Abstract:
A scroll type compressor has both a high pressure lubricant sump and a low pressure lubricant sump. Lubricant from the low pressure lubricant sump is supplied to the various bearings, thrust surfaces and other moving components of the compressor. It is then rested in such a way that it can absorb heat from the motor windings thus maintaining the operating temperature of the motor. Lubricant from the high pressure sump is supplied to the moving compression chambers defined by the scrolls at a point intermediate suction and discharge. The lubricant supplied from the high pressure sump is first cooled and then used to cool the low pressure sump prior to being supplied to the moving compression chambers. The compressed gas is routed through two lubricant separators and a gas cooler prior to being supplied for its intended use.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to scroll-type machinery. More particularly, the present invention relates to scroll-type machinery specifically adapted for use in the compression of natural gas. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Scroll machines are becoming more and more popular for use as compressors in refrigeration systems as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit with respect to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided which operates to drive the scroll members via a suitable drive shaft. 
     As the popularity of scroll machines increase, the developers of these scroll machines continue to adapt and redesign the machines for compression systems outside the traditional refrigeration systems. Additional applications for scroll machines include helium compression for cryogenic applications, air compressors, natural gas compressors and the like. The present invention is directed towards a scroll machine which has been designed specifically for the compression of natural gas and/or LP gas. 
     The cyclic compression of natural gas presents very unique problems with respect to compressor design because of the high temperatures encountered during the compression process. The temperature rise of natural gas during the compression process can be more than twice the temperature rise encountered with the use of a conventional refrigerant. In order to prevent possible damage to the scroll machine from these high temperatures, it is necessary to provide additional cooling for the scroll machine. 
     The present invention comprises a scroll compressor which is specifically adapted for use in the compression of natural gas. The scroll compressor includes the conventional low pressure oil sump in the suction pressure zone of the compressor as well as a second high pressure oil sump located in the discharge pressure zone. An internal oil cooler is located within the low pressure oil sump. Oil from the low pressure oil sump is circulated to the bearings and other movable components of the compressor in a manner similar to that of conventional scroll compressors. A portion of the oil used to lubricate these moving components is pumped by a rotating component onto the windings of the electric motor to aid in cooling the motor. The oil in the high pressure oil sump is routed through an external heat exchanger for cooling and then is routed through the internal oil cooler located in the low pressure oil sump. From the internal oil cooler, the oil is injected into the compression pockets to aid in the cooling of the compressor as well as to assist in the sealing and lubrication of the intermeshed scroll wraps. An internal oil separator is provided in the discharge chamber to remove at least a portion of the injected oil from the compressed gas and replenish the high pressure oil sump. An oil overflow orifice prevents excessive accumulation of oil in the high pressure oil sump. A second external oil separator is associated with the external heat exchanger in order to remove additional oil from the natural gas to provide as close as possible for an oil free pressurized natural gas supply. 
     Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which illustrate the best mode presently contemplated for carrying out the present invention: 
     FIG. 1 is an external elevational view of the scroll machine in accordance with the present invention; 
     FIG. 2 is an external elevational view of the scroll machine shown in FIG. 1 in a direction opposite to that shown in FIG. 1; and 
     FIG. 3 is a vertical cross-sectional view of the compressor shown in FIGS.  1  and  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a scroll machine in accordance with the present invention which is designated generally by the reference numeral  10 . Scroll machine  10  comprises a scroll compressor  12 , a filter  14 , an external oil/gas cooler  16 , an external oil separator  18  and a pressure regulator  20 . 
     Referring to FIG. 3, compressor  12  includes an outer shell  22  within which is disposed a compressor assembly including an orbiting scroll member  24  having an end plate  26  from which a spiral wrap  28  extends, a non-orbiting scroll member  30  having an end plate  32  from which a spiral wrap  34  extends and a two-piece main bearing housing  36  supportingly secured to outer shell  22 . Main bearing housing  36  supports orbiting scroll member  24  and non-orbiting scroll member  30  is axially movably secured to main bearing housing  36 . Wraps  28  and  34  are positioned in meshing engagement such that as orbiting scroll member  24  orbits, wraps  28  and  34  will define moving fluid pockets that decrease in size as they move from the radially outer region of scroll members  24  and  30  toward the center region of the scroll members. 
