CROSS-REFERENCE TO RELATED APPLICATION 
     Benefit is claimed of U.S. Patent Application Ser. No. 61/440,921, filed Feb. 9, 2011, and entitled “Ejector”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
    
    
     BACKGROUND 
     The present disclosure relates to refrigeration. More particularly, it relates to ejector refrigeration systems. 
     Ejectors are used as expansion devices in vapor compression refrigeration systems. Ejectors may be used to recover work to allow operational conditions and/or configurations not available with a traditional expansion device. Earlier proposals for ejector refrigeration systems are found in U.S. Pat. Nos. 1,836,318 and 3,277,660. 
     A typical ejector utilizes a motive (primary) flow of fluid to entrain a secondary (suction) flow. A common ejector configuration includes a motive (primary) inlet coaxial with a downstream outlet. The ejector also has a secondary inlet. The exemplary primary inlet is the inlet of a motive (primary) nozzle nested within an outer member. The outlet is the outlet of the outer member. The primary flow enters the primary inlet and then passes into a convergent section of the motive nozzle. It then passes through a throat section and an expansion (divergent) section and through an outlet of the motive nozzle. The motive nozzle accelerates the primary flow and decreases the pressure of the primary flow. The secondary inlet forms an inlet of the outer member and may be a lateral port. The pressure reduction caused to the primary flow by the motive nozzle helps draw the secondary flow into the outer member. 
     The outer member includes a mixer having a convergent section and an elongate throat or mixing section. The outer member also has a divergent section or diffuser downstream of the elongate throat or mixing section. The motive nozzle outlet is positioned within the convergent section. As the primary flow exits the motive nozzle outlet, it begins to mix with the secondary flow with further mixing occurring through the mixing section which provides a mixing zone. 
     In transcritical refrigeration operation, the primary flow may typically be supercritical upon entering the ejector and subcritical upon exiting the motive nozzle. The secondary flow may be is gaseous (or a mixture of gas with a smaller amount of liquid) upon entering the secondary inlet port. The resulting combined flow may be a liquid/vapor mixture and decelerate and recover pressure in the diffuser while remaining a mixture. 
     SUMMARY 
     Accordingly, one aspect of the disclosure involves an ejector for receiving a motive flow and a suction flow and discharging a combined flow. The ejector has a motive flow inlet, a suction flow inlet, and an outlet. A suction flow flowpath extends from the suction flow inlet. A motive flow flowpath extends from the motive flow inlet to join the suction flow flowpath and form a combined flowpath exiting the outlet. The ejector comprises a plurality of motive flow nozzles along the motive flow flowpath. The motive flow nozzles are oriented to impart a tangential velocity component to the motive flow. A plurality of diffusers are along the combined flowpath and are oriented to recover the tangential velocity from the combined flow. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a first vapor compression system. 
         FIG. 2  is a schematic sectional view of an ejector of the system of  FIG. 1 . 
         FIG. 3  is a transverse sectional view of a motive nozzle portion of the ejector of  FIG. 2  taken along line III. 
         FIG. 4  is a transverse sectional view of a diffuser portion of the ejector of  FIG. 2  taken along line IV. 
         FIG. 5  is a transverse sectional view of an alternate motive nozzle portion in an open condition. 
         FIG. 6  is a view of the motive nozzle portion of  FIG. 5  in a relatively closed condition. 
         FIG. 7  is a partially schematic transverse cutaway view of an alternate diffuser portion. 
         FIG. 8  is a schematic view of an alternate vapor compression system. 
         FIG. 9  is a view of an alternate ejector. 
         FIG. 10  is an axial sectional view of the ejector of  FIG. 9 . 
         FIG. 11  is a view of a second alternate ejector. 
         FIG. 12  is an axial sectional view of the ejector of  FIG. 11 . 
         FIG. 13  is a view of a third alternate ejector. 
         FIG. 14  is an axial sectional view of the ejector of  FIG. 13 . 
         FIG. 15  is a view of a fourth alternate ejector. 
         FIG. 16  is an axial sectional view of the ejector of  FIG. 15 . 
