Abstrict A flow meter comprising a pulsed eddy generator disposed at an
upstream section in the flow passage and an eddy sensor disposed
at a downstream section, wherein the pulsed eddy generator is programmed
to be activated automatically following a predetermined brief period
of deactivation, which brief period of deactivation starts at the
moment the eddy generator is switched from an activation mode to
a deactivation mode by the eddy sensor that senses the leading edge
of the eddy stream generated by the eddy generator during a preceding
activation. As a consequence, the eddy generator generates a series
of pulsed eddy streams created during the activation of the eddy
generator, wherein each of which pulsed eddy streams is interceded
by silent streams created during the deactivation period of the
eddy generator. The representative fluid velocity is obtained by
dividing the distance between the eddy generator and the eddy sensor
by the duration of each activated period of the eddy generator,
which duration is equal to the period of one complete cycle of the
pulsed flow minus the predetermined duration of the deactivated
period of the eddy generator. The actual flow rate is obtained by
calibrating and/or statistically analyzing the representative velocity,
which may be carried out by a microcomputer or microprocessor.
Claims I claim:
1. A pulsed eddy flow meter comprising in combination:
(a) a flow passage;
(b) an eddy generating means disposed within said flow passage
at one section of said flow passage wherein the generation of eddies
in fluid medium flowing across said one section of said flow passage
is enhanced when said eddy generating means is in an activated state
and the generation of eddies in fluid medium flowing across said
one section of said flow passage is suppressed when said eddy generating
means is in a deactivated state;
(c) an eddy sensing means disposed within said flow passage at
another section of said flow passage downstream from said one section;
(d) a transducer converting mechanical effect of eddies on said
eddy sensing means to an electric signal;
(e) a controller receiving said electrical signal from said transducer,
said controller imposing one state out of said activated state and
said deactivated state on said eddy generating means wherein said
controller automatically imposes said activated state following
a deactivated state of a predetermined duration and imposes said
deactivated state at an instant when said eddy sensing means detects
an eddy of an intensity greater than a thresh-hold intensity, which
thresh-hold intensity is greater than the intensity of eddies generated
by said eddy generating means at said deactivated state and is less
that the intensity of eddies generated by said eddy generating means
at said activated state; and
(f) means for obtaining a representative fluid velocity by dividing
the distance between said eddy generating means and said eddy sensing
means by the duration of the imposition of the most recent activated
state.
2. The combination as set forth in claim 1 wherein said combination
includes means for calibrating said representative fluid velocity
to flow rate data of the fluid flowing through said flow passage.
3. The combination as set forth in claim 2 wherein said predetermined
duration of deactivated state preceding said automatic imposition
of said activated state is adjustable.
4. The combination as set forth in claim 3 wherein said thresh-hold
intensity is adjustable.
5. The combination as set forth in claim 2 wherein said thresh-hold
intensity is adjustable.
6. The combination as set forth in claim 2 wherein said combination
includes means for displaying said flow rate data.
7. The combination as set forth in claim 2 wherein said combination
includes means for transmitting said flow rate data usable as an
input signal to a flow control device.
8. A pulsed eddy flow meter comprising in combination:
(a) a flow passage;
(b) an eddy generating means disposed within said flow passage
at one section of said flow passage wherein the generation of eddies
in fluid medium flowing across said one section of said flow passage
is enhanced when said eddy generating means is in an activated state
and the generation of eddies in fluid medium flowing across said
one section of said flow passage is suppressed when said eddy generating
means is in a deactivated state;
(c) an eddy sensing means disposed within said flow passage at
another section of said flow passage downstream from said one section;
(d) a controller imposing said activated state of a finite duration
and said deactivated state of another finite duration on said eddy
generating means in an alternating fashion
(e) means for measuring the time interval between the onset of
each said activated state of a finite duration and the onset of
the sensing of eddies generated by said eddy generating means during
said each said activated state of a finite duration; and
(f) means for obtaining a representative fluid velocity by dividing
the distance between said eddy generating means and said eddy sensing
means by said time interval between the onset of each said activated
state of a finite duration and the onset of the sensing of eddies
generated by said eddy generating means during said each said activated
state of a finite duration.
9. The combination as set forth in claim 8 wherein said combination
includes means for calibrating said representative fluid velocity
to flow rate data of the fluid flowing through said flow passage.
