Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
Turbine for an underwater aerator.
FIELD OF THE INVENTION
The present invention relates to a turbine which is
adapted to form part of an underwater aerator which is used to dissolve
10 oxygen into waste water in a tank.
BACKGROUND OF THE INVENTION
There are various types of aerators for bodies of water
whereby a stream of mixed air and water is introduced beneath the
surface of the water.
The treatment of waste water, such as sewage or other
biodegradable materials, under pressure by air or oxygen is known to the
art. Such treatment has been done, for example, by the use of a
recessed vortex type impeller such as described in U.S. patent No.
4,877,532 issued October 31, 1989 to Haentjens et al. or by the use of an
underwater aerator having an air diffuser rotor such as described in U.S.
patent No. 4,235,720 issued November 25, 1980 to Nakajima et al.
One presently used underwater aerator has a turbine
which is formed of a cylindrical body with a center hole for connection to
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the rotatable drive shaft of a submerged motor. The upper side of the
body is adjacent to a horizontal plate of the aerator and comprises a
series of radially extending rectangular shaped recesses for the passage
of air while the under side comprises a series of obliquely extending
5 elongated recesses having a semi-circular bottom for the passage of
water. Both recesses are opened to their respective lower or upper sides.
It has been found that this type of turbine can not be
used in tanks having an important depth. This is due to the natural
10 increase in water pressure in the vicinity of the turbine when the turbine
is lowered in the tank. Indeed, additional pressure is applied against the
air that is forced out, causing the potential infiltration of water at the
junction between the upper side of the turbine and the horizontal plate of
the aerator, therefore increasing the power requirements of the
15 submerged motor and decreasing the aeration efficiency.
OBJECT AND STATEMENT OF THE INVENTION
An object of the present invention is to provide a turbine
for use in an underwater aerator which overcomes the above mentioned
drawbacks of presently used turbines.
The present invention therefore pertains to turbine which
comprises:
a cylindrical body having a center hole for connection to
a rotatable drive shaft, the body defining an upper side, a lower side and
an outer peripheral wall; the upper side displaying an annular hub portion
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concentric with the center hole and an annular recess surrounding the
hub portion; the lower side displaying a circular central recessed area;
a first series of air passageways traversing the body
from the inner wall of the annular recess to the outer wall of the body; and
a second series of fluid passageways traversing the
body from the central recessed area to the outer wall of the body; each
air passageway of the first series of passageways defining an air exit
opening, at the outer peripheral wall of the body, which is adjacent to a
fluid opening exit defined for each passageway of the second series of
passageways at the outer peripheral wall; each air exit opening being
located immediately downstream of an adjacent fluid exit opening in
relation to the rotational direction of the body when rotatably driven by the
drive shaft.
In one form of the invention, it has been found that
effective aeration is obtained if the fluid passageways have an axis at
about 10~ with respect to the radius of the cylindrical body.
Similarly, it has been found that effective aeration is
obtained if the air p~ss~geway extends at an angle of about 15~ with the
radius of the body.
In a preferred form of the invention, it has been found
that a diameter ratio of 3:1 between the fluid passageway to the air
passageway provides again effective aeration of the waste water.
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In another preferred form of the present invention, the
fluid passageways each define a generally slanted U-shaped channel
open to the lower side of the cylindrical body.
Other objects and further scope of applicability of the
present invention will become apparent from the detailed description
given hereinafter. It should be understood, however, that this detailed
description, while indicating preferred embodiments of the invention, is
given by way of illustration only, since various changes and modifications
within the spirit and scope of the invention will become apparent to those
skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic elevation view of an aerator to
be used underwater in a tank and using a turbine made in accordance
with a first embodiment of the present invention;
Figure 2 is a top perspective view of a turbine according
to a first embodiment of the present invention;
Figure 3 is a top plan view thereof with sections broken
away;
Figure 4 is a bottom perspective view of the turbine of
figure 2;
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Figure 5 is a cross sectional view thereof taken along
lines 5-5 of figure 2;
Figure 6 is a cross sectional view thereof taken along
5 lines 6-6 of figure 2;
Figure 7 is a bottom perspective view of a turbine
according to a second embodiment of the present invention;
Figure 8 is a bottom plan view of the turbine of figure 7;
Figure 9 is a side elevational view of the turbine of figure
7;
Figure 10 is a top plan view, partly in section, of the
turbine of figure 7; and
- Figure 11 is a cross sectional view taken along lines 11-
11 of figure 10.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to figure 1, there is shown an aerator,
25 generally denoted 10, which is adapted to be placed underwater in a
storage tank (not shown) containing water to be treated.
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The aerator comprises a base 12 having legs 14 for
resting on a bottom wall of the storage tank, a casing 16 hermetically
enclosing a motor 18. The casing rests on a support housing 20 through
which extends the drive axle 22 of the motor. The support housing 20
5 defines an enclosed chamber 24 which is in air flow connection with an
air pipe 26 which is opened to air from the outside. To the base 12 is
connected a circumferential arrangement of elongated tubular guide
ducks 28 both ends of which are opened. Preferably, the cross section
of these guide ducks are rectangular or square shape.
A turbine, generally denoted 30, is mounted to the motor
drive axle 22 by means of a shaft 32.
Referring to figures 2 and 4, the turbine 30 defines a
15 cylindrical body which has an upper side 34, an outer peripheral wall 36
and an under side 38. The upper side 34 contacts a plate 35 of the
aerator 10 (see Figure 1).
