Patent Publication Number: US-2023144667-A1

Title: Multistage compressor system with intercooler

Description:
The present application is a continuation-in-part under 35 U.S.C. § 120 of U.S. patent application Ser. No. 16/044,106, filed Jul. 24, 2018, and titled “CONCENTRIC VANE COMPRESSOR,” which itself is a continuation under 35 U.S.C. § 120 of U.S. patent application Ser. No. 15/139,608, filed Apr. 27, 2016, titled “CONCENTRIC VANE COMPRESSOR,” and now issued as U.S. Pat. No. 10,030,658. The present application is also a continuation-in-part under 35 U.S.C. § 120 of U.S. patent application Ser. No. 16/348,059, filed May 7, 2019, and titled “SCROLL COMPRESSOR WITH CIRCULAR SURFACE TERMINATIONS.” U.S. patent application Ser. No. 15/139,608, U.S. patent application Ser. No. 16/044,106, and U.S. patent application Ser. No. 16/348,059 are herein incorporated by reference in their entireties. 
     The present application is also a continuation-in-part of International Application No. PCT/US2016/060807, filed Nov. 7, 2016, and titled, “SCROLL COMPRESSOR WITH CIRCULAR SURFACE TERMINATIONS,” which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     A refrigerant compressor is a device that pressurizes refrigerant gas using power from a device such as an electric motor, a diesel engine, a gasoline engine, and so forth. During the compression process, the gas is heated naturally and routed to a condenser. The condenser cools the gas to a “sub cooled” liquid. The “sub cooled” liquid is routed through an expansion nozzle to an evaporator. The expanding liquid vaporizes in the evaporator and cools the evaporator before being routed to the intake port of the compressor to repeat the refrigeration process. 
     Vane compressors generally include a stationary or fixed cylinder with a slot for a reciprocating vane. An orbiting cylinder is positioned within the fixed cylinder, and the reciprocating vane (e.g., with a vane spring) is inserted into the vane slot on the outer fixed cylinder, with one end maintaining contact with the smaller orbiting cylinder. The vane provides a barrier between high and low pressure regions within a cylinder cavity formed between the stationary or fixed cylinder and the orbiting cylinder. 
    
    
     
       DRAWINGS 
       The Detailed Description is described with reference to the accompanying figures. The use of the same reference numbers in different instances in the description and the figures may indicate similar or identical items. 
         FIG.  1    is a cross-sectional side elevation view illustrating a multistage compressor system with a lower shaft bearing located at the bottom of a compressor and an upper shaft bearing located above a counterweight at the bottom of a motor in accordance with an example embodiment of the present disclosure. 
         FIG.  2    is a cross-sectional side elevation view illustrating another multistage compressor system with a lower shaft bearing located at the bottom of a compressor and an upper shaft bearing located at the top of a motor in accordance with an example embodiment of the present disclosure. 
         FIG.  3    is a schematic cross-sectional side elevation view illustrating a low pressure compressor crankcase system in accordance with an example embodiment of the present disclosure. 
         FIG.  4    is a schematic cross-sectional side elevation view illustrating an intermediate pressure compressor crankcase system in accordance with an example embodiment of the present disclosure. 
         FIG.  5    is a schematic cross-sectional side elevation view illustrating a high pressure compressor crankcase system in accordance with an example embodiment of the present disclosure. 
         FIG.  6    is a partial top plan view illustrating a concentric vane compressor for a compressor system, such as the compressor systems shown in  FIGS.  1  through  5   , in accordance with an example embodiment of the present disclosure. 
         FIG.  7    is a partial cross-sectional isometric view of the concentric vane compressor illustrated in  FIG.  6   . 
         FIG.  8    is a partial exploded isometric view of the concentric vane compressor illustrated in  FIG.  6   . 
         FIG.  9    is an isometric view illustrating two cylinders and an end plate for a concentric vane compressor, such as the concentric vane compressor shown in  FIG.  6   , in accordance with an example embodiment of the present disclosure. 
         FIG.  10    is a cross-sectional side view of the two cylinders and end plate illustrated in  FIG.  9   . 
         FIG.  11    is an isometric view illustrating a cylinder and an end plate with a journal bearing, two intake ports, and two exhaust ports for a concentric vane compressor, such as the concentric vane compressor shown in  FIG.  6   , in accordance with an example embodiment of the present disclosure. 
         FIG.  12    is another partial top plan view of the concentric vane compressor illustrated in  FIG.  6   . 
         FIG.  13    is a side view illustrating a thrust bearing for a concentric vane compressor, such as the concentric vane compressor shown in  FIG.  6   , in accordance with an example embodiment of the present disclosure. 
         FIG.  14    is an end view of the thrust bearing illustrated in  FIG.  13   . 
         FIG.  15    is an end view illustrating a counterweight for a concentric vane compressor, such as the concentric vane compressor shown in  FIG.  6   , in accordance with an example embodiment of the present disclosure. 
         FIG.  16    is an exploded isometric view illustrating a cylinder with a vane slot and a vane for a concentric vane compressor, such as the concentric vane compressor shown in  FIG.  6   , in accordance with an example embodiment of the present disclosure. 