10. The combination as set forth in claim 9 wherein predetermined
duration of said deactivated state of another finite duration is
adjustable.
11. The combination as set forth in claim 10 wherein predetermined
duration of said activated state of a finite duration is adjustable.
12. The combination as set forth in claim 9 wherein predetermined
duration of said activated state of a finite duration is adjustable.
13. The combination as set forth in claim 9 wherein said combination
includes means for displaying said flow rate data.
14. The combination as set forth in claim 9 wherein said combination
includes means for transmitting said flow rate data usable as an
input signal to a flow control device.
Description BACKGROUND OF THE INVENTION
One of the most reliable and consistent methods for measuring the
velocity of a moving fluid medium involves the tagging of a fluid
element and measuring of the time period required for the tagged
fluid element to flow from one station to another of known distance
of separation therebetween. This method of the fluid velocity measurement
is commonly practiced by tagging the moving fluid with a float,
neutrally buoyant marker or by dyeing the fluid with a color. In
spite of this method of fluid velocity measurement practiced for
centries, no one has attempted to construct a flow meter using the
aforementioned principle for industrial and/or scientific applications
because no one has succeeded to provide a means for marking the
moving fluid without adding a foreign object thereto or contaminating
thereof.
The primary object of the present invention is to provide a flow
meter that employs pulsed eddy flows to mark the moving fluid element
in measuring the flow velocity, which pulsed eddy flows are generated
by an eddy generator in an intermittent pattern.
Another object is to provide a flow meter that employs an eddy
sensor disposed at a station downstream from the location of the
eddy generator, wherein the representative flow velocity is obtained
by dividing the distance between the pulsed eddy generator and the
eddy sensor by the time interval between the generation of a pulsed
eddy stream by the pulsed eddy generator and the sensing of the
same pulsed eddy stream by the eddy sensor.
A further object is to provide a flow meter including means for
calibrating and/or statistically analysing the representitive fluid
velocity obtained by the pulsed eddy marking of the moving fluid
element in converting the representative flow velocity into the
rate of flow data.
Yet another object is to provide a flow meter employing a pulsed
eddy generator automatically activated to generate an eddy stream
moving with the flowing fluid following a predetermined brief period
of inactivation providing a silent stream, wherein the eddy generator
under activated mode is deactivated by the eddy sensor at the moment
the eddy sensor detects the leading edge of the eddy stream generated
by the eddy sensor; whereby, the eddy generator produces a series
of eddy streams separated by a series of silent streams.
Yet a further object is to provide a flow meter including means
for obtaining the time rate of flow data from the representative
flow velocity that is calculated by dividing the distance between
the eddy generator and eddy sensor by the time period between sensing
the leading edges of two consecutive pulsed eddy streams measured
by the sensor minus the predetermine duration of each silent stream.
These and other objects of the present invention will become clear
as the description thereof proceeds.
BRIEF DESCRIPTION OF THE FIGURES
The present invention may be described with a great clarity and
specificity by referring to the following figures:
FIG. 1 illustrates a schematic drawing showing a general arrangement
of an embodiment of the pulsed eddy flow meter constructed in accordance
with the principles of the present invention.
FIG. 2 illustrates the pulsed eddy flows as a function of time
which are generated by the eddy generator and sensed by the eddy
sensor in a time delayed relationship.
FIG. 3 illustrates another embodiment of the arrangement including
an eddy generator and an eddy sensor.
FIG. 4 illustrates a further embodiment of the arrangement including
an eddy generator and an eddy sensor.
FIG. 5 illustrates a cross section showing the eddy generator shown
in FIG. 4.
FIG. 6 illustrates a cross section showing an eddy generator of
another embodiment.
