Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/40—Casings; Connections of working fluid
  • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
  • F04D29/44—Fluid-guiding means, e.g. diffusers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/40—Casings; Connections of working fluid
  • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
  • F04D29/44—Fluid-guiding means, e.g. diffusers
  • F04D29/441—Fluid-guiding means, e.g. diffusers especially adapted for elastic fluid pumps
  • F04D29/444—Bladed diffusers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/18—Rotors
  • F04D29/22—Rotors specially for centrifugal pumps
  • F04D29/24—Vanes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
  • F04D29/661—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
  • F04D29/666—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps by means of rotor construction or layout, e.g. unequal distribution of blades or vanes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2250/00—Geometry
  • F05D2250/50—Inlet or outlet
  • F05D2250/52—Outlet

Definitions

• Centrifugal compressors may be employed to provide a pressurized flow of fluid for various applications.
• Such compressors typically include an impeller that is driven to rotate by an electric motor, an internal combustion engine, or another drive unit configured to provide a rotational output.
• the impeller rotates, fluid entering in an axial direction is accelerated and expelled in a circumferential and a radial direction.
• the high-velocity fluid then crosses a diffuser, which converts the velocity head of the fluid into a pressure head (i.e., decreases flow velocity and increases flow pressure).
• the volute or scroll then collects the radially outward flow and directs it into a pipe. In this manner, the centrifugal compressor produces a high-pressure fluid output.
• the overall stage efficiency is a product of how effectively these three components (e.g., the impeller, the diffuser, and the volute or scroll) individually perform as well as how they function together.
• FIG. 1 is an axial view of an exemplary embodiment of a centrifugal compressor stage having an impeller, a non-periodic diffuser, and a scroll;
• FIG. 2 is a perspective view of an exemplary embodiment of a centrifugal compressor stage having an impeller, a non-periodic diffuser, and a scroll;
• FIG. 3 is a perspective view of the impeller and the non-periodic diffuser of the centrifugal compressor stage of FIGS. 1 and 2;
• FIG. 4 is a perspective view of the impeller of FIGS. 1 through 3;
• FIG. 5 is a side view of the impeller of FIGS. 1 through 3;
• FIG. 6 is a perspective view of the non-periodic diffuser of FIGS. 1 through 3;
• FIG. 7 is a perspective view of a periodic diffuser
• FIG. 8 is a partial perspective view of the periodic diffuser taken along line 8-8 of FIG. 7;
• FIG. 9 is an axial view of the non-periodic diffuser of FIGS. 1 through 3 and FIG. 6;
• FIG. 10 is a flow chart of a method for deriving geometries and orientations of a plurality of diffuser vanes arranged in an asymmetrical (e.g., non-periodic) pattern around the mounting surface of the non-periodic diffuser.
• asymmetrical e.g., non-periodic
• Embodiments of the present disclosure include enhancements in the design of radial diffusers (e.g., diffusers used in centrifugal compressor systems).
• the disclosed embodiments match the diffuser with an associated impeller and scroll or volute.
• Diffusers in centrifugal compressor systems serve a number of purposes.
• One of the primary functions of a diffuser is to diffuse (e.g., slow down) compressed gas as it passes from an exit of the impeller to the scroll or volute. Exactly how this is accomplished may have a significant impact on the loss in isentropic efficiency of the overall compressor stage.
• diffuser design was based on a prediction of average flow conditions exiting the impeller. It was further assumed that there were no circumferential pressure distortions imposed by the scroll and no localized pressure distortions caused by the volute tongue. These assumptions are equivalent to assuming that the flow leaving the diffuser enters a dump collector or a vaneless return channel of a classical in-line compressor. In other words, a uniform circumferential pressure distribution at the exit of the diffuser was assumed. This assumption results in a diffuser design that is periodic (e.g., circumferentially symmetric).
