Flow control device for axial flow turbomachines in series

Abstract

A flow control device for constraining fluid flow between axial flow turbomachines in series has a flow constrainer which constrains the fluid flow downstream of the first turbomachine in the series to the blades region of the second turbomachine, preventing fluid flow from impacting the hub or nosecone of the second turbomachine and providing more uniform fluid flow to the second turbomachine. The flow control device includes connective elements for positioning between the downstream region of the first turbomachine and the upstream region of the second turbomachine. The device may be equipped with stator vanes having a variety of optional configurations to further improve the uniformity of the fluid flow load on the second turbomachine.

Claims

1. A flow control device for constraining fluid flow between high hub to tip ratio axial flow turbomachines in series comprising: a flow constrainer having a first end and a second end, the first end having a diameter substantially equal to a diameter of a drive assembly of a first high hub to tip ratio axial flow turbomachine housed in a first housing, and the second end having a diameter substantially equal to a diameter of a hub of a second high hub to tip ratio axial flow turbomachine housed in a second housing, the flow constrainer being attached only to the first and second housings; wherein, when the first and second housings are joined and the flow control device is situated between the first and second high hub to tip ratio axial flow turbomachines, the flow constrainer occupies a volume defined by substantially all the space extending between the drive assembly of the first high hub to tip ratio axial flow turbomachine and the hub of the second high hub to tip ratio axial flow turbomachine, and the flow control device constrains fluid flow downstream of the first high hub to tip ratio axial flow turbomachine to a plurality of blades attached to the hub of the second high hub to tip ratio axial flow turbomachine.

2. The flow control device of claim 1, further comprising a plurality of stator vanes attached to an outer surface of the flow constrainer, the stator vanes having a cross section topology selected from the group consisting of a rectangle, a trapezoid, an ellipse, and an airfoil.

3. The flow control device of claim 2, wherein the stator vanes curve upon the outer surface of the flow constrainer.

4. The flow control device of claim 1, wherein the flow constrainer comprises a substantially rigid material.

5. The flow control device of claim 4, wherein the substantially rigid material is selected from the group consisting of metal, plastic, rubber, resin, polymer, and carbon fiber.

6. The flow control device of claim 5, wherein the flow constrainer has a topology selected from the group consisting of cylindrical, truncated conic, parabolic, semi-parabolic, hyperbolic, quadric, ogee, and compound.

7. The flow control device of claim 1, further comprising an outer ring coaxially concentric with the flow constrainer, the outer ring being connected to the flow constrainer by a plurality of struts, and the outer ring having attachment points for attaching to at least one of the first and second housings.

8. The flow control device of claim 7, wherein the plurality of the struts are stator vanes.

9. The flow control device of claim 8, wherein the stator vanes have a cross section topology selected from the group consisting of a rectangle, a trapezoid, an ellipse, and an airfoil.

10. The flow control device of claim 8, wherein the stator vanes curve upon an outer surface of the flow constrainer.

11. The flow control device of claim 7, wherein the attachment points comprise flanges for attaching to the first and second housings.

12. The flow control device of claim 7, wherein the first and second housings are a first and second stage, respectively, of a single multiple turbomachine housing.

13. A method of constraining fluid flow between the first and the second high hub to tip ratio axial flow turbomachine comprising mounting a flow control device of claim 7 between the first and second axial flow turbomachines, wherein the fluid flow is constrained and directed to the blades of the second axial flow turbomachine.

14. The flow control device of claim 1, wherein the fluid is selected from the group consisting of air and water.

15. The flow control device of claim 1, wherein the drive assembly comprises a motor.

16. The flow control device of claim 1, wherein the first and second housings are a first and second stage, respectively, of a single multiple turbomachine housing.

17. A method of constraining fluid flow between the first and the second high hub to tip ratio axial flow turbomachine comprising mounting a flow control device of claim 1 between the first and second axial flow turbomachines, wherein the fluid flow is constrained and directed to the blades of the second axial flow turbomachine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 depicts a perspective view of an embodiment of the flow control device for axial flow turbomachines in series.

(2) FIG. 2 depicts a side view of an embodiment of the flow control device for axial flow turbomachines in series.

(3) FIGS. 3 and 4 depict perspective views of embodiments of the flow control device for axial flow turbomachines in series.

