CA1205709A - Airfoil for high efficiency/high lift fan - Google Patents
Airfoil for high efficiency/high lift fanInfo
- Publication number
- CA1205709A CA1205709A CA000398169A CA398169A CA1205709A CA 1205709 A CA1205709 A CA 1205709A CA 000398169 A CA000398169 A CA 000398169A CA 398169 A CA398169 A CA 398169A CA 1205709 A CA1205709 A CA 1205709A
- Authority
- CA
- Canada
- Prior art keywords
- suction surface
- airfoil
- bubble
- edge
- fan
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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
- F04D29/32—Rotors specially for elastic fluids for axial flow pumps
- F04D29/38—Blades
- F04D29/384—Blades characterised by form
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
AIRFOIL FOR HIGH EFFICIENCY/HIGH LIFT FAN
Abstract of the Disclosure Airfoil for vehicle fan which operates in low Reynolds number and varying turbulent conditions having a discontinuity formed on the suction surface thereof adjacent to its leading edge to trigger for-mation of a laminar flow bubble so that sufficient suction surface remains downstream of the air bubble whereby air circumventing the bubble can reattach to the suction surface for sufficient pressure recovery for high lift and low drag per-formance.
Abstract of the Disclosure Airfoil for vehicle fan which operates in low Reynolds number and varying turbulent conditions having a discontinuity formed on the suction surface thereof adjacent to its leading edge to trigger for-mation of a laminar flow bubble so that sufficient suction surface remains downstream of the air bubble whereby air circumventing the bubble can reattach to the suction surface for sufficient pressure recovery for high lift and low drag per-formance.
Description
S70~
e OTl OR HICH ~ CIr ~ ~HIGH LI~T FAN
This in~ention relates to fans and more particularly to new and improved high eficiency and high li~t fan airfoils with predetexmined suction surface discontinuity providing ~or induced develop~
ment of a laminar separation bubble at a predetermined forward point on such surface so that separated air flowing over the bubble can reattach to the suction surface for establishment of substantial pxessure recovery.
Automotive engine cooling air ~ans generally operate in a range of low Reynolds nu~bers ana a wide range of turbulence levels and encounter excessive laminar flow separation on their suc~ion surfaces.
This detracts from fan efficiency and air pumping capa-bility. To provide for improved fan operation, clas~ical fan airfoils such as NA~A-65 have been employed.
However, such ~an bIade designs have been unable to supply the higher lift to drag ratiQs now ~?s~red f~-~r surface vehicle applications. In such classical ai~-roll construction, a laminar flow separation bubble occurs on the suction side o~ the blade. This bubble has varying length, which increases as the Re~olds number decreases and/or turbulence level o~ upstream air decreases. The laminar flow separation bubble can accordingly grow to extend across a large part of the suction surface so that the flow circumventing the bubble cannot readily reattach to the suction surface to provide for the high lift and efficiency needed to meet higher standards for vehicle engine cooling fan operation.
To obtain high lift and low drag, flow reattachment and pressure recovery is needed in the shortest possible distance after ~he flow separation bubble~ To this end, this invention tailors an ~L2~D5~
airfoil for the establishment of a bubble at a pre~
described forward point on the suction surface thereof to thereby provide a large pressure recovery area so that there is reattachment of boundary air to such surface and such reattached flow extends across the recovery surface. Generally, with this invention, separated flow is quickly blended and reattached to the airfoil at optimum points on the suction surface at the end of the bubble to provide for high lift and low drag.
In the development of one embodiment of this invention, a mathematical model of a section of the blade surface was made with prescribed velocity or pressure distribution which would give the highest lift and lowest drag. The model was designed to recognize the existence of a laminar separation bubble and to require separation of flow at a pre-determined upstream or forward position on the suction surface thereof. At predetermined pressu~e points on this surface, pressure recovery was required so that flow downstream of the bu~ble blended and reattached to a large area of the suction surface: Accordingly, to maximize lift and minimize drag, the suction surface of the mathema-tical model was designed to obtain a velocity dis-tribution recovery a given pressure difference in the shortest distance without turbulent ~low separa-tion. The blade shape corresponding to the optimized prescribed velocity distributions was then calculated from the model.
