CA1055344A - Heat transfer system employing a coanda effect producing fan shroud exit - Google Patents
Heat transfer system employing a coanda effect producing fan shroud exitInfo
- Publication number
- CA1055344A CA1055344A CA299,755A CA299755A CA1055344A CA 1055344 A CA1055344 A CA 1055344A CA 299755 A CA299755 A CA 299755A CA 1055344 A CA1055344 A CA 1055344A
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- Canada
- Prior art keywords
- fan
- section
- radial
- flat portion
- axially
- 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.)
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Abstract
HEAT TRANSFER SYSTEM EMPLOYING A
COANDA EFFECT PRODUCING FAN SHROUD EXIT
ABSTRACT OF THE DISCLOSURE
A contoured shroud exit having means capable of producing low pressure vortices when a fan generated air stream is expelled therefrom.
COANDA EFFECT PRODUCING FAN SHROUD EXIT
ABSTRACT OF THE DISCLOSURE
A contoured shroud exit having means capable of producing low pressure vortices when a fan generated air stream is expelled therefrom.
Description
~)5534~
,, HEAT TRANSFER SYSTEM EMPLOYING A ~ ~ :
,:
COANDA EFFECT PRODUCING FAN SHROUD EXIT
, ' . .
SP~CIFICATION
~.:
This invention relates to cooling systems or internal combustion engines and, more particularly, to a Coanda effect producing fan shroud exit, involved in the air handling step of the heat transfer process. -Reference should be made to my Canadian appli~i-ation Serial No. 184,880, filed November 2, 1973.
This application is a division of Canadian Serial No. 220,621, filed February 24, 197S.
A standard mode of removing heat from an internal combustion engine is to tra~sfer the heat to a liquid, often 1,: ;
water or a mixture thereof, and from therc to a stream of ;
air. The heated air being dispersed out into the atmosphere.
A substantial body of art exists in the provision of means to transfer the heat from the liquid to the air media. In standard practice such as associated with a truck, for example, heated water is passed through a radiator and a cooling air stream is sucked through the radiator by a fan.
Shroud and shroud exit means are employed to guide the air E~
and improve the efficiency of the fan. Such factors as shroud exit to fan blade clearance, recirculation of the same air in the center portions, the generation of fan noises, and the required horsepower to drive the fan become critical. To the solutions of these difficulties and problems, 1:
.. ..
. : --1-- , .
~Lq3S~i3~
innumerable patents have been directed. It has been dis- ~
covered that there is a relation between tip clearance, driving horsepower or fan cfficiency and fan noises. It is believed at this time that recircu-ation and turbulcnce in thc tip region of ~he fan are responsible for a majorit~
of the fan generated noises and substantially reduce the overall efficiency of the fan to move air.
It is therefore an object of this invention to provide a Coanda effect producing fan shroud means. It is yet another object of this invention to provide a fan shroud exit which is capable of creating low pressure vortices when a s-tream of air is passed thereover.
Another object of this invention is to provide an engine cooling system wherein fan generated noise and engine horse-power requirements are reduced. A further object of this invention is to provide a contoured fan shroud exit having low pressure vortex creating pockets therein. Moreover, another object of this invention is to provide a fan shroud exit means which promotes pressure gradient bending of a fan generated airstream passing thereover.
In accordance with this invention it has been discovered that noise generation and horsepower requirements of a fan assembly can be reduced by the provision of a fan shroud exit which is capable of pressure gradient deflection It is believed that by pressure gradient deflecting or tile achievement of the Coanda effect, fan generated turbulence and recirculation in the tip regions of the fan are reduced and that the other results flow therefrom.
If a jet of fluid is introduced adjacent a curved or flat plate, the jet will l'attach" to the plate ~5S344 and follow th~ ~late ~ven thou~h the re~ullan~ flow ~ h is highly divergent from the original direction o~ the jet. '~
This phenomenon is the CDanda effcct named after its discoverer:
Henri Coanda, a Romanian engineer. The Coanda effect, it is believed, is caused by a stable dynamically formed and sustained pressure gradient across a jet, which pressure gradient bends the jet toward an adjacent boùndary or surface. r For example a jet issuing from a nozzle begins to entrain ambient fluid into ~he jet "mixing region" if the issuance of the jet is in the region of a properly designed wall, adjacent thereto entrained fluid is not easily replaced. On '~
the opposite side of the jet, away from the adjacent wall entrained fluid is easily replaced by ambient fluid. The result is the rapid development of a transverse pressure gradient across the jet and the formation of a "bubble" or vortex which forms a region of low pressure. It is the vortex with its low pressure region, a properly designed adjacent wall, and the pressure of the ambient fluid on the opposite side of the stream that cause it to bend and thus follow the contour of the wall. For reasons yet unknown as the jet flows over the surface it entrains u~ to twenty times the amount of air in the original jet.
At this time there is much uncertainty as ~o the nature of the Coanda effect. That is to say the Coanda effect is not fully understood; however, I have determined that the provision of a fan with a Coanda effect producing fan shroud exit causes surprising and unique results.
