CA1046367A - 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
- CA1046367A CA1046367A CA220,621A CA220621A CA1046367A CA 1046367 A CA1046367 A CA 1046367A CA 220621 A CA220621 A CA 220621A CA 1046367 A CA1046367 A CA 1046367A
- Authority
- CA
- Canada
- Prior art keywords
- fan
- air
- section
- shroud
- annular
- 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
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
- F01P5/00—Pumping cooling-air or liquid coolants
- F01P5/02—Pumping cooling-air; Arrangements of cooling-air pumps, e.g. fans or blowers
- F01P5/06—Guiding or ducting air to, or from, ducted fans
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/40—Casings; Connections of working fluid
- F04D29/52—Casings; Connections of working fluid for axial pumps
- F04D29/522—Casings; Connections of working fluid for axial pumps especially adapted for elastic fluid pumps
- F04D29/526—Details of the casing section radially opposing blade tips
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/40—Casings; Connections of working fluid
- F04D29/52—Casings; Connections of working fluid for axial pumps
- F04D29/54—Fluid-guiding means, e.g. diffusers
- F04D29/541—Specially adapted for elastic fluid pumps
- F04D29/545—Ducts
- F04D29/547—Ducts having a special shape in order to influence fluid flow
Abstract
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.
A contoured shroud exit having means capable of producing low pressure vortices when a fan generated air stream is expelled therefrom.
Description
~0~36~
HEAT TRANSFER SYSTEM EMPLOYING A
COANDA EFFECT PRODUCING FAN SHROUD EXIT
SPECIFICATION
This invention relates to cooling systems for internal combustion engines and, more particularly, to a Coanada effect producing fan shroud exit, involved in the air handling step of the heat transfer process.
Reference should be made to my canadian appli-cation Serial No. 184,880, filed November 2, 1973.
A standard mode of removing heat from an internal combustion engine i9 to transfer the heat to a liquid, often water or a mixture thereof, and from there to a stream of ; air. The heated air beinq dispersed out into the atmosphere.
` 20 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 :
`~ 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, .; ~,,~ .
.~, ~046367 innumerable patents have been directed. It has been dis-covered that there is a relation between tip clearance, driving horsepower or fan efficiency and fan noises. It is believed at this time that recirculation and turbulence in the tip region of the fan are responsible for a majority 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 stream 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 the 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 "attach" to the plate .' .
HEAT TRANSFER SYSTEM EMPLOYING A
COANDA EFFECT PRODUCING FAN SHROUD EXIT
SPECIFICATION
This invention relates to cooling systems for internal combustion engines and, more particularly, to a Coanada effect producing fan shroud exit, involved in the air handling step of the heat transfer process.
Reference should be made to my canadian appli-cation Serial No. 184,880, filed November 2, 1973.
A standard mode of removing heat from an internal combustion engine i9 to transfer the heat to a liquid, often water or a mixture thereof, and from there to a stream of ; air. The heated air beinq dispersed out into the atmosphere.
` 20 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 :
`~ 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, .; ~,,~ .
.~, ~046367 innumerable patents have been directed. It has been dis-covered that there is a relation between tip clearance, driving horsepower or fan efficiency and fan noises. It is believed at this time that recirculation and turbulence in the tip region of the fan are responsible for a majority 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 stream 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 the 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 "attach" to the plate .' .
-2-~04~367 and follow the plate even thou~h th~ resultant flow patll is highly divergent from the original direction of the jet.
This phenomenon is the CDanda effect 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 boundary or surface.
For example a jet issuing from a nozzle begins to entrain ambient fluid into the 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 up to twenty times the amount of air in the original jet.
At this time there is much uncertainty as to 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 vehicle having an engine, and cooling system of the type comprising a radiator, a fan including blades having leading and trailing edges driven by the engine and drawing air
This phenomenon is the CDanda effect 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 boundary or surface.