In a preferred embodiment of this airfoil~
a surface discontinuity, such as a flat, step, scribe mark, cavity~ surface roughness, can be made on the suction surface thereof to precisely establish the origin of the laminar separation bubble. In one preferred design, a flat was added to the ~2~7~3~
suction surface of the calculated blade snape to provide the discontinuity to thereby originate the laminar separation bu~ble at a precise location and to accommodate part o~ all of reattachment of the separated ~lo~ upstream of the pressure recovery region. This airfoil design procedure dictates the s~paration point thxough the discontinuity location and provides ~r the flat geometry in pre~icting the reattachment points of the separated flow.
In this preferred embodiment, the flat forms a ramp that makes a 9 angle with a tangent to the upstream suction surface of the blade to efficien~ly pump under low Reynolds number flow conditions or under a wide range of turbulence level~. Early establishment of the start of the bubble provides a control to prevent catastrophic failure (no reattach-ment of separated flow) so that the design is suitable for the entire range of engine fan cooling operation including idle.
e OTl OR HICH ~ CIr ~ ~HIGH LI~T FAN
This in~ention relates to fans and more particularly to new and improved high eficiency and high li~t fan airfoils with predetexmined suction surface discontinuity providing ~or induced develop~
ment of a laminar separation bubble at a predetermined forward point on such surface so that separated air flowing over the bubble can reattach to the suction surface for establishment of substantial pxessure recovery.
Automotive engine cooling air ~ans generally operate in a range of low Reynolds nu~bers ana a wide range of turbulence levels and encounter excessive laminar flow separation on their suc~ion surfaces.
This detracts from fan efficiency and air pumping capa-bility. To provide for improved fan operation, clas~ical fan airfoils such as NA~A-65 have been employed.
However, such ~an bIade designs have been unable to supply the higher lift to drag ratiQs now ~?s~red f~-~r surface vehicle applications. In such classical ai~-roll construction, a laminar flow separation bubble occurs on the suction side o~ the blade. This bubble has varying length, which increases as the Re~olds number decreases and/or turbulence level o~ upstream air decreases. The laminar flow separation bubble can accordingly grow to extend across a large part of the suction surface so that the flow circumventing the bubble cannot readily reattach to the suction surface to provide for the high lift and efficiency needed to meet higher standards for vehicle engine cooling fan operation.
To obtain high lift and low drag, flow reattachment and pressure recovery is needed in the shortest possible distance after ~he flow separation bubble~ To this end, this invention tailors an ~L2~D5~
airfoil for the establishment of a bubble at a pre~
described forward point on the suction surface thereof to thereby provide a large pressure recovery area so that there is reattachment of boundary air to such surface and such reattached flow extends across the recovery surface. Generally, with this invention, separated flow is quickly blended and reattached to the airfoil at optimum points on the suction surface at the end of the bubble to provide for high lift and low drag.
In the development of one embodiment of this invention, a mathematical model of a section of the blade surface was made with prescribed velocity or pressure distribution which would give the highest lift and lowest drag. The model was designed to recognize the existence of a laminar separation bubble and to require separation of flow at a pre-determined upstream or forward position on the suction surface thereof. At predetermined pressu~e points on this surface, pressure recovery was required so that flow downstream of the bu~ble blended and reattached to a large area of the suction surface: Accordingly, to maximize lift and minimize drag, the suction surface of the mathema-tical model was designed to obtain a velocity dis-tribution recovery a given pressure difference in the shortest distance without turbulent ~low separa-tion. The blade shape corresponding to the optimized prescribed velocity distributions was then calculated from the model.