         FIG. 17  is a view of a fifth alternate ejector. 
         FIG. 18  is a transverse cutaway view of the ejector of  FIG. 17 . 
         FIG. 19  is an axial sectional view of the ejector of  FIG. 17 . 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a vapor compression system  20 . The system includes a compressor  22  having an inlet (suction port)  24  and an outlet (discharge port)  26 . The compressor and other system components are positioned along a refrigerant circuit or flowpath  27  and connected via various conduits (lines). A discharge line  28  extends from the outlet  26  to the inlet  32  of a heat exchanger (a heat rejection heat exchanger in a normal mode of system operation (e.g., a condenser or gas cooler))  30 . A line  36  extends from the outlet  34  of the heat rejection heat exchanger  30  to a primary (motive flow) inlet  40  (liquid or supercritical or two-phase inlet) of an ejector  38 . The ejector  38  also has a secondary (suction flow) inlet  42  (a saturated or superheated vapor or two-phase inlet) and an outlet  44 . A line  46  extends from the ejector outlet  44  to an inlet  50  of a separator  48 . The separator has a liquid outlet  52  and a gas outlet  54 . A suction line  56  extends from the gas outlet  54  to the compressor suction port  24 . The lines  28 ,  36 ,  46 ,  56 , and components therebetween define a primary loop  60  of the refrigerant circuit  27 . A secondary loop  62  of the refrigerant circuit  27  includes a heat exchanger  64  (in a normal operational mode being a heat absorption heat exchanger (e.g., evaporator)). The evaporator  64  includes an inlet  66  and an outlet  68  along the secondary loop  62  and expansion device  70  is positioned in a line  72  which extends between the separator liquid outlet  52  and the evaporator inlet  66 . An ejector secondary inlet line  74  extends from the evaporator outlet  68  to the ejector secondary inlet  42 . 
     In the normal mode of operation, gaseous refrigerant is drawn by the compressor  22  through the suction line  56  and inlet  24  and compressed and discharged from the discharge port  26  into the discharge line  28 . In the heat rejection heat exchanger, the refrigerant loses/rejects heat to a heat transfer fluid (e.g., fan-forced air or water or other fluid). Cooled refrigerant exits the heat rejection heat exchanger via the outlet  34  and enters the ejector primary inlet  40  via the line  36 . 
     The exemplary ejector  38  secondary inlet  42  is an axial upstream inlet along a central longitudinal axis  500  of the ejector. The exemplary primary inlet  40  is the inlet to an inlet plenum  90 . The inlet plenum  90  feeds a plurality of motive nozzles (discussed below). The outlet  44  is an outlet from an outlet plenum  92 . The outlet plenum  92  receives flow from a plurality of diffusers (discussed below). 
       FIG. 2  shows a circumferential array of motive nozzles  100 . The exemplary nozzles are formed in a single nozzle ring (e.g., machined or cast). Each motive nozzle has a radially outboard inlet  102  at the inlet plenum. 
     The primary refrigerant flow  103  ( FIG. 3 ) branches in the inlet plenum into branches  105  entering the inlets  102 . Each primary flow branch  105  then passes into a convergent section  104  of the associated motive nozzle  100 . It then passes through a throat section  106  and an expansion (divergent) section  108  and through an outlet  110  of each motive nozzle  100  to re-merge and re-form the flow  103 . The motive nozzles  100  accelerate the flow  103  and decreases the pressure of the flow. The merging flows have a tangential/circumferential component and a radial inward component. They are then deflected axially by a surface  112  of a centerbody  114  (inlet end centerbody or upstream end centerbody) extending to a downstream rim  116 . An inboard surface  118  of the body defines a channel from the secondary inlet passing the secondary flow  120 . The pressure reduction caused to the primary flow by the motive nozzles helps draw the secondary flow  120  ( FIG. 2 ) into the ejector to form a merged/combined flow  122 . 
     The ejector includes a mixer portion having an elongate mixing section  124  within an outer wall  126 . 