(4) FIGS. 5-7 depict cutaway perspective views of embodiments of the flow control device for axial flow turbomachines in series.

(5) FIGS. 8 and 9 depict side views of embodiments of the flow control device mounted between two axial flow turbomachines.

DETAILED DESCRIPTION OF THE INVENTION

(6) The flow control device of the invention is designed to be mounted between axial flow turbomachines in series. The axial flow turbomachines are situated in housings which generally match in diameter the ducts, pipes, and conduits through which the fluid arrives at the turbomachines and leaves downstream under pressure generated by the turbomachines.

(7) The flow constrainer is constructed such that the diameter of one end matches the outer diameter of the downstream end of the first axial flow turbomachine, while the diameter of the flow constrainer's other end matches the outer diameter of the second axial flow turbomachine's hub, whether or not the hub includes a nose cone. The ends of the flow constrainer need not make actual contact with either the distal end of the first axial flow turbomachine or the upstream hub end of the second axial flow turbomachine. The flow constrainer blocks and occupies a volume defined by substantially all the space extending between the downstream end of the first axial flow turbomachine's motor and the second axial flow turbomachine's hub (the blocked space), such that the flow control device prevents fluid flow within its occupied volume and thereby constrains fluid flow downstream of the first axial flow turbomachine only to an annular exit space defined by the outer surface of the flow constrainer and the inner surface of the housings. The annular exit space has approximately the same dimensions as the annular blade region to which the fluid flows. Depending on the thickness of the outer ring, whether the flanges are inset, and the extent to which the downstream end of the flow constrainer extends axially beyond the outer ring, the annular exit space may be slightly larger than the annular blade region because the blades on the hub must have clearance from the inner surface of the housings in order to rotate freely.

(8) Emerging at the annular exit space, the fluid flows to the annular blade region of the impeller of the second axial flow turbomachine. Constraining and directing the fluid in this fashion is designed to eliminate impinging flow on the hub or nose cone of the second axial flow turbomachine, improving efficiency of the system and reducing the uneven loading of the fluid flow caused by impacts with the hub of the second axial flow turbomachine.

(9) The flow constrainer thus acts as a baffle, preventing fluid flowing through the blocked space between the drive assembly of the first turbomachine and the hub of the second turbomachine and constraining flow to the blades of the impeller. The flow constrainer may be open at both ends, simply occupying the blocked space. Alternatively, its inner region may be sealed closed by a wall or a plurality of walls blocking the interior. In either case, the inner enclosed region may be left empty, or may be filled with a suitable material, such as foam, plastic, sound-reducing material, or the like.

(10) The flow control device mounts between the downstream (or distal) end of the first axial flow turbomachine and the upstream (or proximal) end of the second axial flow turbomachine. In one embodiment, the flow control device has a flow constrainer which may be attached to the downstream end of the first axial flow turbomachine, the second end of the flow constrainer remaining unattached, cantilevered to be positioned close to the upstream hub end of the second axial flow turbomachine. In another embodiment, the flow control device has a flow constrainer disposed centrally, and a coaxially concentric outer ring attached thereto via a plurality of struts.

(11) In some embodiments, the flow control device's outer ring is designed to position the flow control device between the two turbomachines. In some embodiments, the outer ring has flanges on both of its sides, which provide attachment points to the flanges of the two turbomachine housings such that when the flanges of the flow control device are attached to the flanges of both housings, the flow control device is securely mounted between the two turbomachine housings and forms a continuous path for fluid flow. The flanges on the outer ring optionally have rubber boots, gaskets, or the like, attached thereto in order to provide vibration damping between the two housings. Such rubber boots allow for a mechanical connection of the flow control device between the two turbomachines, while providing flexibility to dampen structural and acoustic vibrations within the system. The outer ring has an inner diameter generally ranging from substantially the same as the blade tip to blade tip diameter of the impellers, up to the inner diameter of the housings.

(12) In another embodiment, the outer ring is equipped on its outermost circumference with attachment points for attaching directly to the inside of the housing(s), such as threaded holes adapted to receive screws or bolts which would attach and fix the flow control device within the turbomachine housing(s). Alternatively, the flow control device may be secured to the inner surface of the housing by welding, adhesives, or other means known in the art. In this embodiment, the two turbomachines housings may be joined together by their respective flanges directly, with the flow control device mounted inside between the turbomachines. In these embodiments, the outer ring has substantially the same inner diameter as the blade tip to blade tip diameter of the impellers.

