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
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
  • F04D29/284—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps for compressors
• • 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
  • F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
  • F04D29/056—Bearings
• • 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
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
  • F04D29/30—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
  • F04D29/40—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
• • 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
  • F04D29/60—Mounting; Assembling; Disassembling
  • F04D29/62—Mounting; Assembling; Disassembling of radial or helico-centrifugal pumps
  • F04D29/624—Mounting; Assembling; Disassembling of radial or helico-centrifugal pumps especially adapted for elastic fluid pumps
• • 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
  • F04D29/68—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers
  • F04D29/681—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps

Definitions

• the present invention relates generally to compressors and, more specifically, to secondary flow of process fluid proximate to compressor impeller blades.
• a compressor is a machine which increases the pressure of a process fluid, e.g., a gas, through the use of mechanical energy.
• Compressors are used in a number of different applications, including operating as an initial stage of a gas turbine engine.
• centrifugal compressors in which mechanical energy operates on process fluid input to the compressor by way of centrifugal acceleration, e.g., by rotating a centrifugal impeller (sometimes also called a "rotor") by which the process fluid is passing.
• centrifugal compressors can be said to be part of a class of machinery known as “turbo machines” or “turbo rotating machines”.
• Centrifugal compressors can be fitted with a single impeller, i.e., a single stage configuration, or with a plurality of impellers in series, in which case they are frequently referred to as multistage compressors.
• Each of the stages of a centrifugal compressor typically includes an inlet conduit for the flow of process fluid to be compressed, an impeller including blades which are capable of imparting kinetic energy to the input process fluid and a diffuser which converts the kinetic energy of the process fluid flowing away from the rotor into pressure energy.
• the flow of the process fluid from the inlet to the diffuser may be categorized as primary or secondary.
• Primary flow is desirable and may be considered to be efficient progression of the process fluid through the compressor.
• secondary flows are undesirable and may require the compressor to perform additional work to achieve the demanded pressure rise in the process fluid. Secondary flows are potentially troublesome not only during a compression process, stage or stages, but also, thereafter, when downstream components of the compressor are exposed and potentially compromised or otherwise prevented from performing optimally by such flows.
• While a large percentage of the process fluid may move by way of a primary flow through the compressor, at least some portion of the process fluid may move by way of a secondary flow, particularly process fluid in close proximity to the impeller blades.
• some portion of the process fluid flow may form a boundary layer near the face of an impeller blade and slow down relative to other portions of the process fluid being compressed.
• some portions of the flow may migrate transversely to a desired flow across the impeller blades. These portions may cause or be part of a secondary flow.
• an impeller includes a hub having a direction of rotation, a plurality of impeller blades extending from the hub, each blade having a downstream end, an upstream end, a leading surface facing the direction of rotation of the hub, and a trailing surface facing opposite to the direction of rotation of the hub.
• the impeller further includes a secondary flow reducer extending towards the downstream end and the upstream end of the at least one of the plurality of impeller blades, the secondary flow reducer defining first and second surfaces intersecting one of the leading surface and the trailing surface of the at least one of the plurality of impeller blades.
• the secondary flow reducer further defines a third surface between the first and second surfaces.
• a turbo machine includes a rotor assembly including at least one impeller, a bearing connected to, and for rotatably supporting, the rotor assembly, and a stator.
• the at least one impeller includes a hub having a plurality of impeller blades. At least one of the impeller blades includes a plurality of ribs for reducing a secondary flow proximate to the at least one impeller blade.
• a method of configuring an impeller blade surface to provide reduced secondary flow can include the steps of identifying an ideal streamline of the impeller blade surface and adding a rib to the blade surface coincident with the streamline, the rib defining first and second surfaces intersecting the surface and defining a third surface between the first and second surfaces.
• Figure 1 depicts an exemplary centrifugal compressor.
• Figure 2 depicts an exemplary impeller of the centrifugal compressor of Figure 1.
• Figure 3 shows a cross-sectional view of the impeller shown in Fig. 2.
• Figure 4 shows an impeller blade of the impeller shown in Figs. 2 and 3 including secondary flow reducers according to an exemplary embodiment.
• Figure 5 shows a loss coefficient diagram for an impeller including secondary flow reducers according to the exemplary embodiment of Figure 4, as compared to a conventional impeller.
• Figure 6 shows a work coefficient and flow coefficient diagram for the impeller of Figure 4.
• Figure 7 shows a flow angle versus blade span diagram for the impeller of Figure 4, as compared to a conventional impeller.