In a preferred embodiment of this airfoil~
a surface discontinuity, such as a flat, step, scribe mark, cavity~ surface roughness, can be made on the suction surface thereof to precisely establish the origin of the laminar separation bubble. In one preferred design, a flat was added to the ~2~7~3~
suction surface of the calculated blade snape to provide the discontinuity to thereby originate the laminar separation bu~ble at a precise location and to accommodate part o~ all of reattachment of the separated ~lo~ upstream of the pressure recovery region. This airfoil design procedure dictates the s~paration point thxough the discontinuity location and provides ~r the flat geometry in pre~icting the reattachment points of the separated flow.
In this preferred embodiment, the flat forms a ramp that makes a 9 angle with a tangent to the upstream suction surface of the blade to efficien~ly pump under low Reynolds number flow conditions or under a wide range of turbulence level~. Early establishment of the start of the bubble provides a control to prevent catastrophic failure (no reattach-ment of separated flow) so that the design is suitable for the entire range of engine fan cooling operation including idle.
2~ A feature, object and advantage o~ this invention is to provide a new and impro~ed fan airfoil sectio~ with suction surface discontinuity - providing for induced development of a laminar separation bubble at a predetermined forward point on such surface so that separated air flowing over the bubble can subsequently reattach to the suction surface for establishment of substantial pressure recovery.
Another feature, object and advantage o this invention is to provide a new and improved airfoil for a vehicle fan having a suction surface discontinuity formed thereon to trigger development `
of separation bubble at a predetermined point thereon al]owing detached boundary air sufficient area on the 5UCtiOII surace to reattach for pressure recovery for high lift and low drag.
o~
Another feature, object and advantage of this invention is to provide a new and improved airfoil section for vehicle fan blading in which a laminar separation bubble developed on the suction side of the airfoil is forced to occur in an upstream or forward portion of the airfoil section so that there is sufficient space on the suction surface for reattachment of separated air to provi~e for high lift and low drag operation for improved f~.n efficiency.
Another feature~ object and advantage of this invention is to provide a new and improved airfoil for a vehicle fan in which a surface dis-continuity is formed on a predetermined portion of the upstream suction surface so that a laminar flow separation bubble starts at the same place regardless of low Reynolds number and low turbulence conditions of flow to therehy enable flow reattachment to the suction surface downstream of the bubble for high lift and efficiency.
These and other features, objects and advantages of this invention will be more apparent from the following detailed aescrlption and arawing in which:
Figure 1 is a front elevational view of a ~ultibladed fan for land vehicle use incorporating this in~ention.
Figure 2 is a cross sectional view of the fan of Figure 1 taken along lines 2-2 thereof.
Figure 3 is a sectional view of a classical airfoil configuration.
Figure 4 is a sectional view of one of the airfoils used on the fan of Figure 1 and taken alo:ng lines 4-4 of Figure 1.
Figure 5 .is a perspective view of the airfoil of Figure 4 illustrating cletachment and 'i 70~
reattachment ~f air fl~w acr~ss the sucti~n surface there~f.
Figure 6 is a graph c~mparing ~perating characteristics ~f the airf~ils ~f Figures 3 and .
Figures 7A and 7B are pl~,ts illustrating the devvel~pment ~f the airf~ f Figure 4.
Turning n~w in greater detail t~ the drawing, there is sh~wn in Figures 1 and 2 a multi-bladed fan assembly 10 designated E~r use f~r a land vehicle and particularly f~r inducing air fl~w thr~ugh a radiat~r f~r engine c~ling purp~ses. The fan has a hub 12, a plurality c,f blades 14 extending generally radially fr~m hub 12 and has an ~uter ring-like shr~ud 14 with an annular bell-m~uthed inlet secti~n 16 t~ pr~vide f~r sm~th recirculati~n fl~w int~ the fan blading such as discl~sed in U.S. Patent N~. 4,329,046 assigned t~ the assignee ~f this inventi~n.