FIG. 7 illustrates yet another embodiment of the arrangement including
an eddy generator and an eddy sensor.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
In FIG. 1 there is illustrated a cross section of the flow meter
tubing taken along a plane including the central axis thereof. The
arrangement also includes the control and data processor assembly
including the eddy generator controller, eddy sensor transducer
and flow data processor. The flow meter tube or flow passage 1 includes
an eddy generator means 2 disposed at a section, which means may
include one or more substantially flat elongated members or vanes
having a streamlined cross section which are disposed across the
cross section of the flow passage 1 in parallel configuration as
shwon in FIG. 1 or in a configuration crossing therebetween. These
substantially flat elongated members or vanes are rotatable about
the longitudinal axis thereof and mechanically coupled to an eddy
generator controller 3 that actuates the substantially flat elongated
members or the vanes constituting the eddy generator means 2 to
the deactivated position wherein the vanes are lined up parallel
to the central axis of the flow passage 1 as shown in broken lines
or to the activated position wherein the vanes are positioned substantially
perpendicular to the central axis of the flow passage 1 as shown
in solid lines. An eddy sensor means 4 comprising an aerodynamic
surface sensitively reacting to the eddy stream flowing therearound
is disposed at another section downstream from the section including
the eddy generator means 2. The eddy sensor means 4 includes an
eddy sensor transducer 5 that converts the mechanical effect of
the eddy streams on the eddy sensor 4 into electric or electromagnetic
signals of intensity that varies as a function of the strength level
of the eddy stream. The output from the eddy sensor transducer 5
is transmitted to the eddy generator controller 3 as well as to
a flow data processor 6 that processes the data transmitted from
the eddy sensor transducer and converts it into flow rate data,
which may be the time rate of mass flow, weight flow or volume flow
flowing through the flow passage 1 included in the flow meter. The
flow rate may be displayed by the flow data processor 6 and/or transmitted
therefrom as an output.
In FIG. 2 there is illustrated a diagram showing the magnitude
or severity of the eddy flows represented by the ordinate which
is plotted against the time represented by the abscissa. The ordinate
represents the axial component of the eddy velocity that is equal
to the component U of the actual macroscopic fluid velocity parallel
to the central axis of the flow passage 1 minus the space averaged
or ordered velocity of the fluid medium <U> as well as the
radial component V of the eddy velocity. When the eddy generator
2 is activated for a duration T.sub.H wherein the vanes are lined
up perpendicular to the direction of the flow, a fluid stream of
high level eddy is created. When the eddy generator 2 is deactivated
for a predetermined duration T.sub.L wherein the vanes are lined
up parallel to the direction of the flow, a fluid stream of low
level eddy is created. The eddy generator controller 3 is programmed
in such a way that, when the eddy generator controller 3 is switched
on, it automatically actuates the eddy generator to the "eddy
promoting position" following a predetermined period T.sub.
L of deactivated time interval wherein the eddy generator remains
at the "eddy suppressing position", which period T.sub.L
commences from the moment when the eddy generator controller 3 is
switched on or when the eddy generator controller 3 actuates the
eddy generator to the "eddy supressing position". The
eddy generator controller 3 is also pregrammed to actuate the eddy
generator to the "eddy suppressing" position when the
intensity of the signals from the eddy sensor transducer is greater
than a threshhold value corresponding to the threshhold level of
the eddy V.sub.TH that is greater than the maximum level of the
eddies generated by the eddy generator at the "eddy suppressing
position", but it is less than the maximum level of the eddies
generated by the eddy generator at the "eddy promoting position".
As a consequence, the arrangement of the eddy generator and the
eddy sensor included in the pulsed eddy flow meter shown in FIG.
1 operating under the control sequence described in the preceding
paragraphs continuously produces a series of moving fluid columns
of high intensity eddy and those of low intensity eddy in an alternating
pattern. Since the duration T.sub.H of the high intensity eddy stream
is equal to the time interval between the creation of the leading
edge of the high intensity eddy stream by the eddy generator and
the detection thereof by the eddy sensor, the duration T.sub.H is
equal to the time interval required for the fluid flow carrying
the high intensity eddies therewith to flow from the eddy generating
station to the eddy sensing station. Therefore, the representative
flow velocity <U>.sub.REP is given by the equation
where L is the distance between the eddy generating station and
the eddy sensing station. It should be understood that the fluid
velocity may not be uniformly distributed across the cross section
of the flow passage 1 of the flow meter and, consequently, the time
rate of volume flow cannot be found by multiplying the representative
velocity <U>.sub.REP by the cross section area of the flow
passage 1. The representative velocity <U>.sub.REP can be
calibrated to the time rate of volume flow or mass flow by empirical
methods. The period of the pulsed eddy streams T, which is equal
to the time interval between two consecutive detections of the leading
edge of high intensity eddy streams by the eddy sensor 4 can be
readily detected and determined by processing the output signal
from the eddy sensor transducer 5. The duration T.sub.L of the low
intensity eddy stream is predetermined and programmed into the eddy
generator controller 3 and, consequently, it is a known quantitity.