• the diffuser vanes are arranged in an asymmetrical (e.g., non-periodic) pattern in a circumferential direction around a mounting surface (e.g., a hub, in this particular case) of the diffuser. Due at least in part to the presence of the scroll or volute, the pressure distribution of the fluid being compressed varies at different circumferential locations around the mounting surface. Taking this varying pressure distribution into consideration, the shape, orientation, and/or location of the diffuser vanes may be varied to increase the efficiency of the diffuser. In other words, each individual diffuser vane may be specially designed based on the specific pressure and flow characteristics near the diffuser vane.
• FIG. 1 is an axial view and FIG. 2 is a perspective view of an exemplary embodiment of a centrifugal compressor stage 10 having an impeller 12, a non-periodic diffuser 14, and a scroll 16.
• the centrifugal compressor stage 10 may be employed to provide a pressurized flow of fluid for various reasons
• the impeller 12 may be driven to rotate by an electric motor, an internal combustion engine, or another drive unit configured to provide a rotational output. As the impeller 12 rotates, fluid entering in an axial direction is accelerated and expelled in a circumferential and a radial direction. The high- velocity fluid then crosses the diffuser 14, which converts the velocity head of the fluid into a pressure head (i.e., decreases flow velocity and increases flow pressure). The scroll (or volute) 16 then collects the radially outward flow and directs it into a pipe, for example. In this manner, the centrifugal compressor stage 10 produces a high-pressure fluid output.
• volute and scroll are interchangeable names for the same device that accepts radial flow, may or may not further diffuse the flow, and then directs the flow to an exit pipe.
• the scroll 16 may distort the flow field in the diffuser 14 and, in some cases, the circumferential distortion caused by the scroll 16 may be measured at the exit of the impeller 12.
• the pressure distortion imposed by the scroll 16, is generally variable.
• the scroll 16 may typically operate in one of three flow regions (e.g., neutral, accelerating flow, and decelerating flow).
• the region within which the scroll 16 is operating is determined by the specific application of the centrifugal compressor stage 10. In an application with a relatively high flow rate, the average flow in the scroll 16 will be accelerating as it approaches a tongue of the scroll 16. This imposes a circumferential pressure distortion on the diffuser 14.
• the flow in the scroll 16 is decelerating and imposes a circumferential pressure gradient in the opposite direction of the accelerating flow.
• the degree of distortion roughly correlates with how far the application is from a neutral point.
• the tongue of the scroll 16 may impose pressure and flow field distortions that affect a region of the diffuser 14, but do not extend a full 360 degrees around the diffuser 14 circumferentially. This localized region of flow distortion may extend from the tongue region to an exit of the impeller 12.
• FIG. 3 is a perspective view of the impeller 12 and the non-periodic diffuser 14 of the centrifugal compressor stage 10 of FIGS. 1 and 2.
• the impeller 12 has multiple blades 18.
• an external source e.g., electric motor, internal combustion engine, etc.
• compressible fluid crossing the blades 18 is accelerated toward the diffuser 14 disposed radially about the impeller 12.
• the scroll 16 is positioned directly adjacent to the diffuser 14, and serves to collect the fluid flow leaving the diffuser 14.
• the diffuser 14 is configured to convert the high-velocity fluid flow from the impeller 12 into a high-pressure flow (e.g., convert the dynamic head to pressure head).
• the diffuser 14 includes diffuser vanes 20 coupled to a mounting surface 22 (e.g., a hub, in this particular case) of the diffuser 14 in an asymmetrical (e.g., non-periodic) annular configuration in a circumferential direction 31 around the mounting surface 22.
• the diffuser vanes 20 are configured to increase diffuser efficiency.
• each diffuser vane 20 includes a leading edge section 42 and a trailing edge section 46.
• each diffuser vane 20 includes a pressure surface 50 and a suction surface 52 extending from the leading edge section 42 to the trailing edge section 46 on opposite sides of the diffuser vane 20.
• the efficiency of the diffuser 14 may be increased as compared to conventional, periodic (e.g., symmetrical) diffusers.
• FIG. 4 is a perspective view and FIG. 5 is a side view of the impeller 12 of FIGS. 1 through 3.
• a flow 24 of a compressible fluid may be directed to the impeller 12 opposite to an axial direction 26.
• the flow 24 of compressible fluid may be directed to the impeller 12 along a common central axis of the impeller 12, diffuser 14, and scroll 16.