         FIG.  17    is an exploded isometric view illustrating another cylinder with a vane slot and a vane for a concentric vane compressor, such as the concentric vane compressor shown in  FIG.  6   , in accordance with an example embodiment of the present disclosure. 
         FIG.  18    is an exploded isometric view illustrating a further cylinder with a vane slot and a vane for a concentric vane compressor, such as the concentric vane compressor shown in  FIG.  6   , in accordance with an example embodiment of the present disclosure. 
         FIG.  19    is an exploded isometric view illustrating another cylinder with a vane slot and a vane for a concentric vane compressor, such as the concentric vane compressor shown in  FIG.  6   , in accordance with an example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring generally to  FIGS.  1  through  19   , compressor systems  100  are described. A multi-stage (e.g., two stage) compressor system  100  (e.g., configured as an intercooler) can include a sealed housing  102  (e.g., a crankcase shell). The compressor system  100  can also include one or more positive displacement devices (e.g., compressors  104 ) having a first compressor stage  106  (e.g., a low pressure stage) and/or a second compressor stage  108  (e.g., a high pressure stage) contained by the sealed housing  102 . As described, the first compressor stage  106  is configured for receiving refrigerant  110  or other fluid from outside of the sealed housing  102  and compressing the refrigerant  110 . The second compressor stage  108  is configured for receiving refrigerant  110  or other fluid from within the sealed housing  102  and compressing the refrigerant  110 . It should be noted that while two compressor stages are described herein, more than two compressor stages may be provided (e.g., three compressor stages or more than three compressor stages). 
     The refrigerant  110  supplied to the first compressor stage  106  from outside of the sealed housing  102  can be in a gaseous state when supplied to the first compressor stage  106  and can then be converted to a liquid state after exiting the first compressor stage  106 . The refrigerant  110  supplied to the second compressor stage  108  from within the sealed housing  102  can be in a gaseous state when supplied to the second compressor stage  108 . Thus, the refrigerant  110  can undergo a phase change from gas to liquid (after exiting the first compressor stage  106 ) and then back to gas (prior to the second compressor stage  108 ), enhancing thermal transfer within a compressor system  100 . 
     In some embodiments, a compressor  104  can be a multi-stage compressor including two compression chambers, one larger (e.g., low pressure stage) and one smaller (e.g., high pressure stage), one hundred and eighty degrees (180°) out of phase. For example, the compressor system  100  includes a concentric vane compression device including both the first compressor stage  106  and the second compressor stage  108 . In embodiments of the disclosure, a concentric vane compression device can be implemented as described in U.S. Pat. No. 10,030,658, titled “CONCENTRIC VANE COMPRESSOR,” which is incorporated by reference herein. However, a compressor with two compression cavities is provided by way of example and is not meant to limit the present disclosure. 
     In some embodiments, more than one compressor  104  may be used to provide the first compressor stage  106  and the second compressor stage  108 . For example, the compressor system  100  can include two or more spiral scroll compression devices forming the first compressor stage  106  and the second compressor stage  108 . In embodiments of the disclosure, a spiral scroll compression device can be implemented as described in U.S. patent application Ser. No. 16/348,059, titled “SCROLL COMPRESSOR WITH CIRCULAR SURFACE TERMINATIONS,” which is incorporated by reference herein. The compressor system  100  may also include two or more other types of compressors or other devices that increases the pressure of a gas by reducing its volume, including, but not necessarily limited to: reciprocating compressors, rotary screw compressors, rotary vane compressors, rolling piston compressors, diaphragm compressors, centrifugal compressors, axial compressors, and so forth. 
     The compressor  104  also includes at least one crank  112  (e.g., crankshaft) for mechanically driving compression in the first compressor stage  106  and/or the second compressor stage  108 . In some embodiments, the crank  112  mechanically drives compression in both the first compressor stage  106  and the second compressor stage  108 . For example, a motor  114  includes a stator  116  and a rotor  118  mechanically coupled with a concentric vane compression device by the crank  112  (e.g., as described with reference to  FIGS.  1 ,  2 , and  6  through  19   ). The motor  114  is thus connected to a common crankshaft that drives compression in two differently sized compression cavities (e.g., the first compressor stage  106  and the second compressor stage  108 ). In some embodiments, each compressor  104  has its own crank  112 . For example, a first compressor  104  forming a first compressor stage  106  has a first crank  112 , and a second compressor  104  forming a second compressor stage  108  has a second crank  112 . In this example, each of the two cranks  112  can be connected to a separate motor  114 . For instance, two motors  114  can each be mechanically coupled with a separate respective spiral scroll compression device by a separate crank  112 . 