T~ impr~ve fan eficiency, airf~ils 22 with classical p~files such as the pr~file ~f the MACA-65 series illustrated in Figure 3 have been empl~yed in engine c~ling fans. Such airf~ils devel~p laminar separati~n bubbles which start at a plurality ~f l~cati~ns and gr~w depending ~n fl~w c~nditi~ns such as dictated fan speed. These bubbles cause separati~n ~f air fl~wing acr~ss the sucti~n side ~f the airf~il. This separati~n may bagin at p~int 26, f~r example, immediately beE~re the ~eparati~n bubble. After fl~w separati~n ~r detachment, the air fl~ws ~ver the bubble and usually bec~mes reattached t~ the sucti~n surface ~f the airf~il at s~me p~int d~wnstream ~f the bubble. At l~w Reyn~lds number ~perati~n, such as during l~w relative speed due t~ engine design c~nstraints ~r engine idle, the laminar ~2~0~
separation bubble grows to a point where there is limited surface remaining for reattachment. When this occurs, pressure recovery is reduced so that Iift is materially reduced and drag is increased.
Under extreme conditions which may be termed "bubble busting", the bubble extends across the pressure recovery area of the alrfoil so that reattarhment cannot occur and there is substantial p~rformance failure of the airfoil.
To provide for improved pressure recovery~
a new and improved airfoil 30 shown in Figure 4 is provided by this invention. In this design, a dis-continuity in the form of a sharp edge flat or ramp 32 transverse to the cord of the airfoil ~nd adjacent to the airfoil nose 34 is provided. The fl~t 32 extends rearwardly from a forward sharp edge 36 and is inclined at a predetermined angle wi~h ~espect to a line T, tangent to the upstream blade sur~ace.
This flat extends rearwardly from the sharp edge 36 2Q and smoothly blends into the suction surfao~. of t7l~
blade prior to the pressure recovery profile so th~t there is only one discontinuity and only a single laminar flow separation bubble develops.
Accordingly, with this invention a single laminar separation bubble will develop which has a predetermined starting point as dictated by the dis~
continuity, i.e., the sharp edge 36 of flat 32, and which extends rearwardly along the ramp. At a par~
ticular point along the ramp the bubble will ~er~inate so that the air flowing around the bubble will reattach on the suction side of the blade. This action is illustrated in Figure 5 which is an airfoil section made with a flat in accordance with this invention and painted with a mixture o~ titaniuM
dioxide and oil. This airfoil section was placed in a wind tunnel and the flow visualization photograph, ~s~
Figure 5, was made while the sectlon experienced low Reynolds number flow. The separation bubble 40 is triggered by the sharp edge 36 of the flat during tests includincJ low Reynolds number and a wide range includ-ing low turbulence operation. This bubble terminateson the flat 32 and the air flowing around and over the bubble reattaches on the flat and along the suction surface 42 immediately behind the bubble to provide for improved airfoil operation for high lift and reduced drag.
Figure 6 contains curves C and I respec-tively comparing pressure loss incurred by classical airfoil 22 and the airfoil 30 of this invention for Reynolds numbers decreasing from 200,000 to 100,000.
At point G, the laminar bubble in the classical airfoil starts growing extending into the pressure recovery region of the airfoil. Pressure los sub~
se~uently increases to a point H, for example, in which there is failure to provide appreciable li~t and drag is high. In contrast, the laminar separa~
tion bubble in the blade configuration of this inven-tion illustrated by curve I, is controlled by its predetermined downstream location and the pressure loss is stabilized so that there is high lift and low drag throughout the illustrated Reynolds number operating range.
Figures 7A and 7B illustrate the development of the preferred embodiment of the present illvention.
The curve vf Figure 7A represents the mathematical model of blade surface of velocity distribution which gives the highest lift and lowest drag. At point A
on the suction surface curve S, there is forced separa-tion as close to the origin of the suction surface as practical~ The segment A-B of this curve represents the start of flow separation to the recovery region~
The curve from point B to point D, the trailing edge of the blade, represents the shape of the veloci-ty curve to produce pressure recovery in the shortest practical distance. The pressure curve P extending from the origin 0 to point D~, the trailing edge of the pressure surface, was devised to provide for a practical blade design in terms of blade thickness including thickness o~ the trailing edge. T~s surface is also designed to control the amount of turning of air flow into the blade and, in conjunc-tion with the suction surface, provides for the high lift and low drag. If curve P i~ rotated counterclockwise 90, the area formed between curves S and P represent the maximized high lift obta~ned.
