US20110293421A1 - Rotor blade having passive bleed path - Google Patents
Rotor blade having passive bleed path Download PDFInfo
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- US20110293421A1 US20110293421A1 US12/790,091 US79009110A US2011293421A1 US 20110293421 A1 US20110293421 A1 US 20110293421A1 US 79009110 A US79009110 A US 79009110A US 2011293421 A1 US2011293421 A1 US 2011293421A1
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- blade
- working fluid
- rotor
- inlet
- root
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03D—WIND MOTORS
- F03D1/00—Wind motors with rotation axis substantially parallel to the air flow entering the rotor
- F03D1/06—Rotors
- F03D1/065—Rotors characterised by their construction elements
- F03D1/0675—Rotors characterised by their construction elements of the blades
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C11/00—Propellers, e.g. of ducted type; Features common to propellers and rotors for rotorcraft
- B64C11/16—Blades
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
- F01D5/12—Blades
- F01D5/14—Form or construction
- F01D5/141—Shape, i.e. outer, aerodynamic form
- F01D5/145—Means for influencing boundary layers or secondary circulations
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03D—WIND MOTORS
- F03D1/00—Wind motors with rotation axis substantially parallel to the air flow entering the rotor
- F03D1/06—Rotors
- F03D1/0608—Rotors characterised by their aerodynamic shape
- F03D1/0633—Rotors characterised by their aerodynamic shape of the blades
- F03D1/0641—Rotors characterised by their aerodynamic shape of the blades of the section profile of the blades, i.e. aerofoil profile
-
- 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
- F04D29/32—Rotors specially for elastic fluids for axial flow pumps
- F04D29/321—Rotors specially for elastic fluids for axial flow pumps for axial flow compressors
- F04D29/324—Blades
-
- 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
- F04D29/32—Rotors specially for elastic fluids for axial flow pumps
- F04D29/38—Blades
- F04D29/388—Blades characterised by construction
-
- 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
- F04D29/682—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps by fluid extraction
-
- 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
- F05D2240/00—Components
- F05D2240/20—Rotors
- F05D2240/30—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
- F05D2240/306—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor related to the suction side of a rotor blade
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/72—Wind turbines with rotation axis in wind direction
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T50/00—Aeronautics or air transport
- Y02T50/60—Efficient propulsion technologies, e.g. for aircraft
Definitions
- This invention relates generally to rotors having radially extending working members and, more particularly, to impellers and propellers having blades with fluid passages open to a working fluid.
- Rotors typically include a hub for coupling to some other device like a prime mover or an electrical machine, and one or more radially extending working members for acting on, or reacting with, a working fluid.
- an aircraft propeller typically includes a hub coupled to an engine output shaft, and several blades extending radially outwardly from the hub. The engine output shaft rotates the hub to rotate the blades, which convert rotational forces into aerial thrust forces to propel an aircraft through the air.
- a wind turbine impeller typically includes a hub coupled to a generator input shaft, and several blades extending radially outwardly from the hub. Wind impacts the blades, which convert wind thrust to hub rotation for rotating the generator input shaft to generate electricity within the generator. Similar examples exist for marine propellers, turbine engine rotors, helicopter rotors, and the like.
- a rotor blade includes a root region, a tip region disposed radially outwardly of the root region, leading and trailing surfaces extending between the root and tip regions, and pressure and suction surfaces extending between the root and tip regions and the leading and trailing surfaces.
- the blade also includes a bleed path that opens to the suction surface, extends through the blade, and exits to at least one of the suction or trailing surfaces.
- Working fluid flows through the bleed path under centrifugal pumping forces when the blade rotates, to passively bleed working fluid from the suction surface.
- a rotor including the aforementioned rotor blade, wherein the bleed path is configured such that the working fluid passively flows through the bleed path under negative pressurization, but does not actively flow therethrough by positive pressurization from some external pressurizing device or from a path open to the pressure surface.
- the bleed path includes an inlet in the suction surface to receive the working fluid on the suction surface, a conduit in communication with the inlet to convey the working fluid from the inlet toward the tip region, and an outlet in communication with the conduit and disposed radially outwardly of the inlet to exhaust the working fluid out of the blade.
- a rotor blade that includes a root region, a tip region disposed radially outwardly of the root region, leading and trailing surfaces extending between the root and tip regions, and pressure and suction surfaces extending between the root and tip regions and the leading and trailing surfaces.
- the rotor blade also includes a bleed path opening to the suction surface and including an inlet in the suction surface to receive working fluid on the suction surface.
- the bleed path further includes a conduit in communication with the inlet to convey the working fluid from the inlet toward the tip region, and an outlet in communication with the conduit and disposed radially outwardly of the inlet to exhaust the working fluid out of the blade.
- FIG. 1 is a plan view of an example embodiment of a rotor including a hub and blades;
- FIG. 2 is an enlarged cross-sectional view through line 2 - 2 of one of the blades of FIG. 1 ;
- FIG. 3 is an enlarged fragmentary side view taken along line 3 of one of the blades of FIG. 1 ;
- FIG. 4 is an enlarged fragmentary perspective view of one of the blades of FIG. 1 ;
- FIG. 5 is an enlarged cross-sectional view of a prior art rotor blade, and illustrating laminar separation of a working fluid with respect thereto;
- FIG. 6 is an enlarged cross-sectional view of an exemplary rotor blade having a bleed path, and illustrating attached flow of a working fluid with respect thereto.
