MULTIPLE CHANNEL DIFFUSER

Abstract

A multiple channel diffuser (MCD) having a plurality of radial inlets in an annular configuration, a tangential outlet, a single discharge passage, and a plurality of separate passages extending from the plurality of radial inlets and toward the outlet. The plurality of separate passages are fluidly isolated from each other at their upstream ends, and become merged at one or more merge locations upstream of the single discharge passage. Thus, a flow of fluid entering the plurality of radial inlets is initially separated within the plurality of separate passages, becomes merged within the single discharge passage, and then flows collectively out of the MCD through the outlet. Both mixing losses and viscous losses are reduced.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

N/A.

GOVERNMENT RIGHTS STATEMENT

N/A.

TECHNICAL FIELD

The present technology is related generally to a pump or compressor, and more specifically to a diffuser for a pump or compressor.

BACKGROUND

In a pump or a compressor, such as a turbopump, a diffuser is typically used to convert the dynamic pressure of a flow of fluid exiting the pump or compressor into static pressure rise at the volute exit. There are three commonly used diffusers: vaneless diffusers, airfoil diffusers, and vane island diffusers. The single greatest loss in a turbopump is in the diffuser, and diffuser losses can account for more than 20% of the total pressure loss from the impeller discharge to the volute. Such losses are from the leading edge (incidence loss), the trailing edge (expansion loss), mixing losses, and/or skin friction losses. Of these losses, mixing losses are the greatest and are responsible for more than 90% of the total loss.

Mixing losses are the greatest because of the large pressure and velocity gradient between the diffuser and the volute. An additional contributor to the loss is the asymmetry caused by the volute tongue, which can also cause a circumferential static pressure gradient around the volute that propagates through the diffuser to the impeller. The volute tongue is the primary contributor to the radial side load from the impeller to be reacted by the bearings; however, eliminating the tongue, and this circumferential pressure gradient, eliminates this side load, which increases bearing life and reliability.

Additionally, the radial component of the kinetic energy is nearly unrecoverable once it enters the volute, along with the meridional dynamic pressure. Leading-edge or incidence loss is due to the stagnation condition caused by leading edge and any misalignment between the flow field stream lines and the leading edge. Even if these are perfectly aligned at design point conditions, which is not possible, incidence losses occur at off-design conditions. Trailing-edge losses result from pressure gradients between the pressure and suction side of the diffuser. These losses exist even in symmetric vanes, but are greater in non-symmetric vanes with turning due to the increased pressure and velocity gradients between the pressure and suction sides. Skin friction losses are due to the velocity of the moving fluid in contact with a stationary wall. These losses can be significant in pumps with viscous fluid; however, they are negligible for cryogens such as hydrogen, oxygen, and methane, as these are nearly inviscid. Even non-cryogens with low viscosity, including rocket propellants and any low-viscosity fluids such as water, would have relatively low skin friction losses. To highlight the magnitude of the mixing losses, note than the vaneless diffuser does not have leading edge or trailing edge losses, yet is the least efficient diffuser because of its higher mixing losses.

SUMMARY

Some embodiments advantageously provide a multiple channel diffuser (MCD), such as an MCD for use in turbomachinery.

In one embodiment, a MCD comprises: an annular arrangement of a plurality of inlets; an outlet; and a plurality of separate passages extending from the plurality of inlets and toward the outlet, each of the plurality of separate passages having an increasing flow area, the plurality of separate passages being fluidly isolated from each other at an upstream end and merging at one or more merge locations upstream of the outlet.

In one aspect of the embodiment, the plurality of separate passages are configured as a plurality of rows with each row having a plurality of diffuser channels.

In one aspect of the embodiment, the plurality of inlets are radial inlets.

In one aspect of the embodiment, the outlet is a tangential outlet.

In one aspect of the embodiment, the outlet has a square shaped cross section or a circular shaped cross section.

In one aspect of the embodiment, each of the plurality of separate passages has one of a rectilinear, hexagonal, and elliptical cross-sectional shape.

In one embodiment, a multiple channel diffuser (MCD) comprises: an annular arrangement of a plurality of inlets; an outlet; and a plurality of separate passages extending from the plurality of inlets and toward the outlet, each of the plurality of separate passages having an upstream end and a downstream end, the upstream end of each of the plurality of separate passages being at a corresponding one of the plurality of inlets, each of the plurality of separate passages having an increasing flow area from the upstream end to the downstream end, the plurality of separate passages being fluidly isolated from each other at the upstream end and merging at one or more merge locations upstream of the outlet.

In one aspect of the embodiment, the plurality of separate passages are configured as a plurality of rows with each row having a plurality of diffuser channels.

