Methods and devices for reducing circumferential pressure imbalances in an impeller side cavity of rotary machines

Abstract

An improved rotary machine of the invention may include a rotor with an impeller mounted thereon. A side cavity may be formed between an impeller and the housing. The rotary machine may be further equipped with an annular subdividing disc for segmenting a fluid flow in the cavity into a first fluid flow between the disc and the impeller, and a second fluid flow on the other side of the disc between the disc and the housing. The rotary machine of the invention also features a peripheral annular space formed in the periphery of the housing in the cavity at a location adjacent to a peripheral region of the annular subdividing disc. Importantly, this peripheral annular space is void of restrictions to circumferential fluid flow therein so as to alter the second fluid flow in the cavity in order to reduce pressure variations and flow disturbances along the circumference of the rotary machine. This in turn improves rotational balance of the rotary machine.

Claims

1. A rotary machine, said rotary machine comprising: a housing containing a fluid inlet and supporting a central shaft rotatably connected therein, said housing containing a fluid outlet and a peripheral annular ring spaced concentrically and radially away from said central shaft and adjacent to said fluid outlet, said rotary machine further comprising an impeller mounted on said central shaft, said impeller having at least one radial surface with respect to said central shaft, said housing having at least one interior wall surface proximate to said at least one radial surface of said impeller, such that a cavity is defined therebetween, said impeller forming an impeller tip gap between an outer edge of said at least one radial surface of said impeller and said peripheral annular ring of said housing, said rotary machine further comprising: an annular subdividing disc fixedly attached to said housing for segmenting a fluid flow in said cavity into a first fluid flow between said annular subdividing disc and said at least one interior wall surface of said housing, and a second fluid flow between said annular subdividing disc and said at least one radial surface of said impeller, and an open peripheral annular space formed in said housing as an extension of said cavity in a further distant peripheral direction away from said central shaft and beyond said annular subdividing disc, said open peripheral annular space located between an extension of said at least one interior wall surface of said housing in said further distant peripheral direction and said outer edge of said at least one radial surface of said impeller, such that said peripheral annular ring separates said open peripheral annular space from said fluid outlet, said open peripheral annular space having a perimeter side defined by said extension of said at least one interior wall surface of said housing and located further radially distant from said central shaft than said impeller tip gap, said open peripheral annular space in fluid communication with each of said first fluid flow and said second fluid flow of said cavity, said open peripheral annular space located adjacent to and in fluid communication with said impeller tip gap, such that said open peripheral annular space is configured to receive tangential fluid flow via said impeller tip gap and circumferential fluid flow via said cavity as said impeller rotates, said open peripheral annular space shaped and sized to allow fluid to move tangentially throughout an entire periphery of said housing prior to transforming into said first fluid flow and said second fluid flow in said cavity, thereby reducing local fluid pressure pulsations and causing an averaging of fluid pressure and fluid flow circumferentially within said open peripheral annular space, and such that said fluid flow in said cavity is characterized by reduced pressure variations around a circumference of said rotary machine so as to improve a rotational balance thereof.

2. The rotary machine as in claim 1, further comprising at least one flow redirecting vane positioned between said annular subdividing disc and said at least one interior wall surface of said housing.

3. The rotary machine as in claim 1, wherein said open peripheral annular space is formed with an increased width along said at least one interior wall surface of said housing that exceeds a width of said cavity.

4. The rotary machine as in claim 1, wherein said annular subdividing disc comprises a disc protrusion portion that extends into said open peripheral annular space so as to partially divide said open peripheral annular space into two adjacent peripheral annular zones.

5. The rotary machine as in claim 1, wherein a cross-sectional area of said open peripheral annular space is altered adjacent to one or more volute tongues of said rotary machine.

