Ejectors and Methods of Use

Abstract

An ejector has: a motive flow inlet (40); a secondary flow inlet (42); an outlet (44); a motive flow nozzle (242) having an outlet (110); a primary flowpath from the motive flow inlet through the motive flow nozzle to the ejector outlet; a secondary flowpath from the secondary flow inlet to the ejector outlet, merging with the primary flowpath at the motive nozzle outlet; a control needle (200; 300; 400) shiftable along a range of motion between a first condition and a second condition and seated against the motive nozzle in the second condition. The needle comprises: a main shaft (210); a tip (204); a first portion (220; 320) converging toward the tip; and a shoulder portion (214; 314; 422) between the first portion and the main shaft and seated against the motive nozzle in the second condition and converging toward the tip at a greater angle (?1; ?1 2) than an angle (?2; ?2 2) of the first portion.

Claims

1. An ejector comprising: a motive flow inlet (40); a secondary flow inlet (42); an outlet (44); a motive flow nozzle (242) having an outlet (110); a primary flowpath from the motive flow inlet through the motive flow nozzle to the ejector outlet; a secondary flowpath from the secondary flow inlet to the ejector outlet, merging with the primary flowpath at the motive nozzle outlet; a control needle (200; 300; 400) shiftable along a range of motion between a first condition and a second condition and seated against the motive nozzle in the second condition, wherein the needle comprises: a main shaft (210); a tip (204); a first portion (220; 320) converging toward the tip; and a shoulder portion (214; 314; 422) between the first portion and the main shaft and seated against the motive nozzle in the second condition and converging toward the tip at a greater angle (.sub.1; .sub.1-2) than an angle (.sub.2; .sub.2-2) of the first portion.

2. The ejector of claim 1 wherein: the shoulder portion angle (.sub.1) is 15 to 75; and the first portion angle (.sub.2) is 5 to 60.

3. The ejector of claim 1 wherein: the shoulder portion angle (.sub.1-2) is 75 to 115; and the first portion angle (.sub.2-2) is 5 to 60.

4. The ejector of claim 1 wherein: the shoulder portion angle (O.sub.f) is 10 to 30 greater than the first portion angle (.sub.2).

5. The ejector of claim 1 wherein: the shoulder portion angle (.sub.1-2) is 5 to 80 greater than the first portion angle (.sub.2-2).

6. The ejector of claim 1 wherein: a throat of the motive nozzle has clearance relative to the needle in the second condition.

7. The ejector of claim 1 wherein: the motive nozzle is made of stainless steel; and the needle is made of stainless steel.

8. The ejector of claim 1 wherein: the needle comprises a transition section (330) between the first portion and the second portion and being closer to cylindrical than the first portion and the second portion.

9. The ejector of claim 1 wherein: the motive nozzle is a convergent-divergent nozzle.

10. The ejector of claim 1 further comprising: a mixer comprising a convergent portion at least partially downstream of the motive nozzle; and a divergent diffuser portion downstream of the convergent portion.

11. A vapor compression system comprising: a compressor (22); a heat rejection heat exchanger (30) coupled to the compressor to receive refrigerant compressed by the compressor; the ejector of claim 1; a heat absorption heat exchanger (64); and a separator (48) having: an inlet (50) coupled to the outlet of the ejector to receive refrigerant from the ejector; a gas outlet (54); and a liquid outlet (52).

12. A method for operating the system of claim 11, the method comprising: compressing the refrigerant in the compressor; rejecting heat from the compressed refrigerant in the heat rejection heat exchanger; passing a flow of the refrigerant through the primary ejector inlet; and passing a secondary flow of the refrigerant through the secondary inlet to merge with the primary flow.

13. A method for operating the ejector of claim 1, the method comprising: driving a motive flow along the primary flowpath; and shifting the needle to the second condition so as to stop the motive flow.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic view of a prior art ejector refrigeration system.