In one aspect of the embodiment, the one or more merge locations includes an upstream merge location and a downstream merge location. In one aspect of the embodiment, the MCD further comprises a single discharge passage, the single discharge passage being between the downstream merge location and the outlet. In one aspect of the embodiment, wherein at least two of the plurality of separate passages merge at the upstream merge location and at least two other of the plurality of separate passages merge at the downstream merge location.

In one aspect of the embodiment, each of the plurality of separate passages has one of a rectilinear, hexagonal, and elliptical cross-sectional shape.

In one aspect of the embodiment, the multiple channel diffuser defines an aperture, the aperture being sized and configured to receive at least a portion of a pump impeller therein. In one aspect of the embodiment, the annular arrangement of the plurality of inlets extends around the aperture. In one aspect of the embodiment, the plurality of separate passages extend around the aperture.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of embodiments described herein, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 shows a cross-sectional view of an exemplary embodiment of a multiple channel diffuser (MCD), in accordance with the present disclosure;

FIG. 2 shows a side perspective view of a structural model of the MCD of FIG. 1, in accordance with the present disclosure;

FIG. 3 shows a perspective view of the flow volume of the MCD of FIG. 1; and

FIG. 4 shows a front view of the MCD of FIG. 1, showing a main discharge and merged channels, in accordance with the present disclosure.

DETAILED DESCRIPTION

Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and steps related to a diffuser for a pump or compressor, and more particularly, a multiple channel diffuser (MCD) for pump or compressor turbomachinery, the MCD including an annular-shaped radial inlet and a tangential outlet where the multiple passages are separate from one another in order to limit mixing of the fluid, but that are then merged at one or more locations upstream of the outlet of the MCD. Accordingly, the system and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

Referring now to the figures in which like reference designators are used for like elements, an exemplary embodiment of a MCD is shown in FIGS. 1-4. In one embodiment, the MCD 10 generally includes an outlet 12 and a plurality of inlets 14. In one embodiment, the MCD 10 further includes a plurality of separate passages 16 extending from each of the plurality of inlets 14 toward the outlet 12; however, the plurality of separate passages 16 merges into a single discharge passage 18 at at least one merge location 20 upstream of the outlet 12. In one embodiment, the plurality of passages 16 includes nine passages 16 (for example, as shown in the cross-sectional view of FIG. 1 and the flow volume view of FIG. 3, which shows how the fluid is routed internally within the MCD 10 shown in FIGS. 1, 2, and 4). However, it will be understood that more or fewer passages may be included. In one embodiment, the MCD 10 is stationary and the impeller rotates within the MCD 10 and discharges a fluid outward in an annular arrangement and into the plurality of inlets of the MCD 10.

Continuing to refer to FIGS. 1-4, in one embodiment the MCD 10 is generally ring shaped and is configured to extend around an impeller, and defines an aperture 22 within which the impeller may be seated. In one embodiment, each of the plurality of inlets 14 are radially arranged (radial inlets) about an imaginary center point 24 of the aperture 22 within the MCD 10. In one embodiment, the MCD 10 is stationary and the impeller rotates within the MCD 10 (for example, within its position within the aperture 22) and discharges a fluid outward in an annular arrangement and into the plurality of inlets of the MCD 10.

In one embodiment, each of the plurality of separate passages 16 has an upstream end 16A and a downstream end 16B, and the upstream end 16A of each of the plurality of separate passages 16 meets, is at, is proximate, and/or at least partially defines, and is in fluid communication with, a corresponding one of the plurality of inlets 14. In one embodiment, each of the plurality of separate passages 16 has a gradually increasing cross-sectional area from the associated inlet 14 at the upstream end 16A and leading toward the downstream end 16B and outlet 12. Further, each of the plurality of separate passages 16 is fluidly isolated from each of the other separate passages 16 until the plurality of separate passages 16 meet at one or more merge locations 20. Thus, fluid within each of the plurality of separate passages 16 remains isolated from fluid within any of the other separate passages 16, but then becomes blended with fluid from at least one of the other separate passages 16 at a location upstream of the single discharge passage 18 and the outlet 12, with all separate passages 16 having merged by the time they meet the single discharge passage 18 to allow fluid to flow collectively out of the outlet 12. Each of the plurality of separate passages 16 functions as an individual diffuser without mixing of other fluids, until the merge location 20 and single discharge passage 18, where fluid is allowed to combine along parallel streamlines eliminating the mixing losses. In some embodiments, fluid isolation of the plurality of separate passages 16 from the plurality of inlets 14 eliminates mixing losses; however, the merging of the flow of fluid within the single discharge passage 18 prior to passing out of the outlet 12 also reduces viscous losses.