For example a jet issuing from a nozzle begins to entrain ambient fluid into the 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 up to twenty times the amount of air in the original jet.
At this time there is much uncertainty as to 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 vehicle having an engine, and cooling system of the type comprising a radiator, a fan including blades having leading and trailing edges driven by the engine and drawing air
-3-~ .
104~367 through an air entry side of the radiator, and an improved fan shroud connected to an air exit side of the radiator and encasing the fan. The fan shroud for reducing fan generated noise and 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, and with the duct connecting with the intermediate section along a first vertical plane extending transverse to the axis of the circular cross-section. The intermediate section has a cylindrical body extending co-axially along the axis of the air intake section a predetermined distance from the first plane and connecting with the air discharge section. The air discharge section has an expanding bell shape with an annular lip co-axially with the axis of the intermediate section and extending radially along a second vertical plane which is parallel to the first plane, with the axial distance between the first and second planes being determined by the axial distance between the leading and trailing edges of the fan when viewed transverse to the axis of the fan. The fan is positioned within the inter-mediate and air discharge sections with the leading and trailing edges respectively lying on the first and second planes, 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.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:
~ " ~ '.
::
-104~367 FIGURE 1 is a side view of a tractor showing one embodiment of the invention; and FIGURE 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 FIGURES 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 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.
Referring now to the drawings and, more particularly, to Figure 1 wherein is shown an e~bodiment 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 14 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 -~ 30 (not shown) and the heat exchanger through a series of : ` ' ~ .. . . . . , . . . . . v . . . . .. .
fluid communicating means 18 and 20. Heat from the engine being absorbed into the water media or as often the case a mixture of water and other heat carrying fluids such as anti-freeze, etc., and passed through the heat exchanger.
The heat is th'en 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 shaft means 26 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 i`s not 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 of air or, more particularly, moves a stream of cooling air through 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 of the radiator. The nature of 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 ' ~ - 6 -~ ' '~
..... . . .. ~, . . . :
of this invention t~e~entl~re periphery of the rear area is substantially sealed against 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 ~2 (be it a tapered transition as shown or a box type shroud) con~erges rearwardly through a circular section 38 and connects to a cylindrical intermediate section 46 which extends axially for a distance 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 which 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 turbulence is created in the tip region 42 such that noise pollution is created and the air moving ability of that region i8 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, that is, the lower horsepower requirement to achieve a given cooling rate and - -~ 7 _ '`~
104~3~7 the reduced noise generated in the tip regions result from the employment of the Coanda generating fan shroud exit. It is known from experimentation with a high speed air jet issuing from a nozzle adjacent a Coanda effect 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 this entrainment phenomenon is helping to pull additional ~ -. air through the fan blade. As air passes through the blade it is immediately entrained by the stream 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 air~tream 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 effect. In Figures 2, 3, and 4,it is believed that the annular step 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 the position of the fan blade assembly with regard to the intermediate and air discharge sections 46, 48 of the fan ~-shroud 32 contrlbutes the formation of the Coanda effect.
The embodiments as shown in Figures 2, 3, and 4 ,., $ - 8 -- - :
. . . .
combine smooth curved surfaces and indentations to achieve the Coanda effect in combination with the fan blade. That is, a fan shroud exit means capable of producing the Coanda effect will be one having a low pressure vortex creating means such that when an air stream is 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. Generally situated 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 effect 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 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 pres$ure 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 s,ection 48. The air discharge section 48 .. .. ..
_ g _ :
rt~' .
~0'1~3~ ~
generally expands into a b~ll sh~pe 28 in the direction in which it is desirous of directing the exit airstream passing thereover. The generating radius R of the bell portion or the quarter-annular torus 28 co~responds 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-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 boundary 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 i radially RF from a point of tangency with the smooth curved .
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-tions can vary up to plus or minus twelve percent of the axial width or AW of the fan blade. The axial width or AW
being the shortest axially extending distance between the front and rear or first and second vertical parallel planes , , , when viewed tranæverse to the axis of the fan means 29.
