Centrifugal compressor open impeller

Abstract

A centrifugal compressor impeller (60; 160) has a hub (62; 162) having a gaspath surface (64; 164) extending from a leading end to a trailing end. A plurality of blades (70A, 70B; 170) extend from the hub gaspath surface and each have: a leading edge (72A, 72B; 172); a trailing edge (74A, 74B; 174); a first face (80A, 80B; 180); a second face (82A, 82B; 182); and a tip (78A, 78B; 178). A plurality of flow splitter segments (120, 122; 320, 322) extend between associated twos of the blades and each spaced from both the hub gaspath surface and the tips of the associated two blades.

Claims

1. A centrifugal compressor impeller (60; 160) comprising: a hub (62; 162) having a gaspath surface (64; 164) extending from a leading end to a trailing end; a plurality of blades (70A, 70B; 170) extending from the hub gaspath surface and each having: a leading edge (72A, 72B; 172); a trailing edge (74A, 74B; 174); a first face (80A, 80B; 180); a second face (82A, 82B; 182); and a tip (78A, 78B; 178); and a plurality of flow splitter segments (120, 122; 320, 322) extending between associated twos of the blades and each spaced from both the hub gaspath surface and the tips of the associated two blades, wherein: the plurality of flow splitter segments comprises a plurality of first flow splitter segments forming a first circumferential ring (120; 320); and the plurality of flow splitter segments comprises a plurality of second flow splitter segments forming a second circumferential ring (122; 322).

2. The compressor impeller (60) of claim 1 wherein: the plurality of blades is a first plurality of blades (70A); a second plurality of blades (70B) extending from the hub gaspath surface and each have: a leading edge; a trailing edge; a first face; a second face; and a tip; said leading edges of the second plurality of blades are downstream recessed relative to the leading edges of the first plurality of blades; and the plurality of first flow splitter segments is upstream of the leading edges of the second plurality of blades.

3. The compressor impeller (60; 160) of claim 2 wherein: the plurality of second flow splitter segments is spaced from both the hub gaspath surface and the tips of the first plurality of blades and the second plurality of blades.

4. The compressor impeller (60; 160) of claim 1 wherein: the hub, the plurality of blades, and the plurality of flow splitter segments are formed as a unitary monolithic metallic casting.

5. The compressor impeller (60; 160) of claim 1 wherein: the first circumferential ring is formed separately from the hub and the plurality of blades.

6. The compressor impeller (60; 160) of claim 5 wherein: the hub and the plurality of blades are formed as a first unitary metallic casting; and the first circumferential ring is formed separately from said first unitary metallic casting.

7. The compressor impeller (60; 160) of claim 5 wherein: the hub and the plurality of blades comprise a first alloy; and the first circumferential ring comprises a second alloy different from the first alloy.

8. The compressor impeller (60; 160) of claim 7 wherein: the first alloy is an aluminum alloy; and the second alloy is a titanium alloy.

9. The compressor impeller (60; 160) of claim 1 wherein: the hub, the plurality of blades, and the plurality of flow splitter segments are formed as a unitary monolithic glass-filled nylon.

10. The compressor impeller (60) of claim 1 wherein: the impeller has an axial inlet and a radial outlet.

11. The compressor impeller (160) of claim 1 wherein: the impeller has an axial inlet and an axial outlet.

12. A compressor (20) comprising the compressor impeller (60; 160) of claim 1 and further comprising: a housing (22) having an inlet port (24) and an outlet port (26); a motor (30) mounted within the housing; said compressor impeller coupled to the motor to be driven for rotation about an impeller axis (500); and a shroud (90) facing the tips.

13. A method for using the compressor of claim 12, the method comprising: running the motor to drive the compressor impeller (60; 160) to drive a flow from the inlet to the outlet wherein at least 25% of the flow passes radially outboard of the plurality of first flow splitter segments and at least 25% of the flow passes radially inboard of the plurality of first flow splitter segments.

14. A method for manufacturing the compressor impeller (60; 160) of claim 1, the method comprising: forming the plurality of flow splitter segments of a first alloy; and forming the plurality of blades of a second alloy different from the first alloy.

15. The method of claim 14 comprising additive manufacture.

16. The method of claim 14 comprising additive manufacture of both the plurality of flow splitter segments and the plurality of blades.

17. A method for manufacturing the compressor impeller (60; 160) of claim 1, the method comprising: additive manufacture of both the plurality of flow splitter segments and the plurality of blades as a unit.