[0026] FIG. 2 is an axial sectional view of a prior art ejector.

[0027] FIG. 3 is an axial sectional view of an end of a prior art needle.

[0028] FIG. 4 is an axial sectional view of a needle.

[0029] FIG. 4A is an enlarged view of a tip region of the needle of FIG. 4.

[0030] FIG. 5 is an axial sectional view of an ejector including the needle of FIG. 4 in an open condition.

[0031] FIG. 5A is an enlarged view of a motive nozzle region of the ejector of FIG. 5.

[0032] FIG. 6 is a view of the motive nozzle region in a closed condition.

[0033] FIG. 7 is an enlarged axial sectional view of a tip region of an alternate needle.

[0034] FIG. 8 is an enlarged axial sectional view of the needle of FIG. 7 in a closed condition in an ejector motive nozzle.

[0035] FIG. 9 is an enlarged axial sectional view of a tip region of yet another alternate needle.

[0036] Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0037] FIG. 4 shows an alternative needle 200 extending from a proximal end 202 to a tip 204. Near the proximal end, the needle may have a mounting feature 206 (e.g., an external thread) for mounting to an actuator. The exemplary needle has a main section 210 along which the outer surface portion 212 is cylindrical (e.g., a circular cylinder of diameter D.sub.1). At a downstream end of the section 210 there is a convergent shoulder portion 214 (FIG. 4A) along which the outer surface 216 converges toward the tip 204 at an angle .sub.1 (a half angle of the cone being half of this). There is thus an annular transition 218 between the sections 210 and 214 and their associated surfaces 212 and 214. Similarly, at a downstream end of the section 214 is a section 220 along which the exterior surface portion 222 converges towards the tip at a shallower angle than the surface portion 216. FIG. 4A shows this angle as .sub.2. Again, this leaves an annular junction 224 between the section 220 and section 214 and their associated surfaces 222 and 216.

[0038] FIG. 5A shows the needle in a relatively retracted condition/position. A yet further retracted condition may be possible. In the FIG. 5A condition, the tip 204 is approximately at the throat 240 of the motive nozzle 242. The exemplary throat is formed as a short cylindrical area between a convergent surface 244 upstream and a divergent surface 246 downstream. The exemplary divergent surface 246 extends at a shallow angle to the outlet 110. The exemplary convergent surface 244 is at a slightly greater angle (.sub.3 of FIG. 6) chosen to mate with the surface 216 in a closed condition discussed below. The exemplary motive nozzle 242 is formed as an insert into a body assembly and carries a needle guide 250 (e.g., at a step or discontinuity in the surface 244).

[0039] FIG. 6 shows the needle further inserted into a closed condition wherein the needle tip 204 is concentrically within the divergent section of the nozzle formed by the surface 246. In this closed condition, the surface 216 abuts a terminal portion of the surface 244 to close/seal the motive nozzle. The outer diameter D.sub.2 (FIG. 4A) at the downstream end of the surface 216 may be slightly smaller than the corresponding diameter of the nozzle at the throat 240 to allow clearance and avoid sticking For example, the outer diameter D2 could be 1 to 5% smaller than the corresponding diameter of the throat so as to provide a clearance fit and yet avoid sticking of the needle into the throat upon actuation under pressurized conditions.

[0040] In use, the closing of the ejector may serve the role of the solenoid valve 88 of the FIG. 1 system, thereby allowing elimination of such valve.

[0041] Exemplary .sub.1 is 40, more broadly, 30 to 50 or 15 to 75. Exemplary .sub.2 is 24, more broadly, 20 to 30 or 5 to 60. An exemplary difference between .sub.1 and .sub.2 is at least 2, more particularly at least 5, more particularly, 10 to 30 or 10 to 20. Exemplary .sub.3 is the same as .sub.1 (e.g., within 1 thereof). Relative to the FIG. 3 prior art, the change in taper may be relatively rearward on the top and allow a relatively low angle .sub.2. It is better to have double taper at the back of the needle tip as it allows for better flow control by having a finer needle tip (smaller angle) used to control a typical 2-phase sonic flow conditions that could exist at the throat. Sharp angle changes (as shown by larger sealing angles) near the throat could lead to eddy formation near the throat that could lead to shocks in the divergent section of the motive nozzle leading to energy being lost in the form of heat.