Using the surface coordinate points from the mathe=
matical model, the airfoil section illustrated in Figure 7s is plotted to w~ich the discontinuit~ is subsequently added to form the shape of the air~oil of Figure 4. The location of the flat is determined from the specification of the ~elocity distribution coordinates of the mathematical model and the dis-continuity point corresponding to the peak velocity location.
While a preferred embodiment of the inven-tion has been shown and described, other modifications will become apparent to those skilled in the art. Ac-cordingly, the scope of this invention is set forth in the following claims.
Another feature, object and advantage o this invention is to provide a new and improved airfoil for a vehicle fan having a suction surface discontinuity formed thereon to trigger development `
of separation bubble at a predetermined point thereon al]owing detached boundary air sufficient area on the 5UCtiOII surace to reattach for pressure recovery for high lift and low drag.
o~
Another feature, object and advantage of this invention is to provide a new and improved airfoil section for vehicle fan blading in which a laminar separation bubble developed on the suction side of the airfoil is forced to occur in an upstream or forward portion of the airfoil section so that there is sufficient space on the suction surface for reattachment of separated air to provi~e for high lift and low drag operation for improved f~.n efficiency.
Another feature~ object and advantage of this invention is to provide a new and improved airfoil for a vehicle fan in which a surface dis-continuity is formed on a predetermined portion of the upstream suction surface so that a laminar flow separation bubble starts at the same place regardless of low Reynolds number and low turbulence conditions of flow to therehy enable flow reattachment to the suction surface downstream of the bubble for high lift and efficiency.
These and other features, objects and advantages of this invention will be more apparent from the following detailed aescrlption and arawing in which:
Figure 1 is a front elevational view of a ~ultibladed fan for land vehicle use incorporating this in~ention.
Figure 2 is a cross sectional view of the fan of Figure 1 taken along lines 2-2 thereof.
Figure 3 is a sectional view of a classical airfoil configuration.
Figure 4 is a sectional view of one of the airfoils used on the fan of Figure 1 and taken alo:ng lines 4-4 of Figure 1.
Figure 5 .is a perspective view of the airfoil of Figure 4 illustrating cletachment and 'i 70~
reattachment ~f air fl~w acr~ss the sucti~n surface there~f.
Figure 6 is a graph c~mparing ~perating characteristics ~f the airf~ils ~f Figures 3 and .
Figures 7A and 7B are pl~,ts illustrating the devvel~pment ~f the airf~ f Figure 4.
Turning n~w in greater detail t~ the drawing, there is sh~wn in Figures 1 and 2 a multi-bladed fan assembly 10 designated E~r use f~r a land vehicle and particularly f~r inducing air fl~w thr~ugh a radiat~r f~r engine c~ling purp~ses. The fan has a hub 12, a plurality c,f blades 14 extending generally radially fr~m hub 12 and has an ~uter ring-like shr~ud 14 with an annular bell-m~uthed inlet secti~n 16 t~ pr~vide f~r sm~th recirculati~n fl~w int~ the fan blading such as discl~sed in U.S. Patent N~. 4,329,046 assigned t~ the assignee ~f this inventi~n.
T~ impr~ve fan eficiency, airf~ils 22 with classical p~files such as the pr~file ~f the MACA-65 series illustrated in Figure 3 have been empl~yed in engine c~ling fans. Such airf~ils devel~p laminar separati~n bubbles which start at a plurality ~f l~cati~ns and gr~w depending ~n fl~w c~nditi~ns such as dictated fan speed. These bubbles cause separati~n ~f air fl~wing acr~ss the sucti~n side ~f the airf~il. This separati~n may bagin at p~int 26, f~r example, immediately beE~re the ~eparati~n bubble. After fl~w separati~n ~r detachment, the air fl~ws ~ver the bubble and usually bec~mes reattached t~ the sucti~n surface ~f the airf~il at s~me p~int d~wnstream ~f the bubble. At l~w Reyn~lds number ~perati~n, such as during l~w relative speed due t~ engine design c~nstraints ~r engine idle, the laminar ~2~0~
separation bubble grows to a point where there is limited surface remaining for reattachment. When this occurs, pressure recovery is reduced so that Iift is materially reduced and drag is increased.