The object for the invention is attained by a F
vehicle having an engine, and cooliny system of the type comprising a radiator, and a fan driven by the engine ., ~L~S5344 ~ .
for drawing air through an air entry side of the radiator which includes a plurality of radially extending, circumferentially spaced impeller blades, with each of the impeller blades having a tip portion having an axial width Ineasured axially along the rotational axis of the fan and between a pair of spaced points disposed respectively on the leading and trailing edges thereof. Those points disposed on the leading edges ~f the blade tl~ portions lie substantially in a first plane normal to the rotational axis of the fan and the points disposed on the trailing edges of the blade tip portions lie substantiall~ in a second plane axially spaced a distance from and parallel to 'che first plane. A fan shroud is connected to an air exit side of the radiator and encases the fan. The improved fan shroud for reducing fan generated noisc alld horsepower requirements of the engine is characterized by the fan shroud comprising an air intake section, an intermediate section, and an air discharge section with the air intake section converging from the air exit side of the radiator into a duct of circular cross~section. That duct connects with the intermediate section along a third plane, and the intermediate section has a cylindrical body extending axially along the rotational axis of the fan a predetermined distance from a fourth plane with the air discharge section.
The air discharge section has an expanding bell shape with an annular lip extending radially along the fourth plane, with the third and fourth planes being axially spaced and substantially parallel with respect to each other. The fan is positioned within the intermediate and air discharge sections, and an annular step means is connected to at least one of the shroud sections for creating an area of low pressure for producing a Coanda effect in the fan generated air stream.
':
~ ~ -4-~SS3~
In a further embodiment, the invention contempla-tes a fan shroud struc-ture for use wi-th a rotary, axial flo~
- fan having a plurality of circumferentially spaced, radially extending impeller blades, with the blades having an effective axial width (AW) measured axially along the rotational axis of the ~an between a first plane alld a secolld plane and with the planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rota-tional axis of the fan. The first ancl second planes extend radially, respectively through points on the leading edges of the blades at the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof. The combination, including the fan, comprises a generally cylindrical axially extending throat section encircling the Ean, an annular generally radially extending flat portion which is r.adially spaced outwardly and axially from one axial end of the throat section, and an annular intermediate section extending between the one axial end of the throat section and the radial flat portion, with the throat section, intermediate section, and the radial flat ~ .
portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation. An annular supplementary low pressure vortex creating means is formed .in the throat section, intermediate section and radial flat portion of the fan shroud structure whereb~ an additional .
low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.
Other objects and advantages of the invention will become apparent upon reading the followiny detailed -4a-~5534~
description and upon reference to the drawings, in which:
FIGURE l is a side view of a tractor showing one embodimcnt of the invention; and FI(,URE 2 is a partially broken away side sectional view of the radiator fan shroud and fan shroud exit which forms a region of low pressure; and FIG~RES 3 and 4 are additional embodiments which produce the low pressure vortex necessary to achieve pressure gradient bending of the associated fan generated airstream.
While the invention will be described in connection with preferred embodiments, it is understood that it is ~-not intended to limit the invention to that embodiment. On r~
the contrary, it is intended to cover all alternatives, ;
modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. r Referring now to the drawings and, more particularly,~
to Figure l wherein is shown an e~ibodiment of the invention herein disclosed. A conventional water-cooled heat producing internal combustion engine means 10 carried forwardly on longitudinally extending parallel support means 12 of vehicle means 14, as shown herein vehicle means 19 is a tractor; however as will hereafter become more apparent this invention can be employed with any type of vehicle having a heat generating internal combustion engine or any portable or stationary device requiring an air moving fan and fan shroud exit means. Forwardly mounted is a ~-water cooling radiator or heat exchanger means 16 employed ' to dissipate engine generated heat to an air media. Water flows between the water jacket associated with the engine , ~not shown) and the heat exchanger through a series of ' :
1~5534'~
fluid communicating means 18 and 20. ~leat from the engine being absorbed into the wa-ter media or as often the case 3.
a mixture of water and other heat carrying fluids such as r anti-freeze, etc., and passed through the heat exchanger~ F
The heat is then transferred to a fan generated air stream which in turn is expelled out from the shroud exit as it will be hereafter more fully disclosed~
Located adjacent the forward end of engine means 10 is a fan shat means Z6 whereby power is delivered to drive fan means 29. As is apparent, the particular mode whereby power is transferred to the fan and its particular location in regard to the engine means is no-t critical, and any desired location would be satisfactory and any means of powering could be employed. The fan means 29 herein depicted is a rotatable suction fan positioned opposite ~ -radiator means 16 which normally creates a flow o air or, more particularly, moves a stream of cooling air through r!
the radiator with a subsequent discharge thereof through , the air exit side 36 into fan exit shroud means 32. The fan generated air stream is guided or directed from the radiator to the fan by means of an air intake section 34. The particu-lar shape of the forward air intake section 34 thereof is dependent upon the shape and design of the air exit side 36 o the radiator. The nature o the connection between the air intake section 34 and the air exit side 36 depends upon the particular characteristics of the assembly. That ' is, some connections being provided with air gaps, others are made flexible while in still other situations the entire area between the two elements is sealed over the entire periphery of the enclosure. In the preferred form ~, .