     The compressor system  100  can also include an interior cavity  120  for containing refrigerant  110  and/or other fluid (e.g., air) from the surrounding environment and oil  122  (e.g., in an oil reservoir or bottom portion of the interior cavity  120 ). The sealed housing  102  may be supported by a base plate  124  or other supporting structure. One or more electrical terminals  126  can be connected through the sealed housing  102  to wiring used to supply electrical power to the motor  114  and/or to other components of the compressor system  100 . One or more suction pipes  128  can be used to supply the refrigerant  110  or other fluid to the first and second compressor stages  106  and  108 , and one or more discharge pipes  130  can be used to supply the compressed refrigerant  110  or other fluid from the compressor system  100 . 
     The compressor system  100  can include a first bearing  132  (e.g., a main bearing) and a second bearing  134  (e.g., a sub-bearing). Together, the first bearing  132  and the second bearing  134  can constrain motion of the crank  112  and reduce friction between the crank  112  and other components of the compressor system  100 . In some embodiments, the first bearing  132  is outside of and adjacent to the motor  114 , e.g., as described with reference to  FIG.  1   , where the motor  114  can be pressed into, for instance, a hermetic housing, and the compressor  104  is constrained between the first and second bearings  132  and  134 . In some embodiments, the first bearing  132  is configured as a top bearing bracket, e.g., as described with reference to  FIG.  2   , with the motor  114  and the compressor  104  constrained between the first and second bearings  132  and  134 . In embodiments of the disclosure, the first bearing  132  and/or the second bearing  134  can include one or more vent holes  136 . Mounting pads  138  may extend radially outward from, for example, a flange of the compressor  104  to an inside surface of the sealed housing  102  to constrain the compressor  104  and/or the motor  114 . 
     In some embodiments, the crank  112  can be a hollow shaft, and may include an oil pump  140 , e.g., a centrifugal oil pump with another hollow shaft or a portion of the same crank disposed at one end of the crankshaft and extending into the oil  122  contained in the oil reservoir or bottom portion of the interior cavity  120 . The oil pump  140  can be used to draw the oil  122  into an interior of the crank  112  and then up the crankshaft, where the oil  122  is expelled and sprayed over various components of the compressor  104 . For instance, the crank  112  and/or oil pump  140  can include holes or other apertures along its length, and the oil  122  can be expelled from the interior of the crank  112  through the holes. As described herein, the oil  122  can be used to cool both the refrigerant  110  and various compressor components in addition to lubricating various compressor components. 
     It will be appreciated that the diameter of the crank  112  and/or the oil pump  140 , as well as the number of holes or apertures and their arrangement along the crank  112  and/or the oil pump  140  may be varied to pump different volumes of oil at different rates. For example, a larger diameter crank  112  may be used to pump more oil than a comparatively smaller crank (e.g., more oil over time, more oil by volume, etc.). It should be noted that the centrifugal oil pump  140  described herein is provided by way of example only and is not meant to limit the present disclosure. In other embodiments, an oil pump  140  may be a gear-driven oil pump, an oil pump with paddles (e.g., elastomeric/rubber paddles), and/or another type of oil pump. 
     The compressor systems  100  may also include one or more counterweights, thrust bearings, and/or oil slingers. For example, a counterweight  142  may be fixedly coupled with the crank  112  and, in addition to providing weighted balance to the compressor  104 , may act as an oil slinger. In this manner, the counterweight  142  can facilitate the dispersal/spray of cooling oil, e.g., over a top surface of the compressor  104 . With reference to  FIGS.  13  through  15   , in some embodiments the counterweight  142  can include a mounting bolt hole  144  and alignment posts  146 . The counterweight  142  may be bolted to a lower thrust bearing  148  at a threaded mounting bolt hole  150 , e.g., with a bolt inserted through the mounting bolt hole  144  of the counterweight  142  and fastened to the threaded mounting bolt hole  150  of the thrust bearing  148 . 
     The alignment posts  146  of the counterweight  142  may be used to maintain the rotational orientation of the counterweight  142  with respect to the thrust bearing  148 , the crank  112 , and/or other components of the compressor  104 , such as an eccentrically orbiting cylinder. In some embodiments, the alignment posts  146  may be configured as metal pins cast with the counterweight  142  (e.g., as a unitary part). In other embodiments, the alignment posts  146  can be separate parts connected to the counterweight body. The thrust bearing  148  can be used to control axial movement of the compressor components (e.g., axial movement of an eccentrically orbiting cylinder). In some embodiments, the thrust bearing  148  includes an eccentric bearing  152 , a front shaft bearing  154 , and a rear shaft bearing  156 . With reference to  FIG.  2   , a compressor system  100  may also include an upper thrust bearing  158 . 
     Referring now to  FIGS.  3  through  5   , in embodiments the compressor  104  includes a heat exchanger (e.g., a condenser  160 ) outside of the sealed housing  102  configured to release and/or collect heat energy. The condenser  160  is configured to receive refrigerant  110  from the first compressor stage  106  and exchange heat with the refrigerant  110 . For example, the condenser  160  allows heat to pass from the refrigerant  110  to fluid outside of the condenser  160 , such as outside air, without the refrigerant  110  contacting the outside air or other fluid outside of the condenser  160 . In some embodiments, the condenser  160  includes coils (e.g., copper tubing, aluminum tubing), which may have fins for facilitating heat transfer. As described, the condenser  160  can be used to partially or fully condense discharge gas from the first compressor stage  106  to a sub-cooled liquid state prior to entering the second compressor stage  108 . 