As shown in figure 2, the upper side 34 of the cylindrical
20 body displays a center hole 40 for connection to the drive shaft 32 and an
annular hub 42. The under side also displays an annular planar face 44
and an annular recess 46 which is defined by the outer peripheral wall 48
of the hub, an annular base 49 and the inner wall 50.
As shown in figure 4, the under side 38 displays a frusto
conical face 52 with a central recessed area 54, the latter being deflned
by an annular base 54 and an inner peripheral wall 56.
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Referring now to figures 3, 5 and 6, the cylindrical body
30 defines a first series of passageways 60, eight passageways being
displayed in the present embodiment as cylindrical channels 60a to 60h.
As can be seen in figure 5, these passageways are inclined, extending
parallel to face 38 from the inner wall 56 to the outer peripheral wall 36 of
the body. In figure 3, a line 62 has been drawn to show the radius of the
centrical body while line 64 represents the axis of the cylindrical channel
60a. Lines 62 and 64 intersect at an angle a which is about 10~. Hence,
the p~ss~geways 60 extend tangentially rather than radially with respect
to the center hole 40.
Referring now to figures 3 and 6, the cylindrical body 30
also includes a second series of passageways 66; in the embodiment
illustrated, there are eight passageways 66a to 66h corresponding in
number to the passageways 60. These passageways are inclined
cylindrical channels which traverse the body from the outer peripheral wall
36 to the inner wall 50 of the annular recess. In figure 3, a line 67 has
been drawn to show the radius of the cylindrical body while a line 68
represents the axis of the cylindrical channel 66h. Lines 67 and 68
intersect at an angle ~ which is about 15~. Also illustrated in figure 3,
passageways 60a-60h and 66a-66h are arranged in pairs, the smaller
passageway 66 crossing over the larger passageway 60. In one
preferred form of the invention, the ration of the diameter of the
passageways 60 to the diameter of the passageways 66 is 3:1.
Each passageway 66 terminates at the peripheral wall
36 immediately adjacent the opening of a corresponding passageway 60.
If the rotational direction of the cylindrical body is that indicated by arrow
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70 in figure 2, the location of the opening of each passageway 66 is said
to be downstream of the opening of its associated passageway 60.
The operation of the turbine will now be described in
5 relation to figure 1.
It will be assumed that the entire aerator 10 of figure 1
is immerged in fluid to be treated of a storage tank, with the exception
that the upper outlet of the water pipe 26 is opened to the atmosphere.
Driving motor 18 will cause fluid present in passageways 60 and 66 to
flow outwardly towards and exit at the peripheral wall 36. The outlet of
water from the p~ss~geways 66 causes a vacuum forcing air to enter the
pipe 26, flowing through chamber 24 and into the annular recessed area
46 of the upper side of the turbine and through the various passageways
15 66. The air exiting the passageways 66 mixes with the water exiting the
passageways 60. The bubbles (not shown) created by this action will
flow through the circumferentially spaced guide ducks 28 so that aeration
is adequately distributed over the bottom of the tank. By having the
tubular ducks presenting a rectangular cross section adjacent the
20 openings 60 the combination of several bubbles into a larger bubble is
limited.
As will be easily understood by one of ordinary skills in
the art, since the upper side 34 of the turbine 30 according to an
25 embodiment of the present invention is essentially flat, it may efficiently
contact the horizontal plate 35 of the aerator 10. Therefore, when the
aerator 10 including the turbine 30 of the present invention is immerged
in a tank (not shown), the water pressure, which increases with the
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aerator depth, does not cause water illrilll~lion between the upper side
of the turbine 30 and the plate 35 of the aerator 10. Furthermore, the
vacuum created in the vicinity of the air passageways 66a-66h by the fluid
passageways 60a-60h allow the aerator 10 to be immerged deeper in a
5 waste tank since a greater water pressure is required to overcome the
vacuum and enter the air passageways.
Referring now to figures 7-11, a second embodiment of
a turbine 100 adapted to be installed to the motor drive axle 22 by means
10 of a shaft 32 (see Figure 1), will be described.
The turbine 100 is similar to the turbine 30 and thus,
only differences between these two turbines will be described.
One major difference between the turbine 100 and the
turbine 30 of Figures 2-6 is that the turbine 100 has fluid passageways
160a-160h that are opened to an underside 138. As can be better seen
from Figures 9 and 11, the fluid passageways 160a-160h display an
essentially slanted U-shaped cross section.
The fluid passageways 160a-160h each define an arc
of circle joining a central recessed area 154 and an outer peripheral wall
136.
As can be better seen from Figure 9 and 11, each fluid
passageway 160a-160h includes a leading edge 172 and a trailing edge
174. The determination of the leading and trailing edges is made with
respect to the direction of rotation of the turbine 100 (see arrow 170).
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The leading edge 172 of each fluid passageway 160a-160h includes a
bevelled portion 176 which increases the amount of fluid flowing
outwardly in each fluid passageway 160a-160h, towards the peripheral
wall 136 by providing a positive height difference between the trailing
edge 174 and the leading edge 172.
Another difference between the turbine 100 and the
turbine 30 of figures 2-6 is that turbine 100 includes air passageways
166a-166h which traverse the cylindrical body radially.
The other characteristics of the turbine 100 are
substantially the same as that of turbine 30 of figures 2-6. However, it is
to be noted that the operational direction of rotation (see arrow 70 in
Figure 2) of turbine 30 is the opposite of the operational direction of
rotation (see arrow 170 in Figures 8 and 9) of turbine 100.
Although the invention has been described above with
respect to two specific forms, it will be evident to a person skilled in the
art that these forms may be modified and refined in various ways. It is
20 therefore wished to have it understood that the present invention should
not be limited in scope, except by the terms of the following claims.
