Deflection passages in a diffuser and corresponding methods of designing such diffusers

Abstract

To provide a biased passage for a turbomachine.SOLUTION: There is provided a turbomachine having one or more flow guide features designed to improve the performance of the turbomachine. The flow guide features are designed and configured to bias a circumferential pressure distribution at a diffuser inlet toward circumferential uniformity, otherwise account for such low-frequency spatial pressure variations, to improve controllability of spatial flow field variations or to modify flow field variations, etc. In some examples, diffusers having a row of vanes including a plurality of first vanes and at least one second vane having characteristic different from that of the first vane are disclosed. In some examples, diffusers having an aperiodic section including one or more biased passages for biasing a flow field are disclosed. And in some examples, turbomachines having recessed portions in a flow direction long in one or both of a hub surface and a shroud surface are disclosed.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] Related Application Data

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 155,341, filed Apr. 30, 2015, entitled “Biased Passage(s) Flow Devices For Turbomachinery,” and U.S. Provisional Patent Application No. 62 / 243,415, filed Oct. 19, 2015, entitled “Methods For Designing Turbomachines To Account For Non-Uniform Pressures At Diffuser Inlet And Associated Structures And Devices.” Each of these applications is hereby incorporated by reference in its entirety.

[0002] Field of the Invention

[0002] The present invention generally relates to the field of turbomachines. In particular, the present invention relates to a biased passage for a turbomachine.

Background Art

[0003] Background

[0003] Over the past few decades, a wide variety of diffuser types have been adopted for centrifugal pump stages and compressor stages. In some cases, a good impeller is designed first, and then, in turn, a good diffuser is designed, or the two elements are designed simultaneously. Irrespective of that, essentially all past research has been based on the assumption that the flow at the diffuser inlet is quasi-steady / axisymmetric, which has typically been simply treated as a one-dimensional (1D) velocity triangle model for preliminary design. Most of these assumptions continue when using the numerical fluid dynamics (CFD) models used today. Typically, at some level, regardless of the number of blades, the flow leaving the impeller and then entering the diffuser, also regardless of the number of vanes in this case, is assumed to be essentially periodic and axisymmetric, completely and uniformly filling each diffuser passage.

Summary of the Invention

Means for Solving the Problems

[0004] Summary of the Disclosure

[0004] In one embodiment, the present disclosure relates to a diffuser for a turbomachine, the diffuser including a plurality of diffuser passages disposed around the diffuser and receiving a flow field having a circumferential pressure distribution, the diffuser passages including at least one periodic section and at least one aperiodic section, the at least one aperiodic section including at least one deflection passage arranged, configured, and dimensioned to deflect the circumferential pressure distribution towards circumferential uniformity.

[0005]

[0005] In another embodiment, the present disclosure relates to a diffuser comprising: a plurality of first vanes arranged in a row in a part around the diffuser, each of the first vanes being spaced apart from an adjacent first vane by a first circumferential distance; and at least one second vane located between some of the first vanes, the at least one second vane having a feature different from that of the first vanes, the different feature causing a circumferential pressure distribution of a flow field entering the diffuser to be deflected towards a circumferentially uniform pressure distribution, thereby providing a deflection passage adjacent to the at least one second vane.

[0006]

[0006] In yet another embodiment, the present disclosure relates to a diffuser comprising: a hub and a shroud; a plurality of first vanes extending from the hub to the shroud and arranged in a row in a part around the diffuser; and at least one second vane located between some of the first vanes, the at least one second vane extending from the hub to the shroud and having a feature different from that of the first vanes.

[0007]

[0007] In yet another embodiment, the present disclosure relates to a diffuser comprising: a hub and a shroud; and a plurality of vane groups each including at least two vanes, each of the at least two vanes having a feature different from that of the other ones of the at least two vanes.

[0008]

[0008] In yet another embodiment, the present disclosure relates to a method of designing a diffuser having an inlet and a plurality of vanes for reducing circumferential pressure fluctuations adjacent to the inlet, the pressure fluctuations having a primary spatial frequency less than the spatial frequency of the vanes. The method includes providing a plurality of diffuser passages each having an inlet and located around the diffuser, and arranging at least one deflection diffuser passage between some of the plurality of diffuser passages, the deflection diffuser passage having a cross-sectional area different from that of the plurality of diffuser passages so as to minimize circumferential pressure fluctuations at the inlets of the plurality of diffuser passages.

[0009]

[0009] In yet another embodiment, the present disclosure relates to a method of designing a diffuser, comprising: developing a computational model of an axisymmetric diffuser; calculating the performance of the diffuser when there is a circumferential pressure distribution having a time-averaged low-frequency circumferential variation at the inlet to the diffuser; modifying the computational model to add at least one deflected flow path to the diffuser; calculating the performance of the modified diffuser; and comparing the diffuser performance from the two calculating steps to determine whether the deflected flow path has improved the diffuser performance.

[0010]

[0010] In another embodiment, the present disclosure relates to a method of designing a diffuser, comprising: measuring the circumferential pressure distribution at the inlet to a first diffuser having periodic diffuser passages; replacing the first diffuser with a second diffuser having at least one aperiodic section with at least one deflected diffuser passage; measuring the circumferential pressure distribution at the inlet to the second diffuser; and comparing the pressure distributions from the two measuring steps to determine whether the second diffuser has reduced an undesirable variation in the magnitude of the measured circumferential pressure distribution by a predetermined amount.

[0011]

[0011] In yet another embodiment, the present disclosure relates to a vaneless diffuser comprising an inlet and an outlet, a hub surface and a shroud surface each extending between the inlet and the outlet, and a plurality of flow direction recesses on at least one of the hub surface and the shroud surface, the plurality of flow direction recesses being aperiodic.

[0012]

[0012] In yet another embodiment, the present disclosure relates to a diffuser for a turbomachine, the diffuser including a plurality of diffuser passages located around the diffuser to receive a flow field, the flow field having a circumferential pressure distribution, the diffuser passages including a first set of passages each having a first effective cross-sectional area distribution along the flow direction and at least one deflector passage having a second effective cross-sectional area distribution along the flow direction, the first effective cross-sectional area distribution and the second effective cross-sectional area distribution being different, and the at least one deflector passage being arranged, configured and dimensioned to deflect the circumferential pressure distribution towards circumferential uniformity.

[0013] Brief Description of the Drawings

[0013] For the purpose of illustrating the present invention, the drawings show aspects of one or more embodiments of the present invention. However, it should be understood that the present invention is not limited to the exact arrangements and means shown in the drawings.

Brief Description of the Drawings

[0014]

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Mode for Carrying Out the Invention

[0015] Detailed Description

[0014] Aspect of the present disclosure includes a turbomachine having one or more flow guiding functions designed to improve the performance of the turbomachine. In some examples, the flow guiding function is designed and configured to deflect the circumferential pressure distribution at the diffuser inlet towards circumferential uniformity or otherwise account for such low-frequency spatial pressure fluctuations. In some examples, a diffuser is disclosed that has a row of blades including a plurality of first blades and at least one second blade having a different characteristic from the first blades. In some examples, a diffuser is disclosed that has an aperiodic section including one or more deflection passages for deflecting the flow field. In some examples, a turbomachine is disclosed that has elongated recesses in the flow direction on one or both of the hub surface and the shroud surface. As described herein, the present disclosure includes various combinations of flow guiding functions that can be incorporated into a turbomachine to account for flow field characteristics including, but not limited to, circumferential asymmetry, thereby improving the performance of the turbomachine.