- FIG. 1 illustrates an exemplary embodiment of a rotor 10 including a hub 12 defining a rotational axis A of the rotor 10 , which is intended to rotate in a counter-clockwise direction about the axis A.
- the rotor 10 also includes one or more of a rotor blade 14 extending generally radially outwardly from the hub 12 along a longitudinal axis B of the blade 14 . Although three separate blades 14 are shown, any suitable quantity of blades may be used.
- the components of the rotor 10 can be manufactured according to techniques known to those skilled in the art, including casting, forging, molding, machining, stamping, and/or the like. Likewise, any suitable materials can be used in making the components, such as metals like aluminum or steel, composites, polymeric materials, and/or the like.
- rotor refers not only to aircraft propeller applications, but also to windmill impellers, marine propellers, turbine engine rotors, helicopter rotors, and various other applications, and regardless of the type of working fluid used in conjunction with the rotor.
- the blade 14 includes a root region 16 proximate the hub 12 , and a tip region 18 distal the hub 12 and disposed radially outwardly of the root region 16 .
- the root region 16 may be integrally or separately coupled to the hub 14 for example, by forming, casting, forging, welding, fastening, or in any other suitable manner.
- the tip region 18 may include a radially outermost surface 20 of the blade 14 .
- the blade 14 also includes a leading edge or surface 22 extending between the root and tip regions 16 , 18 , and a trailing edge or surface 24 extending between the root and tip regions 16 , 18 .
- the leading and trailing surfaces 22 , 24 may be rounded, flat, pointed, and/or of any other suitable shape(s).
- the blade 14 further includes a first or pressure surface 26 extending between the root and tip regions 16 , 18 ( FIG. 1 ) and the leading and trailing surfaces 22 , 24 , and a second or suction surface 28 extending between the root and tip regions 16 , 18 ( FIG. 1 ) and the leading and trailing surfaces 22 , 24 .
- the suction surface 28 may be generally convex as shown and the pressure surface 26 may be generally concave as shown, wherein the blade 14 may be shaped as an aerofoil.
- the suction and pressure surfaces 26 , 28 may be of any suitable shape(s) or contour(s) and the blade 14 need not be aerofoil-shaped and may be of any suitable shape and disposed at any suitable angle(s).
- the blade 14 additionally includes a bleed path 30 opening to the suction surface 28 , extending through the blade 14 , and exiting to the suction surface 28 , the trailing surface 24 , or both.
- the bleed path 30 is provided to bleed low energy working fluid from the suction surface 28 to improve blade efficiency.
- Working fluid flows into, through, and out of the bleed path under centrifugal pumping forces to passively bleed working fluid from the suction surface 28 and thereby prevent or reduce boundary layer separation and/or a laminar separation bubble of working fluid on the suction surface 28 .
- the bleed path 30 generally may extend along, or parallel with respect to, the blade axis B. However, the bleed path 30 may be disposed at any suitable angle with respect to the axis B, and need not be centered between the leading and trailing surfaces 22 , 24 . As also shown in FIG. 1 , the bleed path 30 may be disposed radially outwardly of a circumferential axis C that may bisect the length of the blade 14 . In another embodiment, a portion of the bleed path 30 may extend radially inwardly of the axis C. For example, at least part of an inlet portion of the bleed path 30 may extend radially inwardly of the axis C.
- the bleed path 30 includes an inlet 32 located in the suction surface 28 to receive working fluid on the suction surface 28 , and a conduit 34 in communication with the inlet 32 to convey the working fluid from the inlet 32 in a radially outward direction toward the tip region 18 of the blade 14 .
- the bleed path 30 also includes an outlet 36 in communication with the conduit 34 and disposed radially outwardly of the inlet 32 to exhaust the working fluid out of the blade 14 .
- centrifugal pumping forces pull working fluid into the inlet 32 , through the conduit 34 , and out of the outlet 36 .
- Such fluid flow may reduce or thin a boundary layer, and also may at least reduce, and preferably prevent, laminar separation of the working fluid on the suction surface 28 of the blade 14 .
- the working fluid passively flows through the bleed path 30 under vacuum or negative pressurization pulled from the outlet 36 .
- the working fluid may not actively flow through the bleed path 30 under positive pressurization pushed from the inlet 32 toward the outlet 36 , for example, from some external pressurizing device like a pump, or from a path open to the pressure surface 26 and communicated directly to the bleed path 30 , or the like.
- the inlet 32 may be of any suitable size and shape.
- the inlet 32 may be a slot that may extend in a generally radial direction over at least a portion of an area of the suction surface 28 that would experience boundary layer separation but for the slot.
- the inlet 32 may be disposed at any suitable angle with respect to the axis B, and need not be centered between the leading and trailing surfaces 22 , 24 .
- the inlet 32 may be a porous patch on the suction surface 28 .
- the conduit 34 or at least a portion thereof may be covered by a porous surface flush with the suction surface 28 .