     A driving motor  38  is also provided in the lower portion of shell  22 . Motor  38  includes a stator  40  supported by shell  22  and a rotor  42  secured to and drivingly connected to a drive shaft  44 . Drive shaft  44  is drivingly connected to orbiting scroll member  24  via an eccentric pin  46  and a drive bushing  48 . Drive shaft  44  is rotatably supported by main bearing housing  36  and a lower bearing housing  50  which is secured to shell  22 . The lower end of drive shaft  34  extends into an oil sump  52  provided in the bottom of shell  22 . A lower counterweight  54  and an upper counterweight  56  are supported on drive shaft  34 . Counterweights  54  and  56  serve to balance the rotation of drive shaft  34  and counterweight  56  acts as an oil pump as described in greater detail below. In order to prevent orbiting scroll member  24  from rotating relative to non-orbiting scroll member  30 , an Oldham coupling  58  is provided. Oldham coupling  58  is supported on main bearing housing  36  and interconnecting with both orbiting scroll member  24  and non-orbiting scroll member  30 . 
     In order to supply lubricant from oil sump  52  to the bearings and other moving components of compressor  12 , an oil pump is provided in the lower end of drive shaft  44  in the form of a large axial bore  60  which serves to direct oil axially upward through an eccentric axially extending passage  62 . Radial passage  64  is provided to supply lubrication oil to main bearing housing  36 . The oil that is pumped through passage  62  will be discharged from the top of eccentric pin  46  to lubricate the interface between drive bushing  48  and orbiting scroll member  24 . After lubricating these interfaces, the oil accumulates within a chamber  66  defined by main bearing housing  36 . Upper counterweight  56  rotates within chamber  66  and acts as a pump to pump oil through a passage  68  extending through main bearing housing  36 . Passage  68  receives oil from chamber  66  and routes this oil to stator  40  to aid in the cooling of the motor. Upper counterweight  56  also pumps lubricating fluid up through a passage  70  also defined by main bearing housing  36 . Passage  70  receives oil from chamber  66  and directs this oil up towards Oldham coupling  58 , the lower surface of end plate  26  of orbiting scroll member  24  and into the suction port formed by scroll members  24  and  30 . 
     Outer shell  22  includes a lower shell  76 , an upper shell  78 , a lower cover  80  and an upper cap  82 . A partition or muffler plate  84  is also provided extending across the interior of shell  22  and is sealing secured thereto around its periphery at the same point that lower shell  76  is sealingly secured to upper shell  78 . Muffler plate  84  serves to divide the interior of shell  22  into a lower suction chamber  86  and an upper discharge chamber  88 . 
     In operation, suction gas will be drawn into suction chamber  86  through a suction inlet  90  and into the moving pockets defined by scroll wraps  28  and  34 . As orbiting scroll member  24  orbits with respect to non-orbiting scroll member  30 , the fluid pockets will move inwardly decreasing in size and thereby compressing the fluid. The compressed fluid will be discharged into discharge chamber  88  through a discharge port  92  provided in non-orbiting scroll member  30  and a discharge fitting assembly  94  secured to muffler plate  84 . The compressed fluid then exits discharge chamber  88  through a discharge outlet  96 . In order to maintain axially movable non-orbiting scroll member  30  in axial sealing engagement with orbiting scroll member  24 , a pressure biasing chamber  98  is provided in the upper surface of non-orbiting scroll member  30 . A portion of discharge fitting assembly  94  extends into non-orbiting scroll member  30  to define chamber  98 . Biasing chamber  98  is pressurized by fluid at an intermediate pressure between the pressure in the suction area and the pressure in the discharge area of compressor  12 . One or more passages  100  supply the intermediate pressurized fluid to chamber  98 . Chamber  98  is also pressurized by the oil which is injected into chamber  98  by the lubrication system as detailed below. 
     With the exception of discharge fitting assembly  94 , compressor  12  as thus far described is similar to and incorporates features described in general detail in Assignee&#39;s patent numbers U.S. Pat. Nos. 4,877,382; 5,156,539; 5,102,316; 5,320,506; and 5,320,507 the disclosures of which are hereby incorporated herein by reference. 
     As noted above, compressor  12  is specifically adapted for compressing natural gas. The compression of natural gas results in the generation of significantly higher temperatures. In order to prevent these temperatures from being excessive, it is necessary to incorporate various systems for cooling the compressor and the compressed natural gas. In addition to the cooling for the compressor and the natural gas, it is also very important that substantially all oil be removed from the compressed gas before it is supplied to the apparatus using the compressed natural gas. 
     One system which is incorporated for the cooling of compressor  12  is the circulation of cooled lubricating oil. Upper shell  78  and muffler plate  84  define a sump  110  which is located within discharge chamber  88 . The oil being supplied to the suction port formed by scroll members  24  and  30  through passage  70  continuously adds to the volume of oil within sump  110 . An oil overflow fitting  112  extends through muffler plate  84 . Fitting  112  has an oil over flow orifice which keeps the level of oil in sump  110  at the desired level. Oil in sump  110  is routed through an outlet fitting  114  (FIG. 1) extending through upper shell  78  and into oil/gas cooler  16  by a connecting tube  116 . The cooled oil exits oil/gas cooler  16  through a connecting tube  118  and enters lower shell  76  through an inlet fitting  120 . Oil entering fitting  120  is routed through a heat exchanger in the form of a cooling coil  122  which is submerged within oil sump  52 . The oil circulates through cooling coil  122  cooling the oil in oil sump  52  and is returned to inlet fitting  120 . Oil entering inlet fitting  120  from coil  122  is directed to biasing chamber  98  through a connecting tube  124 . The oil enters biasing chamber  98  where it enters the compression chambers formed by wraps  28  and  34  through port  100  to cool compressor  12  as well as assisting in the sealing and lubricating of wraps  28  and  34 . The oil injected into the compression chambers is carried by the compressed gas and exits the compression chambers with the natural gas through discharge port  92  and discharge fitting assembly  94 . 