     As described, the compressor system  100  also includes an oil reservoir  162  or bottom portion of the interior cavity  120  contained by the sealed housing  102 , where the oil  122  is held for lubricating the crank  112  and various components of the compressor system  100 . In embodiments of the disclosure, the oil reservoir  162  receives refrigerant  110  from the condenser  160  and exchanges heat with the refrigerant  110  to cool the oil  122  held in the oil reservoir  162 . For example, the refrigerant  110  is routed through the oil reservoir  162 . The refrigerant  110  is then supplied to the second compressor stage  108 . As described, by using a refrigerant cycle to cool the compressor oil  122 , the lower oil temperatures and higher thermal transfer rates of the oil  122  can be used to provide a more effective cooling system that makes better use of the oil  122 , e.g., for both lubrication and cooling of critical compressor components. 
     In a typical intercooler arrangement, such as for a two stage refrigeration compressor, compressed gas from a first compressor stage discharge port is routed through a heat exchanger to cool the gas prior to the gas entering the intake port of a second compressor stage. However, the temperature reduction in this arrangement is limited to prevent a phase change of the refrigerant (i.e., from a gas state to a liquid state) prior to the refrigerant entering the second compressor stage. This limit on the temperature reduction is used to avoid the phenomenon of “liquid slugging,” or liquid entering a cylinder of a reciprocating compressor and damaging the compressor. 
     As described herein, when the heat exchanger/condenser  160  receives refrigerant  110  from the first compressor stage  106  and exchanges heat with the refrigerant  110 , some or all the refrigerant  110  can be converted to liquid. By then routing the liquid refrigerant  110  through the oil reservoir  162 , hot crankcase compressor oil  122  can be used to convert the liquid refrigerant  110  to gas refrigerant  110  while reducing the temperature of the compressor oil  122 . The cooled compressor oil  122  can be routed through the compressor crankcase, cooling compressor surfaces, the compressor motor, and/or the gas refrigerant  110 , e.g., prior to the gas refrigerant  110  entering the second compressor stage  108 . 
     In some embodiments, the compressor system  100  includes a second heat exchanger  164  in the oil reservoir  162  or bottom portion of the interior cavity  120  contained by the sealed housing  102 . The heat exchanger  164  allows heat to pass from the oil  122  to the refrigerant  110  without the oil  122  contacting the refrigerant  110 . For example, the second heat exchanger  164  may also include coils (e.g., copper tubing, aluminum tubing), which may have fins for facilitating heat transfer. In some embodiments, the coils may surround the compressor  104  (e.g., in a sump-type compressor configuration). However, it should be noted that in some embodiments, rather than routing all the refrigerant  110  through a second heat exchanger, some or all the liquid refrigerant  110  may bypass the oil heat exchanger  164  and be routed directly onto critical compressor components. In embodiments, some of the incoming cool liquid refrigerant  110  from the condenser  160  may be directed onto critical compressor components, while the remaining cool liquid refrigerant  110  may be used to cool the oil  122  (e.g., using the oil  122  for both lubrication and cooling). 
     It is noted that temperature reduction during a compression process generally has a positive effect on compressor efficiency, increasing the efficacy of the apparatus, systems, and techniques of the present disclosure. It is also noted that the energy transfer needed to cause a phase change in the refrigerant  110  from gas to liquid or from liquid to gas is many times greater than the energy transfer associated with a temperature change without a corresponding phase change. Thus, the apparatus, systems, and techniques of the present disclosure that use a phase change in the refrigerant  110  can improve compressor cooling and may have a great effect on increasing the efficiency of the compressor systems  100  described herein. 
     Referring now to  FIG.  3   , in some embodiments the refrigerant  110  is routed from outside the sealed housing  102  into the interior cavity  120  within the sealed housing  102  and then into the first compressor stage  106  to form a low pressure or suction pressure crankcase. It should be noted that in this configuration, a thrust bearing may be used to maintain axial contact sealing between, for example, stationary cylinder(s) and orbiting cylinder(s) (e.g., of a concentric vane compression device). This configuration may also reduce or eliminate liquid slugging relief. 
     Referring to  FIG.  4   , in some embodiments the refrigerant  110  is routed from the oil reservoir  162  into the interior cavity  120  within the sealed housing  102  and then into the second compressor stage  108  to form an intermediate pressure crankcase. This configuration may provide pressure relief for liquid slugging, while allowing minimal axial thrust between stationary cylinder(s) and orbiting cylinder(s) (e.g., of a concentric vane compression device). Further, this arrangement can allow the crankcase pressure to be controlled by the intermediate pressure of the pump, allowing the compressor system  100  to be configurable for a variety of efficiency and wear considerations. 