6. A method for a rotary machine, said method comprising: step (a)providing said rotary machine with a housing containing a fluid inlet and supporting a central shaft rotatably connected therein, said housing containing a fluid outlet and a peripheral annular ring spaced concentrically and radially away from said central shaft and adjacent to said fluid outlet, and an impeller mounted on said central shaft, said impeller having at least one radial surface with respect to said central shaft, said housing having at least one interior wall surface proximate to said at least one radial surface of said impeller, such that a cavity is defined therebetween, said impeller forming an impeller tip gap between an outer edge of said at least one radial surface of said impeller and said peripheral annular ring of said housing, step (b)segmenting a fluid flow in said cavity using an annular subdividing disc fixedly attached to said housing into a first fluid flow between said annular subdividing disc and said at least one interior wall surface of said housing, and a second fluid flow between said annular subdividing disc and said at least one radial surface of said impeller, step (c)forming an open peripheral annular space in said housing as an extension of said cavity in a further distant peripheral direction away from said central shaft and beyond said annular subdividing disc, said open peripheral annular space located between an extension of said at least one interior wall surface of said housing in said further distant peripheral direction and said outer edge of said at least one radial surface of said impeller, such that said peripheral annular ring separates said open peripheral annular space from said fluid outlet, said open peripheral annular space having a perimeter side defined by said extension of said at least one interior wall surface of said housing and located further radially distant from said central shaft than said impeller tip gap, said open peripheral annular space in fluid communication with each of said first fluid flow and said second fluid flow of said cavity, said open peripheral annular space located adjacent to and in fluid communication with said impeller tip gap, such that said open peripheral annular space is configured to receive tangential fluid flow via said impeller tip gap and circumferential fluid flow via said cavity as said impeller rotates, said open peripheral annular space is shaped and sized to allow fluid to move tangentially throughout an entire periphery of said housing prior to transforming into said first fluid flow and said second fluid flow in said cavity, and step (d)reducing local fluid pressure pulsations and causing an averaging of fluid pressure and fluid flow circumferentially within said open peripheral annular space, and such that said fluid flow in said cavity is characterized by reduced pressure variations around a circumference of said rotary machine so as to improve a rotational balance thereof.

7. The method as in claim 6, further comprising step (e)directing said first fluid flow toward said central shaft via at least one redirecting vanes.

8. The method as in claim 6, wherein step (c) further comprises adjusting a bulk swirl velocity in said open peripheral annular space by increasing a width of said open peripheral annular space along said at least one interior wall surface of said housing such that said width of said open peripheral annular space exceeds a width of said cavity.

9. The method as in claim 6, wherein said step (d) further comprises varying flow resistance circumferentially around said open peripheral annular space to compensate for pressure imbalances caused by one or more volute tongues of said rotary machine.

10. The rotary machine as in claim 1, further comprising an impeller wear seal adjacent to said fluid inlet, such that said cavity extends from said impeller wear seal to said open peripheral annular space, wherein an inner radius of said impeller wear seal is equal to or greater than one half of a distance between said impeller wear seal and said outer edge of said at least one radial surface of said impeller, and less than a radius of said impeller.

11. The rotary machine as in claim 1, further comprising a volute downstream from said impeller and said fluid outlet, wherein said open peripheral annular space is defined by an outer radius that is equal to or less than a radius of said volute.

12. The rotary machine as in claim 1, wherein said open peripheral annular space is defined by a width between one and three times larger than a combination of: a distance between said annular subdividing disc and said at least one radial surface of said impeller, and a distance between said annular subdividing disc and said at least one interior wall surface of said housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Subject matter is particularly pointed out and distinctly claimed in the concluding portion of the specification. The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings, in which:

(2) FIG. 1 is a cross-sectional view of an upper half portion of a rotary machine (outer peripheral portion of the impeller) of the prior art design;

(3) FIG. 2 is a cross sectional view of a left upper corner portion of a rotary machine (outer peripheral portion of the impeller) near an impeller exit incorporating a first embodiment of the invention;

(4) FIG. 3 is a cross sectional view of a left upper corner portion of a rotary machine (outer peripheral portion of the impeller) near an impeller fluid exit incorporating a second embodiment of the invention;

(5) FIG. 4A is a cross sectional view of a left upper corner portion of a rotary machine (outer peripheral portion of the impeller) near an impeller fluid exit incorporating a third embodiment of the invention;

(6) FIG. 4B is a cross sectional view of the same as FIG. 4A showing an alternative design of the third embodiment of the invention; and

(7) FIG. 4C is a cross sectional view of the same as FIG. 4A showing yet another alternative design of the third embodiment of the invention.