Under extreme conditions which may be termed "bubble busting", the bubble extends across the pressure recovery area of the alrfoil so that reattarhment cannot occur and there is substantial p~rformance failure of the airfoil.
To provide for improved pressure recovery~
a new and improved airfoil 30 shown in Figure 4 is provided by this invention. In this design, a dis-continuity in the form of a sharp edge flat or ramp 32 transverse to the cord of the airfoil ~nd adjacent to the airfoil nose 34 is provided. The fl~t 32 extends rearwardly from a forward sharp edge 36 and is inclined at a predetermined angle wi~h ~espect to a line T, tangent to the upstream blade sur~ace.
This flat extends rearwardly from the sharp edge 36 2Q and smoothly blends into the suction surfao~. of t7l~
blade prior to the pressure recovery profile so th~t there is only one discontinuity and only a single laminar flow separation bubble develops.
Accordingly, with this invention a single laminar separation bubble will develop which has a predetermined starting point as dictated by the dis~
continuity, i.e., the sharp edge 36 of flat 32, and which extends rearwardly along the ramp. At a par~
ticular point along the ramp the bubble will ~er~inate so that the air flowing around the bubble will reattach on the suction side of the blade. This action is illustrated in Figure 5 which is an airfoil section made with a flat in accordance with this invention and painted with a mixture o~ titaniuM
dioxide and oil. This airfoil section was placed in a wind tunnel and the flow visualization photograph, ~s~
Figure 5, was made while the sectlon experienced low Reynolds number flow. The separation bubble 40 is triggered by the sharp edge 36 of the flat during tests includincJ low Reynolds number and a wide range includ-ing low turbulence operation. This bubble terminateson the flat 32 and the air flowing around and over the bubble reattaches on the flat and along the suction surface 42 immediately behind the bubble to provide for improved airfoil operation for high lift and reduced drag.
Figure 6 contains curves C and I respec-tively comparing pressure loss incurred by classical airfoil 22 and the airfoil 30 of this invention for Reynolds numbers decreasing from 200,000 to 100,000.
At point G, the laminar bubble in the classical airfoil starts growing extending into the pressure recovery region of the airfoil. Pressure los sub~
se~uently increases to a point H, for example, in which there is failure to provide appreciable li~t and drag is high. In contrast, the laminar separa~
tion bubble in the blade configuration of this inven-tion illustrated by curve I, is controlled by its predetermined downstream location and the pressure loss is stabilized so that there is high lift and low drag throughout the illustrated Reynolds number operating range.
Figures 7A and 7B illustrate the development of the preferred embodiment of the present illvention.
The curve vf Figure 7A represents the mathematical model of blade surface of velocity distribution which gives the highest lift and lowest drag. At point A
on the suction surface curve S, there is forced separa-tion as close to the origin of the suction surface as practical~ The segment A-B of this curve represents the start of flow separation to the recovery region~
The curve from point B to point D, the trailing edge of the blade, represents the shape of the veloci-ty curve to produce pressure recovery in the shortest practical distance. The pressure curve P extending from the origin 0 to point D~, the trailing edge of the pressure surface, was devised to provide for a practical blade design in terms of blade thickness including thickness o~ the trailing edge. T~s surface is also designed to control the amount of turning of air flow into the blade and, in conjunc-tion with the suction surface, provides for the high lift and low drag. If curve P i~ rotated counterclockwise 90, the area formed between curves S and P represent the maximized high lift obta~ned.
Using the surface coordinate points from the mathe=
matical model, the airfoil section illustrated in Figure 7s is plotted to w~ich the discontinuit~ is subsequently added to form the shape of the air~oil of Figure 4. The location of the flat is determined from the specification of the ~elocity distribution coordinates of the mathematical model and the dis-continuity point corresponding to the peak velocity location.