     The ejector also has a circumferential array of divergent sections or diffusers  130  at a downstream end  131  of the ejector downstream of the mixing section  124 . The combined flow passes downstream through the mixing section  124  and is redirected radially outward by an outer surface  132  of a centerbody  134 . Exemplary diffusers have inlets  136  and outlets  138 . The combined flow branches into respective branches  139  through each of the diffusers to then recombine into the combined flow  122  in the plenum  92 . Each diffuser has a tangential component near the inlet end essentially opposite the tangential component of the motive nozzles, gradually redirecting the flow more radially to recover the energy associated with the tangential velocity. In exemplary embodiments, there are 4-8 motive flow nozzles (more broadly at least two or 3-10) and 4-16 diffusers (more broadly, at least two or 3-20). 
     In operation, the primary flow  103  may typically be supercritical upon entering the ejector and subcritical upon exiting the motive nozzles. The secondary flow  120  may be gaseous (or a mixture of gas with a smaller amount of liquid) upon entering the secondary inlet port  42 . The resulting combined flow is a liquid/vapor mixture and decelerates and recovers pressure in the diffusers while remaining a mixture. Upon entering the separator, the combined flow is separated back into the flows  103  and  120 . The flow  103  passes as a gas through the compressor suction line as discussed above. The flow  120  passes as a liquid to the expansion valve  70 . The flow  120  may be expanded by the valve  70  (e.g., to a low quality (two-phase with small amount of vapor)) and passed to the evaporator  64 . Within the evaporator  64 , the refrigerant absorbs heat from a heat transfer fluid (e.g., from a fan-forced air flow or water or other liquid) and is discharged from the outlet  68  to the line  74  as the aforementioned gas. 
     The motive nozzles may be controllable to enable the ejector operate under variable system capacities. For instance, when the system is operating at its full-load conditions, all the motive nozzles may be fully open to supply the necessary mass flow  103  into the mixer. However, the mass flow could vary as the speed of the compressor  22  changes without a dramatic change in temperature. In these circumstances, some nozzles may be closed to reduce the net/effective open area and effectively maintain the high tangential velocity entering the mixing section. 
     The system includes a controller  140  which may receive user inputs from an input device  142  (e.g., switches, keyboard, or the like) and sensors (not shown). The controller  140  may be coupled to any controllable system components (e.g., valves, the compressor motor, and the like) via control lines  144  (e.g., hardwired or wireless communication paths). The controller may include one or more: processors; memory (e.g., for storing program information for execution by the processor to perform the operational methods and for storing data used or generated by the program(s)); and hardware interface devices (e.g., ports) for interfacing with input/output devices and controllable system components. 
       FIGS. 5 and 6  show the addition of a rotary gate (or control ring)  150  controlling flow through the inlets  102 . Exemplary gate  150  is a ring concentric with and surrounding the nozzle ring and having a series of open areas  152  (of which  152 A-H are shown) interspersed with blocking portions/areas  154  ( 154 A-H). The exemplary number of open areas  152  and blocking portions  154  is the same as the number of nozzles. However, the exemplary nozzles are at a uniform circumferential spacing and have a uniform circumferential extent of the openings/inlets  102 . In the orientation of  FIG. 5 , each of the blocking portions  154  is clear of the adjacent openings  102  thus providing essentially no occlusion/blocking of the openings. As the ring is rotated toward a second condition of  FIG. 6 , the blocking portions progressively occlude the adjacent inlet  102 . Thus,  FIG. 6  shows a relatively closed condition. By providing the blocking portions  154  at other than even/uniform circumferential spacing and/or uniform circumferential extent, the nature of the closing process may be altered. For example, with uniform size and uniform spacing, each nozzle would be closed/occluded simultaneously in a similar fashion. This may have disadvantages in terms of placing individual nozzles in substantially suboptimal performance conditions. Accordingly, the blocking portions  154 A and  154 E are of relatively large circumferential extent compared with the remainder. These begin to occlude the adjacent nozzles relatively soon after rotating from the  FIG. 5  open condition while the remaining blocking portions remain between nozzle inlets (leaving the associated nozzles unaffected). In the exemplary system, upon reaching the  FIG. 6  condition, the blocking portions  154 A and  154 E fully close off their respective associated nozzles. In a final phase of this exemplary rotation, the remaining blocking portions just begin to occlude their associated nozzles to slightly throttle them down but not so far as to substantially adversely affect performance. In this particular implementation, each blocking portion has a leading surface  156  and a trailing surface  158 . The exemplary trailing surfaces are at uniform circumferential separation so that, in the initial  FIG. 5  orientation, each is adjacent the nozzle one before the nozzle to be occluded by that blocking portion (e.g., the trailing surface of blocking portion  154 A is adjacent opening  152 H). The exemplary ring has an inner surface at an inner diameter which seals against an outer surface of the ring containing the nozzles. For example, the nozzles may be machined or cast as a ring. 