[0042] FIG. 7 shows a needle 300 which may be otherwise similar to the needle 200 of FIG. 4. The main section surface is still shown as 212 and the tip is still shown as 204. The overall tip region may differ from that of the needle 200 in one or more of several aspects. A first exemplary aspect is the angle .sub.1-2 of the surface 316 of a shoulder 314 relative to the angle .sub.1 of the surface 216 of FIG. 4A. In this exemplary embodiment, angle .sub.1-2 is larger than that illustrated for angle .sub.1.

[0043] A second illustrated difference is the presence of a step discontinuity 315 (e.g., shallower than either adjacent section) between the surface 322 of the section 320 and the surface 316 when compared with the intersection of the surface 222 and the surface 216. The exemplary discontinuity in the form of a straight section 330 having a circular cylindrical outer surface 332 and respective junctions 334 and 336 with the surfaces 316 and 322. An exemplary length L.sub.S of the surface 332 is at least 0.01 inches (0.25 mm), more particularly, an exemplary 0.04 inches to 0.2 inches (1 mm to 5 mm) or 0.5 mm to 10 mm.

[0044] Exemplary values for .sub.2-2 are similar to those given above for .sub.2. An exemplary value for .sub.1-2 is 90, more broadly, 75 to 115 or 15 to 145 or 45 to 120. An exemplary difference between .sub.2-2 and .sub.1-2 is at least 2, more particularly at least 5, or 40-70, more broadly, 5-80.

[0045] FIG. 7 shows the needle 300 in a seated/closed condition with at least a portion of the section 336 accommodated in the throat of the nozzle. FIG. 8 shows that there may be angular mismatch between the angle .sub.1-2 and the corresponding angle .sub.3-2 of the convergent portion of the motive nozzle. The exemplary .sub.3-2 is similar to exemplary .sub.3. This mismatch helps with a better (tighter) sealing of the flow.

[0046] In yet alternative embodiments, .sub.2 or .sub.2-2 may go to an exemplary 180 with the associated surface portions being radial. The angels may even go beyond radial. In alternative implementations with such a radial surface or of the shallower surfaces, one or both exemplary surfaces may be formed by separate members carried by the needle or by a main portion of the motive nozzle. FIG. 9 shows a needle 400 which may be otherwise similar to the needle 300 of FIG. 7. Along the straight section 330, the needle carries a ring 420. The exemplary ring 420 is nested up against the junction 334 with the surface 316. The outer diameter (OD) of the ring 420 is less than the main section diameter D.sub.1. A downstream surface 422 of the ring 420 forms a sealing surface for engaging to seal against a fixed surface in the closed condition. An exemplary fixed surface is an upstream-facing surface 432 of a ring 430 inserted within the throat of the nozzle main body to, in turn, form a functional throat of the combination of the main body and ring. Thus, the exemplary surfaces 422 and 432 are essentially radial. Such a radial surface may be easier to machine. It may also be easier to machine by placing it on separate members (the rings). Also the use of separate members allows for selection of ring materials to provide desired sealing properties while not changing material properties of remainders of the needle and the nozzle body.

[0047] Exemplary ejector materials and manufacture techniques may be those conventionally known in the art (e.g., casting and/or machining from various metals and alloys, typically stainless steels). Use may similarly mirror use in the art with, in particular, use including actuating the ejector to fully close off flow therethrough in the absence of a separate valve.

[0048] 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 the particular refrigeration system in which the ejector is to be used may influence details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.