a refrigerant/oil separator or reengineering a configuration of the separator. An initial such separator or configuration is provided having a housing, an inlet conduit having an inlet external to the housing, a separator medium, a refrigerant outlet conduit, and an oil outlet conduit. At least one geometric parameter of a positioning of an outlet of the inlet conduit within the housing is selected to provide a desired control of external sound transmitted by the housing in a remanufactured or reengineered configuration.  
         [0009]     In various implementations, the selecting may move the outlet of the inlet conduit closer to an interior surface portion of the housing. The selecting may effectively extend a terminal portion of the inlet conduit. The selecting may effectively extend straightly a terminal portion of the inlet conduit. The selecting may comprise an iterative optimization. The optimization may include varying of a proximity of the outlet of the inlet conduit to an interior surface portion of the housing. The optimization may further include directly or indirectly determining a parameter of said sound (e.g., until minimized or within one or more desired ranges). The determining may comprise measuring an intensity of said sound at a target frequency for pulsation of a compressor associated with the separator. Other than the inlet conduit, the separator may be left essentially unchanged.  
         [0010]     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  
       [0011]      FIG. 1  is a bottom view of a compressor and separator system.  
         [0012]      FIG. 2  is an inboard side view of the separator of  FIG. 1 .  
         [0013]      FIG. 3  is a transverse sectional view of the separator of  FIG. 2 , taken along line  3 - 3 .  
         [0014]      FIG. 4  is a longitudinal sectional view of the separator of  FIG. 3  taken along line  4 - 4 .  
         [0015]      FIG. 5  is a transverse sectional view of the separator of  FIG. 2  taken along line  5 - 5 .  
         [0016]      FIG. 6  is a partially schematic cut-away view of an alternate compressor and separator system.  
         [0017]      FIG. 7  is a partially schematic cut-away view of an alternate compressor and separator system. 
     
    
       [0018]     Like reference numbers and designations in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0019]      FIG. 1  shows system  20  including a compressor  22  having a housing extending from an inlet  23  to an outlet  24  and containing a motor and one or more working elements (e.g., rotors-not shown) for compressing a working fluid along a compression path to drive the working fluid from the inlet to the outlet.  
         [0020]     The system  20  further includes a separator  30  including a separator vessel  32 . A separator inlet conduit  34  has an upstream end coupled to the compressor outlet  24 . The separator has a refrigerant outlet conduit  36 . An oil return conduit  40  is coupled via a filter  42  to the compressor  22  to return lubricating oil from the separator  30  to the compressor  22 . In operation, refrigerant entering the compressor inlet  23  (potentially with a relatively small oil content) entrains additional oil in the compressor so that a more substantial oil/refrigerant mixture is discharged from the compressor outlet  24 . The separator  30  separates this additional oil so that the relatively oil-depleted refrigerant exits the outlet conduit  36  and the extracted oil returns to the compressor via the oil return conduit  40 .  
         [0021]      FIG. 2  shows further details of the separator vessel  32 . The vessel  32  includes a central essentially circular cylindrical (tubular) portion or body  50  extending about/along a central longitudinal axis  510  from an upstream end  51  to a downstream end  52 . At the upstream and downstream ends, domed end pieces or heads  53  and  54  are secured (e.g., by welding). Exemplary body and head materials are alloys (e.g., steel). In the exemplary implementation, the inlet conduit  34  penetrates the body  50  relatively low and off-center generally centrally within an upstream third thereof. This positioning may be an artifact of available stock components in addition to any engineering to achieve a desired interaction of the refrigerant flow with the housing. Thus alternative conduits could be differently positioned (e.g., laterally and/or vertically on-center and/or or higher). The outlet conduit  36  penetrates the head  54  relatively high and centrally (e.g., directly above the axis  510 ). The oil return conduit  40  penetrates the body  50  relatively high and downstream. An alternative oil return conduit could be formed at a drain port low on the shell.  
         [0022]      FIGS. 3 and 4  show the inlet conduit  34  as an assembly extending from an upstream end  60  ( FIG. 3 ) to a downstream end  62  ( FIG. 4 ). A relatively straight upstream length  66  extends from a fitting at the upstream end  60  to penetrate through the body  50 . At its downstream end, the length  66  joins a first elbow  68 . At its downstream end, the first elbow  68  joins a second elbow  70  whose downstream end  72  faces longitudinally toward an interior surface  74  of the upstream head  53 . A straight terminal conduit section/piece  80  has an upstream end portion received within a downstream end portion of the second elbow  70 . The terminal conduit section  80  extends from the downstream end of the elbow  70  and has a downstream end portion forming the conduit downstream/outlet end  62 . The end  62  is located a distance L 1  from the surface  74 . The section  80  may advantageously be coaxial or close to coaxial with the axis  510 . Available off-the-shelf conduit elbow components may, however, influence the convenience of such location.  
         [0023]     A refrigerant/oil flow  520  exits the end  62  and impinges upon the surface  74 . The impingement helps separate a portion of the oil from the refrigerant. This portion may stick to the surface  74  and flow downward along such surface  74  into an accumulation  90  in the bottom of the vessel. The deflected refrigerant and remaining oil pass downstream as a flow  522  and encounter a separation medium  92  located generally centrally within the vessel. An exemplary medium comprises a metallic wire batting or a mesh assembly having sufficient porosity to pass the refrigerant while having sufficient volume-specific surface area to capture further oil. The porosity also permits oil within the accumulation  90  to flow downstream through the medium  92 . As the flow  522  passes from the upstream surface of the medium to the downstream surface of the medium, oil is progressively removed and flows downward through the medium to join the accumulation  90 . An essentially oil-depleted refrigerant flow  524  exits the downstream surface into a downstream volume of the vessel and may pass out through the refrigerant outlet conduit  36 . An end  98  of the oil return conduit  40  is positioned to be immersed within the accumulation  90  to draw in oil for lubricating the compressor.  