(13) In other embodiments, the two turbomachines may both be mounted within a single multiple turbomachine housing, such that each turbomachine's housing is simply a region of the multiple turbomachine housing. The flow control device is mounted between the turbomachines via attachment points, such as threaded holes adapted to receive screws or bolts. Alternatively, the flow control device may be secured to the inner surface of the housing by welding, adhesives, or other means known in the art.

(14) The flow constrainer is connected to the outer ring by struts, typically three or more. In some applications, these struts serve only to maintain the position of the flow constrainer between the two turbomachines. In other applications, the struts may be configured as stator vanes, imbuing the flow control device with the ability not only to constrain the fluid to the periphery and away from the center, but also to direct the fluid flow in a more uniform direction toward the impeller of the second turbomachine. The stator vanes may be straight or angled, and may be rectangular, trapezoidal, elliptical, airfoil, or other shape in cross-section depending on the application. The stator vanes on the outer surface of the flow constrainer may be aligned with the longitudinal axis of the flow constrainer, or may curve thereupon. Preferably, the number of stator vanes in the flow control device is different from the number of stator vanes which may be present in the turbomachines themselves, in order to minimize any potential flow problems such as resonance and vibration. More preferably, the number of stator vanes is not an even multiple of the number of stator vanes on either of the turbomachines, and the flow control device is positioned such that none of its stator vanes line up with collinearly with those of the turbomachines.

(15) Other types of flow straightening devices may be used such as cell type straighteners with rectangular cells, or other duct passages laid along the axis of the main fluid stream to mitigate the lateral velocity components caused by flow disturbances.

(16) The struts provide a mechanical connection for the flow constrainer to the outer ring. In embodiments in which the struts are stator vanes, they also reduce or eliminate non-uniform flow problems such as pre-swirl or co-swirl in the fluid flow entering the second axial flow turbomachine caused by the rotational motion of the rotor blades of the first axial flow turbomachine. Stator vanes may also be used to impart desirable pre-swirl flow characteristics, depending on the application. The stator vanes help to reduce or eliminate uneven loading conditions on the motor assembly bearings in the second turbomachine which may otherwise lead to bearing and/or motor failure.

(17) In another embodiment of the invention, the flow control device has no outer ring, but instead the flow control device is a flow constrainer with attachment points permitting direct attachment to the downstream end of the first axial flow turbomachine, cantilevered and extending toward the upstream hub end of the second axial flow turbomachine. The housings of the two turbomachines are joined by their flanges, with the flow control device situated inside between the two turbomachines. In this embodiment, the flow control device may still be equipped with stator vanes attached thereto, the outer edges of which are free and unattached.

(18) All elements of the flow control device may be fabricated from a variety of materials for different applications including, but not limited to, metal, plastic, rubber, resin, polymer, and carbon fiber. In some embodiments of the present invention, all the elements are constructed from the same material. In other embodiments, the flow constrainer, the outer ring, and the struts may each be fabricated from different materials. In some embodiments, it may be desirable to control vibration in the system. Optional boots may be attached to the flanges of the flow control device on the sides facing the housings to provide such vibration dampening. Such boots may be constructed from rubber, formable viscoelastic polymer, or other such vibration-damping material.

(19) The flow constrainer may be truncated conical shaped as shown in FIGS. 1 and 2, or may be any gradually curved shape that provides a smooth transition of the fluid flow to the blades of the second axial flow turbomachine. The flow constrainer may have an axial cross-section that is straight (e.g., for a cylindrical transition between axial flow turbomachines), sloped (e.g., for a conical transition between axial flow turbomachines), parabolic, semi-parabolic, hyperbolic, quadric, ogee, or the like. The shape of the flow constrainer may be a compound topology being a combination of such shapes as well. Such an embodiment is shown in, for example, FIGS. 3, 6, and 7, in which the proximal end has a cylindrical portion which transitions to a conical topology throughout the remainder of the flow constrainer.