     Discharge fitting assembly  94  includes a lower seal fitting  126  and an upper oil separator  128  which are secured together sandwiching muffler plate  84  by a bolt  130 . Lower seal fitting  126  sealingly engages and is located below muffler plate  84  and it includes an annular extension  132  which extends into non-orbiting scroll member  30  to close and define biasing chamber  98 . A pair of seals  134  isolate chamber  98  from both suction chamber  86  and discharge chamber  88 . Lower seal fitting  126  defines a plurality of discharge passages  136  which receive compressed natural gas from discharge port  92  and direct the flow of the compressed natural gas towards oil separator  128 . Oil separator  128  is disposed above muffler plate  84 . Compressed natural gas exiting discharge passages  136  contacts a lower contoured surface  138  of oil separator  128  and is redirected prior to entering discharge chamber  88 . The contact between the compressed natural gas and surface  138  causes the oil within the gas to separate and return to sump  110 . During the assembly of compressor  12 , lower seal fitting  126  and upper oil separator  128  are attached to muffler plate  84  by bolt  130 . Bolt  130  is not tightened until the rest of the components of compressor  12  are assembled and secured in place. Once this has been accomplished, bolt  130  is tightened. Access to bolt  130  is provided by a fitting  140  extending through cap  82 . Once bolt  130  is tightened, fitting  140  is sealed to isolate discharge chamber  88 . 
     Compressed natural gas exits discharge chamber  88  through discharge outlet  96 . Discharge outlet  96  includes a discharge fitting  142  and an upstanding pipe  144 . Discharge fitting  142  extends through upper shell  78  and upstanding pipe  144  extends toward cap  82  such that the compressed natural gas adjacent cap  82  is directed out of discharge chamber  88 . By accessing the compressed natural gas adjacent cap  82 , the gas with the least amount of oil contained in the gas is selectively removed. Compressed natural gas exiting discharge chamber  88  through outlet  96  is routed to oil/gas cooler  16  through a connecting pipe  144 . Oil/gas cooler  16  can be a liquid cooled cooler using Glycol or other liquids known in the art as the cooling medium or oil/gas cooler  16  can be a gas cooled cooler using air or other gases known in the art as the cooling medium if desired. The cooled compressed natural gas exits oil/gas cooler  16  through a connecting pipe  146  and is routed to oil separator  18 . Oil separator  18  removes substantially all of the remaining oil from the compressed gas. This removed oil is directed back into compressor  12  by a connecting tube  148  which connects oil separator  18  with connecting tube  118 . The oil free compressed and cooled natural gas leaves oil separator  18  through an outlet  150  to which the apparatus using the natural gas is connected. An accumulator may be located between outlet  150  and the apparatus using the natural gas if desired. A second outlet  152  for the natural gas is connected to pressure regulator  20  by a connecting pipe  154 . Pressure regulator  20  controls the outlet pressure of natural gas at outlet  150 . Pressure regulator  20  is connected to filter  14  and filter  14  includes an inlet  156  to which is connected the uncompressed source of natural gas. 
     Thus, uncompressed gas is piped to inlet  156  of filter  14  where it is supplied to suction inlet  90  and thus suction chamber  86  along with gas rerouted to suction inlet  90  and suction chamber  86  through pressure regulator  20 . The gas in suction chamber  86  enters the moving pockets defined by wraps  28  and  34  where it is compressed and discharged through discharge port  92 . During the compression of the gas, oil is mixed with the gas by being supplied to the compression chambers from biasing chamber  98  through passages  100 . The compressed gas exiting discharge port  92  impinges upon upper oil separator  128  where a portion of the oil is removed from the gas prior to the gas entering discharge chamber  88 . The gas exits discharge chamber  88  through discharge outlet  96  and is routed through oil/gas cooler  16  and then into oil separator  18 . The remaining oil is separated from the gas by oil separator  18  prior to it being delivered to the appropriate apparatus through outlet  150 . The pressure of the gas at outlet  150  is controlled by pressure regulator  20  which is connected to oil separator  18  and to suction chamber  86 . 
     In addition to the temperature problems associated with the compression of the natural gas, there are problems associated with various components of or contaminants within the natural gas such as hydrogen sulfide (H 2 5). All polyester based materials degrade and are thus not acceptable for use in any natural gas application. One area which is of a particular concern is the individual components of motor stator  40 . 
     Motor stator  40  includes a plurality of windings  200  which are typically manufactured from copper. For the compression of natural gas, windings  200  are manufactured from aluminum in order to avoid the degradation of windings  200  from the natural gas. In addition to the change of the material of the coil windings itself, the following table lists the other components of stator  40  which require revision in order to improve their performance when compressing natural gas. 
     