- An example porosity of the porous patch may be 10%-75% porosity.
- FIG. 5 illustrates a prior art blade 114 without the bleed path 30 , wherein laminar separation and turbulent reattachment occurs over a suction surface 128 to create a bubble area 129 of low energy working fluid.
- a bubble area 129 tends to appear at low Reynolds numbers, creates drag and thereby reduces efficiency of the blade 114 and, in a propeller embodiment, requires more power to move the blade 114 .
- FIG. 6 illustrates another exemplary embodiment of a rotor blade 214 .
- This embodiment is similar in many respects to the embodiment of FIGS. 1-4 and like numerals between the embodiments generally designate like or corresponding elements throughout the several views of the drawing figures. Additionally, the descriptions of the embodiments are incorporated by reference into one another and the common subject matter generally may not be repeated here.
- FIG. 6 illustrates a presently disclosed rotor blade 214 having an inlet 232 of a bleed path 230 disposed in area of the suction surface 228 where the bubble area 129 ( FIG. 5 ) would be located if the bleed path 230 were not present.
- the inlet 232 can be provided as a porous surface or patch to cover the bubble area 129 ( FIG. 5 ).
- the inlet 232 may be centered (in a circumferential direction between) over an area where the bubble area 129 ( FIG. 5 ) would be.
- Those of ordinary skill in the art will recognize that such sizing and locating is application specific and may be determined via empirical testing or by modeling or both.
- a plurality of the inlet 32 may be provided, each of which may be sized in correspondence to a radial fluid flow distribution.
- the inlet 32 may be divided in a radial direction into a plurality of separate inlets, as indicated in FIG. 4 , corresponding in size and/or shape to different radial pressure gradients along the blade 14 .
- Such an inlet 32 may be thought of as akin to an input side of a harmonica.
- the conduit 34 may include any suitable device to convey the working fluid.
- the conduit 34 may include one or more separate tubes, pipes, hoses, or the like assembled to the blade 14 in any suitable manner.
- the conduit 14 may include an integral void in the blade 14 that may be formed, cast, forged, machined, or the like in the blade 14 in any suitable manner.
- the conduit 34 may be of any suitable shape and size.
- the outlet 36 may be located in the trailing surface 24 of the blade 14 in one embodiment.
- an outlet 36 ′ may be provided in the suction surface 28 .
- both outlets 36 , 36 ′ may be used.
- the outlet 36 (and/or 36 ′) may be located radially inwardly of the radially outermost surface 20 of the blade 14 .
- the outlet 36 or outlets 36 , 36 ′ may be of any suitable shape(s) and size(s).
- the conduit 14 and/or the outlet(s) 36 ( 36 ′) may be shaped and/or sized to reduce a differential between a velocity of working fluid transmitted from the outlet 36 and a velocity of working fluid in a free stream adjacent the outlet 36 .
- shaping and sizing is application specific and may be determined via empirical testing or by modeling or both.
- the presently disclosed bleed path 30 reduces, eliminates, or prevents boundary layer separation over the suction surface 28 of the rotor blade 14 , with concomitant reduction, elimination, or prevention in drag and inefficiency of the blade 14 .
- the bleed path 30 may be used to reduce, eliminate, or prevent boundary layer separation whether the flow is laminar or turbulent, and may be particularly beneficial for use in applications with low Reynolds numbers.
- the presently disclosed bleed path 30 will reduce power required to rotate a propeller and may increase propeller efficiency particularly for relatively small, slowly rotating propellers at high altitudes.
- the bleed path 30 reduces product weight, is low in cost, and does not have any separate moving parts.
- airfoils are designed such that the boundary layer transitions from laminar to turbulent prior to laminar separation.
- the turbulent boundary layer then naturally remains attached longer because it can tolerate a more adverse pressure gradient than that of a laminar boundary layer.
- the laminar boundary layer may separate before transition occurs. If the laminar flow separates, then the process of separation usually induces rapid transition to turbulence. In many cases, this turbulent flow then reattaches because it is more tolerant of the adverse pressure gradient which caused the laminar flow to separate.
- This laminar separation and turbulent reattachment is called a laminar separation bubble and is a common source of high drag on airfoils used at low Reynolds numbers. In other cases, the separated flow does not reattach, and the resulting drag is even higher.
- the presently disclosed passive bleed path(s) may improve efficiency over a large range of conditions, especially at low Reynolds numbers where laminar separation tends to appear.
- the bleed inlet(s) may be located near the region where laminar separation would occur (if bleed were absent).
- the passive bleed prevents laminar separation such that the boundary layer transitions to turbulent while still attached.
- the turbulent boundary layer is then able to remain attached because it is more tolerant of an adverse pressure gradient. Therefore, a laminar separation bubble can be prevented, and a substantial source of drag can be eliminated.
- the passive bleed may also be beneficial at higher Reynolds numbers, when the flow is already turbulent over the bleed inlet(s).
- the natural turbulent separation point is downstream of the location of the bleed inlet(s), even if bleed were absent.
- the turbulent boundary layer is thinned, thereby delaying separation to a point even farther downstream. This could allow more extreme airfoil shapes to be practical.
