Patent Publication Number: US-2019178259-A1

Title: Variable return channel vanes to extend the operating flow range of a vapor cycle centrifugal compressor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Ser. No. 15/889,962, filed Feb. 6, 2018 which claims the benefit of and priority to U.S. Ser. No. 62/597,927, filed Dec. 12, 2017, both of which are incorporated herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to vapor cycle compressors and, more particularly, to apparatus and methods of widening the operational envelope of flows in centrifugal compressors. 
     Aircraft Vapor Cycle Environmental Control Systems need to operate over a wide range of environmental conditions—from cold days, to hot days. To accommodate these differing environmental requirements, the vapor cycle system (VCS) controls cooling by throttling the evaporator expansion valve while maintaining the difference between the VCS evaporator and condensing pressures. The closed loop nature of the VCS and the variable evaporator expansion valve leads to the vapor cycle compressor pressure ratios to remain high while the compressor flow decreases. The high pressure ratio with the wide mass flow range means that a wide flow compressor is required. 
     To achieve a wide flow range with a centrifugal compressor, the vapor cycle compressor must include variable geometry components. Typically, to achieve a wide flow range variable inlet guide vanes are used. 
     For most vapor cycle systems, the vapor cycle compressor is normally a multi-stage centrifugal compressor. A typical multi-stage compressor has a return channel vane and inlet guide vanes between the separate impeller and diffuser stages. The function of the return channel vane is to straighten the flow prior to it entering the next compressor stage. However, past designs of the return channel vanes and second stage inlet guide vanes have limited the operating flow range. 
     As can be seen, there is a need for improved apparatus and methods to increase the operational envelope in a centrifugal compressor. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a vapor cycle compressor comprises a controller section; a drive section in communication with the controller section; and a compression section operatively engaged with the drive section, wherein the compression section includes: a first stage compression section; a return channel assembly downstream of the first stage compression section; wherein the return channel vane assembly includes return channel vanes that are configured to adjust their angle of orientation; and a second stage compression section downstream of the return channel vane assembly; wherein inlet guide vanes are absent between the return channel vane assembly and the second stage compression section. 
     In another aspect of the present invention, a vapor cycle compressor comprises a controller section; a drive section in communication with the controller section; and a compression section operatively engaged with the drive section, wherein the compression section includes: a first stage inlet guide vane assembly; a first stage diffuser assembly downstream of the first stage inlet guide vane assembly; a variable return channel vane assembly downstream of the first stage diffuser assembly; and a second stage diffuser downstream of the variable return channel vane assembly; wherein second stage inlet guide vanes are absent between the variable return channel vane assembly and the second stage diffuser assembly. 
     In a further aspect of the present invention, a vapor cycle compressor comprises a controller section; a drive section in communication with the controller section; and a compression section operatively engaged with the drive section, wherein the compression section includes: a first stage inlet guide vane assembly; a first stage impeller assembly downstream of the first stage inlet guide vane assembly; a variable return channel vane assembly downstream of the first stage impeller; and a second stage impeller assembly downstream of the variable return channel vane assembly; wherein second stage inlet guide vanes are absent between the variable return channel vane assembly and the second stage impeller assembly. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of an exterior of a vapor cycle compressor according to an embodiment of the present invention. 
         FIG. 1B  is a perspective view of an interior of the vapor cycle compressor of  FIG. 1A . 
         FIG. 2  is a conceptual diagram of a compression section of a vapor cycle compressor according to an embodiment of the present invention. 
         FIG. 3  is a cross sectional schematic view of a compression section of a vapor cycle compressor according to an embodiment of the present invention. 
         FIGS. 4A-4B  are perspective views of a variable return channel vane assembly of a vapor cycle compressor according to an embodiment of the present invention. 
         FIG. 5  is a cross sectional view of a variable return channel vane assembly operatively engaged with a stepper motor assembly according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
     Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not address any of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below. 
     Broadly, the present invention provides a vapor cycle compressor that allows angle variation of return channel vanes and eliminates the need for second stage inlet guide vanes upstream of the second stage impeller. The present invention allows the return channel vanes to rotate about an axis through the vanes, which changes the flow angle of the fluid as it passes through the vanes. The addition of swirl to the flow helps increase flow range in the compressor. 