.
lC~S5344 of this invention the entire periphery of the rear area is substantially sealed ayainst the passage of air from any other direction except through the radiator. From the air exit side 36 of the radiator, the air intake section of the shroud means 32 (be it a tapered transition as shown or a box type shroud) converges rearwardly through a circular -section 38 and connects to a cylindrical intermediate ~-section 46 which extends axially for a dis~ance CF.
The critical feature of a Coanda effect producing shroud is its ability to form a bubble, vortex, or a region of low pressure adjacent the surface parallel to ~hich it is desired to bend the air stream. Fan means 29 includes _ -a plurality of fan blade means 40 (only one as shown here) as is well known in the art. The fan blade means 40 can be divided into the end or tip region 42, the hub region 44 and a middle region 43. At this time,it is believed that with ;, a standard venturi type shroud and fan arrangements substantial ~1 ~
turbulence is created in the tip region 42 such that noise -pollution is created and the air moving ability of that region is substantially impaired. In the hub regions ;
difficulties with the drawing in of air from the rear with subsequent recirculation substantially impairs the air moving abilities of that region. As a result only the middle region of the fan is performing an efficient air moving job.
It is believed at this time for reasons unknown that the provision of a Coanda generating fan shroud exit generally surrounding the fan blade somehow reduces turbulence and improves the overall air moving efficiency of the blade.
The improved efficiency, thaL is, the lower horsepower requirement to achieve a given cooling rate and .
~5s34~
the reduced noise generated in the ti~ recJions result from the employment of the Coanda gerleratin~ fc~n shroud exit. It is known from experimentation with a hic7h s~eed ~ir jet issuing from a nozzle adjacent a Coanda e~fect producing surface that up to twenty times the volume of air in the jet will be entrained thereby, from the ambient air mass that is on the side of the jet opposite the surface. It may be that r this entrainment phenomenon is helpin~ to pull additional air through the fan blade. As air passes through the blade it is immediately entraincd by -the strcam adjacent the Coanda effect producing shroud exit. ;~
It has been determined by experimentation that a vortex forms a region of low pressure which can be created when a high speed air jet is directed over a properly designed curved surface. See for example my Canadian application Serial Number 184,880. It has also been determined that the low pressure regions can be created by a step or groove in the adjacent surface toward which the airstream is bent. In .
an article entitled "Applications of the Coanda Effect" by Imants Reba, Scientific American, June 1966, the provision of steps near the jet exit to generate the Coanda effect is demonstrated. It should also be noted that the author admits that the Coanda effect is not fully understood and the simple provision of a step will probably not suffice to ?: :
create a Coanda efect. In Figures 2, 3, and 4,it is believed that the annular ste~ or groove means 50 which is provided in the shroud 32 produces the vortices shown by air stream arrows. It must also be understood that l ~
the position of the fan blade assembly with regard to the ;~ -intermediate and air discharge sections 46, 48 of the fan shroud 32 contributes the formation of the Coanda effect.
The embodiments as shown in Figures 2, 3, and 4 1 !:
., ` . . :. ,: . . , ~0553~4 combine smooth curved surfaces and indentations to achieve the Coanda effect in combination with the fan blade. That is, a fan shroud exit means capc~ble of producing the Coanda _~
effect will be one having a low pressure vorte~ creating means such that when an air stream i5 passed thereover the ambient pressure on the side of the stream away from the -shroud stream causes it to deviate and "follow" the surface of the shroud. Generallysituated within the shroud is the ~¦
airstream generating fan means.
With reference to Figures 1 and 2 there is shown an air 'ntake section 34 extending rearwardly from the rear or air exit side 36 of the radiator 16. The shroud means 32 is a Coanda efect producing shroud exit means.
Included in the fan shroud means is a cylindrical inter-~, mediate section 46, which extends a distance CF that cor~
responds to one-third the axial width AW of the fan 29 when ~ , viewed transverse to the axis of the fan, and an air discharge section 48 having an expanding bell shape with an l annular lip 58 extending radially along a second plane. The low pressure forming vortex means 50 takes the form here of a step or an annular ring or groove 52 between the two mentioned sections. Generally centrally located between the two sections 46 and 48 is fan means 29. It should be noted that throat section means 46 is substantially sealed to the air intake section 34 and in the preferred embodiment forms '~
a complete circle around the fan means. At an axial distance CF from the front edge of the intermdeiate section 46, an annular step means 50 forms the low pressure vortex forming means. Carried at the periphery of the annular ring 42, which forms the groove or step 50, is the bell-like ,~
air discharge section 48. The air discharge section 48 .
11~)5534~
generally expands into a bell shape 28 in the direction in which it is desirous of directing the exit alrstream passing thereover. The genexating radius R of the bell portion or the quarter-annular torus 28 corresponds to two-thirds of the projected axial width AW of the fan 29.