     The ring  150  may be throttled to or toward the closed condition in response to a part-load condition where mass flow is reduced. For example, the ring position may be adjusted in response to or with a change in compressor speed (e.g., known by the controller which may provide the speed of a variable frequency drive of the compressor) or the output of a refrigerant flow sensor (not shown, e.g., at condenser/gas cooler outlet conditions along the line  36 ). The goal may be to maintain a high tangential velocity entering the ejector. For example, a control map, preprogrammed into the controller may cause the ring to provide particular restrictions associated with particular speeds (or flow rates) or ranges thereof. Similarly, in the situation of valves fully opening or closing individual nozzles, the map may associate the desired number of open nozzles with such ranges of speed or flow rate. 
     Similarly, the angle and area ratio of the outlet diffusers may be made adjustable allowing control in response to operating condition. For example,  FIG. 7  shows a variable vane diffuser such as used in centrifugal compressors and disclosed in U.S. Pat. Nos. 6,547,520 and 6,814,540. The variable vane diffuser has an array of diffuser passageways  170 A- 170 H separated by vanes  172 A- 172 H. Each diffuser passageway has an inboard inlet  174  (between inboard ends  175  of adjacent vanes) and an outboard outlet  176  (between outboard ends  177  of adjacent vanes). Exemplary vanes may articulate so as to allow at least partially independent control of inlet area and outlet area.  FIG. 7  shows the articulation as consisting of a relative rotation of each vane about an inboard pivot  178  between a solid line condition and a broken line condition. The broken line condition effectively slightly increases the inlet area relative to the inlet area of the solid line condition. 
     The rotation may be used to adjust the diffuser inlet angle as well as its area ratio according to the incoming mass flow. This is to make sure that the diffuser is well aligned with the incoming flow angle, also to assure that the flow remains attached against the diffuser wall. 
     The controlling could be performed by a rotating ring (not shown) with pins at the location of vanes&#39; slots. The rotation of the ring will be associated with the vanes being pushed by the pins inside the slots. The rotation may be actuated by a motor and gearing or via a tangential linear actuator. More complex configurations may provide more than one degree of vane adjustment. Similar to the inlet nozzle control, the outlet diffuser orientation may be controlled responsive to or with the compressor speed or refrigerant flow rate. As speed (or mass flow) is reduced, the controller will rotate the vanes to be less radial and more tangential (i.e., from the broken line showing toward the solid line showing). This better aligns the vanes with the velocity vector of discharged refrigerant. An increase in speed or flow rate would be associated with an opposite articulation of the diffuser. 
       FIG. 8  shows an alternate system  200  having an ejector  202 . One or more valves  204  are positioned to provide differential control of flows through the motive nozzles. In one example, the single shared inlet plenum  90  is eliminated and replaced by branch lines  206  feeding individual nozzles. In the example, there is a one-to-one correspondence between valves and motive nozzles so that there may be a fully independent control of flow through the motive nozzles. In other embodiments, valves might be consolidated to feed multiple nozzles (e.g., a switching valve for each two nozzles providing flow through both, one, or none). In yet other versions, a single valve  58  ( FIG. 1 ) may control flow through all the motive nozzles. 
       FIGS. 9-19  show flow patterns for ejectors with alternate configurations of motive nozzles and/or diffusers. Thus, the ejectors are illustrated by the outline of the flows through the ejectors without showing wall thickness, etc. Such ejectors may be used in place of the ejectors above. 