(20) With reference to the Drawings, FIG. 1 shows a perspective view of an embodiment of the flow control device 1 having a truncated conical flow constrainer 2 and an outer ring 6. The flow constrainer 2 has an upstream or proximal end 3 and a downstream or distal end 4. The flow constrainer 2 is connected to the outside ring 6 by struts in the form of stator vanes 5. The outer ring 6 has attachment points in the form of flange 7 and flange 8, inset around the outer ring 6 for attaching to the first turbomachine housing 17 and the second turbomachine housing 18 (as shown in FIG. 9) such that the housings overlap the outer surface of the outer ring.

(21) FIG. 2 shows a side view of a similar embodiment of the flow control device 1 with conical flow constrainer 2 and outer ring 6. Fluid flows from left to right in the view of FIG. 2, and the flow constrainer 2 constrains the fluid to emerge on the downstream right side in an annular exit space 10 with an annular shape, namely the space surrounding the flow constrainer 2 between it and the turbomachine housings 17, 18 shown in FIGS. 11 and 12. The annular exit space 10 has approximately the same dimensions as the annular blade region to which the fluid flows. Because the blades 14 on the hub 15 must have clearance from the inner surface of the housings 17, 18 in order to rotate freely, the annular exit space 10 may be slightly larger than the annular blade region.

(22) A flow constrainer with a compound shape is an embodiment shown in FIGS. 3 and 4, in which the flow constrainer 2 has a cylindrical portion 11 at its proximal end 3, and a truncated conical portion 12 for the remainder of the length of the flow constrainer until its distal end 4. Struts configured as stator vanes 5 are attached to the flow constrainer 2 and the outer ring 6. Where such attachments are welds, it may be preferable to have the welds outside the fluid flow region, in which case the stator vanes 5 may pass through the surfaces of the flow constrainer 2 and the outer ring 6 and be welded at the interior of the flow constrainer 2 and the exterior of the outside ring 6 as shown by the welding sites 13. A wall 9 prevents any stray fluid from passing through the flow constrainer from either side. The exit space 10 is a narrow annular space where the fluid flow has been constrained by the flow control device 1. The outer ring 6 has attachment points in the form of flange 7 and flange 8, flush with the edges of the outer ring 6 for attaching to the first turbomachine housing 17 and the second turbomachine housing 18 (as shown in FIG. 8).

(23) FIG. 5 shows a cutaway view of an embodiment having a conical flow constrainer 2, two walls 9, and inset flanges 7, 8. The flow constrainer has two walls 9 blocking fluid flow. FIGS. 6 and 7 show cutaway views of an embodiment having a compound topology similar to the embodiments shown in FIGS. 3 and 4, having an upstream cylindrical portion 11 and a trailing truncated conical portion 12. A single wall 9 is used in this embodiment, along with flush flanges 7, 8.

(24) Examples of the flow control device 1 mounted between axial flow turbomachines are shown in FIGS. 8 and 9. FIG. 8 illustrates the use of a flow control device 1 having a flow constrainer 2 with compound topology, a cylindrical proximal portion and the remainder a truncated conical portion, and the outer ring 6 has flush flanges 7, 8. FIG. 9 illustrates the use of a flow control device 1 having a flow constrainer 2 with a truncated conical topology, and the outer ring 6 has inset flanges 7, 8. Fluid flows from left to right. The first turbomachine's impeller, with blades 14 attached to a rotating hub 15, accelerates the fluid which flows past stator vanes 16 and around the drive assembly 19, constrained by the drive assembly 19 and the first turbomachine housing 17, finally reaching the end of the drive assembly 23. The drive assemblies 19 are supported within their respective housings 17, 18, by drive assembly supports 22. Conduit 21 provides any necessary electrical or mechanical connections to motors or drive elements within the drive assemblies. The flow control device is mounted between the housings 17, 18 by its flanges 7, 8, which mate to the housings flanges 20. The flow control device is thus positioned precisely between the housed turbomachines.

(25) Following the fluid flow flowing past the end of the drive assembly 23, the fluid then encounters the flow control device 1. The proximal upstream end 3 of the flow constrainer 2 is matched in diameter to the end of the drive assembly 23, thus the fluid is constrained to the available space between the outer surface of the flow constrainer 2 and the inside surface of the outer ring 6. Fluid reaches the distal downstream end 4 of the flow constrainer 2, which is matched to the diameter of the hub 15 of the second axial flow turbomachine. Emerging from the flow constrainer 2, the fluid flow is delivered to the blades 14 of the second turbomachine, constrained by the hub and the second turbomachine housing 18.