     The foregoing can provide a wider operational envelope, an improvement in the coefficient of performance, and the ability to use different refrigerants in the compressor without changing the design. This invention provides a hermetically sealed drive mechanism, redundancy for the drive mechanism, control logic that adjusts the vanes based on performance requirements, and weight reduction. 
     Although described in the exemplary context of an aircraft, the present invention can be used in other environments. 
     In  FIG. 1A , an exemplary vapor cycle compressor  100  can be affixed to a support via mountings  107 . The compressor  100  may include a drive section  101 , a compression section  102  operatively engaged with the drive section  101 , a controller section  120  in communication with the drive section  101 , and a motor section  121  operatively engaged with the compressor section  102 . The controller section  120  and the motor section  121  may be hermetically sealed in a cover/housing  103 . 
     In embodiments, the drive section  101  may include a stepper motor assembly  105  that can be hermetically sealed. The stepper motor assembly  105  may be operatively engaged with an inlet guide vane assembly, and/or a first stage diffuser assembly, and/or a return channel assembly, and/or a second stage diffuser assembly, all of which can be part of the compression section  102  described below. 
     The stepper motor assembly  105  may include a plurality of stepper motor subassemblies  105   a.  One or more of the subassemblies  105   a  may include a stepper motor connector  105   b  and a stepper motor housing  105   c.  The stepper motor connector  105   b  may connect to power from a separate or internally derived source. One or more of the stepper motor subassemblies  105   a  may further include a stepper motor, a worm, a worm shaft, and a worm gear, as described below. Each stepper motor may be paired with and be operatively engaged to one or more of the inlet guide vane assembly, the first stage diffuser assembly, the second stage diffuser assembly, and the return channel assembly. 
     The compression section  102 , according to embodiments, may include an inlet subsection  102   a  and an impeller/diffuser subsection  102   b.  The inlet subsection  102   a  may include a compressor inlet  104  configured to receive a vapor refrigerant. The inlet subsection  102   a  may further include an inlet guide vane assembly described below. 
     The impeller/diffuser subsection  102   b,  in embodiments, may include an upstream first stage impeller assembly, a downstream first stage diffuser assembly, a downstream variable return channel assembly, a downstream second stage impeller assembly, and a downstream second stage diffuser assembly described below. The impeller/diffuser subsection  102   b  may also include a sub-cooling inlet  106  that is configured to increase cooling performance and extend compressor flow range. 
     In  FIG. 1B , according to embodiments, the controller section  120  of the compressor  100  may include a digital signal processor  113  that is configured to provide localized compressor torque and speed control which includes stepper motor function, and a high power switch module  116  that is configured to provide control of the main electric motor  121 . A current sensor transducer  112  can be configured to measure power into the motor section  121 , a motor bus bar  114  can be configured to distribute current, and a stud seal terminal  115  can be configured to pass electric current from the exterior of the compressor to the interior of the compressor. A capacitor  118  can be configured to maintain constant controller DC link voltage, capacitor bus bar  117  can be configured to supply or distribute link voltage, and a power input terminal  119  can be configured to receive power to the compressor. Also provided are a controller data connection port  108 , a cooling sleeve outlet port  110 , a DC link buss bar (controller component)  111 , and a gate driver board (controller component)  116 . 
     In  FIG. 2 , according to embodiments, a compression section  202  may include an inlet subsection  202   a  and an impeller/diffuser subsection  202   b,  all of which can be similar to that described in relation to  FIGS. 1A-1B . Accordingly, reference numbers in  FIG. 2  correspond to like reference numbers in  FIGS. 1A-1B . 
     The inlet subsection  202   a  may include an inlet guide vane assembly  225 . The impeller/diffuser subsection  202   b  may include a first stage impeller assembly  226 , a first stage diffuser assembly  228 , a variable return channel assembly  229 , a second stage impeller assembly  227 , and a second stage diffuser assembly  232 . 