DETAILED DESCRIPTION OF THE FIRST EMBODIMENT OF THE INVENTION

(8) The following description sets forth various examples along with specific details to provide a thorough understanding of claimed subject matter. It will be understood by those skilled in the art, however, that claimed subject matter may be practiced without one or more of the specific details disclosed herein. Further, in some circumstances, well-known methods, procedures, systems, components and/or circuits have not been described in detail in order to avoid unnecessarily obscuring claimed subject matter. In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

(9) FIG. 1 shows an upper half portion of a cross-section of a rotary machine of the prior art containing a housing (8) and an impeller (20) fixedly placed on the central shaft (30). The impeller (20) includes a front disc (3) shown to the left side of the FIG. 1 and the rear disc (3) shown to the right of the FIG. 1 so that these discs serve to direct the fluid flow from the low pressure area at the inlet (6) to the high pressure area at the outlet (6) of the impeller (20).

(10) Two cavities are formed between the impeller (20) and the housing (8): a front cavity (10) and a rear cavity (10). Front cavity (10) is defined generally by the front interior housing wall (11) and the front disc (3). Rear cavity (10) is defined respectively by the rear interior housing wall (11) and a rear disc (3). Cumulative axial thrust on the impeller (20) is a result of the pressure distribution along the front disc (3) and the rear disc (3) in these two respective cavities (10) and (10). In turn, these pressure distributions directly depend on the fluid dynamics in these cavities, the discussion of which will now follow.

(11) The annular subdividing disc (2) in the impeller side cavity (10) and other features such as the impeller front shroud and back hub portions are generally shown in the drawings as perpendicular to the rotor axis for convenience of presentation, while conical or curved surfaces and gaps formed therebetween are more common in practice. And while the specification and the drawings herein indicate impellers having a front shroud, the present invention also has application for rotary machines having unshrouded impellers. Also, such design features as described in any one of the drawings below may be used in any combination with those of the other figures as described herein or with any other features in the '507 and '476 patents mentioned above.

(12) The annular subdividing disc (2) is shown only on the front cavity also for convenience of the presentation. A similar annular subdividing disc may also be installed in the rear cavity (10) or both the front cavity and the rear cavity of the rotary machine.

(13) Also provided are stationary subdividing vanes (1) located near the fluid exit of the impeller (20). In a prior art rotary machine, the fluid exit flow is traditionally divided into a rotary machine outlet flow directed towards the outlet (6) and an annular flow (9) directed towards the front cavity (10) defining a leakage flow Q.sub.L through an impeller wear seal or wear ring (12). Stationary vanes (1) redirect the annular flow and send it down the front cavity (10) towards the center of the rotary machine. An annular subdividing disc (2) separates the flow into a first flow (5) between the housing wall (11) and the annular subdividing disc (2) and a second flow (4) between the annular subdividing disc (2) and the front impeller disc (3).

(14) A detailed description of the present invention follows with reference to the accompanying drawings in which like elements are indicated by like reference numerals. The figures illustrate a portion of one of the stages of a typical rotary machine that may contain one or more stages. The pumping element of the rotor is sometimes referred to as the impeller. Although the geometry of the impeller may vary according to the pumping conditions, such as in so-called radial, mixed flow or axial pumps, they all have the same basic elements, namely the impeller having a front disc and a rear disc, a housing containing that impeller, and seals minimizing the leaks from the high pressure areas at the outlet of the rotary machine to the low pressure areas at the inlet of the rotary machine. The present invention is illustrated only with reference to the radial flow type centrifugal pump, but it can be easily adapted by those skilled in the art to other types of rotary machines.