       
         
               
               
               
             
           
               
                   
               
               
                   
                   
                 Natural Gas 
               
               
                 Item 
                 Current Material 
                 Material 
               
               
                   
               
             
             
               
                 Varnish 
                 PD George 923 
                 Guardian GRC-59 
               
               
                   
                 PD George 423 
               
               
                   
                 Schenectady 800P 
               
               
                 Tie Cord 
                 Dacron 
                 Nomex 
               
               
                   
                   
                 Cotton 
               
               
                   
                   
                 Nylon treated w/ 
               
               
                   
                   
                 acrylic 
               
               
                 Phase Insulation 
                 Mylar 
                 Nomex 
               
               
                   
                   
                 Nomex-Kapton- 
               
               
                   
                   
                 Nomax 
               
               
                 Slot Liner 
                 Mylar 
                 Nomex 
               
               
                   
                   
                 Nomex-Kapton- 
               
               
                   
                   
                 Nomax 
               
               
                 Soda Straw 
                 Mylar 
                 Teflon 
               
               
                 Lead Wire Insulation 
                 Dacron and Mylar (DMD) 
                 Hypalon 
               
               
                 Lead Wire Tubing 
                 Mylar 
                 Teflon 
               
               
                 Terminal Block 
                 Valox 310 
                 Vitem 1000-7100 
               
               
                   
                   
                 Fibcrite 400S-464B 
               
               
                   
                   
                 Ultrason E2010G4 
               
               
                   
               
             
          
         
       
     
     The above modification for the materials reduces and/or eliminates degradation of these components when they are utilized for compressing natural gas. 
     While the above detailed description describes the preferred embodiment of the present invention, it should be understood that the present invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims.