Note: Descriptions are shown in the official language in which they were submitted.
:~L5~
SHROUD ARRANGEMEN~ FOR ENGINE COOLING FAN
.
This invention reIates to engine cooling fans
and, more particularly, to a multibladed cooling fan
having new and improved relativeIy rotatable shrouding
to retard the recirculation of air into a specially
contoured fan inlet provided by a rotatable shroud to
improve fan efficiency and to reduce fan-generated
noises~
Prior to the present invention, various shroud-
ing designs have been devised for automotive engine
cooling fans to reduce fan-generated noise and to
make the fan pump air with higher efficiency. Among
these are shroud assemblies that are fixed with respect to
the engine heat-dissipating radiator which have cylindrical
ejectors within which the fan is immexsed. However,
with higher standards new and improved shrouding
arrangements are required. In my prior patent,
No. 3,937,192 issued February 10, 1976 for Ejector
Fan Shroud Arrangement, a rotating shroud is attached
to the tips of the fan blades, and immersed within the
fixed shroud having a flared extension to provide a
passage therebetween for the improved flow of the
peripheral air from the inlet or suction side of the
fan to the exhaus-t or pressure side. In that
construction, the rotating shroud is provided with a
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diffuser that improves the ~ixing of fan-pu~ped air
and entrained air being discharged between the two
shrouds. While this prior construction provides an
improvement over fixed shroud designs insofar as
efficiency and noise control are concerned, undesired
quantities of air pumped by the fan are recirculated
through the passage between the rotating and
fixed shrouds back into the inlet of the rotating
shroud. Furthermore, when turning the leading edge
or inlet of the rotating shroud, the inner layers of
the recirculating air became detached from the inner
wall of the rotating shroud. W:ith this~detachment,
there was a transition from lam:inar to turbulent
flow. With turbulent air enterlng the fan, the fan
; ;lS ~blades and, in particular, the outer radial portion
thereof which received most of the turbulence, could
not~efficiently handl~e t~e`recirculating air so that
fan pu~ping efficiency~was adversely a~fected and
fan~noise~was generated.
In the present invention, new and improvea
fixed and rotating fan shroud construction is ~
provided with cooperative~action to achieve new 1evel&
of fan efficiency and fan~noise reduction.~T~e
rotating shroud is formed~with a be1l-mouthed inlet o~
sufficient curvature to eliminate or sharply xeduce
recirculating air sep~ration to according1y reduce
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turbulence. Importantly, in this invention, the
rotatable shroud cooperates with an ejec-tor portion of
the fixed shroud so that radial components of the air
pumped by the fan effectively block or further restrict
the passage between the two shrouds. with the passage
between the shrouds reduced, the amount of recirculating
air entering the rotating shroud is markedly reduced
to improve fan efficiency, since less air is repumped
by the fan.
In one embodiment of the invention, the fixed
shroud has a cylindrical non-flaring ejector portion
generally concentric with the bladed fan and the
rotating shroud. This ejector shroud extends a fixed
distance beyond the terminal edges of the fan blades
and the rotating shroud fixed to the tips thexeof.
The radial component of the high veIocity air
discharged by the powered~fan may impinge onto the
`~ ~ inner wall of the fixed shroud to pneumatically restrict~
the clearance between the fixed and rotatlng shrouds so
that the re~circulating flow of air from the high
pressure or exhaust sid~of the fan to the low~
pressure or inlet side thereof is sharply reduced
in volume. With such reduced recirculating flow,
fan efficiency is sharply improved. The air whic~ is
recirculated turns the corner of the bell-mou~hed
inlet of the rotating shroud without separation from
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the inner wall of the bell-mouthed inlet. Without
separation, turbulence of the inflow air into the
fan is reduced. With reduced and smo~ther laminar
flow entering the fan blades, the fan can pump the air
at reduced noise levels anà with higher efficiency
to minimize parasitic effect of the fan on fuel
consumption. :~
In a second embodiment of the invention, a
double radiused inlet section of the rotating shroud
proves for smooth laminar flow .into..the :f:an. blading
supporting this shroud.
~ In another embodiment of the invention, the
fixed shroud is formed with an axially extending but . ~ ~.
shortened ejector which is substantîally concentric ; :
wit~ the outlet end of the:rotatable shroud. The
: terminal ends of the ~ixed~and rotating shrouds are
;~ ~ generally coplaner but wîth variation occuring in
accordance with allowable productîon tolerances and
~variations~in the ~an~and shroud mountings. In .:
this embodiment of the inventîonJ~some~radial
~ : : : ~ : . :: : . . ,
components of the d.ischarged air will restrict
the opening between the fixed and rotatlng shroud so
that the quantity of reclrculating air is reduced. `
While the pneumatic blockage of this embodiment of the
.
25 invention is not as efficient as~that of the first ~ :
mentioned embodiment, clearance between these two
shrouds is preferably held to a:practical minimum
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1~4339
for quantity production so that the recirculating air
passage is substantially equivalent in restriction
as the first embodiment.
Accordingly, it is a feature, object and
advantage of this invention to provide new and improved
rotating and fixed shrouding for multibladed fans in
which the rotatlng shroud is immersed within a fixed
ejector shroud secured to a radiator and has a
bell-mouthed inlet curved to match the flow of
recirculating air entering the suction side of the
fan so that air separation and resultant turbulence
:~ . :
is sharply minimized.
~ nother feature, object and advantage of
this invention is to provide new and improved fan
~construction with relatively rotatable ~hrouding in
which the radial component of discharged air
e~fectively reduces the clearance between the~ ~;
relatively rotating shrouds to thereby reduce amounts
of~air~recircul0tlng from~the pre0sur0 to the
suction side of the fan.
Ano~ther f0ature~,~0bject and~advantage of
this invention is to provide new and improv0d
rotating and fixed shrouding for an engine cooling
fan in which~the rotating shroud, fixed to the tips
2~ of the fan blades, is immersed within a surrounding
fixed shroud which has an ejector portion~ the
extremity of which terminates in the same general
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plane of the extremity of the rotating shroud.
Ano~er feature, object and advantage of this
invention is to provide new and improved relatively
rotating shrouding for a fan in whi h the clearance
5 between the fixed and rotating shrouds is preferably ~.
kept to an optimized minimum. With reduced clearance,
the radial component of discharge air is effective
to block passage between the fixed ana rotating ~ :
shrouds so that recirculating airflow is restricted.
10 The reduced.recirculating airflow is smoothly fed ~.
by the bell-mouthed construction of the rotating shroud ~-
, . .
into the bladed fan without tur.hulence so that there .-~
is increased eficiency and recluced an generated
noises.
lS These and other features, objects and
.:
advantag 9 of this invention will be more apparent ~rom~ :
the ollowing detailed description and drawing, in
whlch~
Figure 1 is an exploded perspective view of
an automotive radlator, engine and enyine cooling
fan and a fan shrouding arrangement illustrating a
first embodiment of this invention; ~ :
.:
Figure 2 is a fragmentary cross-sectional view
of a portion of the fan~and shroud of Figure l:
Fi~ure 3 is a fragmentary cross-sectional view :
similar to the view of Figure l illustrating a second
embodiment o this invention.
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Figure 4 is an exploded perspective view of an
automotive engine cooling radiatvr, cooling fan and
shrouding package embodying a third embodiment of this
invention;
Figure 5 is a top plan view partly in section
of the third embodiment of this invention as viewed
along line 5-5 of Figure 4;
Figure 6 is an enlarged fragmentary view
partly in section of a pOrtiQn of the radiator and
10 fan shrouding of Figure 5. `
Referring now to the drawing in greater
detail, Figure 1 illustrates an automotive internal
combustion engine 10 powering a belt and pulley drive
system 12 operatively mounted on the front end
thereof for drlving accessories including a bladed
cooling fan 14. A radiator 16 hydraulically onnected
to~the vehicle engine dissipates engine~;generated
heat as engine coolant is~circulated therethrough.
The radiator 16 is mounted separately~fr~m the engine
immediately in flont of the cooling fan~14 and supports~
a thln-walled outer;shroud~}8 of plastic material
or sheet metal. The outer shroud is a fixed or
stationary shroud having a~generally rectan~ular
shaped base 20~with a plurality o~ spac~d tab: 22
extending outwardly ~rom;the periphery and adjacent to
the corneFs thereof. Tabs 22 are formed with openings
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8 ~.
24 for receiving threaded fasteners 26 used to secure
the outer shroud 18 to the radiator.
In addition to the rectangular base portion ~ :
20, the outer shroud 18 includes an annular and .:
convexly curved inte~mediate extension 28 and a cylindri~
cal ejector 30 projecting inwardly from the e.xtension ~
28 and terminating in an~annular edge 32 downstream - ~ :
of the trailing edges of the blades 36 of the fan.
: As shown, the blades 36 are arcuately spaced
from one another and extend radially outwardly from the
.
: hub portion of a fan pulley 40 rotatably mounted on ~.
. .
a projecting shaft 42 supported by engine lO. ~s will
be appreciated, the blades 36 a.re pitched to pump
a flow of cooling air through the radiator for engine
: : 15 cooling purposes when the fah :pulley 4~ is driven by
the engine through the belt and pulley system 12.
Attached to the outer extremity of the radial ::
an blades 36~i~ an annular thin~walled shroud 44 which
cooperates with the outer shroud to provide an
increase in fan pumping efficiency while allowing the
fan to operate at a low noise level. The shroud 44
is:a rotating shroud having~aD:annu1ar bell-mouthed
in7 et section 46 disposad forwardly and radially
ou.twardly of the leadlng edges of t~s fan blades 36.
This outwardly flaring inlet sectLon has a smooth
inner surface and:preerably describes an arc of -~.
about 90 degrees or more and terminates in an annular
:
l ~Lt~
outwardly extending edge 47. Wi~h this radial edge,
recirculating air represented by flow arrow A flowing
from the pressure to the suction side of the fan, can
enter the bell-mouthed section without separation
from the inner walls of this section. The recirculating
air is subsequently funneled in a laminar flow pattern
by the inner walls of the bell mouth into the
rotating blades of the fan. Since air turbulence is
.
avoided or sharply minimized in the recirculating air,
the fan can pump alr supplied thereto with high
efficiency and with reduced noise levels.
The ~ell-mouthed inlet: section 46 of the
rotating shroud 44 is housed within the larger
diameter intermediate portion 28 of the fixed outer
shroud 18 to provide sufficient clearance between
these relatively rotating shroud sections. This also
allows for the reduction in clearance ~etween the
ejector portion 30 of the outer shroud and the
rotating shroud illustrated as clearance "C" in Figure
3. The annular clearance "C" between the concentric
extending portions of the fixed and rotating~shrouds
is preferably he1d to a minimum to raduce recirculating -
airflow from the pressure exhaust side of the fan.
However, this olearance must be sufficiently large
to accommodate engine oscillations relative to the
fixed shroud and size and ~lounting variations
occurring in quantity production.
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As shown best by Figure 2~ the skirt portion 48
of the rotating shroud extends inwardly from the
bell-mouthed inlet section and is secured to the tips
of the fan blades. ~he annular skirt portion 48
terminates in an annular end edge 51 within the
confines of the larger diameter ejector 30. The
distance "I" that edge 51 of the rotating shroud is
located from the trailing edge 32 of the ixed shroud
represents the amount of axial immersion of the
rotating shroud into the fixed shroud.
With an immersion of 3.18 mm, a clearance
of 5.56 mm has been found to be acceptable~ However,
smaller and larger clearances may be effectively
employed when appropriataly matl-hed with immersion
depths. Thus, if clearance "C" is larger than 5 56 mm,
~ -
the amount of immersion "I" should he accordingly
increased to provide for high-efficiency, low-noise
fan operation. If the clearance between the shroud ; ;
1s reduced ~from 5.56 mm,~ the~amount of shroud
20, immersion should be accordingly reduced for the
.
improved fan performance. ~
~ Wlth the helL-mouthed inlet section 46
outwardly flared through an axc of about 90 degrees
or more and with the outwardly extending annular edg~
47, a flow control construction is pxovidad that
-orresponds with inlet curvin~ laminar flow of
recirculating air illustrated in Figure 2 by flvw
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~54~39
arrow "A". With this match, there is little or no
separation of the inner layers of air from the walls
of the rotating shroud so that inlet induced
turbulence is held to a minimum. With a smooth flow
of air enterlng the rotatably driven fan blades, the
fan can pump air at a low noise level and with high
efficiency.
With the rotatable fan shrouding appropriately
immersed within the stationary shrouding, the discharged
air pumped by the fan will have a radial component
which is directed onto the inner wall of the fixed
shroud, This portion of the discharged air partially
blocks the clearance "C" and consequently inhibits
the recirculation of air from the discharge side of
the fan through clearance "C" back into the suction
side of the fan and, in particular, into the
bell-mouthed section o~ the~rotating shroud. ~his
blockage or restriction is illustrated in Figure 2
.
by flow arrow "B" whlch extends between ~he terminal ~ ~ -
edges of the~fixed and rotatlng shrouds.
~ ccordingly/ the rotating shroud provides
an inlet section in which airflow separation is
minimized. Furthermore, with the rotating shroud
,
immersed within the~fixed shroud an appropriate
di9tanoe, the fan and rotating æhroud effectively
provide a discharge which cooperate~ with the ~ixed
shroud which, in effect,further reduces the ~ ~.
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clearance "C" so that the quantity of recirculating
air is held to a minimum. With the amount of recirculating
air minimized by the shrouding and with the 90
bell-mouthed inlet, pumping efficiency of a fan is
increased and the fan blading operates at-a low noise
levelO
Figure 3 is similar to the construction of
Figure 2 but has, for some installations, an improved
rotatable shroud having a double-radiused, arcuate
inlet Rl and R2 which is substantially greater than
90. The leading annular edge 47' of the bell mouth
is directed rearwardly and outwardly with respect to
recirculation airflow through the shrouding. Thesa
refinements provide improved fan operation w.ith
~furt~er minimized airflow separation.
In Figure 4, incorporating another embodiment~
of the invention, there is shown an engine cooling
radiator 61 connected through brackats 62 to
elongated upper and lower supports 63 and 65. Tha
radiator is prefarably positioned at the front of the
vehicle on the nutboard side of a transvexsely mountad
internal combustion engine 67 hydraulically connected ;
: : :
to the radiator. Disposed behind ~he radiator 61
is an electric cooling;assembly 69 in which a
three-armed mounting brackat 71, generally Y-shaped in
configuration, providas a central support ~ox an
electric motor 73. The lower arm 75 of the bracket 71
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has a doglegged end portion 77 that seats in the
mounting grommet 79 disposed in a vertical opening in
the lower radiator support 65. The hracket 71 has
upper arms 81 and 83 having forwardly extending ends
5 85 and ~7 for attachment to the upper radiator
support by threaded fasteners 89. The electric motor
73 drives a fan 91~ the blades 93 of which are
preferably unequally spaced and e~tend radially from
the hub of the fan to a terminal rotating shroud 95~
10 This shroud,corresponding to the rotating shroud of the ~:
first embodiment of the invention~ has a bell-mouthed :
inlet section 97 which leads rearwardly into a
cyl.indrical skirt portion 99 tllat is secured to the
tips of the blades 93 of the fan. Di:sposed about the
l5:;~rotatlng shroud is a stationary shroud~101 which
incorporates:a generally rectangular~shell-like body
. .
~ 103 having rearwardly extending projections 105 ~:
.
~: : formed thereon which contact the arms of the bracket
71. Stitching wires 107 clinched over on the shroud
~; 20 side of the bracket~secure the fixed shroud~to the
bracket 71 and thus to upper and:lower radiator:
supportsO~ The fixed shroud prevents tail :winds from
overpowering the fan at idle and causi~n~ reduced airflow
in the area of -the air conditioner heat exchange not ~ : :
25 shown.
As best shown in Figure 5, the fan assembly
is angulated with respect to the plane of the
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~L~5~3~9
radiator. With this construction the fan is backed
from the face of the radiator and without interference
from engine 67 so that the fixed shroud is opened up
and is more effective in funneling air through the
S radiator to the fan Eor engine cooling purposes. The
cylindrical ejector portion extends rearwardly from the
fixed shr4ud and has a terminal, annular edge 109 disposed
ideally in the same plane as the annular edge 111 of
the rotating shroud. However, variations in this
alignment occur in view of allowable tolerances and
differences in mountings. In any event, the annular
clearance 113 between the fixed and rotating shrouds
is limited as much as practical. With such limited
clearance, the radial component of air pumped by
the fan will at least partially block the restricted
recirculating air passage 113 with substantially the
same beneficial effect as in ~he~embodlments of
.
Figures 2 and 3. In Figure 6, for example, the
recirculating airflow illustrated by flow arrows "D" and
"E" is reduced~by the blockage of passage 113 and
the interference from discharge air represented by flow
.
arrow "Fl'.
While a preferred embodiment of the invention
has been shown and described to illustrate the
invention, other partial fixed shrouding and other
modifications will become apparent to those skilled
in the art. Accordingly, the scope of this invention
is set forth in the following claims.
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