(15) A cross-sectional view of the first preferred embodiment of the present invention is depicted in FIG. 2. Shown here is an exemplary close-up view of the upper corner of the rotary machine (outer peripheral portion of the impeller) near the fluid exit so as to illustrate the novel elements of the invention installed in this location. Similar design elements may also be installed in other suitable locations of a rotary machine.

(16) The present invention may be preferably utilized on one or both side cavities of a single stage rotary machine, or in the front or both side cavities of each stage of a multi-stage rotary machine. It is assumed that in the side cavity there is net transit leakage flow entering the impeller side cavity through annular impeller tip gap (119) and exiting through the impeller wear ring (not shown).

(17) The main fluid flow (117) through the impeller is propelled by impeller vanes having a front disc (113) defining in a periphery an impeller tip gap (119) with a peripheral annular ring (110B), which is fixedly attached to or formed together with a stationary housing (118). An annular subdividing disc (112) together with annular bypass channel redirecting vanes (115A) may be fixedly attached to the housing (118), together comprising a return channel for a secondary flow.

(18) During operation, the rotation of the impeller (including impeller front disc (113)) propels fluid in the main flow (117) into the diffuser/volute (116) that circumferentially encompasses the impeller and further down the outlet of the rotary machine. A small portion of that flow leaks through an annular gap (119) formed between the impeller disc (113) and the annular ring (110B) from the area of high pressure towards the area of low pressureshown in FIG. 2 by arrows. This transit leakage through the annular gap (119) has a high tangential velocity and high pulsation quality due to jet/wake pulses caused by the impeller vanes. The inner side of annular ring (110B) forms the outer boundary of an annular channel for such transit leakage flow, while the outer side of the annular subdividing disc (112) forms the inner boundary of this annular flow. The annular flow is directed into a peripheral annular space (110). Fluid in impeller side cavity (114) is centrifuged outward and tangentially by the rotating impeller front disc (113), causing it to also flow through the same annular channel to the peripheral annular space (110).

(19) As compared to the prior art having virtually no or a very small peripheral annular space (110), the inventors of the present invention unexpectedly discovered that providing an annular space (110) which is designed for and sized sufficiently large to allow fluid to move tangentially around the periphery of the rotary machine housing with little to no resistance provides significant benefits in reducing rotational imbalance and smoothing out pressure variations and flow irregularities for a rotary machine.

(20) Fluid in the peripheral annular space (110) exits into annular bypass channel (115) from which it is directed toward the center of the rotary machine. Annular bypass channel redirecting vanes (115A) may be provided within annular bypass channel (115), redirecting incoming peripheral fluid having a high tangential flow component into predominantly radially inward flow toward the impeller shaft. The annular bypass channel redirecting vanes (115A) may occupy all or part of annular bypass channel (115), including potentially more than one set of stationary vanes.

(21) Given that the perimeter side of the peripheral annular space (110) is spaced further away from the rotor axis than the annular gap (119), all annular gap leakage having high tangential velocity will proceed into the peripheral annular space (110). Fluid centrifuged outward by the rotating impeller front disc (113) also having high tangential velocity will also proceed into the more distal peripheral annular space (110).

(22) The peripheral annular space (110) may be specifically designed to facilitate the averaging or normalization of circumferential distortions, including variations in localized pressure, fluid momentums and turbulence of the fluid in the peripheral annular space (110). Fluid entering peripheral annular space (110) has a high degree of flow variations in the normal direction (e.g., vortices), and will initially gravitate to the most distal portion of the peripheral annular space (110). With residence time, vortex lines initially normal to the flow will be tipped into the streamwise direction as they traverse this space. The three-dimensional flow in the distal region of peripheral annular space (110) will become more and more two-dimensional and uniform as the flow migrates to the inner portion of the peripheral annular space (110)and just prior to being directed to the annular bypass channel redirecting vanes (115A).

(23) Circumferential averaging of pressure may be further aided by the repetitive process of: a. a reduction in swirl velocity given a greater radius of a distal portion of peripheral annular space (110), followed by b. an acceleration of swirl as the fluid migrates toward the more proximate (closer to the central shaft) region of peripheral annular space (110) due to a law of conservation of energy, c. just prior to entry into the annular bypass channel redirecting vanes (115A).