[0016]

[0015] Figures 1 - 5 are graphs of static pressure versus circumferential angle for various diffusers and operating conditions, each diffuser being operably disposed downstream of a centrifugal compressor. Each of Figures 1 - 5 shows the time - averaged static pressure at several circumferential positions around the machine, all at positions in the flow direction between the impeller outlet and the diffuser inlet. Figure 1 shows the time - averaged static pressure for various flow rates 102 - 116 all at the same impeller rotational speed, here 120,000 RPM, with curve 104 being the lowest flow rate and curve 102 being the highest flow rate. The data in Figure 1 is from a flat - plate diffuser having 14 vanes. Vane position lines 118 indicate the approximate position of each vane relative to the static pressure measurements. As shown in Figure 1, each of the pressure curves 102 - 116 has a saw - tooth pattern, with peaks corresponding to each vane position 118, and such saw - tooth patterns are due mostly to the natural inter - vane pressure fields present in vane - type diffusers or any blade row of turbomachinery blades. Thus, the pressure curves 102 - 116 have a first spatial frequency that is substantially the same as the spatial frequency of the vanes of the flat - plate diffuser. However, the pressure curves 102 - 116 also have a lower - frequency wave type that overlays the saw - tooth shape, and the lower - frequency waves have a fundamental spatial frequency that is less than the spatial frequency of the vanes. Figure 2 shows a subset of the pressure curves from Figure 1, namely curves 102, 104, and 112. Figure 2 also includes mean pressure curves 202, 204, and 206, which in this example are sixth - order polynomial curves. In the mean pressure curves 202, 204, and 206, low - frequency spatial variations in the time - averaged circumferential static pressure can be seen, and in this example, each flow rate results in low - frequency pressure variations with two maxima and two minima around the machine.

[0017]

[0016] Figures 1 and 2 show that, in contrast to the general assumption made in turbomachinery design that the time-averaged circumferential flow rate and the pressure distribution at the diffuser inlet are substantially axisymmetric, the static pressure actually varies around the machine. In regions of high pressure, the velocity may generally be low, and the blade incidence angle may be closer to one extreme value, e.g., a low or high value, depending on, for example, the phase angle. In regions of low pressure, the velocity may generally be high, and the blade incidence angle may be closer to the other extreme value, e.g., a high or low value. Therefore, in regions of high incidence angle at the diffuser inlet due to this distortion, the possibility of early stall may be higher and the losses may be relatively high. The flow fields in these cases may generate high-flow and low-flow regions with different pressures in order to pass an asymmetric impeller flow through a certain number of diffuser passages.

[0018]

[0017] Figure 3 shows the static pressure test data at three flow rates 302, 304, 306 for the same flat-plate diffuser as in Figures 1 and 2, but with the compressor operating at a different speed, here 135,000 RPM. Curve 304 is the lowest flow rate and curve 302 is the highest flow rate. The mean pressure curves 308, 310, and 312 show low-frequency fluctuations similar to those shown in Figure 2, and also show a circumferential shift at the local maxima and minima as the flow rate decreases and the system approaches surge.

[0019] FIG. 4 and FIG. 5 similarly show the time-averaged circumferential distribution of the static pressure at the diffuser inlet for a double-opening angle channel diffuser operably coupled to a centrifugal compressor impeller operating at 100,000 RPM (FIG. 4) and 135,000 RPM (FIG. 5). In FIG. 4, pressure curves 402 and 404 and mean pressure curves 408, 410 show low-frequency circumferential variations having a primary spatial frequency distribution that is less than the spatial frequency distribution of the diffuser channel, as indicated by blade position 406. Unlike FIGS. 1-3, pressure curves 402 and 404 do not have a higher frequency of local maxima equal to the number of blades at position 406 in a sawtooth pattern. Instead, pockets 412 are present in the data, which shift with flow rate. Pocket 412 suggests that an offset or bypass process may be occurring that allows non-uniform flow to enter the fixed diffuser passage, indicating that the performance of the diffuser passage may be degraded, at least in the region of pocket 412. FIG. 5 includes pressure curves 502, 504, 506 and 508 and mean pressure curves 512, 514, 516 and 518 corresponding to four different flow rates, all at 135,000 RPM. As in FIG. 4, pockets 510 appear at each flow rate.

[0020]

[0019] Through extensive testing and analysis of circumferential pressure data for various diffuser types, it has been shown that the low-frequency circumferential pressure distributions shown in FIGS. 1-5 do not originate from the asymmetric flow paths located upstream or downstream of the diffuser. FIG. 6 shows an example of an asymmetric flow path in the form of a volute 600 located downstream of the diffuser 602. It is well known that volutes such as volute 600 introduce asymmetry, i.e., adjacent start of wrap 604 (also referred to as volute tongue 604), into the flow field of a diffuser such as diffuser 602, resulting in, for example, a volute distortion zone 606 extending between position A and position B. In the illustrated example, the volute distortion zone extends from approximately 90 degrees (position "A") upstream of the start of wrap 604 to approximately 45 degrees (position "B") downstream of the start of wrap. FIG. 7 shows the circumferential pressure versus flow rate for a compressor or pump having a volute. As shown in FIG. 7, the volute results in a strong circumferential distortion of the impeller exit pressure at low flow rates due to strong diffusion within the volute under those conditions, which reduces as the flow rate increases and the volute flow regime switches from diffusion to acceleration. Pressure curves 1 and 2 in FIG. 7 are in the volute distortion zone 606 (FIG. 6).

[0021] Various diffuser designs have been developed to improve diffuser performance in machines with asymmetric flow paths such as volutes, attempting to account for the large circumferential distortion brought about by the volute or other asymmetric flow paths. Other examples of such asymmetric flow paths located upstream or downstream of the diffuser include side entrances on the front of the impeller, asymmetric collectors, etc. The low-frequency pressure fluctuations shown in FIGS. 1-5, rather than the localized bulk pressure distortion brought about by asymmetric flow paths such as volutes, spread across the entire circumference of the machine and are an active phenomenon whose position shifts depending on the operating conditions, and exist with or without an asymmetric flow path. This specification discloses various diffusers having a deflector passage designed and configured to improve diffuser performance in consideration of these low-frequency spatial pressure fluctuations. In some embodiments, a deflector passage is provided that is arranged, configured, and dimensioned to deflect the low-frequency circumferential pressure distribution at the diffuser inlet, such as the low-frequency fluctuations shown in FIGS. 1-5, towards circumferential uniformity. In other examples, the deflector passage is designed and configured to improve the performance of a turbomachine, such as by improving the controllability of spatial flow field fluctuations, altering the flow field fluctuations, and improving the performance of the turbomachine in consideration of the flow field fluctuations.

[0022]

[0021] This specification includes various diffuser design variables or features that can be combined in any number of different combinations to develop a diffuser with a deflected passage adapted to a particular performance and flow field. Non-limiting examples of such diffuser design variables or features include, but are not limited to, blade leading edge position, blade trailing edge position, radial distance of the blade from the diffuser centerline, blade chord length, maximum blade thickness, blade height, blade flow direction shape distribution, blade stagger angle, blade wedge angle, channel opening angle, blade pitch, blade inclination, blade twist angle, blade leading edge shape, such as leading edge serrations, swallowtails or scallops, fixed or movable blades, passage height between the hub surface and the shroud surface, circumferential position of the deflected passage, number of deflected passages, and one or more flow direction channels located on one or both of the hub surface and the shroud surface extending upstream and / or downstream of the diffuser passage. One or more diffuser design variables can be adjusted to provide one or more deflected passages having a cross-sectional flow area distribution in a flow direction different from the cross-sectional flow area distribution of a plurality of other diffuser passages in the same blade row for a subset of blades in the diffuser blade row. Combinations of such diffuser design variables can be applied to any type of diffuser, including, for example, diffusers with blades of any type, including flat plates, airfoils, straight channels, cones, single or tandem types, single or multiple blade types per row, and any solidity, and can also be applied to bladeless diffusers.