     Referring now to  FIG.  5   , in some embodiments the refrigerant  110  is routed from the second compressor stage  108  into the interior cavity  120  within the sealed housing  102  and then out of the sealed housing  102  to form a high pressure crankcase. This configuration may also provide pressure relief for liquid slugging, and may produce higher axial thrust, possibly increasing axial wear between stationary cylinder(s) and orbiting cylinder(s) (e.g., of a concentric vane compression device), having reduced efficiency when compared to the embodiment illustrated in  FIG.  4   . 
     Referring now to  FIGS.  6  through  19   , a compressor system  100  can be implemented with a positive displacement device that includes both the first compressor stage  106  and the second compressor stage  108 , such as a concentric vane compressor  200 . As described herein, a positive displacement device configured as a vane compressor can include two orbiting cylinders, rigidly connected at one end by a plate. In embodiments of the disclosure, the inner orbiting cylinder is smaller than the fixed cylinder and the larger orbiting cylinder is larger than the fixed cylinder. In some embodiments, a common vane may pass through a vane slot in the fixed cylinder wall, maintaining sealing contact with both the inner and outer orbiting cylinder surfaces. In this configuration, the smaller orbiting cylinder controls the vane position from one side while the larger orbiting cylinder controls the vane position from the other side. 
     The concentric vane compressor  200  can provide two compression cavities, each divided into low and high pressure regions. The inner cavity is formed between the inner orbiting cylinder surface and the fixed cylinder surface and has a smaller displaced volume than that of the outer cavity. The outer compression cavity is formed between the fixed cylinder surface and the outer orbiting cylinder surface and has the larger displaced volume. Thus, a concentric vane compressor  200  may be configured as either a single stage compressor or a two stage compressor, e.g., with a single fixed and orbiting cylinder set. For a two stage design, the larger outer cavity may be used for the first stage, and the smaller inner cavity may be used for the second stage. 
     It should be noted that the outer and inner compression cavities, while sharing a common vane and common orbiting and fixed cylinders, are two separate cavities with compression cycles sequenced one hundred and eighty degrees (180°) apart. This configuration can reduce peak compressor torque (e.g., by about one-half) and/or associated noise and vibration while increasing motor running efficiency. Further, dual concentric sequential compression chambers can support the addition of flow control valves for switching between four levels of mass flow and single stage or two stage compression to increase efficiency (e.g., as weather conditions vary) while also enabling start relief (e.g., for the compressor motor). In embodiments of the disclosure, flow control valves can be located within a compressor enclosure and/or outside of the enclosure. When placed outside of a compressor enclosure, ease of maintenance and/or improved control wiring access may be provided. Additionally, an outside placement can provide for simplified control features and/or upgrade options with a common compressor design. Available features may range from a baseline unit without control valves, two or three additional mass flow levels plus single or two stage compression options, a start relief option, and so on. With outside flow control valves, these options may be available from a manufacturer and/or may be added in the field. 
     A concentric vane compressor  200  can be used for various applications, including, but not necessarily limited to, pumping fluid and/or gas. For example, a concentric vane compressor  200  can be used as a compressor for refrigeration and/or air conditioning applications, and so forth. The apparatus, systems, and techniques described herein, can provide low cost, low noise, and/or high efficiency oil lubricated rotary compressors that can be used in, for example, refrigeration compressor applications. Using concentric sequential compression, a low clearance volume may be provided. Further, the concentric vane compressor  200  can facilitate start unloading. In some embodiments, a single wrap design allows for a reduced compressor diameter and/or leakage area (e.g., as compared to a multiple wrap design). Further, a concentric vane compressor  200  can provide higher liquid slugging tolerance (e.g., because the orbiting cylinders are not restricted from moving away from the stationary cylinder to relieve pressure spikes). As described herein, this tolerance for liquid slugging can enable a compressor system  100  to achieve a higher degree of temperature reduction (e.g., as compared to the limited temperature reduction available in a typical intercooler, where such temperature reduction is limited to prevent a phase change of the refrigerant prior to the refrigerant entering the second compressor stage). 
     In embodiments of the disclosure, a concentric vane compressor  200  includes a first cylinder  202  having a wall  204  with an interior surface  206  and an exterior surface  208 . The concentric vane compressor  200  also includes a second cylinder  210  disposed within the first cylinder  202 . The second cylinder  210  has an exterior surface  212 . The interior surface  206  of the first cylinder  202  and the exterior surface  212  of the second cylinder  210  define the second compressor stage  108 . The concentric vane compressor  200  also includes a partition between the interior surface  206  of the first cylinder  202  and the exterior surface  212  of the second cylinder  210  to divide the second compressor stage  108  into a first inner region and a second inner region, where a first intake port  220  is in fluid communication with the first inner region of the second compressor stage  108 , and a first exhaust port  222  is in fluid communication with the second inner region of the second compressor stage  108 . 