(24) The dimensions of peripheral annular space (110) should be sufficiently large to permit the flow of fluid without appreciable resistance in the circumferential direction to enable the averaging of pressure circumferentially. To enable such circumferential flow without appreciable resistance, the inner radius of the peripheral annular space (110) may be selected to be from about the distance between the radius of the impeller tip and that of the wear ring, to about the full radius at the impeller tip. In addition, the outer radius of the peripheral annular space (110) may be as large as that of the volute downstream of the impeller. Further, the width of the peripheral annular space (110) may be as large as one to three times the combined width of the impeller side cavity (114) and bypass return channel (115).

(25) An optional annular ring (110A) may be provided and fixedly attached to (or formed therewith) the annular subdividing disc (112). The annular ring (110A) provides two functions. First, it may increase a mechanical strength of the annular subdividing disc (112), which may be required since the annular subdividing disc (112) extends outward beyond the support of the annular bypass channel redirecting vanes (115A), which may be fixedly attached to the housing (118). Second, given its protrusion into a generally rectangular cross section of the peripheral annular space (110), the annular ring (110A) alters the profile of the peripheral annular space (110), affecting flow dynamics within thereof.

(26) As flow in the peripheral annular space (110) having a high normal flow component becomes more two-dimensional, it gravitates toward the inner side thereof, and due the smaller radius gains swirl velocity. This is the case assuming a uniform width of the annular peripheral space (110). A presence of the annular ring (110A) may alter the width along peripheral annular space (110), resulting in three separate annular regions varying in radial distance to the center of the rotary machine. The most distal portion of the annular region (Zone 1) is most distal to the annular ring (110A) having a maximum width and providing the greatest volumetric area for the normalization of flow. In Zone 1, more two-dimensional (uniform) flow will gravitate toward its inner radius. The area radially adjacent to the annular ring (110A) defines Zone 2 with the step reduction in width produced by the presence of the annular disc (110A). The resulting resistance for fluid to enter Zone 2 bottles up flow in Zone 1, forcing an even greater normalization of fluid distortions in Zone 1. Within Zone 2, more two-dimensional (uniform) flow gravitates toward its inner radius, having greater tangential velocity than the bulk velocity of fluid in Zone 1. Zone 3 is most proximate to the impeller center axis, with the width of the annular ring (110A) tapering from full width to zero at the entrance to annular bypass channel (115). This tapering in effect increases the width of the peripheral annular space (110) available for fluid flow in its proximate annular region, causing a reduction in the swirl velocity as the fluid approaches the annular bypass channel (115) and enters the annular bypass channel redirecting vanes (115A). Similar effects of altering the swirl velocity in the peripheral annular space (110) by altering its width may be achieved by altering the profile of the other side of peripheral annular space (110) (i.e., the left side in FIG. 2) as shown in further detail in FIG. 3.

(27) With respect to providing circumferentially more uniform pressure and flow mass/volume distribution conditions at the wear ring and in the impeller side cavity to improve rotational dynamic performance, one other novel design feature may be incorporated. The main flow (117) generally exits the rotating impeller and enters the volute (116). Volutes may be not symmetrical. They all have a tongue (typically one, and sometimes two). A tongue inherently causes circumferential variances in the pressure and flow at the entrance to the volute. The annular peripheral space (110) and the bypass channel redirecting vanes (115A) are stationary components, like the tongue(s) of the volute. They may be designed to be non-uniform circumferentially to compensate for or correct the circumferentially non-uniform effects of the tongue(s). In embodiments, such design modifications may include circumferentially: a. altering the density (per radial span) or pitch of the bypass channel redirecting vanes (115A), or b. altering the dimensions of the annular peripheral space (110) such as varying respective radii of the distal and proximate walls thereof, or c. varying the width or cross section area of the annular bypass channel (115),
all such modifications utilized to alter or vary local flow resistance around the circumference of the peripheral annular space (110). Various circumferential variations/alterations in surface quality (roughness, etched vanes, etc.) may also be utilized to compensate for the circumferential imbalance inherently present in the vicinity of the tongues of the housing volutes.