• Figure 8 shows process fluid flow vorticity at an exit of an impeller without secondary flow reducers.
• Figure 9 shows process fluid flow vorticity at an exit of the impeller with secondary flow reducers.
• Figure 10 shows streamlines on an impeller blade without secondary flow reducers.
• Figure 11 shows streamlines on the impeller blade with secondary flow reducers.
• Figure 12 shows a partial cross sectional view of the secondary flow reducer shown in Fig. 4.
• Figure 13 shows a partial cross sectional view of another exemplary embodiment.
• Figure 14 shows a partial cross sectional view of another exemplary embodiment.
• Figure 15 shows a partial cross sectional view of another exemplary embodiment.
• Figure 16 shows a partial cross sectional view of another exemplary embodiment.
• Figure 17 shows a partial cross sectional view of another exemplary embodiment.
• Figure 18 shows a partial cross sectional view of another exemplary embodiment.
• Figure 19 is a flowchart illustrating a method of configuring an impeller blade surface to resist secondary flow according to an exemplary embodiment.
• FIG. 1 schematically illustrates a multistage, centrifugal compressor 40 in which impellers 46 are employed in the compression process.
• the compressor 40 includes a box or housing (stator) 42 within which is mounted a rotating compressor shaft 44 that is provided with a plurality of centrifugal rotors or impellers 46.
• the rotor assembly 48 includes the shaft 44 and rotors 46 and is supported radially and axially through bearings 50 which are disposed on either side of the rotor assembly 48.
• the multistage centrifugal compressor operates to take an input process gas from duct inlet 52, to accelerate the process gas particles through operation of the rotor assembly 48, and to subsequently deliver the process gas through various interstage ducts 54 at an output pressure which is higher than its input pressure.
• the process gas may, for example, be any one of carbon dioxide, hydrogen sulfide, butane, methane, ethane, propane, liquefied natural gas, or a combination thereof.
• sealing systems (not shown) are provided to prevent the process gas from flowing to the bearings 50.
• the housing 42 is configured so as to cover both the bearings 50 and the sealing systems, so as to prevent the escape of gas from the centrifugal compressor 40.
• FIGs. 2 and 3 A more detailed, but purely exemplary, illustration of an impeller 46 is provided in Figs. 2 and 3.
• the impeller 46 has a plurality of impeller blades 60 extending from hub 62 to a shroud 64.
• Each impeller blade 60 includes an upstream end 68, a downstream end 72, a leading surface 74 (Fig. 3), and a trailing surface 76 (Fig. 3).
• Each trailing surface 76 of a pair of impeller blades 60 includes a plurality of secondary flow reducers 80 extending towards downstream end 72 (Fig. 2) and upstream end 68 (Fig. 2) of each impeller blade 60.
• each secondary flow reducer 80 may be equally spaced from each other as well as from the hub 60 and shroud 64. Moreover, each secondary flow reducer 80 may terminate at a location on the trailing surface 76 which is spaced from the upstream end 68 of blade 60. As further shown in Fig. 4, each secondary flow reducer 80 may also include a tapering portion 96 which tapers to the location of termination on the trailing surface 76.
• each secondary flow reducer 80 may be coincident with, or follow, an ideal streamline of process fluid progressing across surface 76.
• An ideal streamline may be established in theory, through experimental observation, or other criteria. For example, in existing impeller design applications, an ideal streamline may be established by creating a line on the blade surface 76 which is congruent to the intersection of the blade 60 with the shroud 64. An ideal streamline may also be established during the design process using flow equations as, for example, disclosed in U.S. Patent No. 6,654,710, the disclosure of which is incorporated herein by reference. Additionally, an ideal streamline, as that term is used herein, can refer to a streamline which is substantially parallel to lines associated with the endwalls of the impeller blade.
• a streamline may be unique with respect to other streamlines on the same surface, for example, a streamline proximate to hub 62 may be different from a streamline proximate to shroud 64.
• a single secondary flow reducer 80 may define more than a single streamline, for example, a secondary flow reducer 80 may branch into two interconnected streamlines.
• the secondary flow reducers 80 in Fig. 4 are configured to inhibit the migration of process fluid, which may be part of a secondary flow boundary layer on blade 60, between hub 62 and shroud 64.
• Each secondary flow reducer 80 is also configured to funnel and/or concentrate the flow of process fluid between secondary flow reducers 80.
• the resulting enhanced flow may be characterized not only by reduced secondary flow but also by greater flow uniformity at the downstream end 72 of impeller blade 60.
• FIG. 5 shows a line plot 84 of the loss coefficient achieved by blade 60 including secondary flow reducers 80 as well as a line plot 82 of the loss coefficient of a blade 60 without secondary flow reducers 80.
• the abscissa shows loss coefficient
• the ordinate shows fractional distance from the hub to the downstream end 72 of blade 60.
• the area between the line plots 82 and 84 shows a significant reduction in loss coefficient of an impeller 60 with secondary flow reducers 80 according to the exemplary embodiment of Fig. 4.
• Fig. 6 shows further results of the calculations. Specifically, flow coefficient which is defined as the volume flow of the impeller with respect to a standard volume flow is shown on the abscissa and work coefficient which is defined as the power input to the compressor with respect to a standard power input is shown on the ordinate.
• the plot line 86 shows calculation results of impeller 60 without secondary flow reducers 80 and the plot line 88 shows the calculation results of impeller 60 with secondary flow reducers 80.