(26) The following Examples serve to illustrate the present invention and are not intended to limit its scope in any way.

EXAMPLES

Example 1a Flow Control Device for Axial Flow Turbomachines in Series for Air

(27) A flow control device was constructed from aluminum. The device is equipped with flanges on both sides to mate with the flanges of a typical 21 inch diameter housing with an axial flow turbomachine, in particular, an axial fan, housed within. The device was mounted between two such housed axial fans, on one side to the downstream end of the first axial fan housing, and on the other side to the upstream end of the second axial fan housing. The flow constrainer's first end was 12 inches in diameter to match the 12 inch diameter of the non-rotating downstream end of the first axial fan's motor, and was measured to rest one half inch from the motor. The flow constrainer's second end was 18 inches in diameter to match the 18 inch diameter of the rotating hub of the second axial fan, and was measured to rest one half inch from the hub. The flow control device also was equipped with seven straight stator vanes with rectangular cross section equally spaced around the flow constrainer, joined to both the flow constrainer and to the outer ring. The outer ring had one inch high flanges on both sides, for connecting to the one inch flanges on both axial fans' housings. In operation, it was observed that the air flow was constrained outside the center, could not significantly impact the hub of the second axial fan, and was directed into the blade region of the second axial fan's impeller. It was observed that the air pressure downstream of the second fan was increased approximately two-fold over that produced by the same pair of axial fans in series without the flow control device of the invention. It was also observed that mechanical stress on the system was reduced.

Example 2a Flow Control Device for Axial Flow Turbomachines in Series for Air, with Stator Vanes

(28) A flow control device is fabricated from aluminum. The device is equipped with flanges on both sides to mate with the flanges of axial flow turbomachine housings. In this Example, the flow control device is mounted between two housed axial flow turbomachines (in this case, axial fans), on one side to the downstream end of the first axial fan housing, and on the other side to the upstream end of the second axial fan housing. The flow constrainer's first end matches the non-rotating downstream end of the first axial fan's motor. The flow constrainer's second end matches the diameter of the rotating hub of the second axial fan. The flow control device has stator vanes with a curved cross section defined by a camber line advantageous to the inlet flow conditions, equally spaced around the flow constrainer, joined to both the flow constrainer and to the outer ring. The stator vanes are situated in such a way as to provide advantageous pre-swirl to the downstream fan impeller inlet to ease the aerodynamic load on the downstream impeller assembly. The outer ring has flanges on both sides, for connecting to the flanges on both axial fans' housings. It is observed that the air pressure downstream of the second fan is increased over that produced by the equivalent pair of axial fans in series without the flow control device of the invention. It is also observed that mechanical stress on the system is reduced.

Example 3a Cantilevered Flow Control Device for Ducted Axial Propulsors in Series, for Water

(29) A flow control device is fabricated from steel. In this Example, the axial flow turbomachines are ducted propulsors. The flow control device is a flow constrainer equipped with mounting points on its proximal end for attaching to the end of the non-rotating drive assembly of a first axial propulsor. The flow control device is mounted between two axial propulsors. At the downstream end of the first ducted propulsor, the proximal end of the flow control device and flow constrainer, which matches the diameter of the end of the drive assembly, is attached to the end of the drive assembly. The flow control device is cantilevered to bring the distal end of the flow constrainer into close proximity to the second axial propulsor. The flow constrainer's distal end matches the diameter of the rotating hub of the second axial propulsor. The flow control device has stator vanes with a curved cross section defined by an airfoil shape advantageous to the inlet flow conditions, equally spaced around the flow constrainer, joined to the flow constrainer. The outer edges of the stator vanes are unattached. Optionally, the outer edges of the stator vanes may be attached directly to the inner surface of the housings. It is observed that the water pressure downstream of the second propulsor is increased over that produced by the equivalent pair of axial propulsors in series without the flow control device of the invention. It is also observed that mechanical stress on the system is reduced.

(30) The present invention is not to be limited in scope by the specific embodiments described above, which are intended as illustrations of aspects of the invention. Functionally equivalent methods and components are within the scope of the invention. Various modifications of the invention, in addition to those shown and described herein, will be readily apparent to those skilled in the art from the foregoing description. Such modifications are intended to fall within the scope of the appended claims. All cited documents are incorporated herein by reference.