DETAILED DESCRIPTION OF THE SECOND EMBODIMENT OF THE INVENTION

(28) A cross-section view of the second embodiment of the present invention showing a fragment of a rotary machine next to the outlet of the impeller is depicted in FIG. 3. The benefits of the second embodiment include: (1) improved flow dynamics, (2) a more compact design, and (3) lower production costs.

(29) During operation of the rotary machine, the rotating impeller (including impeller front disc (123)) propels the impeller main flow (127) towards the diffuser/volute (126) that may circumferentially encompass the impeller. Transit leakage flows through the annular gap (129) and has high tangential velocity. The annular leakage then moves into a radially more distal or distant region of the peripheral annular space (120) which is bounded by annular ring (120A). Fluid in impeller side cavity (124) is centrifuged outwardly and tangentially by rotating impeller front disc (123). Its outward and tangential momentum carries the fluid past the impeller tip and into the radially more distal region of the peripheral annular space (120). Fluid in peripheral annular space (120) exits into annular bypass channel (125), and then moves radially inward toward the hub area of the center of the rotary machine (not shown). Annular bypass channel redirecting vanes (125A) may be contained within the annular bypass channel (125). They may also share the same annular cavity area and configured for redirecting incoming fluid having a high tangential flow component into largely radial inward flow toward the hub.

(30) The flow dynamics in peripheral annular space (120) develops as follows. The annular subdividing disc (122) extends radially outward beyond the point where it may be fixedly attached to the annular bypass channel redirecting vanes (125A), forming a protrusion (122) into peripheral annular space (120). Such protrusion of the annular subdividing disc (122) causes formation of two side-by-side annular zones, which are partially separated from each other by the disc (122). The area within peripheral annular space (120) and to the right of the most distal surface of annular subdividing disc (122) in FIG. 3 defines Zone A. The area to the left of the most distal surface of annular subdividing disc (122) defines Zone B. Zone A receives fluid entering into peripheral annular space (120), and fluid exits peripheral annular space (120) via Zone B. Fluid entering Zone A from annular side cavity (124) is centrifuged radially outward by rotating impeller front disc (123) and has high tangential and radial velocity, and fluid entering through annular gap (129) has high tangential velocity. The momentum of these two entering fluid flows having a high degree of flow normal to the flow path is carried to the most distal portion of peripheral annular space (120) where it blends with the fluid already present in Zone B.

(31) Several features shown in FIG. 3 may be utilized to facilitate the movement of the fluid from Zone A to Zone B in their distal (most peripheral) region. First, the annular ring (120B) may be inserted and shaped to gradually reduce the width of Zone A with larger radius, resulting in the most distal region of peripheral annular space (120) being most occupied by Zone B, such distal region having the most non-normal flow. Second, the left outer wall of Zone B may be design to extend to the left of the annular bypass channel (125), increasing the volume of Zone B and especially at its most distal region. This may have an effect of similarly further increasing the distal area of peripheral annular space that is occupied by Zone B. And third, the protrusion portion (122) of the annular subdividing disc may be made beveled so that its most distal edge is on its right side as shown in the figureto cause further increase in the relative proportion of the distal side of the peripheral annular space (120) that forms Zone B.

(32) There may be other benefits derived from the partial separation of the peripheral annular space (120) into two Zones A and B. Compared to the first embodiment shown in FIG. 2, the radially proximate area of the peripheral annular space (120) in the area of Zone A of this embodiment has a much greater effective width than the annular channel formed by annular ring (110B) and annular subdividing disc (112) in FIG. 2. This greater width area has three benefits: a. there is a greater space for a merging of the incoming fluid flows (flow through annular gap (129) and fluid centrifuged by rotating front disc (123)), thereby reducing flow turbulence caused by their merging, b. this greater width which is occupied by incoming fluid flow in effect allows the circumferential normalization of flow to also occur while the fluid is still flowing in the outward direction, thereby starting the process of flow normalization earlier, and c. urging the balancing of pressure circumferentially is facilitated by allowing the bulk circumferential velocity of a region/arc in Zone A to be different from that of Zone B in the same region/arc.