     The concentric vane compressor  200  also includes a third cylinder  224  disposed around the first cylinder  202 . The third cylinder  224  has an interior surface  226 . The exterior surface  208  of the first cylinder  202  and the interior surface  226  of the third cylinder  224  define the first compressor stage  106 . The concentric vane compressor  200  also includes another partition between the exterior surface  208  of the first cylinder  202  and the interior surface  226  of the third cylinder  224  to divide the first compressor stage  106  into a first outer region and a second outer region, where a second intake port  234  is in fluid communication with the first outer region of the first compressor stage  106 , and a second exhaust port  236  is in fluid communication with the second outer region of the first compressor stage  106 . For the purposes of the present disclosure, the term “third cylinder” shall be defined as any three-dimensional shape having a cylindrical interior surface, and shall encompass the shapes described with reference to the accompanying figures, along with other shapes not described in the accompanying figures. For example, a third cylinder as described herein may be a rectangular prism having a cylindrical interior surface, a hexagonal prism having a cylindrical interior surface, and so on. 
     The concentric vane compressor  200  includes one sealing interface for sealing first ends of the second compressor stage  108  and the first compressor stage  106 , and another sealing interface for sealing second ends of the second compressor stage  108  and the first compressor stage  106 . For example, the first cylinder  202  is connected to one end plate  238 , and the second and third cylinders  210  and  224  are connected to another end plate  240 . In embodiments of the disclosure, the second cylinder  210  and the third cylinder  224  are configured to orbit with respect to the center of the first cylinder  202  to create alternating regions of high pressure and low pressure in the first and second inner regions of the second compressor stage  108  and the first and second outer regions of the first compressor stage  106 . For example, the second and third cylinders  210  and  224  and the end plate  240  form a roller that eccentrically orbits the crank  112 . 
     In some embodiments, a concentric vane compressor  200  can be constructed using a through-shaft design. For example, the crank  112  (e.g., a crankshaft) may extend through the end plates  238  and  240 . A drive mechanism, such as a motor, can be used to drive the second and third cylinders  210  and  224  in orbit with respect to the first cylinder  202 . Referring to  FIG.  7   , the end plate  238  can include a journal bearing  244 . Referring to  FIGS.  9  and  10   , the end plate  240  can include an eccentric journal bearing  246 . This configuration may facilitate reduced shaft bearing loads and/or shaft deflection (e.g., because a through-shaft design allows the eccentric bearing load to be shared by the two shaft bearings). Furthermore, a reduction of non-symmetric axial thrust between fixed and orbiting pistons can be achieved (e.g., when the eccentric bearing is located in the plane of the orbiting cylinders). In other embodiments, the concentric vane compressor  200  does not necessarily use a through-shaft design. For example, the second cylinder  210  can be connected to an extending shaft that passes through a bearing in the end plate  238 . 
     Referring now to  FIGS.  10  and  16   , in some embodiments the partition between the interior surface  206  of the first cylinder  202  and the exterior surface  212  of the second cylinder  210 , and the partition between the exterior surface  208  of the first cylinder  202  and the interior surface  226  of the third cylinder  224 , can each be formed by a single vane  252  slidably extending through a vane slot  254  radially formed in the wall  204  of the first cylinder  202 . The vane  252  is in sealing contact with the wall  204  of the first cylinder  202 , the exterior surface  212  of the second cylinder  210 , and the interior surface  226  of the third cylinder  224 . The vane  252  provides a barrier between the high and low pressure regions. For example, in some embodiments, the second and third cylinders  210  and  224  can rotate randomly (e.g., allowing for even wear between the mating surfaces, heat distribution, etc.). In other embodiments, an anti-rotation device can be used to prevent or minimize rotation of the second and third cylinders  210  and  224  as the cylinders orbit the center of the first cylinder  202 . In some embodiments, a separate vane can be included to form each partition (e.g., each using a vane spring and/or another biasing mechanism to maintain contact with the interior and/or exterior surfaces of the cylinders). 
     Referring now to  FIGS.  8  and  11   , in some embodiments the first and second intake ports  220  and  234  are provided for supplying a fluid or gas to the concentric vane compressor  200 , while the first and second exhaust ports  222  and  236  are provided for supplying the fluid or gas from the concentric vane compressor  200 . In some embodiments, the first cylinder  202 , the second cylinder  210 , and the third cylinder  224  can be placed within an outer shell  256 , or an outer compressor housing. As the second and third cylinders  210  and  224  orbit the center of the first cylinder  202 , pockets of space, or compression cavities, are created adjacent to the first and second intake ports  220  and  234 . Fluid or gas enters these compression cavities via the first and second intake ports  220  and  234 . As the second and third cylinders  210  and  224  continue to orbit the center of the first cylinder  202 , the compression cavities are separated from the first and second intake ports  220  and  234  and migrate toward the first and second exhaust ports  222  and  236 . When the compression cavities are adjacent to the first and second exhaust ports  222  and  236 , the fluid or gas is supplied from the concentric vane compressor  200 . For instance, compressed gas may be supplied to a storage tank, or the like. 
     It should be noted that while two second and third cylinders  210  and  224  are illustrated in the accompanying figures, more or fewer cylinders may be included with a concentric vane compressor  200 . For example, the third cylinder  224  may be replaced with a compression spring and/or another biasing mechanism for biasing the vane  252  against the first cylinder  202 . Further, additional cylinders and/or additional vanes may be included to create additional compression chambers. 