The particular embodiment of the intermediate 1 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 edge of the , ;
..
.. .~, . ~ - , 104~367 expanding bell portion 28 of the air discharge section 48 is 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. As shown the low pressure vortex creating means 50 is again in the form of a step. The particular embodiment shown in Figure 4, the low pressure vortex creating means S0 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 vortex creating means or the numbers thereof, 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 to direct the air stream in the desired direction and a fan generally located therein.
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 foregoin~ description. Accordingly, it is intended to embrace all ~uch alternatives, modifications and variations as fall within the spiFit and broad scope of the appended claims.
- 11- ,. -.
. . . , . . . :: . ~ ,
104~367 through an air entry side of the radiator, and an improved fan shroud connected to an air exit side of the radiator and encasing the fan. The fan shroud for reducing fan generated noise and 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, and with the duct connecting with the intermediate section along a first vertical plane extending transverse to the axis of the circular cross-section. The intermediate section has a cylindrical body extending co-axially along the axis of the air intake section a predetermined distance from the first plane and connecting with the air discharge section. The air discharge section has an expanding bell shape with an annular lip co-axially with the axis of the intermediate section and extending radially along a second vertical plane which is parallel to the first plane, with the axial distance between the first and second planes being determined by the axial distance between the leading and trailing edges of the fan when viewed transverse to the axis of the fan. The fan is positioned within the inter-mediate and air discharge sections with the leading and trailing edges respectively lying on the first and second planes, 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.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:
~ " ~ '.
::
-104~367 FIGURE 1 is a side view of a tractor showing one embodiment of the invention; and FIGURE 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 FIGURES 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 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.
Referring now to the drawings and, more particularly, to Figure 1 wherein is shown an e~bodiment 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 14 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 -~ 30 (not shown) and the heat exchanger through a series of : ` ' ~ .. . . . . , . . . . . v . . . . .. .
fluid communicating means 18 and 20. Heat from the engine being absorbed into the water media or as often the case a mixture of water and other heat carrying fluids such as anti-freeze, etc., and passed through the heat exchanger.
The heat is th'en 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 shaft means 26 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 i`s not 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 of air or, more particularly, moves a stream of cooling air through 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 of the radiator. The nature of 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 ' ~ - 6 -~ ' '~
..... . . .. ~, . . . :
of this invention t~e~entl~re periphery of the rear area is substantially sealed against 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 ~2 (be it a tapered transition as shown or a box type shroud) con~erges rearwardly through a circular section 38 and connects to a cylindrical intermediate section 46 which extends axially for a distance 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 which 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 turbulence is created in the tip region 42 such that noise pollution is created and the air moving ability of that region i8 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, that is, the lower horsepower requirement to achieve a given cooling rate and - -~ 7 _ '`~
104~3~7 the reduced noise generated in the tip regions result from the employment of the Coanda generating fan shroud exit. It is known from experimentation with a high speed air jet issuing from a nozzle adjacent a Coanda effect 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 this entrainment phenomenon is helping to pull additional ~ -. air through the fan blade. As air passes through the blade it is immediately entrained by the stream 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 air~tream 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 effect. In Figures 2, 3, and 4,it is believed that the annular step 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 the position of the fan blade assembly with regard to the intermediate and air discharge sections 46, 48 of the fan ~-shroud 32 contrlbutes the formation of the Coanda effect.
The embodiments as shown in Figures 2, 3, and 4 ,., $ - 8 -- - :
. . . .
combine smooth curved surfaces and indentations to achieve the Coanda effect in combination with the fan blade. That is, a fan shroud exit means capable of producing the Coanda effect will be one having a low pressure vortex creating means such that when an air stream is 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. Generally situated 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 effect 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 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 pres$ure 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 s,ection 48. The air discharge section 48 .. .. ..
_ g _ :
rt~' .