For optimum results to be achieved a front or first vertically extending plane passes or extends through the leading edge means 54 of fan means 29 and also inter- r sects the connection of the circular portion 38 of the air intake section 34 and the intermediate cylindrical section or throat means 46. Also a trailing or second vertically extending plane or a rear parallel plane passes or extends ;
through the trailing edge 56 and forms the bo-mdary of the rearward expansion of the annular lip 58 of the bell shaped air discharge section means 48. The annular lip portion !
58 is located on the second vertical plane and extends , radially RF from a point of tangency with the smooth curved r bell portion28 to a distance corresponding to one-third of the projected axial width AW of the fan means 29. It should be understood, however, that these respective rela- i, tions can vary up to plus or minus twelve percent of the ' `
axial width or AW of the fan blade. The axial ~idth or AW ~;~
being the shortest axially extending distance between the front and rear or first and second vertical parallel planes when viewed transverse to the axis of the fan means 29.
The particular embodiment of the intermediate and air discharge sections 46, 48 shown in Figure 3 again has the leading and trailing edges 54, 56 of the fan means 29 located between the first and second vertical parallel planes within the stated plus or minus twelve percent ranges or tolerances. However, the leading ed~e of the ~55344 expanding bell portion 28 of -the air discharge section 48 ~ '~
ls now secured directly to the trailing edge of the cylindrical intermediate section 46 at an axial distance CF from the first vertical plane while the low pressure vortex creating means or annular ring 50 is connected the annular lip 58 and extends axially inwardly towards the radiator 16 and terminates in a radially extending annular flange 60. ~s shown the low pressure vortex creating means 50 is again in the form of a step. ~he particular embodiment shown in ~igure 4, the low pressure vorte~
creating means 50 takes the form of a bend located in the curve of the bell portion 28 of the air discharge section.
As previously stated applicant does not believe a unique design necessary to produce the low pressure vortex. In regard to the location of the low pressure vorte~ creating means or the numbers th~reof, applicant believes this will or may vary from one particular design to another. However, the exit shroud means must be designed and provided with sufficient low pressure vortex means, a curve surface ~o `-direct the alr stream in the desired direction and a fan generally located thereln.
Thus it is apparent that there has been provided, in accordance with the invention, a heat transfer system that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with~specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. ~ccordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the appended claims.
,1 .
, . _ , . .
,, HEAT TRANSFER SYSTEM EMPLOYING A ~ ~ :
,:
COANDA EFFECT PRODUCING FAN SHROUD EXIT
, ' . .
SP~CIFICATION
~.:
This invention relates to cooling systems or internal combustion engines and, more particularly, to a Coanda effect producing fan shroud exit, involved in the air handling step of the heat transfer process. -Reference should be made to my Canadian appli~i-ation Serial No. 184,880, filed November 2, 1973.
This application is a division of Canadian Serial No. 220,621, filed February 24, 197S.
A standard mode of removing heat from an internal combustion engine is to tra~sfer the heat to a liquid, often 1,: ;
water or a mixture thereof, and from therc to a stream of ;
air. The heated air being dispersed out into the atmosphere.
A substantial body of art exists in the provision of means to transfer the heat from the liquid to the air media. In standard practice such as associated with a truck, for example, heated water is passed through a radiator and a cooling air stream is sucked through the radiator by a fan.
Shroud and shroud exit means are employed to guide the air E~
and improve the efficiency of the fan. Such factors as shroud exit to fan blade clearance, recirculation of the same air in the center portions, the generation of fan noises, and the required horsepower to drive the fan become critical. To the solutions of these difficulties and problems, 1:
.. ..
. : --1-- , .
~Lq3S~i3~
innumerable patents have been directed. It has been dis- ~
covered that there is a relation between tip clearance, driving horsepower or fan cfficiency and fan noises. It is believed at this time that recircu-ation and turbulcnce in thc tip region of ~he fan are responsible for a majorit~
of the fan generated noises and substantially reduce the overall efficiency of the fan to move air.
It is therefore an object of this invention to provide a Coanda effect producing fan shroud means. It is yet another object of this invention to provide a fan shroud exit which is capable of creating low pressure vortices when a s-tream of air is passed thereover.
Another object of this invention is to provide an engine cooling system wherein fan generated noise and engine horse-power requirements are reduced. A further object of this invention is to provide a contoured fan shroud exit having low pressure vortex creating pockets therein. Moreover, another object of this invention is to provide a fan shroud exit means which promotes pressure gradient bending of a fan generated airstream passing thereover.
In accordance with this invention it has been discovered that noise generation and horsepower requirements of a fan assembly can be reduced by the provision of a fan shroud exit which is capable of pressure gradient deflection It is believed that by pressure gradient deflecting or tile achievement of the Coanda effect, fan generated turbulence and recirculation in the tip regions of the fan are reduced and that the other results flow therefrom.