While a preferred embodiment of the inven-tion has been shown and described, other modifications will become apparent to those skilled in the art. Ac-cordingly, the scope of this invention is set forth in the following claims.
Claims (6)
1. An airfoil for a land vehicle fan which operates at low Reynolds number and varying turbulence intensity conditions, said airfoil having a suction surface and a pressure surface extending from a leading edge to a trailing edge thereof, said suction surface being curved and having a discrete surface discontinuity formed therein starting at a predeter-mined point closely adjacent to the leading edge of said airfoil to trigger establishment of a laminar flow separation bubble which substantially starts at said predetermined point and extends rearwardly therefrom to a discrete terminal end before said trailing edge of said airfoil to effect the separation of laminar air flowing on the surfaces of said airfoil from said suction surface adjacent to said predetermined point and forward of said bubble, said suction surface being smooth and continuous downstream of said discontinuity to the trailing edge of said airfoil to provide a surface enhancing reattachment of separated air circumventing said laminar separation bubble subsequent to passage over said bubble to thereby provide for high lift and low drag for high efficiency fan performance.
2. An airfoil for a land vehicle engine cooling fan which efficiently operates in low Reynolds number and a wide range of turbulence air flow conditions, said airfoil having a curved suction surface and a pressure surface extending from a leading edge to a trailing edge thereof, said airfoil having a discontinuity with a sharp forward edge formed on said suction surface closely adjacent to the leading edge of said airfoil and transverse to the chord thereof to trigger establishment of a laminar flow separation bubble adjacent to said sharp forward edge for a wide range of Reynolds numbers and turbulence conditions and which extends rearwardly to a discrete terminal end on said suction surface downstream of said sharp forward edge, said bubble being operative to effect the separation of laminar boundary air flowing on the suction surface of said airfoil at a predetermined point forward of said bubble, said suction surface being smooth and uninterrupted from said sharp forward edge of said discontinuity to said trailing edge to thereby provide for the reattachment of air circumventing said laminar flow separation bubble on said suction surface subsequent to passage over said bubble for high lift and low drag airfoil operation.
3. In a vehicle fan for circulating air for engine cling, said fan having a centralized hub and a plurality of airfoils extending generally radially from said hub and terminating in tip portions, each of said airfoils having a pressure surface and a suction surface, aid suction surface being curved, a discon-tinuity in the form of a flat transverse to the chord of said airfoil, said flat having a sharp forward edge on said suction surface closely adjacent the leading edge of said airfoil to effect establishment of a discrete laminar flow separation bubble starting at a predetermined location on said suction surface adjacent to said forward edge and terminating prior to the trailing edge of said airfoil, said flat extending rearwardly from said sharp edge into a smooth blend with said suction surface and whereby a laminar boundary layer of air becomes initially detached from said suction surface at the start of said bubble and flows over said bubble and subsequently becomes reattached in a pressure recovery region on said suction surface to produce high lift and low drag.
4. In a vehicle fan for circulating air for engine cooling, said fan having a centralized hub and a plurality of airfoils extending generally radially from said hub to terminal points, each of said airfoils having a pressure surface on the lower side thereof and a curved suction surface on the upper side thereof, a discontinuity having a forward edge on said suction surface transverse to the chord of said airfoil and closely adjacent to the leading edge thereof to induce establishment of a laminar air flow separation bubble starting at a predetermined location on said suction surface substantially at said forward edge of said discontinuity and closely adjacent to the leading edge of said airfoil, said bubble terminating without bursting and before the trailing edge of said airfoil, a flat rearwardly of said forward edge allowing detached boundary air flowing across said suction surface and circumventing said bubble to reattach to said flat of said suction surface downstream of said bubble to provide for high lift and low drag.