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Abstract
A rotor blade includes a bleed path opening to a suction surface, extending through the blade, exiting to at least one of the suction or a trailing surface, and through which working fluid flows under centrifugal pumping forces when the blade rotates, to passively bleed working fluid from the suction surface.
Description
- 1. Technical Field
- This invention relates generally to rotors having radially extending working members and, more particularly, to impellers and propellers having blades with fluid passages open to a working fluid.
- 2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
- Rotors typically include a hub for coupling to some other device like a prime mover or an electrical machine, and one or more radially extending working members for acting on, or reacting with, a working fluid. For example, an aircraft propeller typically includes a hub coupled to an engine output shaft, and several blades extending radially outwardly from the hub. The engine output shaft rotates the hub to rotate the blades, which convert rotational forces into aerial thrust forces to propel an aircraft through the air. In another example, a wind turbine impeller typically includes a hub coupled to a generator input shaft, and several blades extending radially outwardly from the hub. Wind impacts the blades, which convert wind thrust to hub rotation for rotating the generator input shaft to generate electricity within the generator. Similar examples exist for marine propellers, turbine engine rotors, helicopter rotors, and the like.
- A rotor blade includes a root region, a tip region disposed radially outwardly of the root region, leading and trailing surfaces extending between the root and tip regions, and pressure and suction surfaces extending between the root and tip regions and the leading and trailing surfaces. The blade also includes a bleed path that opens to the suction surface, extends through the blade, and exits to at least one of the suction or trailing surfaces. Working fluid flows through the bleed path under centrifugal pumping forces when the blade rotates, to passively bleed working fluid from the suction surface.
- Additionally provided is a rotor including the aforementioned rotor blade, wherein the bleed path is configured such that the working fluid passively flows through the bleed path under negative pressurization, but does not actively flow therethrough by positive pressurization from some external pressurizing device or from a path open to the pressure surface. The bleed path includes an inlet in the suction surface to receive the working fluid on the suction surface, a conduit in communication with the inlet to convey the working fluid from the inlet toward the tip region, and an outlet in communication with the conduit and disposed radially outwardly of the inlet to exhaust the working fluid out of the blade.
- Also provided is a rotor blade that includes a root region, a tip region disposed radially outwardly of the root region, leading and trailing surfaces extending between the root and tip regions, and pressure and suction surfaces extending between the root and tip regions and the leading and trailing surfaces. The rotor blade also includes a bleed path opening to the suction surface and including an inlet in the suction surface to receive working fluid on the suction surface. The bleed path further includes a conduit in communication with the inlet to convey the working fluid from the inlet toward the tip region, and an outlet in communication with the conduit and disposed radially outwardly of the inlet to exhaust the working fluid out of the blade.
- These and other features and advantages will become apparent to those skilled in the art in connection with the following detailed description and drawings of one or more embodiments of the invention, in which:
-
FIG. 1 is a plan view of an example embodiment of a rotor including a hub and blades; -
FIG. 2 is an enlarged cross-sectional view through line 2-2 of one of the blades ofFIG. 1 ; -
FIG. 3 is an enlarged fragmentary side view taken alongline 3 of one of the blades ofFIG. 1 ; -
FIG. 4 is an enlarged fragmentary perspective view of one of the blades ofFIG. 1 ; -
FIG. 5 is an enlarged cross-sectional view of a prior art rotor blade, and illustrating laminar separation of a working fluid with respect thereto; and -
FIG. 6 is an enlarged cross-sectional view of an exemplary rotor blade having a bleed path, and illustrating attached flow of a working fluid with respect thereto. -
FIG. 1 illustrates an exemplary embodiment of arotor 10 including a hub 12 defining a rotational axis A of therotor 10, which is intended to rotate in a counter-clockwise direction about the axis A. Therotor 10 also includes one or more of arotor blade 14 extending generally radially outwardly from the hub 12 along a longitudinal axis B of theblade 14. Although threeseparate blades 14 are shown, any suitable quantity of blades may be used. In general, the components of therotor 10 can be manufactured according to techniques known to those skilled in the art, including casting, forging, molding, machining, stamping, and/or the like. Likewise, any suitable materials can be used in making the components, such as metals like aluminum or steel, composites, polymeric materials, and/or the like. - The example embodiment will be described and illustrated with reference to its use in an aircraft propeller environment. However, it will be appreciated as the description proceeds that the invention is useful in many different applications and may be implemented in many other embodiments. In this regard, and as used herein and in the claims, it will be understood that the term “rotor” refers not only to aircraft propeller applications, but also to windmill impellers, marine propellers, turbine engine rotors, helicopter rotors, and various other applications, and regardless of the type of working fluid used in conjunction with the rotor.