18. A centrifugal compressor impeller (60; 160) comprising: a hub (62; 162) having a gaspath surface (64; 164) extending from a leading end to a trailing end; a plurality of blades (70A, 70B; 170) extending from the hub gaspath surface and each having: a leading edge (72A, 72B; 172); a trailing edge (74A, 74B; 174); a first face (80A, 80B; 180); a second face (82A, 82B; 182); and a tip (78A, 78B; 178); and a plurality of flow splitter segments (120, 122; 320, 322) comprising pairs of a first flow splitter segment (120; 320) and second flow splitter segment (122; 320), each pair extending between associated twos of the blades and each spaced from both the hub gaspath surface and the tips of the associated two blades, wherein: the plurality of flow splitter segments (120, 122; 320, 322) is entirely within an upstream third or a downstream third of a flowpath length from the leading edges to the trailing edges.

19. The compressor impeller (60; 160) of claim 18 wherein: the first flow splitter segments (120; 320) are entirely within said upstream third and the second flow splitter segments (122; 322) are entirely within said downstream third.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a front view of a compressor.

(2) FIG. 2 is a longitudinal section view of the compressor of FIG. 1 taken along line 2-2.

(3) FIG. 2A is an enlarged view of an impeller region of the compressor of FIG. 2.

(4) FIG. 3 is a front view of the impeller.

(5) FIG. 4 is a partial axial sectional view of the impeller taken along line 4-4 of FIG. 3.

(6) FIG. 5 is a partial side view of the impeller.

(7) FIG. 6 is a central axial sectional view of a second impeller.

(8) FIG. 7 is a partial transverse sectional view of a ring-to-vane intersection on an impeller.

(9) Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

(10) FIG. 1 shows a compressor 20 having a housing or case (assembly) 22 with an inlet or suction port 24 and an outlet or discharge port 26. A flowpath between the suction port and discharge port may compress a vapor flow 400 (FIG. 2).

(11) FIG. 2 shows the compressor 20 as including a motor 30 in a motor case section of the housing. The motor has a stator 32 and a rotor 34. The rotor 34 includes a shaft 36 extending outward to mate with and drive a transmission 40. The exemplary transmission 40 includes a driving gear 42 mated to the shaft 36 to be driven about a shaft axis 502. The exemplary shaft 36 is supported by bearings 44, 46 for rotation about the axis 502. The transmission 40 further includes a driven gear 50 mounted to an impeller shaft 52 held for rotation about an axis 500 by bearings 54 and 56. An impeller 60 is mounted to a forward end portion of the impeller shaft 52. The impeller has a hub 62 having an outboard surface (gaspath surface) 64 (FIG. 2A) along a flowpath through the compressor. An inner diameter (ID) surface of the impeller hub receives the impeller shaft 52.

(12) The impeller 60 includes a plurality of vanes (also known as blades) protruding from the surface 64. The exemplary impeller is configured with two sets of interdigitated vanes 70A and 70B (FIG. 5). The exemplary vanes 70A are longer along the flowpath with a leading edge 72A at the inlet end of the impeller. The leading edges 72B of vanes 70B are recessed. Downstream or trailing edges 74A, 74B of the vanes may be at like position along the flowpath. In the illustrated embodiment, the downstream edges extend axially along a radial outlet of the impeller. The vanes have proximal or inboard boundaries at the surface 64 (FIG. 4) and extend to outboard or distal edges 78A, 78B serving as blade tips. The vanes have opposite first surfaces (faces) 80A, 80B and second surfaces (faces) 82A, 82B (FIG. 3). A vane height may be measured as the distance of the edge 78A, 78B measured normal to the surface 64. An alternative parameter of vane height may be the radial span of a vane at the inlet end or the axial span of the vane at the outlet end.

(13) FIG. 2 further shows a fixed shroud 90 and an inlet guide vane array 94 upstream thereof. The guide vanes may be rotated about their respective axes by an actuator (e.g., servomotor or the like). Exemplary actuation involves a single actuator moving all vanes in synchrony via geared or pulley interaction. FIG. 2 further shows a diffuser 100 having diffuser passageways 102 extending between the impeller outlet and a discharge plenum 104 feeding the discharge port.

(14) As so far described, the compressor is illustrative of one example of numerous compressors to which the following teachings may be applied.

(15) In FIG. 3, the illustrated impeller comprises a pair of rings 120, 122. The exemplary rings are circumferential rings extending essentially exactly circumferentially (e.g., not having an axial or radial spiral). The exemplary first ring 120 is in an upstream third of the flowpath along the impeller spaced ahead of the second vanes 70B so as to define segments between adjacent first vanes 70A.

(16) The exemplary ring 120 has a generally rectangular central axial cross-section (FIG. 4) extending from an upstream (leading) edge 130 (FIG. 5) to a downstream (trailing) edge 132. The ring 120 and its segments thus also have an inboard face or surface 134 (FIG. 4) and an outboard face or surface 136. The inboard surface 134 faces and is relatively close to the hub gaspath surface 64. Alternative cross-sections may be more arcuate to conform to bending of the flowpath.