[0023]

[0022] In yet another example, a diffuser fabricated in accordance with the present disclosure includes a plurality of blade groups, each blade group including two or more blades, each blade having one or more features that are different from the other blades in the group. The groups can be arranged in a periodic arrangement around the machine or in an aperiodic arrangement, thereby providing one or more deflection passages. One or more features that can vary between blades within a blade group include, but are not limited to, blade leading edge position, blade trailing edge position, radial distance of the blade from the diffuser centerline, blade chord length, maximum thickness of the blade, blade height, blade flow direction shape distribution, blade stagger angle, blade skew angle, channel opening angle, blade pitch, blade inclination, blade twist angle, blade leading edge shape, such as leading edge serrations, swallowtail or scalloped, fixed or movable blades, and passage height between the hub surface and the shroud surface. One or more of these features can be varied. Such groups can be designed, configured, and arranged to improve the performance of a turbomachine, such as by improving the controllability of spatial flow field fluctuations, changing the flow field fluctuations, and considering the flow field fluctuations such as the circumferential pressure fluctuations described above to improve the performance of the turbomachine.

[0024]

[0023] Examples of vaneless diffusers with biasing passages include vaneless diffusers having flow direction recesses, such as channels, grooves, or other recesses, located on the hub surface or shroud surface so as to change the passage height at one or more circumferential positions. As will be described further below, examples of elongated recesses include, but are not limited to, flow direction channels having substantially square edges and flow direction grooves having rounded edges. In some examples, the vaneless diffuser can have a non-periodic arrangement of flow direction recesses. The flow direction length of such recesses can vary from the longer recesses that extend into the impeller upstream of the diffuser and downstream of the diffuser to any shorter recesses of any shorter length located at any flow direction position of the diffuser. The biasing passages disclosed herein can have a cross-sectional area that is larger than the cross-sectional area of other passages in the diffuser row. Such passages with an increased flow area can provide a biasing escape passage that can be designed and configured to allow for an asymmetric portion of the impeller exit flow and can result in a more uniform distribution of flow into the other non-biasing passages. In other examples, the biasing passages disclosed herein can have a reduced cross-sectional area compared to the cross-sectional area of other non-biasing passages, including fully closed passages. Thus, the biasing passages with a reduced area as used herein include fully closed passages or the absence of diffuser passages at positions where there would be passages in a fully periodic diffuser passage arrangement. Such biasing passages with a reduced flow area can be designed and configured to relocate or otherwise affect the asymmetric impeller exit flow field, thereby providing a more uniform distribution of flow in the non-biasing passages.

[0025]

[0024] The present disclosure also includes experimental and computational methods for designing the flow structure for a turbomachine to improve performance. In one example, a computational model of the turbomachine and / or diffuser can be developed. The circumferential pressure distribution can be calculated at one or more operating conditions and the performance of the diffuser can be analyzed. In some cases, the low-frequency circumferential variation of the pressure is calculated at the diffuser inlet. The computational model of the diffuser can be iteratively adjusted by adding one or more deflection passages, and the circumferential pressure distribution and diffuser performance can be calculated for each case to identify an optimized deflection passage design. In other examples, instead of calculating the circumferential pressure distribution, a seeded perturbation or other equivalent technique at the diffuser inlet pressure can be applied to the computational model for various diffuser designs to obtain an optimized deflection passage arrangement. In yet other examples, experimental methods for determining the deflection passage design can be implemented, such as instrumenting a test platform with sufficient pressure measurements around the diffuser inlet to fully characterize the primary component of any circumferential pressure variation. The circumferential pressure variations for various diffuser designs can be measured with or without deflection passages, and an improved deflection passage design can be determined.

[0026]

[0025] Figures 8-20 illustrate exemplary embodiments of a bladed diffuser having one or more deflection passages. FIG. 8 shows a portion of an exemplary flat plate low solidity diffuser 800 with blades that extend between a hub 804 and a shroud 806 and extend in the flow direction between a diffuser 808 and an outlet 810. The row 802 of blades includes a plurality of first blades 812 and at least one second blade 814. Although only three are shown, the first blades 812 are equally spaced around one or more portions of the diffuser 800. As shown, the second blade 814 has a different characteristic, here a different height, from the first blade 812, and the second blade 814 is a partial height blade attached to the hub 804. The partial height of the second blade 814 results in a deflection passage 816 having a cross-sectional area distribution different from that of the passage 816 between the first blades 812 in the flow direction. Thus, the diffuser 800 has a plurality of passages located around the diffuser, including at least one periodic section of the passage 816 that extends between the first blades 812, and that section is periodic because the first blades 812 are equally spaced at regular intervals around the diffuser centerline. The diffuser 800 also includes at least one aperiodic section that includes a deflection passage 818, and that section is aperiodic because of a discontinuity in the periodic nature of the first blades 812, here a deflection passage 818 having a cross-sectional flow area larger than that of the passage 816. The exemplary diffuser 800 is designed and configured to receive a flow field having a circumferential pressure distribution, and the deflection passage 816 is arranged, configured, and dimensioned to deflect the circumferential pressure distribution toward circumferential uniformity, e.g., to deflect low frequency spatial pressure fluctuations such as those shown in FIGS. 1-5. The deflection passages can also be arranged, configured, and dimensioned to improve the performance of a turbomachine, such as by improving the controllability of spatial flow field fluctuations, altering the flow field fluctuations, and accounting for the flow field fluctuations to improve the performance of the turbomachine. The diffuser 800 can have one or more of the deflection passages 816 located at any position around the diffuser.FIG. 9 shows a diffuser 900 that is substantially the same as diffuser 800, including a first vane 902 extending between a hub 904 and a shroud 906 and at least one second vane 908, where the second vane is of partial height and provides a deflecting passage. Different from diffuser 800, the second vane 908 is attached to the shroud 906 rather than the hub 904. Alternative embodiments can include a combination of second vanes 814 and 908, for example, a single diffuser with one or more partial height vanes attached to the shroud surface and one or more partial height vanes attached to the hub surface.

[0027]

[0026] FIG. 10 shows an exemplary diffuser 1000 that has a plurality of first vanes 1002 and at least one second vane 1004 with different characteristics, here a radial distance from the centerline 1005 of the diffuser 1000 and a stagger angle, thereby forming a deflecting passage 1006. The dashed line 1008 indicates the location where one of the first vanes 1002 would be located if the periodic nature of the first vanes continued, for example, a periodic first vane position, as in the case of an existing diffuser. The dashed line 1010 indicates that the stagger angle can be varied plus / minus from the stagger angle of the first vanes. Only a portion of the diffuser 1000 is shown, but the diffuser can include one or more deflecting passages 1006. The first vanes 1002 and the second vanes 1004 can all be of full height, or one or both can be of partial height. As shown, an exemplary second vane 1004 retreats along the flow direction compared to the periodic first vane position 1008, such that both the leading edge 1012 and the trailing edge 1014 are at a greater radial distance from the centerline 1005 than the leading edge 1016 and the trailing edge 1018 of the first vanes 1002. The deflecting passage 1006 results in an aperiodic section in the diffuser 1000 in the form that the cross-sectional flow area at the inlet 1020 of the diffuser 1000 is larger.