If a jet of fluid is introduced adjacent a curved or flat plate, the jet will l'attach" to the plate ~5S344 and follow th~ ~late ~ven thou~h the re~ullan~ flow ~ h is highly divergent from the original direction o~ the jet. '~
This phenomenon is the CDanda effcct named after its discoverer:
Henri Coanda, a Romanian engineer. The Coanda effect, it is believed, is caused by a stable dynamically formed and sustained pressure gradient across a jet, which pressure gradient bends the jet toward an adjacent boùndary or surface. r For example a jet issuing from a nozzle begins to entrain ambient fluid into ~he jet "mixing region" if the issuance of the jet is in the region of a properly designed wall, adjacent thereto entrained fluid is not easily replaced. On '~
the opposite side of the jet, away from the adjacent wall entrained fluid is easily replaced by ambient fluid. The result is the rapid development of a transverse pressure gradient across the jet and the formation of a "bubble" or vortex which forms a region of low pressure. It is the vortex with its low pressure region, a properly designed adjacent wall, and the pressure of the ambient fluid on the opposite side of the stream that cause it to bend and thus follow the contour of the wall. For reasons yet unknown as the jet flows over the surface it entrains u~ to twenty times the amount of air in the original jet.
At this time there is much uncertainty as ~o the nature of the Coanda effect. That is to say the Coanda effect is not fully understood; however, I have determined that the provision of a fan with a Coanda effect producing fan shroud exit causes surprising and unique results.
The object for the invention is attained by a F
vehicle having an engine, and cooliny system of the type comprising a radiator, and a fan driven by the engine ., ~L~S5344 ~ .
for drawing air through an air entry side of the radiator which includes a plurality of radially extending, circumferentially spaced impeller blades, with each of the impeller blades having a tip portion having an axial width Ineasured axially along the rotational axis of the fan and between a pair of spaced points disposed respectively on the leading and trailing edges thereof. Those points disposed on the leading edges ~f the blade tl~ portions lie substantially in a first plane normal to the rotational axis of the fan and the points disposed on the trailing edges of the blade tip portions lie substantiall~ in a second plane axially spaced a distance from and parallel to 'che first plane. A fan shroud is connected to an air exit side of the radiator and encases the fan. The improved fan shroud for reducing fan generated noisc alld horsepower requirements of the engine is characterized by the fan shroud comprising an air intake section, an intermediate section, and an air discharge section with the air intake section converging from the air exit side of the radiator into a duct of circular cross~section. That duct connects with the intermediate section along a third plane, and the intermediate section has a cylindrical body extending axially along the rotational axis of the fan a predetermined distance from a fourth plane with the air discharge section.
The air discharge section has an expanding bell shape with an annular lip extending radially along the fourth plane, with the third and fourth planes being axially spaced and substantially parallel with respect to each other. The fan is positioned within the intermediate and air discharge sections, and an annular step means is connected to at least one of the shroud sections for creating an area of low pressure for producing a Coanda effect in the fan generated air stream.
':
~ ~ -4-~SS3~
In a further embodiment, the invention contempla-tes a fan shroud struc-ture for use wi-th a rotary, axial flo~
- fan having a plurality of circumferentially spaced, radially extending impeller blades, with the blades having an effective axial width (AW) measured axially along the rotational axis of the ~an between a first plane alld a secolld plane and with the planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rota-tional axis of the fan. The first ancl second planes extend radially, respectively through points on the leading edges of the blades at the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof. The combination, including the fan, comprises a generally cylindrical axially extending throat section encircling the Ean, an annular generally radially extending flat portion which is r.adially spaced outwardly and axially from one axial end of the throat section, and an annular intermediate section extending between the one axial end of the throat section and the radial flat portion, with the throat section, intermediate section, and the radial flat ~ .
portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation. An annular supplementary low pressure vortex creating means is formed .in the throat section, intermediate section and radial flat portion of the fan shroud structure whereb~ an additional .
low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.
Other objects and advantages of the invention will become apparent upon reading the followiny detailed -4a-~5534~
description and upon reference to the drawings, in which:
FIGURE l is a side view of a tractor showing one embodimcnt of the invention; and FI(,URE 2 is a partially broken away side sectional view of the radiator fan shroud and fan shroud exit which forms a region of low pressure; and FIG~RES 3 and 4 are additional embodiments which produce the low pressure vortex necessary to achieve pressure gradient bending of the associated fan generated airstream.
While the invention will be described in connection with preferred embodiments, it is understood that it is ~-not intended to limit the invention to that embodiment. On r~
the contrary, it is intended to cover all alternatives, ;
modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. r Referring now to the drawings and, more particularly,~
to Figure l wherein is shown an e~ibodiment of the invention herein disclosed. A conventional water-cooled heat producing internal combustion engine means 10 carried forwardly on longitudinally extending parallel support means 12 of vehicle means 14, as shown herein vehicle means 19 is a tractor; however as will hereafter become more apparent this invention can be employed with any type of vehicle having a heat generating internal combustion engine or any portable or stationary device requiring an air moving fan and fan shroud exit means. Forwardly mounted is a ~-water cooling radiator or heat exchanger means 16 employed ' to dissipate engine generated heat to an air media. Water flows between the water jacket associated with the engine , ~not shown) and the heat exchanger through a series of ' :
1~5534'~
fluid communicating means 18 and 20. ~leat from the engine being absorbed into the wa-ter media or as often the case 3.