~0'1~3~ ~
generally expands into a b~ll sh~pe 28 in the direction in which it is desirous of directing the exit airstream passing thereover. The generating radius R of the bell portion or the quarter-annular torus 28 co~responds 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-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 boundary 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 i radially RF from a point of tangency with the smooth curved .
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-tions can vary up to plus or minus twelve percent of the axial width or AW of the fan blade. The axial width or AW
being the shortest axially extending distance between the front and rear or first and second vertical parallel planes , , , when viewed tranæverse to the axis of the fan means 29.
The particular embodiment of the intermediate 1 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 edge of the , ;
..
.. .~, . ~ - , 104~367 expanding bell portion 28 of the air discharge section 48 is 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. As shown the low pressure vortex creating means 50 is again in the form of a step. The particular embodiment shown in Figure 4, the low pressure vortex creating means S0 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 vortex creating means or the numbers thereof, 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 to direct the air stream in the desired direction and a fan generally located therein.
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 foregoin~ description. Accordingly, it is intended to embrace all ~uch alternatives, modifications and variations as fall within the spiFit and broad scope of the appended claims.
- 11- ,. -.
. . . , . . . :: . ~ ,
Claims (7)
1. In a vehicle having an engine, and cooling system of the type comprising a radiator, a fan including blades having leading and trailing edges driven by the engine and drawing air through an air entry side of the radiator, and a fan shroud connected to an air exit side of the radiator and encasing the fan, an improved fan shroud for reducing fan generated noise and horsepower requirements of the engine, characterized by:
the fan shroud comprising an air intake section, an intermediate section, and an air discharge section, the air intake section converging from the air exit side of the radiator into a duct of circular cross-section, the duct connecting with the intermediate section along a first vertical plane extending transverse to the axis of the circular cross-section, the intermediate section having a cylindrical body extending co-axially along the axis of the air intake section a predetermined distance from the first plane and connecting with the air discharge section, the air discharge section having an expanding bell shape with an annular lip co-axially with the axis of the intermediate section and extending radially along a second vertical plane which is parallel to the first plane, the axial distance between the first and second planes being determined by the axial distance between the leading and trailing edges of the fan when viewed transverse to the axis of the fan, the fan being positioned within the intermediate and air discharge sections with the leading and trailing edges respectively lying on the first and second planes, and an annular step means 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.
the fan shroud comprising an air intake section, an intermediate section, and an air discharge section, the air intake section converging from the air exit side of the radiator into a duct of circular cross-section, the duct connecting with the intermediate section along a first vertical plane extending transverse to the axis of the circular cross-section, the intermediate section having a cylindrical body extending co-axially along the axis of the air intake section a predetermined distance from the first plane and connecting with the air discharge section, the air discharge section having an expanding bell shape with an annular lip co-axially with the axis of the intermediate section and extending radially along a second vertical plane which is parallel to the first plane, the axial distance between the first and second planes being determined by the axial distance between the leading and trailing edges of the fan when viewed transverse to the axis of the fan, the fan being positioned within the intermediate and air discharge sections with the leading and trailing edges respectively lying on the first and second planes, and an annular step means 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.
2. The invention according to Claim 1 further characterized by:
the trailing edge of the blades having a tolerance of plus or minus twelve-percent with the second plane.
the trailing edge of the blades having a tolerance of plus or minus twelve-percent with the second plane.
3. The invention according to Claim 2 further characterized by:
the annular step means being between and connected to the intermediate and air discharge sections.
the annular step means being between and connected to the intermediate and air discharge sections.
4. The invention according to Claim 2 further characterized by:
the annular step means being connected to the annular lip of the air discharge section.
the annular step means being connected to the annular lip of the air discharge section.
5. The invention according to Claim 3 further characterized by:
the annular step means being an annular groove in the expanding bell shape of the air discharge section in the space between the annular lip and the connection to the intermediate section.
the annular step means being an annular groove in the expanding bell shape of the air discharge section in the space between the annular lip and the connection to the intermediate section.