- Still referring to
FIG. 1 , theblade 14 includes aroot region 16 proximate the hub 12, and atip region 18 distal the hub 12 and disposed radially outwardly of theroot region 16. Theroot region 16 may be integrally or separately coupled to thehub 14 for example, by forming, casting, forging, welding, fastening, or in any other suitable manner. Thetip region 18 may include a radiallyoutermost surface 20 of theblade 14. Theblade 14 also includes a leading edge orsurface 22 extending between the root andtip regions surface 24 extending between the root andtip regions surfaces - Referring also to
FIG. 2 , theblade 14 further includes a first orpressure surface 26 extending between the root andtip regions 16, 18 (FIG. 1 ) and the leading and trailingsurfaces suction surface 28 extending between the root andtip regions 16, 18 (FIG. 1 ) and the leading and trailingsurfaces suction surface 28 may be generally convex as shown and thepressure surface 26 may be generally concave as shown, wherein theblade 14 may be shaped as an aerofoil. However, the suction and pressure surfaces 26, 28 may be of any suitable shape(s) or contour(s) and theblade 14 need not be aerofoil-shaped and may be of any suitable shape and disposed at any suitable angle(s). - With continuing reference to
FIGS. 1 and 2 , theblade 14 additionally includes ableed path 30 opening to thesuction surface 28, extending through theblade 14, and exiting to thesuction surface 28, the trailingsurface 24, or both. Thebleed path 30 is provided to bleed low energy working fluid from thesuction surface 28 to improve blade efficiency. Working fluid flows into, through, and out of the bleed path under centrifugal pumping forces to passively bleed working fluid from thesuction surface 28 and thereby prevent or reduce boundary layer separation and/or a laminar separation bubble of working fluid on thesuction surface 28. - As shown in
FIG. 1 , thebleed path 30 generally may extend along, or parallel with respect to, the blade axis B. However, thebleed path 30 may be disposed at any suitable angle with respect to the axis B, and need not be centered between the leading and trailingsurfaces FIG. 1 , thebleed path 30 may be disposed radially outwardly of a circumferential axis C that may bisect the length of theblade 14. In another embodiment, a portion of thebleed path 30 may extend radially inwardly of the axis C. For example, at least part of an inlet portion of thebleed path 30 may extend radially inwardly of the axis C. - Still referring to
FIG. 1 , thebleed path 30 includes aninlet 32 located in thesuction surface 28 to receive working fluid on thesuction surface 28, and aconduit 34 in communication with theinlet 32 to convey the working fluid from theinlet 32 in a radially outward direction toward thetip region 18 of theblade 14. As shown inFIGS. 1 and 3 , thebleed path 30 also includes anoutlet 36 in communication with theconduit 34 and disposed radially outwardly of theinlet 32 to exhaust the working fluid out of theblade 14. - Referring to
FIG. 4 , and as depicted by the arrows, centrifugal pumping forces pull working fluid into theinlet 32, through theconduit 34, and out of theoutlet 36. (SeeFIG. 1 for example location ofoutlet 36 in the blade 14) Such fluid flow may reduce or thin a boundary layer, and also may at least reduce, and preferably prevent, laminar separation of the working fluid on thesuction surface 28 of theblade 14. The working fluid passively flows through thebleed path 30 under vacuum or negative pressurization pulled from theoutlet 36. In other words, the working fluid may not actively flow through thebleed path 30 under positive pressurization pushed from theinlet 32 toward theoutlet 36, for example, from some external pressurizing device like a pump, or from a path open to thepressure surface 26 and communicated directly to thebleed path 30, or the like. - As shown in
FIG. 1 , theinlet 32 may be of any suitable size and shape. For example, theinlet 32 may be a slot that may extend in a generally radial direction over at least a portion of an area of thesuction surface 28 that would experience boundary layer separation but for the slot. However, theinlet 32 may be disposed at any suitable angle with respect to the axis B, and need not be centered between the leading and trailingsurfaces inlet 32 may be a porous patch on thesuction surface 28. For instance, theconduit 34 or at least a portion thereof may be covered by a porous surface flush with thesuction surface 28. An example porosity of the porous patch may be 10%-75% porosity. - Prior art
FIG. 5 illustrates aprior art blade 114 without thebleed path 30, wherein laminar separation and turbulent reattachment occurs over asuction surface 128 to create abubble area 129 of low energy working fluid. Such abubble area 129 tends to appear at low Reynolds numbers, creates drag and thereby reduces efficiency of theblade 114 and, in a propeller embodiment, requires more power to move theblade 114. -
FIG. 6 illustrates another exemplary embodiment of arotor blade 214. This embodiment is similar in many respects to the embodiment ofFIGS. 1-4 and like numerals between the embodiments generally designate like or corresponding elements throughout the several views of the drawing figures. Additionally, the descriptions of the embodiments are incorporated by reference into one another and the common subject matter generally may not be repeated here. In contrast to prior artFIG. 5 ,FIG. 6 illustrates a presently disclosedrotor blade 214 having aninlet 232 of ableed path 230 disposed in area of thesuction surface 228 where the bubble area 129 (FIG. 5 ) would be located if thebleed path 230 were not present. In this embodiment, theinlet 232 can be provided as a porous surface or patch to cover the bubble area 129 (FIG. 5 ). Theinlet 232 may be centered (in a circumferential direction between) over an area where the bubble area 129 (FIG. 5 ) would be. Those of ordinary skill in the art will recognize that such sizing and locating is application specific and may be determined via empirical testing or by modeling or both. - In a further embodiment, shown in