Therefore, T.sub.H can be determined from two known quantities T
and T.sub.L by the equation
Substitution of equation (2) into (1) yields the relation
The flow data processor and display module 6 includes means for
carrying out the calculation appearing in the right-hand-side of
the equation (3) and means for executing the methematical operations
caliburating and converting the information on <U>.sub.REP
given by the equation (3) into the time rate of the flow, which
is either displayed or transmitted as an output signal. It becomes
clear from the equation (3) that L should be made large enough to
result in T having measurably large enough values. It is recommended
to include means for varying the preset value of T.sub.L in the
electronics, whereby the operator of the flow meter is provided
with an option to select suitable values for T.sub.L resulting in
the most accurate and consistent flow velocity measurement for different
ranges of the flow velocity. It is also disirable to include means
for varying the thresh-hold eddy level V.sub.TH in the electronics,
whereby the operators of the flow meter can select an appropriate
value of V.sub.TH for different ranges of flow velocity that clearly
and consistently distinguishes the high intensity eddies from the
low intensity eddies and vice versa.
In FIG. 3 there is shown a cross section of the tube or flow passage
7 included in a pulsed eddy flow meter, that comprises an eddy generator
means 8 including one or more cylindrical elongated members having
a substantially round cross section disposed across the cross section
of the flow passage 7. Each of the elongated members is made of
dielectric material and includes an electrically conducting wire
9 disposed axially therethrough adjacent to the trailing edge in
the cross section thereof. The electrically conducting wires 9 are
connected to an electrically charged source 10 such as a battery
or condenser through an eddy generator controller switch 11. When
the controller switch 11 is closed charging the electrically conducting
insulated wires 9 electrically, the electric field created thereby
pulls the fluid flow all the way to the trailing edge of the elongated
members 8 and, consequently, surpresses the eddies by preventing
the flow separation from the elongated members 8. When the controller
switch 11 is open, the fluid flow around the elongated members 8
separates and, consequently, high intensity eddies are generated.
The closing and opening of the controller switch 11 is programmed
and operated in the same way as the eddy generator controller 3
included in FIG. 1 in generating a seires of fluid columns of high
intensity eddies and those of low intensity eddies in an alternating
pattern, which operation relies on the input signals transmitted
from the eddy sensor transducer 12 producing electrical output signals
as a function of mechanical action on the eddy sensor 13 imposed
by the eddy streams passing thereby. For brevity of the illustration,
the flow data processor and display module is not shown in FIG.
3. As explained in conjuction with FIG. 2 the eddy flow has the
axial component as well as the radial component. The eddy sensor
4 in FIG. 1 is designed to detect the magnitude of the radial component
of the eddy flows wherein the alternating pitching moment or alternating
lift force exerted on the airfoil like eddy detector 4 is converted
to electric signals by means of piezo-electric principles or by
other transducer technology. The eddy detector 13 senses the alternating
pitching moment or alternating lift force exerted on the airfoil-like
eddy detector by the axial component of the eddy flows. It should
be understood that the technology of eddy detection and measurement
is well developed and is a very broad field. The specific embodiments
of the eddy sensors shown in FIGS. 1 and 3 are to exemplify the
teachings, and principles of the present invention of the pulsed
eddy flow meter without limiting the claims thereof to any particular
method of eddy detection and sensing. For example, a wire under
a tension stretched across the cross section of the flow passage
and connected to a piezo-electric junction or the well-known "hot-wire"
method may be employed in place of the specific eddy sensors shown
in FIGS. 1 and 3.
In FIG. 4 there is illustrated a further embodiment of the pulsed
eddy flow meter having essentially the same construction as that
shown in FIG. 1 with one exception being that the eddy generator
assembly 14 includes one or more vibrating elongated members 15
having a streamlined cross section, which is lined up parallel to
the direction of the flow. The elongated member 15 is vibrated in
a direction substantially perpendicular to the central axis of the
flow passage and substantially perpendicular to the lengthwise direction
of the elongated member 15 by an electromagnet 16 of a flat cross
section that is energized by alternating electric currents energizing
the coil 17. When airfoil-like elongated member 15 is vibrated intermediate
two extreme positions thereof as shown in broken lines, it generates
high intensity eddies, while eddy generation is suppressed when
the airfoil-like elongated member 15 is stationary. The eddy generator
controller 18 taking input signals from the eddy sensor transducer
19 is programmed and operates in the same mode as that described
in conjunction with FIGS. 1 and 2.
In FIG. 5 there is illustrated a cross section of the arrangement
shown in FIG. 4 taken along plane 5--5 as shown in FIG. 4 which
cross section view shows the arrangement of the airfoil-like elongated
member disposed across the cross section of the flow passage and
the electromagnet 16 of a substantially flat cross section secured
to and extending from the wall of the flow passage in an angle substantially
90 degrees to the airfoil-like elongated member 15. The electric
coil 17 energizing the electromagnet 16 is disposed externally to
the wall of the flow passage. One extremity of the core 20 of the
electromagnet 16 made of a ferro magnetic material is connected
to at least one extremity of the airfoil-like elongated member 15
in order to provide a closed path for the magnetic flux.
In FIG. 6 there is illustrated another embodiment of the vibrating
airfoil eddy generator that is constructed in a way similar to that
shown in FIGS. 4 and 5 with a few modifications. A pair of airfoil-like
elongated members 21 and 22 anchored to and extending from two diametrically
opposite portions of the wall of the flow passage 23 are disposed
across the cross section of the flow passage 23 in line. The flat
electromagnet 24 disposed in essentially the same way as the element
16 shown in FIGS. 4 and 5 includes a core 24 with two extremities
respectively connected to the extremities of the airfoil-like elongated
members 21 and 22 anchored to the wall of the flow passage 23.
In FIG. 7 there is illustrated an embodiment of the eddy generator
comprising a plurality of airfoil-like elongated members disposed
at a zero angle of attack across the cross section of the flow passage
in a parallel configuration, wherein the plurality of the airfoil-like
elongated members 26 27 28 etc. are tied to each other by a thin
wire 29 secured thereto and disposed thereacross. This assembly
of the airfoil-like elongated members is vibrated by a pair of flat
electromagnets 31 and 31 respectively anchored to and extending
in a direction substantially perpendicular to the airfoil-like elongated
members from two diametrically opposite portions of the wall of
the flow passage, which are alternatively energized by a pair of
electric coils 32 and 33 respectively.
It should be understood that there are many other ways to generate
high intensity eddies in an intermittent pattern, which may use
mechanical, acoustical, electrical or electromagnetic principles
to promote and suppress the generation of high intensity eddy flows
in an alternating pattern. The claims and teachings of the present
invention are not limited to the eddy generators of specific construction
as shown in FIGS. 1 3 4 5 6 and 7.
It should be understood that the pulsed eddy flow meters shown
in FIG. 1 through 7 can be operated in a mode somewhat different
from that described in conjunction with FIG. 2. In this mode of
operation, the eddy generator is programmed to actuate the eddy
generator in a pulsed pattern at a fixed frequency or at a frequency
programmed to increase with the fluid velocity, wherein the time
interval between the moment the eddy generator is activated and
the moment the eddy sensor senses the leading edge of the eddy stream
is directly measured by a timer using inputs from the eddy generator
controller and the eddy sensor transducer. It is desirable that
the frequency of the activation of the eddy generator in a pulsed
pattern is fixed or varied as a function of the flow velocity being
measured in such a way that there is at most a single column of
the high intensity eddy stream intermediate the eddy generator and
the eddy sensor at any given instances, which makes the timing between
the eddy generation and eddy sensing a lot easier and simpler. Of
course, the pulsed eddy flow meter can certainly be operated at
a frequency of pulsed eddy generation that results in more than
one fluid column of high intensity eddy streams existing intermediate
the eddy generator and eddy sensor at a given instance. The representative
flow velocity is obtained by dividing the distance between the eddy
generator and the eddy sensor by the time interval required for
each fluid column of high intensity eddy streams to flow therebetween,
which time interval is measured by the timer taking input from the
eddy generator controller and the eddy sensor transducer. The time
rate of flow is obtained by calibrating the representative flow
velocity by a microprocessor or computer executing the empirically
obtained caliburation analysis.
While the principles of the present invention have now been made
clear by the illustrative embodiments, there will be immediately
obvious to those skilled in the art many modifications of the structures,
arrangements, porportions, elements, materials and components which
are particularly adapted to specific working environments and operating
conditions in the practice of the invention without departing from
those principles.
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