U.S. patent number 3,795,367 [Application Number 05/348,043] was granted by the patent office on 1974-03-05 for fluid device using coanda effect.
This patent grant is currently assigned to S.R.C. Laboratories, Inc.. Invention is credited to Zenon R. Mocarski.
United States Patent |
3,795,367 |
Mocarski |
March 5, 1974 |
FLUID DEVICE USING COANDA EFFECT
Abstract
A device using the Coanda effect by which a primary fluid of
high velocity, small volume induces flow of a secondary fluid with
the exhaust fluid being a combination of both fluids.
Inventors: |
Mocarski; Zenon R. (Easton,
CT) |
Assignee: |
S.R.C. Laboratories, Inc.
(Fairfield, CT)
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Family
ID: |
23366415 |
Appl.
No.: |
05/348,043 |
Filed: |
April 5, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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153172 |
Jun 15, 1971 |
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Current U.S.
Class: |
239/265.17;
60/269; 239/DIG.7; 264/176.1; 417/197; 417/198 |
Current CPC
Class: |
B05B
7/0416 (20130101); B05B 7/0087 (20130101); D02G
1/16 (20130101); B63H 11/12 (20130101); Y10S
239/07 (20130101) |
Current International
Class: |
B63H
11/12 (20060101); D02G 1/16 (20060101); B63H
11/00 (20060101); B05B 7/04 (20060101); B63h
025/46 (); B64c 015/10 () |
Field of
Search: |
;239/265.17,DIG.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: King; Lloyd L.
Attorney, Agent or Firm: Junkins; Ernest M.
Parent Case Text
This is a continuation, of application Ser. No. 153,172 filed June
15, 1971, now abandoned.
Claims
1. A nozzle for effecting movement of a secondary fluid by a
pressurized primary fluid comprising means forming a passageway
having an entrance and an exhaust and an intermediate throat, said
throat being the smallest cross-sectional area of the passageway
nearest the entrance, a slit communicating with the passageway
between the throat and the entrance, said throat and slit each
having a diameter and being axially spaced along the passageway,
said entrance being open to the secondary fluid and a source of
pressurized primary fluid being adapted to be connected to the slit
whereby flow of primary fluid through the slit induces flow of
secondary fluid into and through the passageway with both fluids
being discharged from the exhaust, the improvement comprising said
slit being located closely adjacent said throat with the ratio of
the throat diameter divided by the linear axial distance between
the throat and slit being greater than essentially 3 and with the
ratio of the throat diameter to
2. The invention as defined in claim 1, in which the range of the
ratio of
3. The invention as defined in claim 1 in which the angle of
discharge between the slit and the axis of the passageway is
greater than essentially 60.degree. and is determined by the
complement of the tangent of the angle of the ratio of the
difference between the throat and slit radii divided by the linear
axial distance between the throat and slit.
4. The invention as defined in claim 1 in which the entrance has an
entrance end and in which the ratio of the linear axial distances
from the throat to the entrance end and the throat to the slit is
in the range of 2
5. A fluid device for inducing movement of a secondary fluid by the
use of an ejected primary fluid with the discharge being a
combination of the two fluids comprising a first and a second
surface, said surfaces being aligned and having one end common to
define a throat, a common reference with said throat being the
nearest part of the surfaces to the reference, the first surface
forming an exhaust and diverging from the reference as it recedes
from the throat and being shaped to effect laminar flow of fluid
thereover, said second surface forming an entrance and diverging
from the reference as it progresses from the throat in the opposite
direction to the receding of the first surface and having its other
end form an entrance end that is positioned in a supply of
secondary fluid, a slit formed through the second surface and means
adapted to connect the slit to a source of primary fluid under
pressure so that a flow of primary fluid under pressure through the
slit induces a flow of secondary fluid from the entrance along a
path past the slit and throat and the first surface to have the
combined fluids discharge from the first surface, the improvement
comprising said throat having essentially no length along the path,
the slit is just slightly further from the reference than the
throat is from the reference and is located closely adjacent the
throat with the ratio of twice the distance from the reference to
the throat divided by the linear distance along the reference
between the throat and slit being greater than essentially 3 and
with the ratio of the distance from the reference to the slit
divided by the distance from the reference to the throat being less
than 1.5.
Description
In U.S. Pat. No. 2,052,869 granted Sept. 1,1936 to H. Coanda there
is disclosed a principle of fluid flow now sometimes referred to as
the Coanda effect. Basically the effect involves discharging a
small volume of fluid under high velocity from a nozzle with there
being a shaped surface adjacent the nozzle. The stream of fluid
(herein called the primary fluid) tends to follow the shaped
surface and as it does it induces surrounding fluid (secondary
fluid) to flow with it. Thus, along the shaped surface there is
discharged an exhaust consisting of a combination of both the
primary and secondary fluids.
This effect has been known for many years and at least the
discoverer thereof has secured many patents on devices utilizing
the principle (for example those disclosed in U.S. Pat. Nos.
2,713,510, 2,920,448 and 3,047,208). However, insofar as the
present Applicant is aware, devices utilizing this effect have not
been found to have widespread commercial acceptance even though
they would appear to be capable of functioning. One reason which
perhaps could serve as a basis for a lack of wide acceptance is
that the efficiency of heretofore constructed devices has been of
such relatively low value that it renders the devices somewhat
commercially impractical.
It is accordingly an object of the present invention to provide
fluid devices utilizing the Coanda effect which are more efficient
than heretofore known devices.
Another object of the present invention is to achieve the above
object simply by altering the relative relationship of the parts
and the shapes of the surfaces.
A further object of the present invention is to provide a fluid
device utilizing the Coanda effect for inducing movement of one
fluid by the discharging of another fluid which though attaining
the above objects is extremely simple in construction and reliable
in use.
One type of device which has been suggested using the Coanda effect
is conveniently called a nozzle and it is used for moving a
quantity of available air (secondary fluid) by use of a discharge
of compressed air (primary fluid) thereinto. Such a device consists
of a tubular member having an entrance open to the atmosphere or
other source of secondary fluid and an exhaust with a portion
therebetween having a restricted cross-sectional area which forms a
throat. The throat serves as a boundary between the exhaust and
entrance and secondary fluid flows from the entrance through the
throat to be discharged from the exhaust. Formed in the tube prior
to the throat along the line of movement of the secondary fluid is
an annular slit through which the primary fluid is ejected to cause
the flow of the secondary fluid so that both fluids flow through
the throat and the exhaust to be discharged as a jet containing
both fluids in combination.
As the discharge involves both fluids and has velocity, one manner
of measuring the efficiency of such a nozzle consists of
determining the thrust which the discharged fluid has and comparing
it to the thrust which the primary fluid is capable of causing. If
the thrust of the primary fluid is considered to be 1 then the
values of thrust reported in heretofore available literature of
this type of device has been on the order of 1.23 to 1.4 and
generally referred to as the thrust agumentation ratio. Thus the
device augments the thrust of the primary fluid by a factor of .23
to .4 as the 1 in the ratio is that thrust which the primary fluid
introduces in the system.
In similar devices constructed according to the present invention
as hereinafter described, such nozzles have consistently achieved a
thrust augmentation ratio of 1.8. This is an increase in the thrust
augmentation ratio over the highest heretofore known or reported
ratio of .4 and when compared to the latter, provides when just
thrust increase is considered, an increase of more than 25 percent
(.4 over 1.4). However, the ratio also indicates that the flow of
secondary fluid has essentially doubled (from .4 to .8) and if the
device is used as a pump for pumping secondary fluid, the
efficiency has been increased by about 100 percent.
The substantial increase in efficiency has been obtained by
altering the relationship of the parts and the shapes of the
surfaces from that heretofore known and suggested. Specifically the
throat is made to be extremely thin, essentially just a line caused
by the junction between adjacent boundaries of the entrance surface
and the exhaust surface, the exhaust surface diverges outwardly
from the throat as it recedes from the throat but in a shape which
maintains laminar flow of both fluids, the entrance is shaped to
diverge exceedingly rapidly from the throat as it progresses
therefrom and the primary fluid annular slit is positioned
extremely adjacent the throat. These particular relationships have
been found to all contribute to the substantial increase in
efficiency of devices utilizing the Coanda effect for moving a
secondary fluid by use of a primary fluid.
Other features and advantages will hereinafter appear.
In the drawing:
FIG. 1 is an axial section of a fluid device using the Coanda
effect and is particularly referred to herein as a nozzle.
FIG. 2 is an enlarged detail of the annular slit through which the
primary fluid is ejected.
FIG. 3 is a representation of a linear device in which the present
invention is incorporated.
Referring to the drawing, one embodiment of a fluid device
utilizing the present invention is shown in FIGS. 1 and 2 and
generally is indicated by the reference numeral 10. This device may
conveniently be referred to as a nozzle as it is circular, having
an entrance 11 and an exhaust 12 with fluid being discharged from
the exhaust. The exhausted fluid is made up of the combination of a
primary fluid and a secondary fluid. The secondary fluid surrounds
the end 11a of the entrance 11 (as so indicated in FIG. 1) and the
flow of the secondary fluid through the nozzle is caused by
introducing the primary fluid into an inlet 13 and ejecting it
through an annular slit 14. The secondary fluid flow is indicated
by arrows 15 while the primary fluid flow is indicated by arrows 16
and the fluids combine to produce a discharge at the end 12a of the
exhaust.
Structurally the nozzle 10 is formed of just two annular parts 17
and 18 with the part 17 serving to define the portion of the
entrance 11 that is prior to the slit while the part 18 defines the
remainder of the entrance 11, and all the exhaust 12. Each of the
parts may be made of rigid material such as metal.
The part 17 has the diametric cross-section shown and includes an
annular flange 19 formed with threads 20. The part 18 also has the
diametric cross-sectional shape shown and is formed to provide an
annular passageway 21 which communicates with the inlet 13. The
interior of the inlet may be threaded to facilitate connection to a
source of primary fluid. Additionally, the part 18 has threads 22
which mate with the threads 20 to effect unifying of two parts, and
serve as a seal to prevent primary fluid escaping from the
passageway 21.
Referring to FIG. 2 there is shown an enlarged section of the shape
of the adjacent portions of the two parts 17 and 18 which define
the slit 14. Particularly the part 17 has a flat surface 17a while
the part 18 is formed to also provide a surface 18a which is also
somewhat flat but has a small radius 18b (such as .030 inch) at its
end between the surface 18a and the interior of the part 18. The
two surfaces may be parallel and basically perpendicular to the
axis of the nozzle or there may be a slight angle to one, as for
example, 5 degrees for the surface 17a but in any even the exiting
of primary fluid through the slit 14 will be caused to follow the
surface of the part 18 in the direction of the arrow 16 by reason
of the Coanda effect.
It will be understood that the width of the slit between the
surfaces 17a and 18a is one factor in setting the quantity of
primary fluid that may flow, and typical values of the width range
on the order of .002 to .010 inch for the specific embodiments
hereinafter described. The extent of the width may be
advantageously controlled by relative rotation between the parts 17
and 18 which provides linear movement along the axis of the nozzle
through the cooperating threads 20 and 22.
The exterior shape of the nozzle is not particularly critical and,
as shown, is generally cylindrical while the shape of the interior
path through the nozzle has been found to be extremely critical in
obtaining the substantial increase in efficiency of the present
invention. The path includes a throat 23 which defines the smallest
cross-sectional area of the path and serves as a boundary between
the entrance 11 and the exhaust 12. The exhaust 12 may have the
frusto-conical shape 26 shown in solid lines when it is desired to
maximize thrust; or a more bell shape as shown by the dotted line
26a when it is desired to provide for maximum flow or a shape such
as shown by the dotted line 26b when it is desired to more
accurately control the direction of the discharged fluid. With all
shapes the exhaust increases in area from the throat by diverging
from the reference axis as it recedes from the throat in such a
manner that it maintains laminar flow of the fluid and does not
create turbulence.
The entrance 11 has been found to be quite critical in its shape
and it enlarges from the throat 23 towards the entrance end 11a
with the increase being at an increasing rate as the entrance
progresses from the throat. The sharp increase in the size of the
entrance has been found to be essential to the present invention
for reasons which are not yet completely understood but the shape
of the entrance should be such as to enable the secondary fluid to
have laminar flow and not turbulence upon entering the path.