(17) The second ring 122 is within a downstream third of the flowpath length along the impeller. The exemplary second ring 122 also has a generally rectangular cross-section having a leading edge 140 (FIG. 3), a trailing edge 142, an inboard face 144 (FIG. 5), and an outboard face 146. The second ring 122 spans all vanes (thus its segments each extend between one of the first vanes and one of the second vanes).

(18) By recessing the faces 136, 146 of the segments from the edges 78A, 78B, the rings 120, 122 thus each split the flow through the impeller into an inboard portion (between the surface 64 on the one hand and the faces 134 and 144 on the other hand) and an outboard portion (between the shroud on the one hand and the faces 136 and 146 on the other hand). An exemplary recessing may leave at least 10% of a vane height beyond the faces 136 and 146. Thus, the ring segments alternatively may be described as flow splitter segments splitting the flow into inboard and outboard portions.

(19) The presence of the rings 120, 122 may limit resonant behavior of the impeller in a desired speed range. This may have one or more of several consequences including allowing thinner/lighter/more efficient vanes, allowing higher speed operation, allowing reduction in other anti-vibration measures, and improving service life.

(20) The exemplary first ring 120 is shown recessed along the height of the vanes 70A. This recessing allows machining of the edges 78A, 78B to select blade height for a given application even while using one form of impeller precursor (e.g., a raw casting with blade precursors or a machined casting with otherwise fully functional blades already formed at a maximum height). Similarly, the ring 122 is radially recessed from the trailing edges 74A, 74B. This also allows radial trimming of the impeller at the impeller outlet.

(21) The compressor may be made using otherwise conventional or yet-developed materials and techniques. A particular method for manufacturing the integral rings is to sand cast, injection mold, or five axis mill. This may be of a unitary single-alloy casting forming at least a portion of the hub along with the vanes and ring(s). For example, some known impellers feature aluminum alloy cast over a steel hub core/bushing.

(22) Additive manufacturing techniques can be used. Additive manufacturing may be used such as when the ring(s) are made out of a different material than are the impeller hub and vanes (see FIG. 7). In one example, a multi-feed additive manufacturing apparatus (e.g., fused deposition modeling (FDM) or the like) is used with one feed for impeller hub and vane material and another for ring material. Relative to hub/vane material, the ring material may be one or more of a more expensive material, a stronger material, and a less machinable material. For example, consider an aluminum alloy (e.g., majority Al by weight) for the hub/vanes and a titanium alloy (e.g., majority Ti by weight) for the ring(s). In such a process the ring alloy of each ring may form a continuous full annulus through the vanes for hoop strength.

(23) Alternative bimetallic manufacturing involves pre-forming the ring(s) such as by machining and then over-casting the hub/vanes.

(24) Yet alternative manufacture involves non-metallic materials. One example is use of glass filled polymer such as a glass-filled polyamide (e.g., Nylon 12 GF). Grades of Nylon 12 GF are commercially available for laser sintering manufacture techniques. Thus, monolithic additive manufacture of the impeller including the vanes and ring(s) by selective laser sintering (SLS) is a possible technique.

(25) FIG. 6 shows an alternate impeller 160 for a mixed flow compressor wherein the impeller has an axial inlet and an axial outlet. In FIG. 6, the reference numbers for parts equivalent to those shown in FIGS. 3 to 5 are increased by 100. Thus, for example, in FIG. 6 there is a leading edge 240, equivalent to leading edge 140 in FIG. 3. Despite the axial outlet, the gaspath still substantially diverges radially from impeller inlet to impeller outlet. Thus, exemplary gaspath outer diameter at the impeller outlet is still at least about 130% of that at the impeller inlet and the median between the hub surface and vane OD diverges more (e.g., median diameter at the outlet at least about 150% of that at the inlet).

(26) This particular FIG. 6 example has rings 220, 222 formed of a different material than the vanes, but unitary monolithic variants are also possible. The rings 220, 222 and their segments thus have a leading edge 230, 240, a trailing end 232, 242, an inboard face or surface 234, 244, and an outboard face or surface 236, 246. The impeller has a hub 162 with a gaspath surface 164 and vanes 170 extending radially outward therefrom. Two exemplary differences of the impeller 160 relative to the impeller 60 are the axial outlet and the lack of two different lengths of vane 170. The vanes 170 thus each have leading edge 172, trailing edge 174, outboard or distal edge 178, first faces 180 and opposite second faces 182.

(27) The use of first, second, and the like in the description and following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as first (or the like) does not preclude such first element from identifying an element that is referred to as second (or the like) in another claim or in the description.

(28) One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing basic system, details of such configuration or its associated use may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.