[0028]

[0027] FIG. 11 shows an exemplary diffuser 1100, which has a plurality of first vanes 1102 and at least one second vane 1104 having a different characteristic, here thickness, thereby forming a deflection passage 1106. Only a part of the diffuser 1100 is shown, but the diffuser can include two or more deflection passages 1106. The first vanes 1102 and the second vanes 1104 can all be of full height, or one or both can be of partial height. As shown, the exemplary second vane 1104 is thinner than the first vane 1102, and as a result, the deflection passage 1106 has a cross-sectional area distribution different from that of the passage 1108, resulting in an aperiodic section in the form of a larger cross-sectional flow area adjacent to the second vane 1104 in the diffuser 1100.

[0029]

[0028] FIG. 12 shows an exemplary diffuser 1200, which is similar to the diffuser 1100 (FIG. 11) and has a plurality of first vanes 1202 and at least one second vane 1204 having a different characteristic, here maximum thickness, thereby forming a deflection passage 1206. Only a part of the diffuser 1200 is shown, but the diffuser can include two or more deflection passages 1206. The first vanes 1202 and the second vanes 1204 can all be of full height, or one or both can be of partial height. As shown, the exemplary second vane 1204 is thicker than the first vane 1202, and as a result, the deflection passage 1206 has a cross-sectional area distribution different from that of the passage 1208, resulting in an aperiodic portion in the form of a larger cross-sectional flow area adjacent to the second vane 1204 in the diffuser 1200.

[0030]

[0029] FIG. 13 shows an exemplary diffuser 1300, which is similar to diffusers 1100 and 1200 (FIGS. 11 and 12), and has a plurality of first vanes 1302 and at least one second vane 1304 having a different characteristic, here chord length, thereby forming a deflection passage 1306. Only a portion of diffuser 1300 is shown, but the diffuser can include two or more deflection passages 1306. The first vanes 1302 and the second vanes 1304 can all be full height, or one or both can be partial height. As shown, the exemplary second vane 1304 is longer than the first vane 1302, such that the deflection passage 1306 has a different flow direction cross-sectional area distribution than passage 1308, resulting in an aperiodic section in diffuser 1300 proximate the second vane 1304. FIG. 14 shows a diffuser 1400 that is substantially the same as diffuser 1300, with equivalent components having the same name and the same reference suffix. Different from diffuser 1300, the second vane 1404 can have a stagger angle different from that of the first vane 1402, as shown by dashed line 1410, showing one possible alternative stagger angle. The specific stagger angle of the second vane 1404 can be varied, including both positive and negative angles with respect to the stagger angle of the first vane 1402.

[0031]

[0030] FIG. 15 shows an exemplary diffuser 1500, which is similar to diffusers 1100-1400 (FIGS. 11-14) and has a plurality of first vanes 1502 and at least one second vane 1504, the second vane 1504 having a different characteristic, here pitch, such that the circumferential spacing between the second vane 1504 and an adjacent vane is different from the spacing between adjacent first vanes 1502, thereby forming deflection passages 1506a and 1506b. Deflection passage 1506a has a cross-sectional area smaller than passage 1508, and deflection passage 1506b has a cross-sectional area larger than passage 1508. Only a portion of diffuser 1500 is shown, but the diffuser can include two or more deflection passages 1506a, 1506b. The first vanes 1502 and the second vanes 1504 can all be full height, or one or both can be partial height. As shown, the exemplary second vane 1504 has the same pitch, shape, and chord length as the first vane 1202 but is arranged at a circumferential position different from the periodic first vane positions, resulting in an aperiodic section, and the diffuser 1500 has a non-uniform and aperiodic circumferential vane pitch distribution.

[0032]

[0031] FIG. 16 shows an exemplary diffuser 1600, which includes a plurality of first vanes 1602 (only two of the twelve are labeled), and two second vanes 1604a, 1604b, each having a different characteristic from the first vanes, here, a maximum thickness and chord length, which results in deflection passages 1606a and 1606b. The second vane 1604a has the same thickness as the first vane 1602 but a longer chord length, and as a result, the deflection passage 1606a has a different flow direction cross-sectional area distribution from the passage 1608. The second vane 1604b has a greater thickness than the first vane 1602, and as a result, the deflection passage 1606b has a different flow direction cross-sectional area distribution from the passage 1608, including a smaller cross-sectional area than the passage 1608. The first vanes 1602 and the second vanes 1604a, 1604b can all be of full height or one or more can be of partial height. As shown, the deflection passages 1606a, 1606b associated with the second vanes 1604a, 1604b are approximately 180 degrees apart around the diffuser 1600. The first vanes 1602 are equally spaced from adjacent first vanes, providing two periodic sections 1610, and the second vanes 1604a, 1604b result in two aperiodic sections 1612.

[0033]

[0032] FIG. 17 shows an exemplary diffuser 1700, which has a plurality of first vanes 1702 (only two of the seven are labeled) and a plurality of second vanes 1704 (only two of the seven are labeled), each having a different characteristic than the first vanes 1702, here chord length. Unlike diffuser 1600, diffuser 1700 has an equal number of first vanes 1702 and second vanes 1704 and a completely periodic arrangement of passages 1706a, 1706b. All of the first vanes 1702 and second vanes 1704 can be full height, or one or more can be partial height. The first vanes 1702 and second vanes 1704 are arranged in vane groups, here two vanes per group, where diffuser 1700 has a periodic arrangement of a plurality of vane groups, and each vane group includes first vanes 1702 and second vanes 1704, each having a different characteristic than the other vanes in the group. FIG. 18 shows a diffuser 1800 that is substantially the same as diffuser 1700, which includes a plurality of first vanes 1802 (only two of the seven are labeled) and a plurality of second vanes 1804 (only two of the seven are labeled), each having a different characteristic than the first vanes 1802, here chord length. Unlike diffuser 1700, each of the second vanes 1804 also has a different flow direction position than the first vanes 1802, and the position of the leading edge 1812 is at a different, here greater, radial distance from the diffuser centerline 1814 than the radial distance of the first vane leading edge 1816 from the diffuser centerline. For example, each of the second vanes 1804 is recessed in the flow direction compared to the periodic first vane positions. Similar to diffuser 1700, diffuser 1800 includes first vanes 1802 and second vanes 1804, which are arranged in a plurality of vane groups, here two vanes per group, and diffuser 1800 has a periodic arrangement of a plurality of vane groups. In other examples, one or more characteristics of one or more of the first vanes 1702, 1802 and / or the second vanes 1704, 1804 can be changed to provide one or more aperiodic sections having a deflected passage configured to address an asymmetric pressure field, such as the asymmetric pressure fields shown in FIGS. 1-5.One or more features can include any of the features described herein, such as blade height, stagger angle, pitch, blade shape, blade leading edge position and trailing edge position, and chord length, etc.

[0034]

[0033] FIG. 19 shows an exemplary diffuser 1900, which has a plurality of first blades 1902 (only two of seven are labeled) and a plurality of second blades 1904 (only two of seven are labeled), each having a different feature from the first blades 1902, here chord length and stagger angle. The diffuser 1900 has an equal number of first blades 1902 and second blades 1904 and a completely periodic arrangement of passages 1906a, 1906b when all the second blades 1904 are at the same stagger angle. The first blades 1902 and the second blades 1904 can all be of full height or one or more can be of partial height. The first blades 1902 and the second blades 1904 are arranged in blade groups, here two blades per group, and the diffuser 1900 has a periodic arrangement of a plurality of blade groups. As shown by the dashed line 1910, the stagger angle of the second blades 1904 can be the same as that of the first blades 1902 or can be changed in a positive or negative direction from the stagger angle of the first blades. In some embodiments, the stagger angle of the second blades 1904 can be changed and arranged to form an aperiodic arrangement with one or more deflection passages. For example, all but one of the second blades 1904 can have the same stagger angle as the first blades 1902, and one of the second blades can have a different stagger angle, thereby providing two deflection passages on both sides of the full-height second blade with the changed angle. In other examples, the stagger angles of other numbers of the second blades 1904 can be changed.