FIG. 4 , a plurality of theinlet 32 may be provided, each of which may be sized in correspondence to a radial fluid flow distribution. For example, theinlet 32 may be divided in a radial direction into a plurality of separate inlets, as indicated inFIG. 4 , corresponding in size and/or shape to different radial pressure gradients along theblade 14. Such aninlet 32 may be thought of as akin to an input side of a harmonica. - Referring to
FIGS. 1-4 , theconduit 34 may include any suitable device to convey the working fluid. In one embodiment, theconduit 34 may include one or more separate tubes, pipes, hoses, or the like assembled to theblade 14 in any suitable manner. In another embodiment, theconduit 14 may include an integral void in theblade 14 that may be formed, cast, forged, machined, or the like in theblade 14 in any suitable manner. Theconduit 34 may be of any suitable shape and size. - As shown in
FIG. 3 , theoutlet 36 may be located in the trailingsurface 24 of theblade 14 in one embodiment. In another embodiment, anoutlet 36′ may be provided in thesuction surface 28. In an additional embodiment, bothoutlets outermost surface 20 of theblade 14. Theoutlet 36 oroutlets - In one embodiment, the
conduit 14 and/or the outlet(s) 36 (36′) may be shaped and/or sized to reduce a differential between a velocity of working fluid transmitted from theoutlet 36 and a velocity of working fluid in a free stream adjacent theoutlet 36. Those of ordinary skill in the art will recognize that such shaping and sizing is application specific and may be determined via empirical testing or by modeling or both. - The presently disclosed
bleed path 30 reduces, eliminates, or prevents boundary layer separation over thesuction surface 28 of therotor blade 14, with concomitant reduction, elimination, or prevention in drag and inefficiency of theblade 14. For example, thebleed path 30 may be used to reduce, eliminate, or prevent boundary layer separation whether the flow is laminar or turbulent, and may be particularly beneficial for use in applications with low Reynolds numbers. For instance, it is believed that the presently disclosedbleed path 30 will reduce power required to rotate a propeller and may increase propeller efficiency particularly for relatively small, slowly rotating propellers at high altitudes. Moreover, thebleed path 30 reduces product weight, is low in cost, and does not have any separate moving parts. - Generally, airfoils are designed such that the boundary layer transitions from laminar to turbulent prior to laminar separation. The turbulent boundary layer then naturally remains attached longer because it can tolerate a more adverse pressure gradient than that of a laminar boundary layer. However, at low Reynolds numbers, the laminar boundary layer may separate before transition occurs. If the laminar flow separates, then the process of separation usually induces rapid transition to turbulence. In many cases, this turbulent flow then reattaches because it is more tolerant of the adverse pressure gradient which caused the laminar flow to separate. This laminar separation and turbulent reattachment is called a laminar separation bubble and is a common source of high drag on airfoils used at low Reynolds numbers. In other cases, the separated flow does not reattach, and the resulting drag is even higher.
- The presently disclosed passive bleed path(s) may improve efficiency over a large range of conditions, especially at low Reynolds numbers where laminar separation tends to appear. The bleed inlet(s) may be located near the region where laminar separation would occur (if bleed were absent). At low Reynolds numbers, the passive bleed prevents laminar separation such that the boundary layer transitions to turbulent while still attached. The turbulent boundary layer is then able to remain attached because it is more tolerant of an adverse pressure gradient. Therefore, a laminar separation bubble can be prevented, and a substantial source of drag can be eliminated.
- Although the bleed inlet(s) may be located near the region of laminar separation, the passive bleed may also be beneficial at higher Reynolds numbers, when the flow is already turbulent over the bleed inlet(s). In this case, the natural turbulent separation point is downstream of the location of the bleed inlet(s), even if bleed were absent. With passive bleed present, the turbulent boundary layer is thinned, thereby delaying separation to a point even farther downstream. This could allow more extreme airfoil shapes to be practical.
- This description, rather than describing limitations of an invention, only illustrates example embodiments of the invention recited in the claims. The language of this description is therefore exclusively descriptive and non-limiting. Obviously, it's possible to modify this invention from what the description teaches. Within the scope of the claims, one may practice the invention other than as described above.
Claims (20)
1. A rotor blade comprising:
a root region;
a tip region disposed radially outwardly of the root region;
a leading surface extending between the root and tip regions;
a trailing surface extending between the root and tip regions;
a pressure surface extending between the root and tip regions and the leading and trailing surfaces;
a suction surface extending between the root and tip regions and the leading and trailing surfaces; and
a bleed path opening to the suction surface, extending through the blade, exiting to at least one of the suction or trailing surfaces, and through which working fluid flows under centrifugal pumping forces when the blade rotates, to passively bleed working fluid from the suction surface.
2. The rotor blade of claim 1 , wherein the working fluid passively flows through the bleed path under negative pressurization, but the working fluid does not actively flow through the bleed path by positive pressurization from some external pressurizing device or from a path open to the pressure surface.
3. The rotor blade of claim 1 , wherein the bleed path includes:
an inlet in the suction surface to receive working fluid on the suction surface;
a conduit in communication with the inlet to convey the working fluid from the inlet toward the tip region; and
an outlet in communication with the conduit and disposed radially outwardly of the inlet to exhaust the working fluid out of the blade.