DETAILED DESCRIPTION OF THE THIRD EMBODIMENT OF THE INVENTION

(33) Several cross-sectional views of alternative embodiments of the third embodiment of the present invention are depicted in FIGS. 4A, 4B, and 4C. The benefits of the third embodiment of the present invention include: (1) an even more compact design, (2) further cost reduction opportunities.

(34) The main fluid flow (137) through the rotary machine is propelled by impeller vanes having a front disc (133) defining in a periphery an impeller tip gap (139) with a peripheral annular ring (130A), which is fixedly attached to or formed together with a stationary housing (138). An annular subdividing disc (132) together with annular bypass channel (135) occupied partially of completely by redirecting vanes (135A) may be fixedly attached to the housing (138), together comprising a return channel for the secondary flow.

(35) During operation, the rotating impeller including impeller front disc (133) urges the impeller main flow (137) into the diffuser/volute (136) that may circumferentially encompass the impeller. Transit leakage flows through an annular gap (139) with high tangential velocity. This leakage proceeds into a radially more distal region of the peripheral annular space (130). Fluid in the impeller side cavity (134) is centrifuged outward and tangentially by the rotating impeller front disc (133). Its outward and tangential momentum carries the fluid past the impeller tip and into the radially more distal region of the peripheral annular space (130). Fluid in peripheral annular space (130) exits into annular bypass channel vanes (135A), and then moves radially toward the central hub area. Annular bypass channel redirecting vanes (135A) may be contained within the annular bypass channel (135) as they may share the same annular cavity area, thereby redirecting incoming fluid having a high tangential flow component into a largely radial inward flow toward the central hub.

(36) The embodiments shown in FIG. 4A, FIG. 4B and FIG. 4C are examples of possible designs configured for altering the extent of circumferential uniformity of the fluid achieved within the peripheral annular space (130, 140, or 150) prior to the fluid entering the annular bypass channel redirecting vanes (135A, 145A, or 155A).

(37) In embodiments shown in FIG. 4A, the redirecting vanes (135A) extend all the way to the most peripheral area of the peripheral annular space (130) while annular subdividing disc (132) is terminated at a shorter radius to allow flow to enter from the peripheral annular space (130) into the channel (135).

(38) In embodiments shown in FIG. 4B, the both the annular subdividing disc (142) and the redirecting vanes (145) extent radially to the same point within the peripheral annular space (140).

(39) In embodiments shown in FIG. 4C, the annular subdividing disc (152 protrudes further outwards in the peripheral annular space (150) as compared with the redirecting vanes (155A).

(40) The design shown in FIG. 4A may produce less circumferential uniformity than design of FIG. 4B, which in turn may be less effective in achieving circumferential uniformity than the design of FIG. 4C. This is because the exit of fluid from peripheral annular space (130) into annular bypass channel redirecting vanes (135A) is more distal from the rotor axis than that of peripheral annular space (140), and even more so from peripheral annular space (150). Fluid having the greatest component of flow normal to the streamwise flow may be at the outside of the flow, or flowing along distal portion of the peripheral annular space (130), so fluid exiting the peripheral annular space at a smaller radius may have a smaller normal component and therefore have a more two-dimensional and circumferentially uniform flow. As a general rule, the less distal the radius at entry to the annular bypass channel redirecting vanes (135A, 145A or 155A), then the greater circumferential uniformity of the fluid may be achieved.

(41) Similarly, increased circumferential uniformity can be achieved by having the annular bypass channel redirecting vanes (145A) not occupy the most distal portion of annular bypass channel (145), as shown in FIG. 4B and FIG. 4C. In effect, this distal non-vane area of the annular bypass channel (155) provides an adjoining open peripheral annular space in parallel annular communication with peripheral annular space (150), resulting in a less distal entrance into the annular bypass channel redirecting vanes (155A) than (145A) and therefore achieving a more circumferentially uniform flow.