     In embodiments of the disclosure, surfaces on both the second and third cylinders  210  and  224 , and the first cylinder  202 , are circular in cross-section, or formed by constant radii. Because the vane  252  inserted between the second and third cylinders  210  and  224  is a separate part, the constant radius compression cavity surfaces on the second and third cylinders  210  and  224 , and the first cylinder  202 , can be machined using conventional turning processes, which may be performed with greater accuracy and/or at a comparatively lower cost (e.g., when compared to a non-constant radius configuration). 
     Referring now to  FIG.  12   , in some embodiments, a series of mathematical equations can be used to define the relationships between the geometry of the first cylinder  202 , the second and third cylinders  210  and  224 , and four defining radii. These relationships may provide a continuous seal in the compression cavities. For the following discussion, S is equal to the stroke, or the travel distance of the second and third cylinders  210  and/or  224  in a straight line (e.g., twice the crankshaft eccentricity). W is equal to the thickness of the wall  204  of the first cylinder  202 . R 1  is equal to the outside radius of the exterior surface  212  of the second cylinder  210 , or the radius of the compression surface of the second cylinder  210 . This radius may be selected based upon space requirements. For example, if the central region of the second cylinder  210  is enlarged to pass the crank  112  through, the outside radius R 1  of the second cylinder  210  may be determined by space requirements for the compressor shaft, eccentric, and eccentric bearing, plus a minimum wall thickness for the second cylinder  210 . 
     R 2 , which is equal to the inside radius of the interior surface  226  of the third cylinder  224 , or the radius of the compression surface of the third cylinder  224 , can then be determined as follows: 
         R 2= R 1+ S+W    
     R 3 , which is equal to the inside radius of the interior surface  206  of the first cylinder  202 , or the radius of the inside compression surface of the first cylinder  202 , can be determined as follows: 
         R 3= R 1+ S/ 2 
     R 4 , which is equal to the outside radius of the exterior surface  208  of the first cylinder  202 , or the radius of the outer compression surface of the first cylinder  202 , can be determined as follows: 
         R 4= R 3+ W    
     In embodiments of the disclosure, VW, which is equal to the width of the vane  252 , can be selected to allow the vane  252  to travel radially through the first cylinder  202 , while providing minimum clearance for gas sealing purposes. The width of the vane  252  may be selected based upon space requirements, and the width of the vane slot  254  in the first cylinder  202  may be equal to the vane width VW plus a desired seal clearance. It should be noted that a comparatively small vane width VW may increase the bending stress on the vane  252  (e.g., due to gas pressure and/or friction between the vane  252  and the second and third cylinders  210  and  224 ). Further, a vane width VW that permits the second and third cylinders  210  and  224  to contact the edge of the vane  252  may cause a loss of vane seal and/or excessive wear between the vane  252  and the orbiting surfaces the second and third cylinders  210  and  224 . Thus, the width of the vane  252  can be selected to be greater than at least a minimum vane width. For instance, VW m , which is Equal to this Minimum vane width, can be determined as follows: 
         VW   m   =S *( R 2− R 1)/( R 2+ R 1)
 
     VL, which is equal to the length of the vane  252 , or the distance between the two outer ends of the vane, can be determined as follows: 
         VL=R 2− R 1
 
     In embodiments of the disclosure, the vane  252  includes a tip radius, or a radius at the two outer ends of the vane. VTR, which is equal to this vane tip radius, can be determined as follows: 
         VTR=VL/ 2 
     It should be noted that the concentric vane compressor  200  may include other dimensional relationships and that the dimensional relationships heretofore described are provided by way of example only and not meant to limit the present disclosure. Thus, the concentric vane compressor  200  of the present invention is not necessarily limited to these dimensional relationships. Additionally, for the purposes of the present disclosure, the term “equal to” shall be understood to mean equal to within the limits of precision machinability. 
     Because the surfaces on the second and third cylinders  210  and  224  are circular, rotational orientation of the second and third cylinders  210  and  224  is not necessarily required. Thus, the need for an external anti-rotation device may be eliminated, allowing the second and third cylinders  210  and  224  to freely rotate while orbiting the center of the first cylinder  202 . A cost savings may be achieved by eliminating the anti-rotation device. Additionally, wear on the surfaces of the second and third cylinders  210  and  224 , which may be caused by the vane  252 , the first cylinder  202 , and/or the shell  256 , can be uniformly distributed over the entire mating surfaces (e.g., rather than being concentrated in a small region). Additionally, free rotation of the second and third cylinders  210  and  224  can uniformly distribute the heat of gas compression over the entire mating surfaces (e.g., again, rather than being concentrated in a small region). The apparatus, systems, and techniques described herein can provide a reduced peak wear rate and/or uniformity of temperature over the second and third cylinders  210  and  224 , and reduction of temperatures in the high pressure region, resulting in less part distortion, lower gas temperatures, and so forth. 