6. The invention according to Claim 3 further characterized by:
the annular step means being at the predetermined distance from the first plane which distance corresponds to one-third the axial distance between the leading and trailing edges of the fan when viewed transverse to the axis of the fan.
the annular step means being at the predetermined distance from the first plane which distance corresponds to one-third the axial distance between the leading and trailing edges of the fan when viewed transverse to the axis of the fan.
7. The invention according to Claim 4 further characterized by:
the annular step means including an annular flange connected axially inwardly from the second plane to a cylindrical ring which is concentric with the intermediate section and is connected to the annular lip.
the annular step means including an annular flange connected axially inwardly from the second plane to a cylindrical ring which is concentric with the intermediate section and is connected to the annular lip.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA299,755A CA1055344A (en) | 1974-05-17 | 1978-03-28 | Heat transfer system employing a coanda effect producing fan shroud exit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US47078774A | 1974-05-17 | 1974-05-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1046367A true CA1046367A (en) | 1979-01-16 |
Family
ID=23869030
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA220,621A Expired CA1046367A (en) | 1974-05-17 | 1975-02-24 | Heat transfer system employing a coanda effect producing fan shroud exit |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS50160629A (en) |
| BR (1) | BR7502787A (en) |
| CA (1) | CA1046367A (en) |
| DE (1) | DE2518498B2 (en) |
| FR (1) | FR2271392B2 (en) |
| GB (1) | GB1502000A (en) |
| IT (1) | IT1032274B (en) |
| NL (1) | NL7505616A (en) |
| SE (2) | SE7505579L (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT8353039V0 (en) * | 1982-03-15 | 1983-03-10 | Sueddeutsche Kuehler Behr | AXIAL FAN PARTICULARLY FOR WATER COOLED THERMAL ENGINE COOLING RADIATORS |
| IT1194156B (en) * | 1982-03-15 | 1988-09-14 | Sueddeutsche Kuehler Behr | AXIAL FAN, ESPECIALLY FOR COOLING WATER COOLED HEAT ENGINE RADIATORS |
| DE102006037641B4 (en) * | 2006-08-10 | 2019-04-04 | Mahle International Gmbh | Cooling device adapted for a motor vehicle with a coolant radiator and an axial fan |
| GB2597442B (en) * | 2020-06-25 | 2023-03-22 | Mosen Ltd | Vortex generators for jet fans |
-
1975
- 1975-02-24 CA CA220,621A patent/CA1046367A/en not_active Expired
- 1975-03-11 IT IT48555/75A patent/IT1032274B/en active
- 1975-04-25 DE DE19752518498 patent/DE2518498B2/en not_active Ceased
- 1975-05-06 GB GB18946/75A patent/GB1502000A/en not_active Expired
- 1975-05-07 BR BR3557/75D patent/BR7502787A/en unknown
- 1975-05-13 NL NL7505616A patent/NL7505616A/en not_active Application Discontinuation
- 1975-05-15 SE SE7505579A patent/SE7505579L/en unknown
- 1975-05-16 FR FR7515535A patent/FR2271392B2/fr not_active Expired
- 1975-05-16 JP JP50058506A patent/JPS50160629A/ja active Pending
-
1979
- 1979-09-03 SE SE7907319A patent/SE7907319L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB1502000A (en) | 1978-02-22 |
| NL7505616A (en) | 1975-11-19 |
| DE2518498B2 (en) | 1976-12-02 |
| JPS50160629A (en) | 1975-12-26 |
| BR7502787A (en) | 1976-04-13 |
| FR2271392A2 (en) | 1975-12-12 |
| SE7505579L (en) | 1975-11-18 |
| SE7907319L (en) | 1979-09-03 |
| IT1032274B (en) | 1979-05-30 |
| DE2518498A1 (en) | 1975-11-27 |
| FR2271392B2 (en) | 1980-10-03 |
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