[0035]

[0034] FIG. 20 shows an exemplary diffuser 2000, which is substantially the same as diffuser 1900, and equivalent components have the same name and the same reference suffix. Unlike diffuser 1900, where the stagger angle of the second blade 1904 can be changed, in diffuser 2000, as shown by dashed line 2010, the stagger angle of the first blade 2002 can be changed. Similar to diffuser 1900, the stagger angle of some but not all of the first blades 2002 can be different from that of the other first blades, thereby providing a non-periodic arrangement and one or more deflection passages. The first blades 2002 and the second blades 2004 are arranged in blade groups, here two blades per group, and diffuser 2000 has a periodic arrangement of multiple blade groups. In other examples, features of diffusers 1900 and 2000 can be combined, such as changing the stagger angle of selected ones of both the first and second blades, or a subset of the first blades 1902, 2002 or a subset of the second blades 1904, 2004.

[0036]

[0035] In another embodiment, an exemplary diffuser can include a plurality of blade groups, where each blade in a group has a different height. For example, a blade group can include two partial-height blades, such as a first partial-height blade attached to the hub surface or shroud surface and a second adjacent partial-height blade attached to the hub surface or shroud surface. The diffuser can include a periodic arrangement of such groups. For example, in one instance, the first partial-height blades and the second partial-height blades can all be equally spaced around the machine. In one example, the first partial-height blade can have a different height than the second partial-height blade. For example, the first partial-height blade can have a height of approximately 15% to approximately 65% of the passage height, and in some examples approximately 50% of the passage height. The second partial-height blade can have a height of approximately 5% to approximately 45% of the passage height, and in some examples approximately 15% of the passage height. In one example, the first partial-height blade and the second partial-height blade in each blade group can be attached to opposite sides of the passage. For example, the first partial-height blade can be attached to the shroud, and the second partial-height blade can be attached to the hub. Such partial-height blade groups can reduce leading-edge metal blockage and increase the flow area, particularly enabling the reorganization of the flow near the choke, thereby improving performance. In still other examples, a blade group can include three or more blades, and such blade groups are repeated at the outer periphery of the diffuser. In still other examples, by arranging such blade groups adjacent to the periodic section, one or more deflected passages can be formed. For example, in a diffuser with 14 blades, instead of 2 to 12 of the 14 blades at one or more circumferential positions, two blade groups including a first partial-height blade and a second partial-height blade can be used to provide one or more deflected passages.

[0037]

[0036] FIG. 21 shows a channel-type diffuser 2100 according to the prior art, and FIGS. 22 to 33 show exemplary embodiments of a channel-type diffuser fabricated according to the present disclosure. As shown in FIG. 21, the prior art channel-type diffuser 2100 includes a plurality of vanes 2102 (only one is labeled) that define a passageway 2104 (only one is labeled) in the form of a channel. The diffuser 2100 is similar to the diffuser used to generate the test data shown in FIGS. 4 and 5. The diffuser 2100 is completely periodic and symmetric, each of the vanes 2102 has the same stagger angle S and wedge angle W, and each passageway 2104 has the same opening angle D.

[0038]

[0037] FIG. 22 shows an exemplary channel diffuser 2200 having a plurality of passages 2202 (only one labeled) extending between first vanes 2204 (only one labeled). However, unlike the diffuser 2100 of the prior art, each passage 2202 also includes a second vane 2206 located between adjacent first vanes 2204. Exemplary second vanes 2206 are flat plates, each having a leading edge 2208 downstream from the diffuser inlet 2210 and a trailing edge 2212 disposed upstream of the diffuser outlet 2214. The second vanes 2206 are full height. In other examples, one or more of the first vanes 2204 and / or the second vanes 2206 may be partial height. In the illustrated example, the second vanes 2206 have a chord length shorter than the length of the passages 2202 and are substantially centered within the passages in both the circumferential and flow directions. The first vanes 2204 and the second vanes 2206 are arranged in vane groups, here two vanes per group, and the diffuser 2200 has a periodic arrangement of multiple vane groups. The exemplary passages 2202 are periodic, but one or more features of one or more of the first vanes 2204 and / or the second vanes 2206 can be modified to provide one or more deflected passages. Modifying one or more features of one or more of the first vanes 2204 and / or the second vanes 2206 can provide one or more asymmetric sections having deflected passages configured to address an asymmetric pressure field, such as the asymmetric pressure fields shown in FIGS. 1-5. One or more features can include, for example, any of the features described herein such as vane height, stagger angle, pitch, vane shape, vane leading edge position and trailing edge position, and chord length. For example, the second vanes 2206 can be of any type including airfoils and need not all be centered within the passages 2202, i.e., at least one can be repositioned or sized to provide a deflected passage including a partial height design.

[0039]

[0038] Figure 23 shows an exemplary channel diffuser 2300, which is similar to the channel diffuser 2200, and equivalent components have the same name and the same suffix number. The diffuser 2300 includes a plurality of passages 2302 (only one is labeled) that extend between first vanes 2304 (only one is labeled). Each passage 2302 also includes second vanes 2306 that are located between adjacent first vanes 2304. An exemplary second vane 2306 is a flat plate. Compared with the second vane 2206 (FIG. 22), the second vane 2306 is narrower and positioned more upstream. In this example, the leading edge 2308 is located at the diffuser inlet 2310, and the trailing edge 2312 is located further upstream of the diffuser 2314. The second vane 2306 is of full height. In other examples, one or more of the first vanes 2304 and / or the second vanes 2306 may be of partial height. In the illustrated example, the second vane 2306 has a chord length that is shorter than the length of the passage 2302, is substantially centered in the passage in the circumferential direction, and is located upstream of the midpoint of the passage 2302 in the flow direction. The first vanes 2304 and the second vanes 2306 are arranged in vane groups, here two vanes per group, and the diffuser 2300 has a periodic arrangement of a plurality of vane groups. The exemplary passage 2302 is periodic, but one or more features of one or more of the first vanes 2304 and / or the second vanes 2306 can be changed to provide one or more deflected passages. One or more features of one or more of the first vanes 2304 and / or the second vanes 2306 can be changed to provide one or more asymmetric sections having deflected passages configured to address an asymmetric pressure field, such as the asymmetric pressure fields shown in FIGS. 1-5 here. Examples of one or more features include any of the features described herein, such as vane height, stagger angle, pitch, vane shape, vane leading edge position and trailing edge position, and chord length. For example, the second vane 2306 can be of any type including an airfoil, and not all need to be centered in the passage 2302, i.e., at least one can be repositioned or sized to provide a deflected passage including a partial height design.