Continuing to refer to FIGS. 1-4, in one embodiment the MCD 10 includes more than one merge location 20, with the most downstream merge location being at the upstream portion 18A of the single discharge passage 18. In one embodiment, the downstream portion 18B of the single discharge passage 18 defines the outlet 12. As an example, in one embodiment some (fewer than all) of the plurality of separate passages 16 merge at at least one upstream merge location 20A and other (fewer than all) of the plurality of separate passages 16 merge at the downstream, or most downstream, merge location 20B at or proximate the upstream portion 18A of the single discharge passage 18 (for example, as shown in FIG. 1). Regardless of the number of merge locations 20, the fluid flows as a merged fluid, from the plurality of separate passages 16, through the length of the single discharge passage 18 before exiting the MCD 10 through the outlet 12. In one embodiment, when the channels are at sufficient circumferential and axial position to form a common and uniform structural wall, the separation between the separate passages 16 is eliminated, allowing for the merging of, for example, two of the separate passages 16 before reaching a common merging location, such as the upstream merge location 20A or the downstream merge location 20B at or proximate the discharge passage 18. These merging locations occur at some percentage of total channel length relative to the inlet 14 location and to the discharge passage 18, with larger passage lengths having smaller overall length percentages required until merging could occur. Put another way, in some embodiments each of the separate passages 16 travels a percentage of its overall length before it is merged with another separate passage 16. In one non-limiting example, this percentage decreases based on the overall length of the separate passage 16, wherein the shortest separate passage 16 may travel approximately 100% (±5%) of its length before merging and the longest separate passage 16 may travel only approximately 10% (±5%) of its length before merging.

Such exemplary configuration is shown in the front view of the MCD 10 in FIG. 4. Through the outlet 12, the single discharge passage 18, which terminates at its downstream portion 18B at the outlet 12, is visible. In the single discharge passage 18, some of the plurality of separate passages 16 are visible, as they merge at the downstream merge location 20, whereas others of the plurality of separate passages 16 have merged at a more upstream merge location 20 (for example, as shown in FIG. 1), and the individual separate passages 16 are no longer visible through the outlet 12 near the single discharge passage 18. Further, as is shown in FIGS. 3 and 4 and described in greater detail below, in some embodiments the plurality of separate passages 16 begin in a radial arrangement at the plurality of inlets 14 and spiral out in a slightly helical arrangement to form a more matrix-like or grid-like arrangement at or proximate the upstream portion 18A of the single discharge passage 18. In one example, the plurality of separate passages 16 are arranged to form a plurality of rows, with each row including one or more separate passages 16, to form the matrix-like or grid-like arrangement.

Additionally, the embodiment of the MCD 10 shown in FIGS. 1-4 includes a radial inlet (that is, a plurality of radially arranged inlets) with a tangential outlet. However, in other embodiments MCD 10 includes an axial inlet (that is, a plurality of axially arranged inlets) and an outlet that is not tangential. For example, an axial flow pump or compressor may discharge a flow of fluid into an annular arrangement of axial inlets each having a passage separate from others such that each discharges into the single discharge passage 18 that is not tangential to the axis of the pump or compressor.

Continuing to refer to FIGS. 1-4, in one embodiment the outlet 12 of the MCD 10 has a round or circular cross-sectional shape. However, it will be understood that the outlet 12 may have any suitable cross-sectional shape, including but not limited to round, square, polygonal (for example, hexagonal), rectilinear, elliptical, or the like. Further, each of the plurality of separate passages 16 is shown with a square cross-sectional shape. However, it will be understood that other suitable cross-sectional shapes may be used, including but not limited to round, polygonal, rectilinear, elliptical, or the like.

In some embodiments, the MCD 10 includes one or more additional features. For example, in one embodiment one or more of the plurality of separate passages 16 are separated from the other separate passages 16 to define a tap-off channel for a portion of the flow of fluid. In some embodiments, one or more second stage discharge configurations are used, such that the MCD 10 includes more than one single discharge portion, one or more outlets, and one or more sets of separate passages 16.

Continuing to refer to FIGS. 1-4, in one embodiment the leading edge 26 of the MCD 10 is similar to that of an airfoil diffuser, except that each of the plurality of separate passages 16 is unique and extended and continually expands to define an increasing cross-sectional diameter (thereby expanding the flow of fluid) as it wraps around the aperture 22 and around the impeller (when in use). FIGS. 1-4 each illustrate how the plurality of separate passages 16 are distributed internally to achieve the matrix-like or grid-like arrangement that is partially shown in the front view of FIG. 4. Unwrapped (that is, unwound or straightened out to eliminate the aperture 22), in one embodiment the MCD 10 is a conical diffuser of square, diamond, trapezoid, rectangular, or other suitable cross-sectional shape. In one embodiment, the expansion angle is very small due to the length, which enables highly efficient diffusion with minimal loss. For example, in some embodiments the expansion angle is between approximately 0° and approximately 150 (±0.05±°), depending on the requirements of specific use. In one embodiment, after the dynamic pressure has been diffused to static pressure rise, the plurality of separate passages 16 are then merged within the single discharge passage 18, resulting in a volute discharge that looks and functions like discharges used in currently known diffusers. Additionally, since each of the plurality of separate passages 16 is independent of the other separate passages 16, the separate passages 16 can be bundled or separated and redirected for other purposes and configurations. For the same reason, the plurality of separate passages 16 can additionally or alternatively be configured in planar arrangements, rather than bundles, to enable a variety of packaging configurations.