5. An airfoil for a land vehicle engine cooling fan which operates in a low Reynolds number and a wide range of air turbulence conditions, said airfoil having a continuously smooth curved suction surface on the side thereof and a curved pressure surface on the other side thereof, said airfoil having a leading edge and a trailing edge, said suction surface having a sharp edged discontinuity formed in said curved surface thereof closely adjacent to the leading edge of said airfoil to establish the start of a laminar separation bubble at a predetermined forward location on said suction surface and a flat downstream of said discontinuity whereby laminar flow bounding said airfoil becomes detached at a predetermined point on said suction surface and forward of said separation bubble and becomes reattached after flow around said bubble in a pressure recovery location downstream of said bubble and on said flat to provide for high lift and low drag for high efficiency fan operation.
6. In a vehicle fan for circulating air for engine cooling, said fan having a centralized hub and a plurality of arcuately-spaced airfoils extending generally radially from said hub and terminating in tip portions, an annular bell-mouthed shroud attached to said tip portions for directing laminar flow recirculating air into said airfoils, each of said airfoils having a pressure surface and a suction surface, a discontinuity on said suction surface having an elongated sharp forward edge closely adjacent the leading edge thereof to effect establishment of a laminar flow separation bubble starting at a predetermined location on said suction surface and a flat extending downstream from said sharp forward edge and smoothly blending into said suction surface whereby laminar air flowing into said airfoil becomes initially detached from said suction surface near said sharp forward edge and circumvents said bubble and subsequently becomes reattached to said suction surface on said flat for optimized pressure recovery to provide for high lift and low drag.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US29787481A | 1981-08-31 | 1981-08-31 | |
| US297,874 | 1981-08-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1205709A true CA1205709A (en) | 1986-06-10 |
Family
ID=23148074
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000398169A Expired CA1205709A (en) | 1981-08-31 | 1982-03-11 | Airfoil for high efficiency/high lift fan |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5888499A (en) |
| CA (1) | CA1205709A (en) |
| DE (1) | DE3227997A1 (en) |
| GB (1) | GB2104975B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2250322A (en) * | 1989-09-08 | 1992-06-03 | Frederick Eggleton | Axial flow air compressor blade |
| US6071077A (en) * | 1996-04-09 | 2000-06-06 | Rolls-Royce Plc | Swept fan blade |
| WO1997040260A1 (en) * | 1996-04-22 | 1997-10-30 | Vitara Trading Company Ltd. | Surfaces for movement of media |
| EP0991866B2 (en) * | 1997-06-24 | 2011-06-01 | Siemens Aktiengesellschaft | Compressor blade and use of the same |
| JP2009008014A (en) * | 2007-06-28 | 2009-01-15 | Mitsubishi Electric Corp | Axial flow fan |
| RU2633221C1 (en) * | 2016-06-07 | 2017-10-11 | Федеральное государственное казенное военное образовательное учреждение высшего образования "Военный учебно-научный центр Военно-воздушных сил "Военно-воздушная академия имени профессора Н.Е. Жуковского и Ю.А. Гагарина" (г. Воронеж) Министерства обороны Российской Федерации | Axial compressor |
| RU2695872C1 (en) * | 2018-11-12 | 2019-07-29 | Публичное акционерное общество "ОДК-Уфимское моторостроительное производственное объединение" | Blade machine of stator of axial compressor |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1933947A (en) * | 1933-01-16 | 1933-11-07 | Weber Max | Suction fan wheel |
| JPS55112898A (en) * | 1979-02-23 | 1980-09-01 | Toshiba Corp | Axial flow fan |
-
1982
- 1982-03-11 CA CA000398169A patent/CA1205709A/en not_active Expired
- 1982-07-22 GB GB08221246A patent/GB2104975B/en not_active Expired
- 1982-07-23 DE DE19823227997 patent/DE3227997A1/en active Granted
- 1982-08-31 JP JP15020082A patent/JPS5888499A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5888499A (en) | 1983-05-26 |
| GB2104975A (en) | 1983-03-16 |
| GB2104975B (en) | 1984-10-17 |
| DE3227997C2 (en) | 1987-03-05 |
| DE3227997A1 (en) | 1983-03-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |