Note: Descriptions are shown in the official language in which they were submitted.
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DOUBLE CONE FOR GENERATION OF A PRESSURE DIFFERENCE
BACKGROUND
The present invention relates to a double-cone arrangement
for creating a pressure difference in a fluid flowing
through the double-cone arrangement. Specifically, the
present invention deals with a double-cone device that
produces enhanced suction and reduced wear and tear.
A double-cone device comprises an.entry unit, an exit unit,
each of hollow frustroconical shape, and a central section
referred to*as orifice. When fluid flows through such a
device, the orifice'section exhibits suction properties. The
suction property makes a double-cone device useful for many
applications ranging from well pumping to separation
processes such as desalination and deionization. The double-
cone device is used in these applications for providing
pressure amplification to the fluids used in these
processes.
The double-cone device has been described in the US patent
application US4792284 titled "Device for creating and
exploiting pressure difference and the technical
applications thereof". The double-cone device, as described
in this patent, is illustrated in FIG.1.
Double-cone device 100 consists of two coaxial
frustroconical sections, referred to as entry cone 102 and
exit cone 104, held together by a cylindrical tube 110.
Entry cone 102 is characterised by its length L1, larger
diameter D1, smaller diameter d1, and conical angle 01.
Similarly, exit cone 104 is characterised by its length L2,
larger diameter D2, smaller diameter d2 and conical angle
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02. The region of minimum diameter between the two sections
is referred to as orifice 106. Double-cone device 100 is fed
with a feed flow that enters entry cone 102 and discharges
out through exit cone 104. The feed flow can be any fluid
i.e. either liquid or gas.
Cylindrical connecting tube 110 surrounds the area around
the orifice. An inlet 108 on cylindrical connecting tube 110
allows suction of fluid from outside device 100 to be drawn
into orifice 106.
During the flow within double-cone device 100, the feed flow
undergoes a pressure variation that is a function of the
geometry of double-cone device 100 and the fluid velocity at
the inlet of entry cone 102. This pressure variation within
double-cone device 100 is illustrated in FIG.2. As shown in
FIG.2, the pressure within double-cone device 100 gradually
falls as the fluid flows through entry cone 102 and then
again rises in exit cone 104. The pressure is minimum at
point (Z=0) within orifice 106. Also, pressures P1 at the
beginning (z= - L1) of the entry cone 102 and P2 at outlet
point (z= L2) of exit cone 104 are different. This
difference in pressure AP = P1 - P2 is referred to as the
pressure-drop across device 100.
Behaviour of the feed flow or the pressure variation within
the device is a function of various factors including
geometrical parameters such as the conical angles of the
entry and exit cones, external pressures at the inlet of the
entry cone and the outlet of the exit cone. Specifically,
higher the external pressure lower the pressure at the
orifice. This results in a higher suction force at the
orifice.
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The performance of a double-cone device is usually measured
in terms of its pressure amplification. Pressure
amplification for a double-cone device is defined as the
ratio of the pressure P2 at the outlet of the exit cone to
the pressure-drop AP across the device. Pressure
amplification can be improved by reducing the pressure-drop
or increasing the exit pressure. Another performance
measuring parameter is the noise that is generated by a
double-cone device. High noise level can lead to rapid wear
and tear of the device and is generally considered to be
environmentally unacceptable. Further, wear and tear of the
device must be minimised so as to ensure that the device has
a long lifecycle.
Various modifications have been made in basic double-cone
design to improve its performance.
One such modification has been described in PCT patent
application PCT/CH99/00403 titled õDouble-cone for
generation of a pressure difference". The patent describes a
double-cone device comprising an entry and an exit cone
connected by their small diameter ends to create an orifice.
Further, the inlet is provided in the exit cone away from
the orifice. The entry conical angle 01 has also been
refined to be less than 50. These modifications decrease
noise and wear and tear of the double-cone device.
Another modification has been described in PCT patent
application PCT/CH02/00134 titled õDouble-cone device and
pump". The double-cone device comprises an entry cone and an
exit cone that are connected through a third cone. An inlet
is provided in the exit cone. The smaller diameter ends of
the entry cone and the third cone are connected to form an
orifice. The conical angle of the third cone is less than
that of the exit cone. Further, the conical angle of the
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third cone must be in the range 10 to 50. The introduction
of the third cone and the positioning of the inlet away from
the orifice reduce wear and tear.-This is because the wall
material is not subjected to a very high stress, as is the
case with the original double-cone structure. Pressure-drop
across the device also reduces, leading to better suction
performance.
While various modifications have been made to the double-
cone design, further improvements can be made to enhance the
pressure amplification, reduce the noise levels and to
stabilise the flow. For example, in the existing device
under certain running conditions, the noise generation can
reach the order of 110 to 115 decibels whilst the human
noise tolerance level is around 85 decibel. Hence, there is
a need for a double-cone device with lower noise levels.
Further, in the existing double-cone devices, the flow
within the device destabilises at high flow rates. Hence,
there is a need to improve the design to stabilise the flow
at high flow rates.
SUMMARY
An object of the present invention is to provide a double-
cone device with enhanced pressure amplification.
Another object of the present invention is to provide a
double-cone device with enhanced suction pressure at the
inlet.
Another object of the present invention is to provide a
double-cone device with reduced noise levels.
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Another object of the present invention is to reduce the
wear and tear in a double-cone device thereby increasing its
lifetime.
Another object of the present invention is to improve the
flow profile of the fluid flowing through a double-cone
device.
Another object of the present invention is to provide a
double-cone device with reduced working temperature.
Yet another object of the present invention is to provide a
double-cone device, which can work efficiently at higher
flow velocities, as compared to the existing double-cone
devices.
The above objectives are attained by using a double-cone
device having a continuous geometry. Specifically, the
double-cone device comprises two frustroconical sections
referred to as the entry cone and the exit cone. The entry
and exit cones have a common smaller diameter face. This
common diameter region is referred to as the orifice.
Further, there is a plurality of holes on the exit cone
close to the orifice.
The present invention achieves a higher pressure
amplification, higher suction force and lower noise than
that possible with the existing double-cone devices. This is
achieved by using a continuous geometry and circular holes
acting as the inlet for suction.
Holes are made in the exit cone, downstream of the orifice,
but within the section of the exit cone with a diameter less
than 1.5 times diameter of the orifice. The size of the
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holes is less than or equal to half the diameter of the orifice.
The conical angle of the entry cone is less than or equal to 5 while
the conical angle of the exit cone is less than or equal to 4 . This leads to
reduction in energy consumption, reduced noise levels and higher flow rates.
In an alternate embodiment of the present invention, the holes on
the exit cone away from the orifice are replaced by a porous section, modelled
as
region with infinite holes of very small size, between the exit cone and the
orifice.
This porous section is made of material such as ceramics.
Another alternate embodiment of the present invention comprises
two frustroconical units referred to as entry and exit cones, an orifice
region and
an insert section. In this device, the insert section provides the path for
the flow of
the material to be sucked into the orifice region. Further, the exit cone
angle is
less than 2 .
In accordance with this invention there is provided a double-cone
device of continuous geometry for creating a pressure difference in a fluid
flowing
through the device, the device comprising: a. a first tapering section having
an
interior space of hollow frustroconical shape; b. a second porous diverging
section
having an interior space of hollow frustroconical shape, the first tapering
section and
the second porous diverging section meeting at a neck at the smaller diameter
end
of the interior space of the first tapering section, the second porous
diverging
section extending from the neck, to achieve suction, the second porous
diverging
section having holes with sizes in the range of 50 to 500 m to provide
relatively
silent suction of the fluid without reducing the suction capacity; and c. a
third
diverging section having an interior space of hollow frustroconical shape,
extending
from the larger diameter end of the interior space of the second porous
section.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiments of the invention will hereinafter be
described in conjunction with the appended drawings provided to illustrate and
not
to limit the invention, wherein like designations denote like elements, and in
which:
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FIG. 1 illustrates a double-cone arrangement described in Patent
Number US4792284 titled "Device for creating and exploiting pressure
difference
and the technical applications thereof';
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FIG.2 shows the pressure variation of the feed flow as it
flows across the various sections of the double-cone device;
FIG.3 illustrates a continuous geometry double-cone device
in accordance with the preferred embodiment;
FIG.4 illustrates a continuous geometry double-cone device
with a porous section;
FIG.5 illustrates a double-cone device with an insert
section.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention discloses a double-cone device with
continuous geometry having a first tapering section and a
second diverging section. A plurality of holes on the second
section, beyond the orifice, facilitates suction into the
device. The orifice is the point at which the tapering
section ends and the diverging section begins, which is also
the section of minimum diameter of the device.
FIG. 3 illustrates a double-cone device 300 of continuous
geometry in accordance with a preferred embodiment of the
present invention. Device 300 comprises two hollow
frustroconical sections referred to as first tapering
section (hereinafter entry cone) 302 and a second diverging
section (hereinafter exit cone) 304 and a plurality of holes
306 on exit cone 304. The section of minimum diameter of
device 300 is also referred to as orifice 308. Orifice 308
is also the exit section of entry cone 302 and entry section
of exit cone 304. In a preferred embodiment, edge of the
orifice should be sharp and the section should be perfectly
circular. It should be apparent to one skilled in the art
that edge can also be smooth.
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Entry cone 302 is characterised by its length L1, larger
diameter D1 and conical angle 01. Similarly, exit cone 304
is characterised by its length L2, larger diameter D2 and
conical angle 02.
In a preferred embodiment of the present invention, entry
conical angle 01 is less than or equal to 5 while the exit
conical angle 02 is less than or equal to 4 . Values of L1,
D1, L2 and D2 can be-chosen corresponding to the chosen
value of 01 and 02. It must be apparent to one skilled in
the art that other, values of the entry cone angle and the
exit cone angle can be used without deviating from the scope
of the present invention. However, for the provided choice
of angles, the device achieves reduced noise levels and
requires a lower energy input.
Double-cone device 300 is fed with feed flow 310 that enters
entry cone 302 and discharges through exit cone 304. Feed
flow 310 can be any fluid such as a liquid or a gas.
Feed flow 310 undergoes a pressure variation within double-
cone device 300. Pressure within double-cone device 300
gradually falls as feed flow 310 flows through entry cone
302 and then again rises in exit cone 304. The pressure is
minimum at orifice 308. Low pressure around the region of
orifice 308, in the exit cone, allows material 312 from
outside of device 300 to be sucked into device 300 through
holes 306.
Holes can be of any shape such as square shaped, elliptical
shaped and circular shaped. In a preferred embodiment,
circular shaped holes are used. Further in the preferred
embodiment of the invention, holes 306 are inclined in the
direction of flow. It must be apparent to one skilled in the
art that the alignment of the axis.of the holes can be in
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any direction with respect to the direction of the feed
flow, such as normal to the surface of the exit cone or
against the direction of the feed flow, without deviating
from the scope of the invention.
Size of holes 306 is a function of feed flow material 310
and the size of orifice 308. The nature of the material that
is to be sucked affects the size of the holes substantially.
For example, if water is the material to be sucked, then the
diameter of holes relative to the orifice diameter should be
less than 0.5 and in absolute terms limited to <10 mm. If a
non-Newtonian fluid is used, then the maximum diameter of
the hole is limited to 4-5 mm. Further, for a non-Newtonian
liquid, size of the hole is strongly dependent on the
liquid's mechanical properties. In the preferred embodiment,
the size of the holes < 0.2 times the orifice diameter is
preferred. Small hole to orifice size ratio is preferred
because if the ratio is too high then the stability of flow
feed is adversely affected.
A plurality of holes is used so as to enable suction of a
large amount of material. The position of the holes is kept
as close to the orifice as possible because the suction
force decreases as one moves away from the orifice plane. In
a preferred embodiment of the invention, the holes are made
at a section of exit cone 304 such that the diameter of the
section is less than 1.5 times the diameter of the orifice
308.
In an alternative embodiment of the present invention, the
entry section of the exit cone is made of porous material,
instead of having the plurality of holes. This embodiment is
described using FIG.4.
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FIG.4 shows a double-cone device 400 comprising entry cone
302, exit cone 304, and a porous section 402. The geometry
of the device is continuous and entry cone 302 and exit cone
304 are made of first material, which can be the standard
material used for making double-cone devices, such as steel.
Porous section 402 is made of a porous material such as
ceramic or glass compounds. Porous concrete compounds are
ideal for use in large double-cone devices. Other examples
can be creation of porous section by chemical leaching of
suitable materials. For instance, compounds composed of
various alloys and plastics can be used to form the geometry
and the porous section is then formed by subjecting the
appropriate region to chemical or electrical attack. Feed
flow 310 flows through device 400 moving from the inlet of
entry cone 302 and discharging into outlet of exit cone 304.
The discharge includes feed flow 310 as.well as sucked
material 404. Material 404 is sucked into device 400 through
porous section 402.
For the porous material, hole sizes in the range of 50 to
500 m are used to provide a relatively silent suction (low
noise levels) without reducing the suction capacity. Also,
the diameter of porous section 402 should preferably be less
than 1.5 times the diameter of orifice 308.
ADVANTAGES
The present invention provides enhanced pressure
amplification and reduced noise.
Noise in a double-cone device is generated by a flow profile
that does not respect the chosen geometry. In other words,
the flow is not fully in contact with the double-cone walls.
Also, in existing devices, the flow profile changes sharply
as feed flow moves from the entry cone to the orifice
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region. The present invention reduces this noise by creating
a flow profile that more closely follows the wall geometry
than in existing double-cone devices.
The continuous geometry of the double-cone device of the
present invention causes the feed flow profiles in orifice
308 and exit cone 304 to remain in contact with the wall.
This is because the continuous geometry does not allow flow
feed 310 to become free, as is the case in existing double-
cone devices. Hence, there is no drastic change in the flow
profile as feed flow 310 moves from orifice 308 to exit cone
304. This improved flow profile leads to a significant
reduction in the noise levels. Further, the improved flow
profile reduces the wear and tear of the device.
Additionally, improved flow profile allows the device to
work efficiently at much higher flow rates than that
possible with the existing devices.
Continuous geometry also leads to an increase in the
pressure amplification as compared to the existing double-
cone devices. The pressure amplification that can be
achieved is a function of the flow regime within the double-
cone. Specifically, the pressure amplification is a function
of the axial flow velocity component. More dominant the
axial flow velocity component, greater is the amplification
that can be achieved. The continuous geometry reduces the
tendency for the non-axial flow velocity components to
increase in magnitude resulting in the increase in pressure
amplification.
For example, a continuous geometry double-cone device
results in around 50% increase in pressure amplification as
compared to the performance of an existing double-cone
device. The noise generated by the continuous geometry
double-cone device also decreases. For the existing double-
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cone device, a noise level of around 100 dB is generated
while the continuous geometry double-cone generates noise of
around 80 db. Specifically, in one experiment performed on
continuous geometry double-cone of entry conical angle 5
and exit conical angle 2 , a pressure-drop of only 10 bar
was developed whilst developing a pressure amplification of
1.8 at a noise level of - 80db. This performance was - 50%
better in pressure amplification than an existing device of
comparable power.
Further, for 01<= 5 the tendency of feed flow to rotate
within device 300 is reduced. Rotation of the feed flow
causes energy consumption. Hence, the provided choice of
entry angle reduces the energy consumption due to rotation.
The reduction in energy consumption results in increase in
the pressure amplification that can be achieved.
For 02 <= 4 , the flow profile of feed flow within exit cone
304 is stabilised. Stability in flow allows device 300 to be
used efficiently even at higher flow rates. Energy consumed
by device 300 is also reduced. Further, the noise generated
by device is reduced.
For example, an existing double-cone device with entry
conical angle 5 and exit conical angle 5 failed to perform
efficiently when used as a specific hydraulic reverse
pumping application. On the other hand, the double-cone
device according to the present invention with an exit
conical angle 2 worked without any problem.
The use of holes, as opposed to sliced sections removed from
the exit cone in the existing double-cone devices, leads to
an enhanced suction pressure downstream of the orifice 308.
The suction force depends on the pressure that is generated
in the neighbourhood of the orifice 308. The pressure in
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this region is a function of various parameters. The
parameters include geometry of double-cone device 300,
pressure applied at the outlet of exit cone 304 and the
position of inlets to suck the material into device 300.
Specifically, if the inlet for sucking the material is
closer to the orifice, the suction force is higher. This is
because the suction force depends on the pressure existing
in orifice 308. Lower the pressure in orifice 308, higher is
the suction force. The pressure rises dramatically with
distance from the orifice 308. Hence, to maximise the
suction force, the suction inlet should be as close to
orifice 308 as possible. The present invention utilises this
fact to achieve higher suction by using plurality of holes
306'near the orifice.
Holes 306 are used since they can be placed closer to
orifice plane than a slice taken out of the exit cone, as is
the case with existing devices. When a slice is removed from
the exit cone a free jet is created that does not re-
establish contact with the exit cone walls until well into
the exit cone. This problem is aggravated by flow speed. If
the removed slice is too close to the orifice the jet speed
is too high for the exit cone to exercise an adequate
influence on the main flow near the orifice. Hence, the
slice cannot be'placed close to the orifice.
Another embodiment of the present invention uses an insert
section between the entry and exit cone. This embodiment is
shown using FIG.5.
FIG.5 illustrates a double-cone device 500 comprising two
hollow frustroconical sections referred to as first tapering
section (hereinafter referred as entry cone) 502 and second
diverging section (hereinafter referred to exit cone) 504
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and an insert section 508 instead of a continuous section
with holes.
The conical angle of exit cone 504 is less than 2 . For this
choice of the conical angle, the device achieves sharp
reduction in noise. However, it must be apparent to one
skilled in the art that other values of the exit cone angle
can be used without deviating from the scope of the
embodiment.
Feed flow 510 flows from inlet of entry cone 502 through
orifice 506 and discharges into outlet of exit cone 504.
The discharge includes feed flow 510 as well as sucked
material 512. Material 512 is sucked into device 500
through insert section 508.
Insert section 508 comprises a central hollow frustroconical
section extending from the smaller diameter end of entry
cone 502 to the beginning of exit cone 504. The smaller
diameter of the central hollow section is matched to the
smaller diameter end of entry cone 502 while the larger
diameter end of the central hollow section is matched to the
beginning of exit cone 504. Further, insert section 508 has
a plurality of radial holes on the central hollow section
for suction of material into device 500.
The use of insert section leads to substantial decrease in
noise. For example, if the pressure at the outlet of exit
cone-is 19 bar, noise generated by the existing double-cone
devices is 110-115 decibels (dB). On the other hand, the
noise generated by device 500 is 85-90 dB.
While the preferred embodiments of the invention have been
illustrated and described, it will be clear that the
invention is not limited to these embodiments only. Numerous
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modifications, changes, variations, substitutions and
equivalents will be apparent to those skilled in the art
without departing from the spirit and scope of the invention
as described in the claims.