• a flow 28 of accelerated fluid may be directed at least partially in a radial direction 30.
• the radial direction 30 of the impeller 12 may be any direction perpendicular to the axial direction 26, which coincides (in both location and direction) with the common central axis of the impeller 12, diffuser 14, and scroll 16.
• the accelerated fluid may be directed at least partially in a circumferential direction 31 , which may be any rotational direction around the common central axis of the impeller 12, diffuser 14, and scroll 16.
• FIG. 6 is a perspective view of the non-periodic diffuser 14 of FIGS. 1 through 3.
• the diffuser 14 shares a common central axis in an axial direction 26 with the impeller 12 of FIGS. 4 and 5.
• the radial direction 30 with respect to the diffuser 14 is the same as the impeller 12.
• the radial direction 30 of the diffuser 14 may be any direction perpendicular to the axial direction 26, which coincides (in both location and direction) with the common central axis of the impeller 12, diffuser 14, and scroll 16.
• the diffuser 14 includes diffuser vanes 20 arranged in an asymmetrical pattern in a circumferential direction 31 around the mounting surface 22 of the diffuser 14.
• the shape, orientation, and/or location of the diffuser vanes 20 are non-periodic (e.g., asymmetrical) from one diffuser vane 20 to the next diffuser vane 20.
• the circumferential direction 31 of the diffuser 14 may be any rotational direction around the common central axis of the impeller 12, diffuser 14, and scroll 16.
• FIG. 7 is a perspective view of a periodic diffuser 32.
• FIG. 8 is a partial perspective view of the periodic diffuser 32 taken along line 8-8 of FIG. 7. As illustrated in FIG.
• the periodic diffuser 32 includes a plurality of substantially identical diffuser vanes 34 disposed in a symmetrical (e.g., periodic) pattern in a circumferential direction 31 around a mounting surface 36 (e.g., a hub, in this particular case) of the periodic diffuser 32.
• a symmetrical (e.g., periodic) pattern in a circumferential direction 31 around a mounting surface 36 (e.g., a hub, in this particular case) of the periodic diffuser 32.
• FIG. 8 illustrates a single diffuser vane 34 of the periodic diffuser 32, which will be used as a reference vane.
• a reference surface 38 may be defined along a reference plane whose normal coincides with the axial direction 26.
• the reference surface 38 is defined by an outer surface of the diffuser vane 34.
• the analysis described herein may be utilized for any axial height of the diffuser vane 34.
• the reference plane may be defined at any axial height of the diffuser vanes 34.
• the reference plane includes the reference center point z ref , which passes through the common central axis of the impeller 12, diffuser 14, and scroll 16.
• the reference surface 38 may be characterized by a collection of unique points defined by a radial distance r from the reference center point z ref , an angular location ⁇ , and an axial height z.
• the axial height z for the collection of unique points will be the same.
• the radial distance r and the angular location ⁇ will be different and will define each unique point of the reference surface 38 in the reference plane.
• a leading edge point 40 corresponding to the leading edge section 42 of the diffuser vane 34 may be defined as a baseline point of the reference surface 38 and, as such, may be defined by a radial distance r 0 and an angular location ⁇ 0 equal to 0 degrees.
• a trailing edge point 44 corresponding to the trailing edge section 46 of the diffuser vane 34 may be defined by a radial distance n and an angular location ⁇ .
• a pressure surface point 48 may be defined by a radial distance r 2 and an angular location ⁇ 2 .
• a pressure surface 50 of the diffuser vane 34 may be defined by the plurality of points along the pressure surface 50 of the diffuser vane 34.
• a suction surface 52 of the diffuser vane 34 may be similarly defined. Indeed, there may be an infinite number of unique points in the reference surface 38 of the reference diffuser vane 34 illustrated in FIG. 8. However, the number of unique points used to define the design of the individual diffuser vanes 34 may be limited to facilitate computation of the shape, orientation, and/or location of the diffuser vanes 34.
• each of the diffuser vanes 34 of the diffuser 32 of FIG. 7 may similarly include a collection of unique points along the reference plane.