The throat 23 is shown as a line caused by the abutting of the
entrance 11 and exhaust 12 and it has been found that the length of
the throat along the path should be minimum. Accordingly, the
throat is essentially only a line which may be somewhat visually
absent if the boundary between the entrance 11 and the exhaust 12
is caused to be radiused so as to elimininate a sharp intersection.
It is also pointed out that the slit 14 must be quite close to the
throat in order to achieve the substantial efficiency increase.
The nozzle portrayed in FIG. 1 is a scale drawing of a tested
nozzle drawn four times actual size and hence the shapes shown are
accurate representations of those which an existing nozzle has. In
order to enable a person skilled in the art to practice the
invention there is herein tabulated dimensions (in inches) for four
nozzles which have been found to achieve the increased efficiency
with model 00 being the model for the nozzle shown in FIG. 1 as it
appears by testing to date to be the most efficient nozzle.
##SPC1##
The dimension A in the table is the throat diameter; B is the
exhaust end (12a) diameter; C is the slit diameter; D is the
entrance end (11a) diameter; E is the distance from the slit to the
throat; F is the distance from the entrance end 11a to the throat
and G the distance from the throat to the exhaust end 12a.
With respect to the above table it will be appreciated that certain
ratios are useful in the design of the nozzle. One ratio is the
distance from the entrance end to the throat divided by the
distance from the slit to the throat (F divided by E) along the
reference axis and this has been typically found to be about 3 and
thus within a range of 2 to 4. It will also be understood that F
and E may vary slightly as the width of the slit 14 is varied with
the slit width being normally as small as possible to cause the
primary fluid to be ejected with as large a velocity as possible
and yet at a quantity which will maintain laminar flow and effect
ejection of the necessary mass of primary fluid to induce the flow
of the secondary fluid.
Another important ratio is the diameter of the slit 14 (C) as
compared to the diameter of the throat (A). This has typically been
found to be about 1.2 (C divided by A) which falls within a range
of 1.1 to 1.3.
Another ratio which is also considered to be of importance in the
present invention is the ratio between the throat diameter (A) and
the entrance end diameter (D) with the throat diameter being about
2.35 for the first nozzle and falling within the range of about 2.0
to 3.0 for the remaining nozzles thus showing that the entrance
diameter is substantially larger than the throat diameter but yet
the entrance end area is only a short axial length from the
throat.
As to the dimensions B and C which are those of the exhaust end 12a
and the axial distance that the end is from the throat, they are
not especially critical provided the exhaust is shaped to provide
laminar flow. The length of the exhaust section is again variable
depending upon whether it is desired to use the nozzle for volume
flow, thrust or to control the direction of the discharged
fluid.
Shown in FIG. 3 is a further embodiment of the present invention in
which rather than providing a closed path for the fluids such as
the nozzle 10, they follow the upper surface 30 of a linear section
31. The primary fluid may be directed through a slit 32 to induce
flow of secondary fluid over the surface 30 to thereby create lift
or a vacuum above the section. The shape of the upper surface is
identical with the shape of the entrance, exhaust and throat of the
path through the nozzle and the above-noted ratios apply. However,
the various distances instead of being diameters are distances
(equal to radii) from a reference plane 33 located above the
section and corresponding to the axis of the path of the nozzle in
FIG. 1. They are indicated in this embodiment by using the same
letter with the addition of a prime thereto.
It will accordingly be appreciated that there has been disclosed a
fluid device which utilizes the Coanda effect on a primary fluid to
cause movement of a secondary fluid into which the primary fluid is
ejected. The particular construction and relationship of the parts
wherein the throat is made to have essentially no axial length, the
entrance is made to very substantially increase from the throat and
the primary inlet is placed close the throat together with having
the exhaust extend from the throat outwardly in a shape which
maintains laminar flow of the combined fluids enables the present
invention to provide a substantial increase in efficiency over the
heretofore known similar type devices.
Variations and modifications may be made within the scope of the
claims and portions of the improvements may be used without
others.
* * * * *