a mixture of water and other heat carrying fluids such as r anti-freeze, etc., and passed through the heat exchanger~ F
The heat is then transferred to a fan generated air stream which in turn is expelled out from the shroud exit as it will be hereafter more fully disclosed~
Located adjacent the forward end of engine means 10 is a fan shat means Z6 whereby power is delivered to drive fan means 29. As is apparent, the particular mode whereby power is transferred to the fan and its particular location in regard to the engine means is no-t critical, and any desired location would be satisfactory and any means of powering could be employed. The fan means 29 herein depicted is a rotatable suction fan positioned opposite ~ -radiator means 16 which normally creates a flow o air or, more particularly, moves a stream of cooling air through r!
the radiator with a subsequent discharge thereof through , the air exit side 36 into fan exit shroud means 32. The fan generated air stream is guided or directed from the radiator to the fan by means of an air intake section 34. The particu-lar shape of the forward air intake section 34 thereof is dependent upon the shape and design of the air exit side 36 o the radiator. The nature o the connection between the air intake section 34 and the air exit side 36 depends upon the particular characteristics of the assembly. That ' is, some connections being provided with air gaps, others are made flexible while in still other situations the entire area between the two elements is sealed over the entire periphery of the enclosure. In the preferred form ~, .
.
lC~S5344 of this invention the entire periphery of the rear area is substantially sealed ayainst the passage of air from any other direction except through the radiator. From the air exit side 36 of the radiator, the air intake section of the shroud means 32 (be it a tapered transition as shown or a box type shroud) converges rearwardly through a circular -section 38 and connects to a cylindrical intermediate ~-section 46 which extends axially for a dis~ance CF.
The critical feature of a Coanda effect producing shroud is its ability to form a bubble, vortex, or a region of low pressure adjacent the surface parallel to ~hich it is desired to bend the air stream. Fan means 29 includes _ -a plurality of fan blade means 40 (only one as shown here) as is well known in the art. The fan blade means 40 can be divided into the end or tip region 42, the hub region 44 and a middle region 43. At this time,it is believed that with ;, a standard venturi type shroud and fan arrangements substantial ~1 ~
turbulence is created in the tip region 42 such that noise -pollution is created and the air moving ability of that region is substantially impaired. In the hub regions ;
difficulties with the drawing in of air from the rear with subsequent recirculation substantially impairs the air moving abilities of that region. As a result only the middle region of the fan is performing an efficient air moving job.
It is believed at this time for reasons unknown that the provision of a Coanda generating fan shroud exit generally surrounding the fan blade somehow reduces turbulence and improves the overall air moving efficiency of the blade.
The improved efficiency, thaL is, the lower horsepower requirement to achieve a given cooling rate and .
~5s34~
the reduced noise generated in the ti~ recJions result from the employment of the Coanda gerleratin~ fc~n shroud exit. It is known from experimentation with a hic7h s~eed ~ir jet issuing from a nozzle adjacent a Coanda e~fect producing surface that up to twenty times the volume of air in the jet will be entrained thereby, from the ambient air mass that is on the side of the jet opposite the surface. It may be that r this entrainment phenomenon is helpin~ to pull additional air through the fan blade. As air passes through the blade it is immediately entraincd by -the strcam adjacent the Coanda effect producing shroud exit. ;~
It has been determined by experimentation that a vortex forms a region of low pressure which can be created when a high speed air jet is directed over a properly designed curved surface. See for example my Canadian application Serial Number 184,880. It has also been determined that the low pressure regions can be created by a step or groove in the adjacent surface toward which the airstream is bent. In .
an article entitled "Applications of the Coanda Effect" by Imants Reba, Scientific American, June 1966, the provision of steps near the jet exit to generate the Coanda effect is demonstrated. It should also be noted that the author admits that the Coanda effect is not fully understood and the simple provision of a step will probably not suffice to ?: :
create a Coanda efect. In Figures 2, 3, and 4,it is believed that the annular ste~ or groove means 50 which is provided in the shroud 32 produces the vortices shown by air stream arrows. It must also be understood that l ~
the position of the fan blade assembly with regard to the ;~ -intermediate and air discharge sections 46, 48 of the fan shroud 32 contributes the formation of the Coanda effect.
The embodiments as shown in Figures 2, 3, and 4 1 !:
., ` . . :. ,: . . , ~0553~4 combine smooth curved surfaces and indentations to achieve the Coanda effect in combination with the fan blade. That is, a fan shroud exit means capc~ble of producing the Coanda _~
effect will be one having a low pressure vorte~ creating means such that when an air stream i5 passed thereover the ambient pressure on the side of the stream away from the -shroud stream causes it to deviate and "follow" the surface of the shroud. Generallysituated within the shroud is the ~¦
airstream generating fan means.
With reference to Figures 1 and 2 there is shown an air 'ntake section 34 extending rearwardly from the rear or air exit side 36 of the radiator 16. The shroud means 32 is a Coanda efect producing shroud exit means.