[0040]

[0039] Figure 24 shows an exemplary channel diffuser 2400, which is the same as the prior art diffuser 2100 (Figure 21), but differs in that it includes a plurality of first vanes 2402 and one second vane 2404 having a feature different from the first vanes 2402, here a wedge angle. In the exemplary example, the diffuser 2400 includes a single second vane 2404 disposed at the periodic positions of the first vanes 2402 or at the locations where the first vanes 2402 were disposed in the prior art arrangement. The second vane 2404 has a wedge angle W2 that is smaller than the wedge angle W1 of the first vanes 2402. The smaller wedge angle W2 of the second vane 2404 results in two deflection passages 2406. The diffuser 2400 includes a periodic section 2408 of the first vanes 2402 and associated passages 2410 and an aperiodic section 2412 that includes the two deflection passages 2406. In other examples, one or more additional first vanes 2402 can be replaced with second vanes 2404 that can have one or more features different from the first vanes 2402, thereby resulting in one or more additional deflection passages.

[0041]

[0040] FIG. 25 shows an exemplary channel diffuser 2500, which is similar to diffuser 2400 (FIG. 24), and equivalent components have the same name and the same suffix numbers. Diffuser 2500 includes a plurality of first vanes 2502 and one second vane 2504 that has a different feature than the first vanes 2502, here a wedge angle. Different from diffuser 2400, second vane 2504 has a larger wedge angle than first vanes 2502. In the illustrated example, diffuser 2500 includes a single second vane 2504 disposed at the periodic positions of first vanes 2502 or where first vanes 2502 were disposed in the prior art arrangement. Second vane 2504 has a wedge angle W2 that is larger than the wedge angle W1 of first vanes 2502. The larger wedge angle W2 of second vane 2404 results in two deflection passages 2506 having a smaller cross-sectional area than passage 2510. Diffuser 2500 includes a periodic section 2508 of first vanes 2502 and associated passage 2510 and an aperiodic section 2512 that includes two deflection passages 2506. In other examples, one or more additional first vanes 2502 can be replaced with second vanes 2504 that can have one or more features different from first vanes 2502, thereby resulting in one or more additional deflection passages.

[0042]

[0041] FIG. 26 shows an exemplary channel diffuser 2600, which is similar to diffusers 2400 (FIG. 24) and 2500 (FIG. 25), and equivalent components have the same name and the same suffix numbers. The diffuser 2600 includes a plurality of first vanes 2602 and one second vane 2604 having a feature different from the first vanes 2602, here a chord length. In the illustrated example, the diffuser 2600 includes a single second vane 2604 disposed at the periodic positions of the first vanes 2602 or at the locations where the first vanes 2602 were disposed in the prior art arrangement. The longer second vane 2604 results in two deflected passages 2606 having a flow direction cross-sectional area distribution different from that of the passage 2610, whereby the trailing edge of the second vane 2604 acts as an additional flow guide at the diffuser outlet to reduce losses at the diffuser outlet. The diffuser 2600 includes a periodic section 2608 of the first vanes 2602 and the associated passage 2610 and an aperiodic section 2612 including the two deflected passages 2606. In other examples, one or more additional first vanes 2602 can be replaced with second vanes 2604 having one or more features different from the first vanes 2602, thereby providing one or more additional deflected passages.

[0043]

[0042] Figure 27 shows an exemplary channel diffuser 2700, which is similar to diffusers 2400 (FIG. 24), 2500 (FIG. 25), and 2600 (FIG. 26), and equivalent components have the same name and the same suffix number. The diffuser 2700 includes a plurality of first vanes 2702 and one second vane 2704 that has a different characteristic than the first vanes 2702, here a vane stagger angle, which results in a different passage opening angle. In the illustrated example, the diffuser 2700 includes a single second vane 2704 disposed approximately where the first vanes 2702 were disposed in a prior art arrangement. As indicated by the dashed line, the stagger angle of the second vane 2704 can be changed in the plus / minus direction with respect to the stagger angle of the first vanes 2702, which results in two deflected passages 2706 having a flow direction cross-sectional area distribution different from that of the passage 2710. The diffuser 2700 includes a periodic section 2708 of the first vanes 2702 and the associated passage 2710 and an aperiodic section 2712 that includes the two deflected passages 2706. In other examples, one or more additional first vanes 2702 can be replaced with second vanes 2704 that can have one or more characteristics different from the first vanes 2702, thereby resulting in one or more additional deflected passages.

[0044]

[0043] FIG. 28 shows an exemplary channel diffuser 2800, which is similar to diffusers 2400 (FIG. 24), 2500 (FIG. 25), 2600 (FIG. 26), and 2700 (FIG. 27), and equivalent components have the same name and the same suffix numbers. The diffuser 2800 includes a plurality of first vanes 2802 and one second vane 2804 having a different characteristic than the first vanes 2802, here a vane pitch, thereby changing the vane circumferential position and spacing. In the illustrated example, the diffuser 2800 includes a single second vane 2804 in place of one of the first vanes 2802. As shown, the pitch of the second vane 2804 is different from the pitch of the first vanes 2802, resulting in two deflected passages 2806a, 2806b having a different flow direction cross-sectional area distribution than the passage 2810. The diffuser 2800 includes a periodic section 2808 of the first vanes 2802 and associated passage 2810 and an aperiodic section 2812 including the two deflected passages 2806a, 2806b. In other examples, one or more additional first vanes 2802 can be replaced with second vanes 2804 having one or more characteristics different from the first vanes 2802, thereby providing one or more additional deflected passages.

[0045]

[0044] Figure 29 shows an exemplary diffuser 2900 that combines the features of diffusers 2500 (Figure 25) and 2600 (Figure 26). As shown, diffuser 2900 includes a plurality of first vanes 2902 and two second vanes 2904a, 2904b, each having a feature different from that of the first vanes 2902. Second vane 2904a has a chord length larger than that of first vane 2902, and second vane 2904b has a wedge angle W2 larger than the wedge angle W1 of first vane 2902, resulting in deflected passages 2906a and 2906b having a flow direction cross-sectional area distribution different from that of passage 2910. Diffuser 2900 includes periodic sections 2908a, 2908b of first vanes 2902 and associated passage 2910, and aperiodic sections 2912a, 2912b each including deflected passages 2906a, 2906b. In other examples, one or more additional first vanes 2902 can be replaced with second vanes 2904 having one or more features different from those of first vanes 2902, thereby providing one or more additional deflected passages.

[0046]

[0045] Figure 30 shows an exemplary channel diffuser 3000, which has a plurality of first vanes 3002 (only one is labeled) and a plurality of second vanes 3004 (only one is labeled), and each of the second vanes has a feature different from that of the first vane 3002, here the chord length. The diffuser 3000 has an equal number of first vanes 3002 and second vanes 3004 and a completely periodic arrangement of passages 3006a, 3006b. Similar to any of the channel diffusers disclosed herein, all of the first vanes 3002 and second vanes 3004 can be at the same height, or one or more can be at a partial height. Figure 31 shows a diffuser 3100 similar to the diffuser 3000, which includes a plurality of first vanes 3102 (only one is labeled) and a plurality of second vanes 3104 (only one is labeled), and each of the second vanes has a feature different from that of the first vane 3102, here the chord length and the flow direction position. Each of the second vanes 3104 has a flow direction position different from that of the first vane 3102, and the position of the leading edge 3112 is a radial distance from the diffuser centerline 3114 different from the radial distance of the first vane leading edge 3116 from the diffuser centerline, here a greater distance. For example, each of the second vanes 3104 is recessed in the flow direction compared to the periodic first vane positions. One or more features of the first vanes 3002, 3102 and / or the second vanes 3004, 3104 can be changed to provide one or more aperiodic sections having a deflected passage configured to address an asymmetric pressure field, such as the asymmetric pressure fields shown in FIGS. 1-5. One or more features can include any of the features described herein, such as vane height, stagger angle, pitch, vane shape, vane leading edge position and trailing edge position, and chord length, etc.