4. The rotor blade of claim 3 , wherein the bleed path is configured to cause centrifugal pumping forces to pull the working fluid into the inlet, through the conduit, and out of the outlet when the blade rotates.
5. The rotor blade of claim 3 , wherein the bleed path is located radially outward of a circumferential axis bisecting the blade.
6. The rotor blade of claim 3 , wherein the inlet is a slot extending in a generally radial direction along the blade.
7. The rotor blade of claim 3 , further comprising a plurality of the inlet radially spaced from one another in correspondence to radial pressure gradients.
8. The rotor blade of claim 3 , wherein the conduit is at least one of shaped or sized to reduce a differential in velocity of working fluid transmitted from the outlet and velocity of working fluid in a free stream adjacent the outlet.
9. The rotor blade of claim 3 , wherein the outlet is located in at least one of the suction surface or the trailing surface.
10. The rotor blade of claim 3 , wherein the outlet is located radially inward of a radially outermost tip of the blade.
11. The rotor blade of claim 1 , wherein the rotor blade is a working member of at least one of an aircraft propeller, a marine propeller, a helicopter rotor, a turbine engine rotor, or a windmill impeller.
12. A rotor comprising:
a hub defining a rotational axis of the rotor; and
a rotor blade extending radially outwardly from the hub, and including:
a root region;
a tip region disposed radially outwardly of the root region;
a leading surface extending between the root and tip regions;
a trailing surface extending between the root and tip regions;
a pressure surface extending between the root and tip regions and the leading and trailing surfaces;
a suction surface extending between the root and tip regions and the leading and trailing surfaces; and
a bleed path opening to the suction surface and including:
an inlet in the suction surface to receive working fluid on the suction surface;
a conduit in communication with the inlet to convey the working fluid from the inlet toward the tip region; and
an outlet in communication with the conduit and disposed radially outwardly of the inlet to exhaust the working fluid out of the blade;
wherein the bleed path is configured such that working fluid flows through the bleed path under centrifugal pumping forces when the blade rotates, to passively bleed working fluid from the suction surface, such that the working fluid passively flows through the bleed path under negative pressurization, but the working fluid does not actively flow through the bleed path by positive pressurization pushed from the inlet toward the outlet from some external pressurizing device or from a path open to the pressure surface.
13. The rotor of claim 12 , wherein the bleed path is located radially outward of a circumferential axis bisecting the blade, and the inlet is a slot extending in a generally radial direction along the blade.
14. The rotor of claim 12 , wherein the outlet is located in at least one of the suction surface or the trailing surface, and is located radially inward of a radially outermost tip of the blade.
15. The rotor of claim 12 , wherein the rotor is at least one of an aircraft propeller, a marine propeller, a helicopter rotor, a turbine engine rotor, or a windmill impeller.
16. A rotor blade comprising:
a root region;
a tip region disposed radially outwardly of the root region;
a leading surface extending between the root and tip regions;
a trailing surface extending between the root and tip regions;
a pressure surface extending between the root and tip regions and the leading and trailing surfaces;
a suction surface extending between the root and tip regions and the leading and trailing surfaces; and
a bleed path opening to the suction surface and including:
an inlet in the suction surface to receive working fluid on the suction surface;
a conduit in communication with the inlet to convey the working fluid from the inlet toward the tip region; and
an outlet in communication with the conduit and disposed radially outwardly of the inlet to exhaust the working fluid out of the blade.
17. The rotor blade of claim 16 , wherein the bleed path is configured such that working fluid flows through the bleed path under centrifugal pumping forces when the blade rotates, to passively bleed working fluid from the suction surface, and such that the working fluid passively flows through the bleed path under negative pressurization, but the working fluid does not actively flow through the bleed path by positive pressurization from some external pressurizing device or from a path open to the pressure surface.
18. The rotor blade of claim 16 , wherein the bleed path is located radially outward of a circumferential axis bisecting the blade, and the inlet is a slot extending in a generally radial direction along the blade.
19. The rotor blade of claim 16 , wherein the outlet is located in at least one of the suction surface or the trailing surface, and is located radially inward of a radially outermost tip of the blade.