Included in the fan shroud means is a cylindrical inter-~, mediate section 46, which extends a distance CF that cor~
responds to one-third the axial width AW of the fan 29 when ~ , viewed transverse to the axis of the fan, and an air discharge section 48 having an expanding bell shape with an l annular lip 58 extending radially along a second plane. The low pressure forming vortex means 50 takes the form here of a step or an annular ring or groove 52 between the two mentioned sections. Generally centrally located between the two sections 46 and 48 is fan means 29. It should be noted that throat section means 46 is substantially sealed to the air intake section 34 and in the preferred embodiment forms '~
a complete circle around the fan means. At an axial distance CF from the front edge of the intermdeiate section 46, an annular step means 50 forms the low pressure vortex forming means. Carried at the periphery of the annular ring 42, which forms the groove or step 50, is the bell-like ,~
air discharge section 48. The air discharge section 48 .
11~)5534~
generally expands into a bell shape 28 in the direction in which it is desirous of directing the exit alrstream passing thereover. The genexating radius R of the bell portion or the quarter-annular torus 28 corresponds to two-thirds of the projected axial width AW of the fan 29.
For optimum results to be achieved a front or first vertically extending plane passes or extends through the leading edge means 54 of fan means 29 and also inter- r sects the connection of the circular portion 38 of the air intake section 34 and the intermediate cylindrical section or throat means 46. Also a trailing or second vertically extending plane or a rear parallel plane passes or extends ;
through the trailing edge 56 and forms the bo-mdary of the rearward expansion of the annular lip 58 of the bell shaped air discharge section means 48. The annular lip portion !
58 is located on the second vertical plane and extends , radially RF from a point of tangency with the smooth curved r bell portion28 to a distance corresponding to one-third of the projected axial width AW of the fan means 29. It should be understood, however, that these respective rela- i, tions can vary up to plus or minus twelve percent of the ' `
axial width or AW of the fan blade. The axial ~idth or AW ~;~
being the shortest axially extending distance between the front and rear or first and second vertical parallel planes when viewed transverse to the axis of the fan means 29.
The particular embodiment of the intermediate and air discharge sections 46, 48 shown in Figure 3 again has the leading and trailing edges 54, 56 of the fan means 29 located between the first and second vertical parallel planes within the stated plus or minus twelve percent ranges or tolerances. However, the leading ed~e of the ~55344 expanding bell portion 28 of -the air discharge section 48 ~ '~
ls now secured directly to the trailing edge of the cylindrical intermediate section 46 at an axial distance CF from the first vertical plane while the low pressure vortex creating means or annular ring 50 is connected the annular lip 58 and extends axially inwardly towards the radiator 16 and terminates in a radially extending annular flange 60. ~s shown the low pressure vortex creating means 50 is again in the form of a step. ~he particular embodiment shown in ~igure 4, the low pressure vorte~
creating means 50 takes the form of a bend located in the curve of the bell portion 28 of the air discharge section.
As previously stated applicant does not believe a unique design necessary to produce the low pressure vortex. In regard to the location of the low pressure vorte~ creating means or the numbers th~reof, applicant believes this will or may vary from one particular design to another. However, the exit shroud means must be designed and provided with sufficient low pressure vortex means, a curve surface ~o `-direct the alr stream in the desired direction and a fan generally located thereln.
Thus it is apparent that there has been provided, in accordance with the invention, a heat transfer system that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with~specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. ~ccordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the appended claims.
,1 .
, . _ , . .
Claims (13)
1. A fan shroud structure for use with a rotary, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades, said blades haying an effective axial width (AW) measured axially along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respectively through points on the leading edges of the blades at the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof, the combination including said fan, comprising, a generally cylindrical axially extending throat section encircling the fan;
an annular generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from one axial end of said throat section;
an annular intermediate section extending between said one axial end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation; and an annular supplementary low pressure vortex creating means formed in said throat section, intermediate section and radial flat portion of the fan shroud structure whereby an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.
an annular generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from one axial end of said throat section;
an annular intermediate section extending between said one axial end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation; and an annular supplementary low pressure vortex creating means formed in said throat section, intermediate section and radial flat portion of the fan shroud structure whereby an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.
2. A fan shroud structure as set forth in Claim 1, wherein said throat section, flat portion, and inter-mediate section have an overall axial length measured along the rotational axis of the fan substantially equal to AW
plus or minus 25 percent of AW.
plus or minus 25 percent of AW.
3. A fan shroud structure as set forth in Claim 1, wherein said fan is axially positioned with respect to said intermediate section so that said second plane is substantially coincident with the radial plane containing the end of said intermediate section opposite tile end thereof operatively connected to said one axial end of said throat section.
4. A fan shroud structure as set forth in Claim 1, wherein said fan is axially positioned with respect to said throat section so that said first plane is sub-stantially coincident with the radial plane containing one axial end of said throat section.