• each of the diffuser vanes 34 may include a two-dimensional area defined by a collection of unique points along the reference plane, such as the reference surface 38 of the reference diffuser vane 34 illustrated in FIG. 8.
• the rotation of each of these points by an integer multiple of 360.0 divided by N will yield a point that lies within a two-dimensional domain in the reference plane for another diffuser vane 34, where N is the number of diffuser vanes 34 of the diffuser 32.
• the diffuser 32 illustrated in FIG. 7 includes nine diffuser vanes 34.
• the rotation of the point by 40 degrees, 80 degrees, 120 degrees, 160 degrees, 200 degrees, 240 degrees, 280 degrees, and 320 degrees yields a point that lies within the two-dimensional domain in the reference plane for another diffuser vane 34.
• FIG. 9 is an axial view of the non- periodic diffuser 14 of FIGS. 1 through 3 and FIG. 6 having a plurality of diffuser vanes 54, 56, 58, 60, 62, 64, 66, 68, and 70 arranged in a non-periodic (e.g., an asymmetrical) pattern around a circumferential direction 31 of the mounting surface 22.
• a non-periodic e.g., an asymmetrical
• reference points A, B, C, D, E, F, G, H, and I are located at equally spaced circumferential locations around the mounting surface 22.
• the diffuser 14 of FIG. 9 includes nine diffuser vanes 20.
• the reference points A, B, C, D, E, F, G, H, and I are equally spaced at arc angles ⁇ of 40 degrees (e.g., 360.0 degrees divided by nine).
• Each of the illustrated diffuser vanes 54, 56, 58, 60, 62, 64, 66, 68, and 70 are generally associated with one of the reference points A, B, C, D, E, F, G, H, and I (e.g., diffuser vane 54 with reference point A, diffuser vane 56 with reference point B, diffuser vane 58 with reference point C, diffuser vane 60 with reference point D, diffuser vane 62 with reference point E, diffuser vane 64 with reference point F, diffuser vane 66 with reference point G, diffuser vane 68 with reference point H, and diffuser vane 70 with reference point I).
• diffuser vane 54 with reference point A diffuser vane 56 with reference point B
• diffuser vane 58 with reference point C diffuser vane 60 with reference point D
• diffuser vane 62 with reference point E diffuser vane 64 with reference point F
• diffuser vane 66 with reference point G diffuser vane 68 with reference point H
• diffuser vane 70 with reference point I
• the reference points A, B, C, D, E, F, G, H, and I are used to illustrate how the shape, orientation, and/or location of the diffuser vanes 54, 56, 58, 60, 62, 64, 66, 68, and 70 may change from diffuser vane to diffuser vane along a circumferential direction 31 of the mounting surface 22.
• reference points B, C, D, E, F, G, H, and I which correspond to reference point A rotated through arc angles of 40 degrees, 80 degrees, 120 degrees, 160 degrees, 200 degrees, 240 degrees, 280 degrees, and 320 degrees, do not all lie within the two-dimensional domain in the reference plane for the other diffuser vanes 56, 58, 60, 62, 64, 66, 68, and 70.
• reference points E, F, G, H, and I do not lie within the two- dimensional domain in the reference plane for diffuser vanes 62, 64, 66, 68, and 70.
• the diffuser 14 illustrated in FIG. 9 is a non-periodic (e.g.,
• the asymmetrical (e.g., non-periodic) pattern of diffuser vanes 20 in a circumferential direction 31 around the mounting surface 22 may be determined by taking into consideration pressure and fluid flow characteristics of a fluid flowing from the impeller 12 across the diffuser 14 and through the scroll 16.
• FIG. 10 is a flow chart of a method 72 for deriving the shape, orientation, and/or location of a plurality of diffuser vanes 20 arranged in an asymmetrical (e.g., non-periodic) pattern around the mounting surface 22 of the non-periodic diffuser 14.
• Pressure and fluid flow characteristics of the fluid being compressed by the centrifugal compressor stage 10 may be determined across the entire impeller-diffuser-scroll set (e.g., from the impeller 12 across the diffuser 14 and through the scroll 16) such that perturbations of the flow field may be taken into consideration when deriving the shape, orientation, and/or location of each individual diffuser vane 20 of the diffuser 14 (block 74).