• the data shows an improvement in compressor performance associated with the inclusion of secondary flow reducers 80 on the blades of impeller 60.
• the impeller 60 with secondary flow reducers 80 provides both an improved work coefficient and an improved flow coefficient versus an impeller 60 without flow reducers 80.
• the flow angle of the process fluid leaving impeller 46 is shown on the abscissa and the distance across the span from the hub 62 to the shroud 64 is shown on the ordinate.
• the plot line 118 shows the calculation results for an impeller 60 without secondary flow reducers 80 and the plot line 122 shows the calculation results of impeller 60 with secondary flow reducers 80.
• the inclusion of secondary flow reducers 80 decreases the angle at which process fluid leaves the blade particularly at points on the impeller closer to the shroud 64 thereby reducing secondary flow and generating greater flow uniformity at the blade exit 72.
• Figs. 8 and 9 show the magnitude of fluid vorticity proximate to the shroud 64.
• the magnitude of the flow vorticity is shown by the shaded regions 124.
• the magnitude of the flow vorticity for impeller blades including secondary flow reducers is shown in the regions 126. Regions 126 are smaller than regions 124 thereby indicating the improved performance of an impeller 60 which includes secondary flow reducers 80 according to the present invention.
• Fig. 10 shows simulated streamlines 128 of process fluid across a blade 60 without secondary flow reducers 80 and Fig. 10 shows simulated streamlines 132 of process fluid across blade 60 with secondary flow reducers 80.
• a higher percentage of streamlines 132 extend to the downstream end 72 of the impeller 60 including secondary flow reducers 80 than the streamlines 128 of the impeller without secondary flow reducers 80.
• Figs. 10 and 11 further show that secondary flow reducers 80 have a channeling or "combing" effect on the process fluid flow which causes a higher percentage of the process fluid to flow along the ideal streamlines 132.
• secondary flow reducer 80 includes a first surface 102 intersecting the trailing surface 76 of impeller blade 60, and a second surface 104 spaced apart from first surface 102 and also intersecting the trailing surface 76 of impeller blade 60.
• a third surface 106 of secondary flow reducer 80 extends from the first surface 102 to the second surface 104.
• intersection 103 of the first surface 102 with blade surface 76 defines a first curvilinear line and the intersection 105 of the second surface 104 with blade surface 76 defines a second curvilinear line.
• the curvilinear lines defined by intersection 103 and intersection 105 are parallel, however, in other exemplary embodiments the intersection 103 of first surface 102 with blade surface 76 and the intersection 105 of second surface 104 with blade surface 76 may define non-parallel lines, for example, each intersection 103 and 105 may define a line having a wave pattern.
• first surface 102 and/or second surface 104 may be planar or non-planar, for example, concave, convex, or other surface.
• a secondary flow reducer 80 in the form of a rib 78 is included on the leading surface 74 of impeller 80.
• a secondary flow reducer 80 in the form of a channel 98 is included on the leading surface 74 of impeller 80.
• surfaces 102 and 104 converge towards surface 106 and thus define a tapering rib 78.
• surfaces 102 and 104 may be parallel to each other or diverge towards surface 106, i.e. surfaces 102 and 104 may be closer to each other at the intersection 103 or 105 with blade surface 76 than at the transition to third surface 106.
• third surface 106 defines a rounded profile 110.
• third surface 106 may define other profiles.
• third surface 106 may be defined by the extension and intersection of surfaces 102 and 104 to a pointed profile 112.
• third surface 106 is shown having a polygonal profile 114 and a concave profile 116, respectively.
• the profile of third surface 106 may be configured to further enhance the capacity of the secondary flow reducer 80 to inhibit and/or reduce a secondary flow, to enhance the uniformity of process fluid flow, and/or to otherwise improve the efficiency and performance of compressor 40.
• secondary flow reducers 80 may be implemented without introducing a change to the overall shape or design of the impeller blade 60.
• secondary flow reducers 80 may also provide a lower cost solution for reducing secondary flow, and otherwise improve the efficiency and performance of a compressor.
• a method (1000) of configuring an impeller blade surface to provide reduced secondary flow can include the steps of identifying (1002) an ideal streamline of the impeller blade surface and adding (1004) a rib to the blade surface coincident with the streamline, the rib defining first and second surfaces intersecting the blade surface, the rib further defining a third surface between the first and second surfaces.

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

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Citations (7)

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• 2013
  • 2013-06-13 IT IT000024A patent/ITCO20130024A1/it unknown
• 2014
  • 2014-06-11 MX MX2015016450A patent/MX2015016450A/es unknown
  • 2014-06-11 KR KR1020157034044A patent/KR20160019418A/ko not_active Application Discontinuation
  • 2014-06-11 BR BR112015029639A patent/BR112015029639A2/pt not_active IP Right Cessation
  • 2014-06-11 RU RU2015150305A patent/RU2667855C2/ru active
  • 2014-06-11 WO PCT/EP2014/062158 patent/WO2014198790A1/en active Application Filing
  • 2014-06-11 CN CN201480031336.2A patent/CN105556129A/zh active Pending
  • 2014-06-11 US US14/895,224 patent/US20160123345A1/en not_active Abandoned
  • 2014-06-11 CA CA2913026A patent/CA2913026A1/en not_active Abandoned
  • 2014-06-11 AU AU2014280238A patent/AU2014280238A1/en not_active Abandoned
  • 2014-06-11 JP JP2016518475A patent/JP2016521821A/ja active Pending
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