The MCD 10 eliminates mixing losses and viscous losses, resulting in a greater increase in pressure recovery. In some embodiments, the dynamic pressure of the impeller discharge pressure is expanded gradually and efficiently within the plurality of fluidly isolated, separate passages 16. Once the flow of fluid has been fully expanded, it is merged and combined with adjacent passages after the merge location(s) 20 within the single discharge passage 18. However, because the flow is fully expanded (and because there is no turning), there are no significant pressure or velocity gradients to cause mixing losses. Holding the turbopump, engine size, and stage constant, this results in an increase in chamber pressure for additional stage capability (higher orbits, higher orbit inclinations, and/or heavier payloads). Alternatively, holding specific impulse and thrust constant, both the maximum diameter and overall length shrink significantly, resulting in a smaller, lower weight stage with a significant increase in mission capability.

Diffusers and volutes typically have thick housings to contain the high pressure. A discharge pressure is the same regardless of diffuser or passage size. Therefore, the wall thickness is solely dependent on the passage size. A single large volute requires a thick wall, whereas a small passage requires only a thin wall, particularly those separate passages 16 located exterior to the others. Separate passages 16 located on the interior, or those separate passages 16 surrounded by other separate passages 16, have no pressure gradient on the wall due to the adjacent passage and, as a result, can be even thinner. Consequently, additional weight savings, beyond the weight savings resulting from a smaller engine, are possible just from the diffuser and volute housings of the MCD 10. Further, the MCD 10 does not have a tongue, seen on traditional volute and diffuser combinations, which nearly eliminates the rotor side load currently known diffuser systems, thereby providing improved rotordynamic and system life.

As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention.

Claims

1. A multiple channel diffuser comprising: an annular arrangement of a plurality of inlets;a tangential outlet; anda plurality of separate passages extending from the plurality of inlets and toward the outlet,the plurality of separate passages being fluidly isolated from each other at an upstream end and merging at one or more merge locations upstream of the outlet, each of the plurality of separate passages having an increased flow area from a corresponding one of the plurality of inlets toward a corresponding one of the one or more merge locations.

2. The multiple channel diffuser of claim 1, wherein the plurality of separate passages are configured as a plurality of axial rows with each row having a plurality of diffuser channels.

3. The multiple channel diffuser of claim 1, wherein the plurality of inlets are radial inlets.

4. (canceled)

5. The multiple channel diffuser of claim 1, wherein the outlet has a square shaped cross section or a circular shaped cross section.

6. The multiple channel diffuser of claim 1, wherein each of the plurality of separate passages has one of a rectilinear, hexagonal, and elliptical cross-sectional shape.

7. A multiple channel diffuser comprising: an annular arrangement of a plurality of inlets;a tangential outlet; anda plurality of separate passages extending from the plurality of inlets and toward the outlet, each of the plurality of separate passages having an upstream end and a downstream end, the upstream end of each of the plurality of separate passages being at a corresponding one of the plurality of inlets,each of the plurality of separate passages having an increasing flow area from the upstream end to the downstream end,the plurality of separate passages being fluidly isolated from each other at the upstream end and merging at one or more merge locations at the downstream end and at a location upstream of the outlet.

8. The multiple channel diffuser of claim 7, wherein the plurality of separate passages are configured as a plurality of rows with each row having a plurality of diffuser channels.

9. The multiple channel diffuser of claim 7, wherein the one or more merge locations includes an upstream merge location and a downstream merge location.

10. The multiple channel diffuser of claim 9, further comprising a single discharge passage, the single discharge passage being between the downstream merge location and the outlet.

11. The multiple channel diffuser of claim 10, wherein at least two of the plurality of separate passages merge at the upstream merge location and at least two other of the plurality of separate passages merge at the downstream merge location.

12. The multiple channel diffuser of claim 7, wherein each of the plurality of separate passages has one of a rectilinear, hexagonal, and elliptical cross-sectional shape.

13. The multiple channel diffuser of claim 7, wherein the multiple channel diffuser defines an aperture, the aperture being sized and configured to receive at least a portion of a pump impeller therein.

14. The multiple channel diffuser of claim 13, wherein the annular arrangement of the plurality of inlets extends around the aperture.

15. The multiple channel diffuser of claim 14, wherein the plurality of separate passages extend around the aperture.

16. The multiple channel diffuser of claim 1, wherein each of the one or more merge locations at which the plurality of separate passages merge lie along a parallel axis with an adjacent passage.