         [0024]     According to the present invention, the relationship between the inlet conduit  34  and the vessel may be tuned to provide a degree of sound attenuation. The flow  520  is subject to pressure pulsations. The pulsation frequency is a function of the compressor speed and the geometry of its working elements (e.g., the number/combination of rotor lobes in a screw-type compressor). In a specific implementation, this tuning may be achieved by appropriate selection of the separation length L 1 . The tuning may be appropriate in a variety of circumstances. For example, the same basic separator components may be used with different compressors. Additionally or alternatively, various applications for the same basic compressor and separator may involve different characteristic operating speeds (and thus pulsation frequencies). Given the compressor configuration and target operating condition (or multiple conditions or range of conditions) an appropriate length L 1  may be selected to minimize effects of pulsation at a given frequency, and/or maintain desirably low target levels at one or more frequencies or over a range of frequencies. Such optimizations may be performed iteratively on actual hardware or by simulation or may be performed by calculation. An exemplary optimization involves selecting an appropriate terminal conduit piece  80  length L 2 . This optimization may be performed, for example, by swapping out pieces  80  of different sizes or by trimming or by more complicated arrangements such as adjustable telescoping terminal sections.  
         [0025]     The optimization may be performed as part of a remanufacturing of an existing separator or a reengineering of an existing separator configuration. For example, a baseline system may lack the terminal piece  80 , instead terminating at the elbow downstream end  72 . The piece  80  may be added in an appropriate length to provide the desired sound attenuation. In an exemplary optimization, in addition to measuring a sound parameter (e.g., intensity of sound near the housing) other parameters may be measured. One noteworthy parameter is backpressure. If the conduit outlet is too close to the housing wall, the proximity acts as a flow restriction thereby increasing backpressure in the conduit and upstream thereof and reducing compressor output and efficiency. The backpressure may be directly or indirectly measured (e.g., indirectly measured by measuring a downstream pressure). The optimization may involve choosing a proximity which balances any marginal gain in sound reduction against any marginal loss in backpressure.  
         [0026]     In an original engineering, a calculated theoretical baseline separation may be determined and further optimization performed. We have used quarter wave resonator theory to establish a baseline. Such theory is discussed, in detail, in M. L. Munjal, Acoustics of Ducts and Mufflers, John Wiley &amp; Sons, New York, pages 68-70, 1987. Such a calculation modeling the separator as a reversal-expansion extended tube resonator, however, produced an excessive separation which was downwardly optimized, reducing sound until the creation of undesirable backpressure.  
         [0027]      FIG. 6  shows a compressor/separator system  200  having a common housing assembly  202 . The housing assembly has a refrigerant inlet  204  and a refrigerant outlet  206 . The housing assembly contains one or more working elements  208  (e.g., enmeshed lobed rotors) which may be driven by a motor  210  also within the housing assembly. When so driven, the working elements compress refrigerant from a suction plenum  212  to a discharge plenum  214 . A separator inlet conduit  220  extends from an upstream/inlet end at a discharge plenum outlet  222  to a downstream/outlet end  224  and may pass through a separation medium  226 . In an exemplary implementation, there may be two conduits  220  on either side of an oil filter  230 .  
         [0028]     In the exemplary system  200 , the housing assembly includes a domed end member  232  accommodating the medium  226  and defining a volume  234  distally of the medium  226 . A volume  236  proximally of the medium  226  may be defined by the member  232  and a housing main member  238  containing the working elements  208 . The exemplary member  232  has a slightly domed end  240  joining a sidewall  242  and may have a proximal mounting flange mated to a complementary flange of the housing main member. The conduit outlet end  224  is in close facing proximity to the housing interior surface  244  along the end  240 . The outlet end  224  discharges a refrigerant stream  250  containing oil to impact the surface  244  along the end  240 . The impact causes a partial depletion of oil which drains down along the surface  244  to join an oil accumulation  252 . A resulting partially oil-depleted deflected refrigerant stream  254  passes through the medium  226  which operates in a similar fashion to the medium  92 . The medium  226  further separates oil to join the accumulation  252  and passes a substantially oil-depleted refrigerant stream  256  into the volume  236  to then be discharged through the port  206 . The oil may be drawn from the accumulation and returned to lubricate the compressor through a port (not shown) communicating with suction or intermediate conditions. A basic reengineering of such an existing general configuration may involve moving the conduit outlet end/port  224  closer to the surface  244  (e.g., from a baseline location shown as  224 ′).  
         [0029]      FIG. 7  shows a system  300  formed as a more extensive reengineering of the baseline version of the system  200 . This reengineering involves a rerouting of the conduit to a configuration shown as  302  and having an outlet  304 . The rerouting may be accompanied by a repositioning of the discharge plenum outlet(s) to location(s)  306  (e.g., by reconfiguring a discharge end bearing case). The rerouting may address any structural problems associated with the decreased separation of the outlet  304  from the surface  244 . For example, the conduit  302  may be relatively straighter than the conduit  220 .  
         [0030]     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, when applied as a remanufacturing or reengineering, details of the existing separator configuration may influence details of any particular implementation. The principles may be implemented in more complex forms and the relevant components combined with components serving other functions. Accordingly, other embodiments are within the scope of the following claims.