     The ejector  300  of  FIGS. 9 and 10  features motive nozzles  302  and diffusers  304 . Each nozzle  302  has an associated inlet  310 , a convergent section  312  downstream thereof, and a throat  314  downstream of the convergent section. In the exemplary configuration, each nozzle  302  has its own beginning of a divergent section  316  downstream of the throat  314 . These sections  316  feed into an outboard upstream end  318  of the ejector core between an inboard wall  330  and an outboard wall  332 . The inboard wall may, effectively, be the outboard wall of an upstream end centerbody similar to the centerbody  114  of  FIG. 2 . The wall  332  may form the outer wall of the mixing section in a similar fashion as the outer wall  126  of  FIG. 2 . The exemplary wall  330  is radially outwardly convex as the flows from the sections  316  merge and pass downstream, they continue to expand. Accordingly, an upstream outboard portion  334  of the core effectively provides the remainder of the expansion. The exemplary centerbody has an inboard wall  340  which meets the outboard wall  330  at a junction  342  wherein the motive and secondary flows mix. The convex profile of the surface  330  helps minimize losses associated with flow separation. 
     The diffuser centerbody may be similar to the centerbody  134  described above. Each exemplary diffuser  334  may extend from an inlet  350  at the downstream end of the core to an outlet  352  radially outboard thereof with a divergent section  354  therebetween. 
     The exemplary ejector  400  of  FIGS. 11 and 12  features motive nozzles  402  and diffusers  404 . The downstream centerbody has a nearly conical outer surface  430  which extends relatively forward to near or even upstream of the upstream centerbody rim  432  (e.g., upstream of so as to axially overlap). The upstream centerbody inboard surface  434  diverges radially, but the presence of the centerbody  430  may partially counter any expansive effect on the secondary flow. The upstream section centerbody outer surface  436  is shown as generally frustoconical, although other configurations may be used. 
     The exemplary ejector  600  of  FIGS. 13 and 14  features motive nozzles  602  and diffusers  604 . The exemplary downstream centerbody outboard surface  630  is generally frustonical but extends yet further upstream compared to the surface  430  of  FIG. 12 . The expansion portion of the core wherein the motive flow expands prior to encountering the suction flow is relative foreshortened leaving only a small annular upstream centerbody having a downstream rim  632 . In the illustrated configuration, the outer/outboard wall  640  of the core and mixing section diverges radially outward downstream. This divergence may help convert some of the tangential momentum into pressure as the motive flows mix with the suction flow. 
     The exemplary ejector  700  of  FIGS. 15 and 16  features motive nozzles  702  and diffusers  704 . Otherwise similar to the ejector  400 , the diffusers expand the flow both circumferentially and axially and have a slight axial orientation (away from the inlet end) to help recover some of the axial momentum. 
     The exemplary ejector  800  of  FIGS. 17-19  may have an array of motive nozzles along the lines of any discussed above and schematically shown as  802 . The diffusers  804  are relatively axial having inlets  806  and axial outlets  808 . 
     Although an embodiment is described above in detail, such description is not intended for limiting the scope of the present disclosure. It will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, details of particular uses may influence details of the particular ejector. Accordingly, other embodiments are within the scope of the following claims.
An ejector ( 38) has ports ( 40, 42, 44) for receiving a motive flow and a suction flow and discharging a combined flow. The ejector has a motive flow inlet, a suction flow inlet ( 42), and an outlet ( 44). A suction flow flowpath extends from the suction flow inlet. A motive flow flowpath extends from the motive flow inlet to join the suction flow flowpath and form a combined flowpath exiting the outlet. The ejector comprises a plurality of motive flow nozzles ( 100, 302, 402, 602, 702, 802) along the motive flow flowpath. The motive flow nozzles are oriented to impart a tangential velocity component to the motive flow. A plurality of diffusers ( 130, 304, 404, 604, 704, 804) are along the combined flowpath and are oriented to recover the tangential velocity from the combined flow.