(42) Methods of the Invention

(43) The main objective of the present invention is to reduce local pressure imbalances in the secondary flows of centrifugal rotary machines, and the methods of the invention to achieve that goal involve making available an additional separate annular area or space to permit the circumferential balancing of pressure (peripheral annular space). The methods include providing this peripheral annular space to be low in resistance to flow to encourage the migration of fluid from high-pressure areas to low-pressure areas, implementing the function of circumferential balancing. The methods include steps of providing this peripheral annular space in the periphery of the impeller side cavities, the area with the highest degree of distortion in flow and pressure and therefore the area where the most impact can be made. The methods also include a step of providing the outer radial surface of the peripheral annular space to be positioned radially more distal than the impeller tip, resulting in incoming fluid (transit leakage fluid and fluid centrifuged by the rotating impeller shroud) naturally flowing into the peripheral annular space given its tangential momentum. The methods further include steps of providing the ability to vary the resistance to flow around the peripheral annular space in efforts to adjust or compensate for the peripheral circumferential imbalances caused by the tongue(s) of the diffuser/volute.

(44) The methods further include steps of providing the ability to alter the bulk swirl velocity of fluid at different radial bands within the peripheral annular space by altering its width. The methods further include steps of providing the ability to vary the extent of circumferential imbalances reduction within the peripheral annular space and bypass channel vanes by altering the radial difference between the peripheral surface of the peripheral annular space and the entrance to the bypass channel redirecting vanes. This in effect allows varying the extent of normalization of the fluid prior to entry into the bypass channel. The methods further include steps of providing a side-by-side dual-zone peripheral annular space having communication at its perimeter to permit the stratification of the incoming fluid to be quasi-isolated from that of outgoing fluid. This in turn allows circumferential balancing given the varying flow qualities of outward flowing fluid (incoming fluid) vs. that gravitating toward lower radius (outgoing fluid), thereby permitting the tailoring (i.e., width, flow direction, etc.) of each space having different flow qualities to its own function.

(45) It is contemplated that any embodiment discussed in this specification can be implemented with respect to any method of the invention, and vice versa. It will be also understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims.

(46) All publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

(47) The use of the word a or an when used in conjunction with the term comprising in the claims and/or the specification may mean one, but it is also consistent with the meaning of one or more, at least one, and one or more than one. The use of the term or in the claims is used to mean and/or unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and and/or. Throughout this application, the term about is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

(48) As used in this specification and claim(s), the words comprising (and any form of comprising, such as comprise and comprises), having (and any form of having, such as have and has), including (and any form of including, such as includes and include) or containing (and any form of containing, such as contains and contain) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. In embodiments of any of the compositions and methods provided herein, comprising may be replaced with consisting essentially of or consisting of. As used herein, the phrase consisting essentially of requires the specified integer(s) or steps as well as those that do not materially affect the character or function of the claimed invention. As used herein, the term consisting is used to indicate the presence of the recited integer (e.g., a feature, an element, a characteristic, a property, a method/process step or a limitation) or group of integers (e.g., feature(s), element(s), characteristic(s), propertie(s), method/process steps or limitation(s)) only.

(49) The term or combinations thereof as used herein refers to all permutations and combinations of the listed items preceding the term. For example, A, B, C, or combinations thereof is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

(50) As used herein, words of approximation such as, without limitation, about, substantial or substantially refers to a condition that when so modified is understood to not necessarily be absolute or perfect but would be considered close enough to those of ordinary skill in the art to warrant designating the condition as being present. The extent to which the description may vary will depend on how great a change can be instituted and still have one of ordinary skilled in the art recognize the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding discussion, a numerical value herein that is modified by a word of approximation such as about may vary from the stated value by at least 1, 2, 3, 4, 5, 6, 7, 10, 12, 15, 20 or 25%.

(51) All of the devices and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the devices and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the devices and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.