20. The rotor blade of claim 16 , wherein the rotor blade is a working member of at least one of an aircraft propeller, a marine propeller, a helicopter rotor, a turbine engine rotor, or a windmill impeller.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/790,091 US20110293421A1 (en) | 2010-05-28 | 2010-05-28 | Rotor blade having passive bleed path |
EP11165283.0A EP2390178A3 (en) | 2010-05-28 | 2011-05-09 | Rotor blade having passive bleed path |
JP2011116994A JP2011247419A (en) | 2010-05-28 | 2011-05-25 | Rotor blade having passive bleed path |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/790,091 US20110293421A1 (en) | 2010-05-28 | 2010-05-28 | Rotor blade having passive bleed path |
Publications (1)
Publication Number | Publication Date |
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US20110293421A1 true US20110293421A1 (en) | 2011-12-01 |
Family
ID=44065541
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US12/790,091 Abandoned US20110293421A1 (en) | 2010-05-28 | 2010-05-28 | Rotor blade having passive bleed path |
Country Status (3)
Country | Link |
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US (1) | US20110293421A1 (en) |
EP (1) | EP2390178A3 (en) |
JP (1) | JP2011247419A (en) |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20110211952A1 (en) * | 2011-02-10 | 2011-09-01 | General Electric Company | Rotor blade for wind turbine |
CN102556345A (en) * | 2012-01-18 | 2012-07-11 | 朱晓义 | Aircraft power device |
CN102589837A (en) * | 2012-02-09 | 2012-07-18 | 朱晓义 | Large fluid pressure wind tunnel |
US20120189457A1 (en) * | 2011-01-25 | 2012-07-26 | Occhipinti Anthony C | Propeller slipstream enhancer |
US20170029100A1 (en) * | 2014-11-17 | 2017-02-02 | Xiaoyi Zhu | Power device capable of generating greater power |
US11001389B2 (en) | 2018-11-29 | 2021-05-11 | General Electric Company | Propulsion engine thermal management system |
US11008090B2 (en) * | 2017-04-26 | 2021-05-18 | Xiaoyi Zhu | Aircraft generating larger lift by reduction of fluid resistance |
CN114738161A (en) * | 2022-04-20 | 2022-07-12 | 武汉大学 | Automatic suction synergistic horizontal shaft tidal current energy water turbine blade |
US20230312088A1 (en) * | 2019-05-29 | 2023-10-05 | Lockheed Martin Corporation | Securing assembly for a rotor blade |
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US9512821B2 (en) * | 2013-08-15 | 2016-12-06 | Lockheed Martin Corporation | Active bleed for airfoils |
JP5886475B2 (en) * | 2014-03-04 | 2016-03-16 | 中国電力株式会社 | Wind power generator |
WO2018196810A1 (en) | 2017-04-26 | 2018-11-01 | 朱晓义 | Aircraft gaining greater propulsion and lift from fluid continuity |
CN110685976B (en) * | 2019-09-12 | 2020-09-08 | 武汉大学 | Suction jet device for blade boundary layer |
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DE102005047016A1 (en) * | 2005-09-30 | 2007-04-05 | Mtu Aero Engines Gmbh | Moving blade for axial turbomachine has flow duct formed so that discharge openings lie radially further outside intake openings whereby driving pressure gradient at relevant operating points is large enough to permit suction and discharge |
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- 2010-05-28 US US12/790,091 patent/US20110293421A1/en not_active Abandoned
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- 2011-05-25 JP JP2011116994A patent/JP2011247419A/en not_active Withdrawn
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US2156133A (en) * | 1936-06-16 | 1939-04-25 | Theodore H Troller | Propeller |
US4045146A (en) * | 1976-05-17 | 1977-08-30 | Avco Corporation | Helicopter rotor blade |
US5480284A (en) * | 1993-12-20 | 1996-01-02 | General Electric Company | Self bleeding rotor blade |
US7320575B2 (en) * | 2004-09-28 | 2008-01-22 | General Electric Company | Methods and apparatus for aerodynamically self-enhancing rotor blades |
US7435057B2 (en) * | 2005-07-13 | 2008-10-14 | Jorge Parera | Blade for wind turbine |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20120189457A1 (en) * | 2011-01-25 | 2012-07-26 | Occhipinti Anthony C | Propeller slipstream enhancer |
US20110211952A1 (en) * | 2011-02-10 | 2011-09-01 | General Electric Company | Rotor blade for wind turbine |
CN102556345A (en) * | 2012-01-18 | 2012-07-11 | 朱晓义 | Aircraft power device |
CN102589837A (en) * | 2012-02-09 | 2012-07-18 | 朱晓义 | Large fluid pressure wind tunnel |
US11524774B2 (en) | 2014-11-17 | 2022-12-13 | Xiaoyi Zhu | Automobile engine |
US20170029100A1 (en) * | 2014-11-17 | 2017-02-02 | Xiaoyi Zhu | Power device capable of generating greater power |
US11866160B2 (en) | 2014-11-17 | 2024-01-09 | Xiaoyi Zhu | Power device capable of generating greater propelling force |
US11008090B2 (en) * | 2017-04-26 | 2021-05-18 | Xiaoyi Zhu | Aircraft generating larger lift by reduction of fluid resistance |
US20210237858A1 (en) * | 2017-04-26 | 2021-08-05 | Xiaoyi Zhu | Aircraft generating larger lift by reduction of fluid resistance |
US11565793B2 (en) * | 2017-04-26 | 2023-01-31 | Xiaoyi Zhu | Aircraft generating larger lift by reduction of fluid resistance |
US11001389B2 (en) | 2018-11-29 | 2021-05-11 | General Electric Company | Propulsion engine thermal management system |
US20230312088A1 (en) * | 2019-05-29 | 2023-10-05 | Lockheed Martin Corporation | Securing assembly for a rotor blade |
CN114738161A (en) * | 2022-04-20 | 2022-07-12 | 武汉大学 | Automatic suction synergistic horizontal shaft tidal current energy water turbine blade |
Also Published As
Publication number | Publication date |
---|---|
JP2011247419A (en) | 2011-12-08 |
EP2390178A3 (en) | 2014-12-17 |
EP2390178A2 (en) | 2011-11-30 |
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