     Notably absent from the compression section  202  and, in particular, from the impeller/diffuser subsection  202   b,  is a second stage inlet guide vane assembly which might otherwise be present between the return channel vane assembly  229  and the second stage impeller assembly  227 . The use of second stage inlet guide vanes is shown, for example, in U.S. Pat. No. 2,300,766. In contrast, the present invention eliminates the need for second stage inlet guide vanes by the use of variable return channel vanes described below. This can result in weight reduction of the vapor compressor. 
     As further described in U.S. Ser. No. 15/889,962 (which is incorporated herein by reference), the motor section may, in embodiments, include a motor (not shown) that can have a stator (not shown) and a rotor (not shown). A tie rod (not shown) may extend from within the motor, through a thrust bearing disk (not shown), and into the compression section. Thereby, the motor section may drive the first stage and second stage impeller assemblies of the compression section. In so doing, a vapor refrigerant may be compressed while flowing in a vapor refrigerant path through the inlet guide vane assembly, then through the first stage impeller assembly, then through the first stage diffuser assembly, then through the variable return channel assembly, then through the second stage impeller assembly, and then through the second stage diffuser assembly. 
     In  FIG. 3 , a compression section  302  and a stepper motor assembly  305 , according to embodiments, are shown. The compression section  302  may be similar to that described in relation to  FIGS. 1A-1B and 2 . Accordingly, reference numbers in  FIG. 3  correspond to like reference numbers in  FIGS. 1A-1B and 2 . 
     The compression section  302  may include an inlet guide vane assembly  325  that can receive vapor refrigerant. From there, vapor refrigerant may be compressed in two stages. A first compression stage may include a first stage impeller assembly  326  directly downstream of the inlet guide vane assembly  325 . Also in the first compression stage, a first stage diffuser assembly  328  may be directly downstream of the first stage impeller assembly  326 . 
     The first compression stage and the inlet guide vane assembly  325  may be within a housing  338 . The housing  338  may further enclose the stepper motor assembly  305  to provide hermetic sealing of the compression section  302  and the stepper motor assembly  305 . 
     In embodiments, the compression section  302  may include a variable return channel assembly  329  (having variable return channel guide vanes described below), directly downstream of the first stage diffuser assembly  328 , and that may direct vapor refrigerant directly from the first compression stage and into the second compression stage. In other words, vapor refrigerant may flow from the first compression stage to the second compression stage in the absence of vapor refrigerant having to flow through inlet guide vanes between the first and second compression stages. 
     The second compression stage may include a second stage impeller assembly  327  directly downstream of the return channel assembly  329 —with no inlet guide vanes therebetween. In the second compression stage, a second stage diffuser assembly  332  may be directly downstream of the second stage impeller assembly  327 . The second compression stage may be within a housing  337  for hermetic sealing. 
     In the compression section  302 , according to embodiments, an inlet (not shown) may provide vapor refrigerant to an inlet scroll (not shown) that can be configured to provide additional flow to the second stage, while an outlet scroll (not shown) may be configured to direct vapor refrigerant out of the second compression stage, via an outlet (not shown). The inlet and outlet scrolls may be within the housing  337 . A housing (not shown) may enclose a thrust disk (not shown). 
     Still referring to  FIG. 3 , the stepper motor assembly  305  may be similar to that described in relation to  FIGS. 1A-1B and 2 . Accordingly, reference numbers in  FIG. 3  correspond to like reference numbers in  FIGS. 1A-1B and 2 . 
     According to embodiments, the stepper motor assembly  305  may include a plurality of stepper motor subassemblies. A respective stepper motor subassembly may be operatively engaged to at least the return channel assembly  329  and optionally to one or more of the inlet guide vane assembly  325 , the first stage diffuser assembly  328 , and the second stage diffuser assembly  332  as described below. 
       FIGS. 4A-4B  depict an exemplary variable return channel vane assembly  429 . The return channel vane assembly  429  may be similar to that described in relation to  FIGS. 2 and 3 . Accordingly, reference numbers in  FIGS. 4A-4B  correspond to like reference numbers in  FIGS. 2 and 3 . 
     According to embodiments, the return channel vane assembly  429  may be configured to receive a vapor refrigerant flow, which can be, for example, from a first compression stage and, in particular, a first stage impeller assembly. The return channel vane assembly  429  may include a plurality or set of downstream variable vanes  429   a  that receives the refrigerant flow. 