[0047]

[0046] FIG. 32 shows an exemplary channel diffuser 3200, which is substantially the same as diffuser 3000 (FIG. 30), and equivalent components have the same name and the same suffix numbers. Different from diffuser 3000 where the wedge angles, blade stagger angles, and channel opening angles of the first blade 3002 and the second blade 3004 are the same, the stagger angle of the first blade 3202 and the associated channel opening angle of the adjacent passage 3206 can be changed in either direction from the stagger angle of the second blade 3204. In some examples, the stagger angle of some of the first blades 3202, except for some of them, can be made different from that of the other first blades, thereby resulting in an asymmetric arrangement and one or more modified passages 3206. FIG. 33 shows a diffuser 3300, which is substantially the same as diffuser 3200, but differs in that instead of changing the stagger angle of the first blade 3302, the stagger angle of one or more of the second blades 3304 and the associated channel opening angle of the adjacent passage 3306 can be changed. In some examples, the stagger angle of some of the second blades 3304, except for some of them, is changed, and as a result, diffuser 3300 can have one or more aperiodic sections having one or more deflected passages. In other examples, any one or more of the blade feature deformations shown in FIGS. 22 to 33 can be combined in any combination.

[0048]

[0047] FIG. 34 is an isometric view of a turbomachine 3400 including an impeller 3402 and a vaneless diffuser 3404. The diffuser 3404 extends between a shroud 3406 and a hub 3407. The shroud 3406 extends from an impeller inlet 3408 across an impeller outlet / diffuser inlet 3410 to a diffuser outlet 3412. FIGS. 35 and 36 are further views of the shroud 3406 and the hub 3407. As shown in FIGS. 35 and 36, an exemplary shroud 3406 includes a plurality of flow direction grooves 3502 (only one is labeled), which extend in the flow direction from a location upstream of the diffuser inlet and an adjacent impeller 3402 to a location downstream of the diffuser inlet, in this example to the diffuser outlet 3412 (FIG. 34). The flow direction grooves 3502 are located on the surface of the shroud 3406, have rounded edges 3504, and provide a circumferential profile that approximates a periodic waveform to the shroud wall. The exemplary grooves 3502 can be designed and configured to guide a portion of the fluid flow within the impeller 3402 into the diffuser 3404 at a preferred angle, thereby improving the performance of the turbomachine 3400. FIGS. 37-39 show a turbomachine 3700, which is substantially the same as the turbomachine 3400 and equivalent components have the same name and the same suffix numbers. Unlike the turbomachine 3400, the turbomachine 3700 has flow direction grooves 3802 that are spaced closer together than the flow direction grooves 3502 (FIG. 35), and the edges 3804 of adjacent grooves 3802 are substantially in contact in the leading edge region of the grooves.

[0049]

[0048] Figures 40 - 42 illustrate an exemplary turbomachine 4000, which has the same impeller 3402 and shroud 3406 as the turbomachine 3400 (Figs. 34 - 36), but, as best shown in Fig. 42, also has an alternative hub 4002 with flow direction grooves that, in this example, extend in the flow direction from the diffuser inlet 4204 to the diffuser outlet 4206. In the illustrated example, the diffuser 4004 has the same number of grooves 4202 as the grooves 3502 in the shroud 3406 and, similarly, has grooves with rounded edges 4208. The grooves 4202 are circumferentially aligned with the grooves 3502. Similar to the grooves 3502, the hub - side grooves 4202 can be designed and configured to guide a portion of the working fluid in a preferred direction so as to improve the performance of the diffuser 4004. Figs. 43 and 44 illustrate a configuration different from Figs. 40 - 42, where the circumferential position of the hub - side grooves 4202 has been shifted clockwise relative to the shroud - side grooves 3502. In this example, each of the hub - side grooves 4202 is aligned with the mid - point between adjacent shroud - side grooves 3502. In other examples, any other relative circumferential positioning can be used.

[0050]

[0049] Figs. 45 and 46 illustrate an exemplary shroud 4502 and hub 4504, each having flow direction grooves 4506 and 4508, respectively. Different from the embodiments shown in Figs. 40 - 44, the shroud 4502 and hub 4504 also include diverging passages 4510, 4512 in the form of enlarged flow direction grooves having a cross - sectional area larger than the grooves 4506, 4508. Such diverging passages can be arranged, configured, and dimensioned to deflect the circumferential pressure distribution towards circumferential uniformity and / or to provide other performance improvements described herein. In other examples, one or both of the shroud 4502 and hub 4504 can have additional diverging flow direction grooves, or one or more diverging flow direction grooves can be located in only the shroud or only the hub. The examples shown in Figs. 45 and 46 include a periodic portion of the passage in the form of the flow direction grooves and, in the illustrated example, an aperiodic portion having one diverging passage.

[0051]

[0050] FIG. 47 is a cross-sectional elevation view of a defuser passage 4702 disposed between passages 4704. The defuser passage 4702 has an increased passage height H1 from a recess 4706 located within a shroud 4708 and a recess 4710 located within a shroud 4712. The recesses 4706 and 4710 may be similar in shape and position to the grooves 3502 (FIG. 35), 4202 (FIG. 42), or may have other configurations, such as different leading and / or trailing edge positions, widths, flow direction lengths, etc. For example, in some embodiments, the recesses 4706 and 4710 may have a trailing edge located at the diffuser inlet. In the example shown in FIG. 47, only one of the recesses 4706, 4710 is located within the hub and shrouds 4708, 4712, thereby providing an aperiodic portion having a defuser passage with a larger cross-sectional area than the other passages of the diffuser 4700. In other examples, a plurality of diffuser passages may have an increased height from one or more recesses located within the hub and / or shroud.

[0052]

[0051] FIG. 48 is an isometric view of a turbomachine 4800 including an impeller 4802 and a vaneless diffuser 4804. The diffuser 4804 extends between a shroud 4806 and a hub 4807. The shroud 4806 extends from an impeller inlet 4808 across an impeller outlet / diffuser inlet 4810 to a diffuser outlet 4812. FIG. 49 is a further view of the shroud 4806 and the hub 4807. As shown in FIGS. 48 and 49, exemplary shrouds 4806 and hubs 4807 each include a plurality of flow direction channels 4820, 4822 (only one of each is labeled) that extend in the flow direction. Channels 4820, 4822 are all elongated recesses in the flow direction, similar to the flow direction grooves 3502 (FIG. 35), 3802 (FIG. 38), 4202 (FIG. 42). Channels 4820 and 4822 differ from grooves 3502, 3802, 4202 in the cross-sectional shape of the recesses, with the channels having a substantially square edge 4902 (FIG. 49) and the grooves having a rounded edge 3504 (FIG. 35). The shroud surface channels 4820 extend from a position upstream of the diffuser inlet 4810 and the adjacent impeller 4802 to a position downstream of the diffuser inlet, to the diffuser outlet 4812 in this example. The hub surface channels 4822 extend across the entire length of the hub 4807 from the diffuser inlet 4810 to the diffuser outlet 4812. The flow direction channels 4820 are located on the surface of the shroud 4806, have a substantially square edge 4902, and provide a peripheral contour that approximates a periodic square waveform with respect to the shroud wall. Similarly, the flow direction channels 4822 are located on the surface of the hub 4807, have a substantially square edge 4904, and provide a peripheral contour that approximates a periodic square waveform with respect to the hub wall. Exemplary channels 4820 and 4822 can be designed and configured to guide a portion of the fluid flow within the impeller 4802 into the diffuser 4804 at a preferred angle, thereby improving the performance of the turbomachine 4800. In other embodiments, one or both of the features of channels 4820, 4822, such as channel depth, width, and number, can be changed.In the example shown in FIGS. 48 and 49, channels 4820 and 4822 are circumferentially aligned, but in other examples, the relative position can be moved clockwise so that the hub channel and the shroud channel are not aligned.