• the pressure and fluid flow characteristics across the entire impeller-diffuser-scroll set may be used to derive the shape, orientation, and/or location of each individual diffuser vane 20 of the diffuser 14 such that at least one of the diffuser vanes 20 is not derived by simply performing a theoretical rotation of each of the other diffuser vanes 20 through an arc angle equal to an integer multiple of 360.0 degrees divided by N, where N is equal to the number of diffuser vanes 20 of the diffuser 14 (block 76).
• an optimal number of diffuser vanes 20 may be determined for the diffuser 14. The method 72 of FIG.
• the computer 10 may be executed on a computer specifically programmed to derive the shape, orientation, and/or location of the diffuser vanes 20.
• the computer may be any suitable computer (e.g., a laptop, desktop, server, and so forth) including one or more processors that may communicate with a memory and execute computer instructions such as those illustrated by the method 72 of FIG. 10.
• each of the individual diffuser vanes 20 may enable adjustments of the diffuser vanes 20, which may reduce adverse affects of perturbations of the flow field due, for example, to the presence of the tongue of the volute or scroll.
• the non- periodic diffuser 14 may lead to overall efficiency gains of its respective
• centrifugal compressor stage 10 deriving an asymmetrical (e.g., non-periodic) pattern of diffuser vanes 20 that takes variations of the fluid flow field into consideration may lead to compressor stage efficiency increases of approximately 0.5%, 1 .0%, 1.5%, or even more.
• the asymmetrical (e.g., non-periodic) pattern of diffuser vanes 20 may include an asymmetrical geometry, an asymmetrical orientation, or both from a first diffuser vane 20 to a second diffuser vane 20.
• an asymmetrical geometry may include a change in the pressure surface 50 from a first diffuser vane 20 to a second diffuser vane 20.
• an asymmetrical geometry may include a change in the suction surface 52 from a first diffuser vane 20 to a second diffuser vane 20.
• an asymmetrical orientation may include a change in radial location from a first diffuser vane 20 to a second diffuser vane 20.
• an asymmetrical orientation may include a change in circumferential location with respect to equally spaced reference points from a first diffuser vane 20 to a second diffuser vane 20.
• an asymmetrical orientation may include a change in angular orientation from a first diffuser vane 20 to a second diffuser vane 20.
• the optimum design of the diffuser vanes 20 minimizes the creation of loss-producing fluid structures near the diffuser vanes 20.
• the optimum shape, orientation, and/or location for the individual diffuser vanes 20 results in one or more of the diffuser vanes 20 no longer being spatially symmetric along equally spaced radial lines defined at arc angles equal to 360.0 degrees divided by the number of diffuser vanes 20.
• the individual diffuser vanes 20 may include transformed two- dimensional cascade, three-dimensional sculpted flat plate designs, three- dimensional twisted airfoils, or arbitrary three-dimensional surfaces, for example.
• the exit flow field of the impeller 12 and the exact volute geometry will determine the optimum diffuser vane surface shapes.
• Each individual diffuser vane 20 may be specially designed based on the specific local pressure and fluid flow characteristics imposed by both the impeller 12 and the scroll 16. The final design will share one common characteristic across all applications; namely, the diffuser 14 will be non-periodic (not circumferentially symmetric) because the diffuser vanes 20 are locally optimized.

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• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

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• 2010
  • 2010-11-30 US US13/522,704 patent/US20120294711A1/en not_active Abandoned
  • 2010-11-30 KR KR1020127020206A patent/KR20120125483A/ko not_active Application Discontinuation
  • 2010-11-30 JP JP2012551966A patent/JP5753199B2/ja not_active Expired - Fee Related
  • 2010-11-30 CN CN2010800632181A patent/CN102822533A/zh active Pending
  • 2010-11-30 WO PCT/US2010/058439 patent/WO2011096981A1/en active Application Filing
  • 2010-11-30 EP EP10787644A patent/EP2531733A1/en not_active Withdrawn

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