     It should be noted that while the compression cavities created by the inner and outer second and third cylinders  210  and  224  may share a common vane  252 , they can act as separate compression chambers, sequenced one hundred and eighty degrees (180°) apart. The apparatus, systems, and techniques described herein can reduce peak torque for single stage compressors, and may provide a two stage compressor design using the second and third cylinders  210  and  224 . For a two stage design, the larger outer cavity can be used for the first stage, and the smaller inner cavity can be used for the second stage. For example, in some embodiments, the first intake port  220  can be connected to (e.g., in fluid communication with) the second exhaust port  236  to form a two stage compressor. 
     It is noted that a large contributor to vane wear in typical stationary vane compressors is the pressure differential across the vane. Since these are predominantly single stage compressors, the maximum pressure differential across the vane is the discharge pressure minus the suction pressure. In the two stage version of the concentric vane compressor  200  described herein, the intermediate pressure is between the suction pressure and the discharge pressures. The differential pressure across the first stage end of the vane is the intermediate pressure minus the suction pressure. The differential pressure across the second stage end of the vane is the discharge pressure minus the intermediate pressure. Both of these differential pressures and resulting vane forces may be significantly lower than those of a typical stationary vane compressor. Thus, the resulting vane wear of a concentric vane compressor  200  may be comparatively lower than that of a typical stationary vane compressor. 
     As described herein, the center region of a concentric vane compressor  200  can be enlarged, moving the discharge port and compression cavities radially outward, without increasing the dead space adjacent to the discharge port at the end of the compression cycle. This configuration may yield a high compression ratio design. Enlarging the central region can be done to allow room for an eccentric, an eccentric bearing, a shaft, and shaft bearings, with the shaft passing through the eccentric and supported by shaft bearings on each side of the eccentric. This can reduce the radial forces on the shaft bearings, allowing the use of smaller bearings and/or shafting. Additionally, the eccentric can be located axially within the plane of the second and third cylinders  210  and  224  and the first cylinder  202 , allowing radial pressure forces between the second and third cylinders  210  and  224  to pass through the plane of the eccentric bearing and reduce non-symmetric axial thrust between the second and third cylinders  210  and  224  and the first cylinder  202 . 
     A concentric vane compressor  200  may have one or both the second and third cylinders  210  and  224  and/or the first cylinder  202  coated with an abradable coating of enough thickness to cause interference at all sealing surfaces between the members. During the manufacturing or assembly sequence, the second and third cylinders  210  and  224 , and the first cylinder  202 , can be assembled and operated, causing the excess coating to abrade away leaving a near perfect match between the surfaces of the second and third cylinders  210  and  224  and the first cylinder  202 . This process may reduce the need for precise machining. 
     Referring now to  FIGS.  16  through  19   , in some embodiments the first cylinder  202  and/or the vane  252  may include slots or channels  258  to facilitate lubrication of the vane  252 . For example, semicircular channels  258  may be provided on one or both sides of the vane slot  254  of the first cylinder  202  (e.g., as shown in  FIGS.  16  through  19   ). Additionally, slots or channels  258  may be provided in the vane  252  (e.g., as shown in  FIGS.  17  through  19   ). In some embodiments, one or more channels  258  may be provided on a side or sides of the vane  252  (e.g., proximate to the channels  258  defined at the vane slot  254 ), as shown in  FIG.  17   . In some embodiments, one or more channels  258  may be provided on a top and/or bottom surface of the vane  252  (e.g., between the channels  258  defined at the vane slot  254 ), as shown in  FIG.  18   . 
     It should be noted that other components of a compressor system  100  may also include slots or channels to facilitate both lubrication and cooling of various components, including, but not necessarily limited to, bearing surfaces of the vane  252 , the vane slot  254 , radial bearings, and thrust bearings. For example, oil flow paths can be provided through and/or around the crank  112 , first bearing  132 , second bearing  134 , thrust bearing  148 , eccentric bearing  152 , front shaft bearing  154 , rear shaft bearing  156 , upper thrust bearing  158 , and so forth. Further, the flow paths and/or flow areas for the oil  122  can be adjusted to keep various components at temperatures more consistent with adjacent or proximal components. For example, flow areas around the vane  252  can be configured to keep the vane  252  at a temperature close to that of the first cylinder  202 , the second cylinder  210 , and/or the third cylinder  224 . 
     Further, in some embodiments, one or more channels  258  may be provided on a side or sides of the vane  252  (e.g., proximate to the channels  258  defined at the vane slot  254 ) and on a top and/or bottom surface of the vane  252  (e.g., between the channels  258  defined at the vane slot  254 ), as shown in  FIG.  19   . As described, the oil  122  may flow upwardly from the shaft oil pump  140  (e.g., through a channel  258  on one side of the vane slot  254  and/or a channel  258  on one side of the vane  252 ), horizontally across a top and/or bottom surface of the vane  252  (e.g., through a channel  258  in a top surface of the vane  252 ), and then downwardly into the oil sump (e.g., through a channel  258  on an opposite side of the vane slot  254  and/or a channel  258  on an opposite side of the vane  252 ). 
     Although the subject matter has been described in language specific to structural features and/or process operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.