[0053]

[0052] FIGS. 50 and 51 show an alternative diffuser 5000, which is similar to diffuser 4804 (FIG. 48) and includes a hub 5002 and a shroud 5004 having a hub flow direction channel 5006 and a shroud flow direction channel 5008. Unlike diffuser 4804, one of each of channels 5006 and 5008 has a feature different from the other channels 5006, 5008, where each of channels 5006a and 5008a has an enlarged depth, thereby providing a deflection passage. In other examples, the features of only the hub channel 5006 or only the shroud channel 5008 can be changed from the others of the hub channel and the shroud channel to provide a deflection passage. In some examples, features other than depth can be changed, such as cross-sectional shape (e.g., groove vs. channel), width, length, leading edge position, and trailing edge position. In some examples, two or more of hub channel 5006 and / or shroud channel 5008 can be changed to provide a larger aperiodic section having two or more deflection passages, or two or more aperiodic sections. In still other examples, the diffuser fabricated in accordance with the present disclosure can have fewer flow direction recesses arranged at selected circumferential positions rather than a plurality of flow direction recesses equally spaced around the entire circumference of the machine. For example, the diffuser fabricated in accordance with the present disclosure can have only one, two, three, etc. flow direction recesses arranged at selected positions around the circumference of the machine.

[0054]

[0053] FIGS. 52 and 53 show an exemplary bladed diffuser 5200 having a shroud 5202 and a hub 5204, the shroud extending from an impeller inlet 5206 across a diffuser inlet 5208 to a diffuser outlet 5210. The shroud 5202 includes flow direction channels 5212 that extend to positions upstream and downstream of the diffuser inlet 5208 and are separated by an upper leg 5214 of a leading edge 5216 of a blade 5218. In the example shown, the leading edge 5216 has a scalloped shape, also referred to herein as a swallowtail shape. In the example shown, the hub 5204 does not include any flow direction recesses. In other examples, the hub 5204 can include flow direction recesses, such as channels or grooves.

[0055]

[0054] As shown in FIGS. 52 and 53, the deflector channel 5212a has features that are different from the other channels 5212, here a leading edge position 5220 that is further upstream than the leading edge position 5222 of the channel 5212 (best shown in FIG. 52) and a depth that is greater than the depth of the channel 5212 (best shown in FIG. 53). The deflector channel 5212a provides a deflector passage in an aperiodic section of the diffuser 5200.

[0056] [

[0055] ]The above has been a detailed description of exemplary embodiments of the present invention. In this specification and the appended claims, conjunctive language such as "at least one of X, Y, and Z" and "one or more of X, Y, and Z" is to be interpreted, unless otherwise specifically stated or indicated, as each item in the conjunctive list can be present in any number, excluding all other items in the list, or in any number in combination with any or all other items in the conjunctive list (any or all other items can also be present in any number). Applying this general rule, the conjunctive language in the above example where the conjunctive list consists of X, Y, and Z shall each include one or more of X, one or more of Y, one or more of Z, one or more of X and one or more of Y, one or more of Y and one or more of Z, one or more of X and one or more of Z, and one or more of X, one or more of Y, and one or more of Z.

[0057] [

[0056] ]Without departing from the spirit and scope of the present invention, various changes and additions can be made. Each feature of the various embodiments described above can, if necessary, be combined with the features of other described embodiments to provide various combinations of features in related new embodiments. Further, although the above describes a plurality of separate embodiments, what is described herein is merely illustrative of the application of the principles of the present invention. Additionally, although a particular method in this specification may be illustrated and / or described as being performed in a given order, this ordering is highly variable within the ordinary techniques for achieving the aspects of this disclosure. Accordingly, this description is not intended to limit the scope of the present invention in any other way, but is intended to be construed merely as an example.

[0058] Exemplary embodiments have been disclosed above and are shown in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions can be made to what is specifically disclosed herein without departing from the spirit and scope of the present invention.

Claims

1. A diffuser, comprising: an inlet, a hub and a shroud; and a row of blades including a plurality of blade groups, each blade group including a first partial-height blade attached to one of the hub and the shroud, and a second partial-height blade spaced circumferentially from the first partial-height blade and attached to the other of the hub and the shroud; the first partial-height blade having a first height greater than 55% of the passage height of the diffuser and at most 65%; the second partial-height blade having a second height greater than 35% of the passage height and at most 45%; the first and second heights being selected such that the sum of the first and second heights is greater than the passage height to form an overlap in the spanwise direction extending between the hub and the shroud.

2. The diffuser according to claim 1, wherein at least some of the blades in the row have different stagger angles from each other.

3. The diffuser according to claim 1, wherein the row of blades includes at least one full-height blade.

4. The diffuser according to claim 1, wherein each of the first and second partial-height blades has a leading edge, and the leading edges of the first and second partial-height blades are aligned in the flow direction.

5. The diffuser according to claim 1, wherein the diffuser has an inlet, and at least one of the first and second partial-height blades is located at the inlet.

6. The diffuser according to claim 1, wherein the first partial-height blade is attached to the hub and is the most upstream blade, and the first height is greater than or equal to the height of all partial-height blades attached to the hub.

7. The diffuser according to claim 1, comprising a plurality of the first partial-height blades, the plurality of the first partial-height blades being the only partial-height blades attached to the hub, and the first partial-height blades having leading edges aligned in the flow direction.

8. The diffuser according to claim 1, comprising a plurality of said first partial height blades and a plurality of said second partial height blades, the rows of blades defining a plurality of passages, each passage extending in the spanwise direction between said hub and said shroud and having a height extending circumferentially between adjacent blades of said first partial height blades and said second partial height blades, the plurality of passages including at least one skewed passage, the spanwise height of said at least one skewed passage being greater than the spanwise height of the other passages of the plurality of passages.

9. The diffuser according to claim 1, comprising a plurality of said first partial height blades and a plurality of said second partial height blades, said first and second partial height blades being positioned in an alternating and repeating spatial arrangement.

10. The diffuser according to claim 1, wherein the diffuser is a single row diffuser and the row of blades is the only row of blades in the diffuser.

11. The diffuser according to claim 1, wherein the hub includes a hub surface, the shroud includes a shroud surface, and the diffuser includes at least one elongated flow direction recess located on at least one of the hub surface and the shroud surface.

12. The diffuser according to claim 11, wherein the at least one elongated flow direction recess includes a plurality of elongated flow direction recesses having an aperiodic arrangement around the perimeter of the diffuser.

13. The diffuser according to claim 1, comprising a plurality of said first partial height blades and a plurality of said second partial height blades, the plurality of said first and second partial height blades being stationary and having a space fixed between adjacent blades of said first partial height blades and said second partial height blades.

14. The diffuser according to claim 1, wherein the row of blades is a first row of vanes positioned downstream of the inlet of the diffuser.

15. The diffuser according to claim 1, comprising a plurality of said first partial height vanes and a plurality of said second partial height vanes, wherein the row of vanes includes at least one aperiodic section, and the at least one aperiodic section includes at least one skewed passage defined by at least one vane having characteristics different from those of the first and second partial height vanes.

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