A fan shroud structure as set forth in Claim 1, wherein said fan is axially positioned with respect to said throat section, intermediate section, and flat portion so that said first plane is axially spaced from and on either axial side of said radial plane containing said one axial end of said throat section a distance of 0 to 12 percent of AW and said second plane is axially spaced from and on either axial side of said radial plane containing said end of said intermediate section opposite the end thereof operatively connected to said throat section a distance of 0 to 12 percent of AW.
6. A fan shroud structure for use with a rotary, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades, said blades having an effective axial width (AW) measured axially along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respective-ly, through points on the leading edges of the blades of the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof, comprising, a generally cylindrical axially extending throat section encircling the fan;
an annular, generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from one axial end of said throat section;
an annular, radially and axially curved, intermediate section extending between said one end of said throat section and said radial flat portion, said throat section, inter-mediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation, and the following relationships exist: RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R = 2AW/3 plus or minus 12 percent of AW where RF is the radial length of the radial flat portion, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section; and an annular supplementary low pressure vortex creating means formed in said throat and intermediate section, and radial flat portion of the fan shroud structure such that an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.
an annular, generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from one axial end of said throat section;
an annular, radially and axially curved, intermediate section extending between said one end of said throat section and said radial flat portion, said throat section, inter-mediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation, and the following relationships exist: RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R = 2AW/3 plus or minus 12 percent of AW where RF is the radial length of the radial flat portion, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section; and an annular supplementary low pressure vortex creating means formed in said throat and intermediate section, and radial flat portion of the fan shroud structure such that an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.
7. A fan shroud structure as set forth in Claim 5 or Claim 6, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersections of said throat section and said intermediate section.
8. A fan shroud structure as set forth in Claim 5 or Claim 6, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersection of said intermediate section and said radial flat portion.
9. A fan shroud structure as set forth in Claim 5 or Claim 6, wherein said supplementary low pressure vortex creating means is disposed intermediate the axial ends of said intermediate section.
10. A fan shroud structure for use with a rotary, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades, said blades having an effective axial width (AW) measured axially along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respective, through points on the leading edges of the blades at the radial tip portions thereof and through points on the trail-ing edges of the blades at the radial tip portions thereof, comprising, a generally cylindrical, axially extending throat section encircling the fan, said first plane being sub-stantially coincident with the radial plane containing one axial end of said throat section;
an annular, generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from the other axial end of said throat section;
an annular intermediate section extending between said other axial end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation, said intermediate section being radially and axially curved, and the following relation-ships exist: RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R = 2AW/3 plus or minus 12 percent of AW where RF is the radial length of the radial flat portion, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section, and said first plane may be axially spaced from and on either axial side of radial plane containing said one axial end of said throat section a distance of 12 percent of AW and said second plane may be axially spaced from and on either axial side of a radial plane containing said end of said intermediate section opposite the end thereof operatively connected to said throat section a distance of 12 percent of AW; and an annular supplementary low pressure vortex creating means formed in said throat and intermediate sections, and radial flat portion of the fan shroud structure whereby an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.
an annular, generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from the other axial end of said throat section;
an annular intermediate section extending between said other axial end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation, said intermediate section being radially and axially curved, and the following relation-ships exist: RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R = 2AW/3 plus or minus 12 percent of AW where RF is the radial length of the radial flat portion, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section, and said first plane may be axially spaced from and on either axial side of radial plane containing said one axial end of said throat section a distance of 12 percent of AW and said second plane may be axially spaced from and on either axial side of a radial plane containing said end of said intermediate section opposite the end thereof operatively connected to said throat section a distance of 12 percent of AW; and an annular supplementary low pressure vortex creating means formed in said throat and intermediate sections, and radial flat portion of the fan shroud structure whereby an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.
11. A fan shroud structure as set forth in Claim 10, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersection of said throat section and said intermediate section and includes an annular, radially extending step operatively connected to and extending radially outwardly from one axial end of said throat section, said step being operatively connected to one end of said intermediate section.
12. A fan shroud structure as set forth in Claim 10, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersection of said inter-mediate section and said radial flat portion and includes an annular, axially extending step operatively connected to and extending axially toward said throat section from the radially outermost end of said intermediate section, said step being operatively connected to the radially innermost end of said radial flat portion.
13. A fan shroud structure as set forth in Claim 10, wherein said supplementary low pressure vortex creating means is disposed intermediate the axially spaced ends of said intermediate section and includes an annular, concave groove formed in the surface of said intermediate section over which the air stream flows when the fan is in operation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US47078774A | 1974-05-17 | 1974-05-17 | |
| CA220,621A CA1046367A (en) | 1974-05-17 | 1975-02-24 | Heat transfer system employing a coanda effect producing fan shroud exit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1055344A true CA1055344A (en) | 1979-05-29 |
Family
ID=25667838
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA299,755A Expired CA1055344A (en) | 1974-05-17 | 1978-03-28 | Heat transfer system employing a coanda effect producing fan shroud exit |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1055344A (en) |
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| US9151299B2 (en) | 2012-02-06 | 2015-10-06 | Dyson Technology Limited | Fan |
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| US9982677B2 (en) | 2014-07-29 | 2018-05-29 | Dyson Technology Limited | Fan assembly |
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