     The set of return vanes  429   a,  and each individual return vane  429   a  in such set, can be characterized by an angle of orientation. The angle of orientation may be measured by an angle about which each return vane may rotate around an axis of rotation. The axis of rotation may be substantially parallel to a longitudinally extending tie rod, described above, which can extend through an aperture  429   g.  As described below, the angle of orientation may be adjusted or varied. 
     In embodiments, the return channel vane assembly  429  may further include a return plate  429   b  that can support on one planar side thereof, via connectors  429   c,  the return vanes  429   a.  On an opposed planar side of the return vane assembly  429 , a unison ring  429   d  may be operatively engaged to one or more driver arms  429   e.  The unison ring  429   d  may also be operatively engaged to one or more worm gears  405   g.  One or more rollers  429   f  may rotatably support the unison ring  429   d  at an inner circumference thereof. 
     With the above, the variable return channel vanes  429   a  can rotate about an axis through the vane and change the flow angle of the fluid through the vane and received by the next stage of the compressor. The addition of swirl to the flow helps increase flow range in the compressor. 
     For an inlet guide vane to turn the fluid flow through the vane to an angle “x”, the vane must rotate the same angle value “x”. The variable return channel vanes of the present invention allow the fluid flow through the vane to turn the fluid to an angle “x”, by rotating the vane by an angle less than “x”. As an example, with the variable return channel vanes of the present invention, inlet swirl angles of 49 degrees were achieved by turning the return channel vane through an angle of 20 degrees. The ability to turn the fluid flow 49 degrees while only turning the vane 20 degrees allows the actuation mechanism to be simpler as the amount the vane needs to turn can be reduced by a factor of 2. 
     Although  FIGS. 4A-4B  depict an exemplary return channel vane assembly, it should be understood that similar components and the assembly thereof can also be used for one or more of the first stage inlet guide vanes, the first stage diffuser assembly, and the second stage diffuser assembly, such as that depicted in  FIGS. 2 and 3 . 
       FIG. 5  depicts an exemplary stepper motor assembly  505  operatively engaged to a plurality or set of variable return channel vanes, such as those that may be included in a return channel assembly, as described above with regard to  FIGS. 2, 3, and 4A -B. Accordingly, reference numbers in  FIG. 5  correspond to like reference numbers in  FIGS. 2, 3 and 4A -B. 
     The stepper motor assembly  505  may include one or more stepper motor subassemblies  505   a.  One or more of the stepper motor subassemblies  505   a  may include one or a pair of redundant stepper motors  505   d  connected by a worm shaft  505   f  there between. Accordingly, if one of the paired stepper motors  505   d  fails, the other of the paired motors may be used. A stepper motor connector  505   b  may be provided at each stepper motor  505   d  to provide power. 
     In embodiments, one or more of the stepper motor subassemblies  505   a  may include at least one worm  505   e  that is operatively engaged to at least one worm gear  505   g  which, in turn, can be operatively engaged to the set of variable return vanes (not shown). 
     The variable return vanes can be supported by a plate  529   b.  The plate  529   b  may support one or more driver arms  529   e  that can be operatively engaged, via one or more connectors  529   c,  to one or more of the variable vanes. Also, one or more of the driver arms  529   e  may be operatively engaged to a unison ring  529   d.  One or more rollers  529   f  may support the ring  529   d.    
     In operation, a single stepper motor  505   d,  or one of the paired stepper motors  505   d,  may rotate the worm shaft  505   f.  In turn, the worm  505   e  may rotate, which can cause the worm gear  505   g  to rotate. The rotation of the worm gear  505   g  causes the unison ring  529   d  to rotate. In turn, one or more of the driver arms  529   e  can rotate. Via the connector  529   c  associated with the rotating arms  529   e,  one or more of the vanes rotate about a longitudinal axis of the connector  529   c.    
     It can be appreciated that the stepper motor assembly, upon control from the controller section, can rotate one or more of the sets of variable vanes of the inlet guide vane assembly, the first stage diffuser assembly, the return channel assembly, and the second stage diffuser assembly. 
     It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.