Abstrict A fluidic flow meter comprising a fluidic oscillator having an
oscillation chamber, a power nozzle for issuing a jet of fluid into
the oscillation chamber, an outlet for issuing fluid from the oscillation
chamber. A bendable fiber optic wave guide loop has a section adapted
to lose light as a result of flexing or bending is mounted in a
flow path in the oscillation chamber and subjected to oscillatory
flow of the fluid. Light is injected into one end of the fiber optic
wave guide and a detector senses the oscillatory loss of light in
the fiber optic wave guide as a measure of fluid flow through the
fluidic oscillator.
Claims We claim:
1. A fluidic flow sensor comprising a fluidic oscillator having
an oscillation chamber, a power nozzle for issuing a jet of fluid
into said at least one oscillator chamber, an outlet for issuing
fluid from said oscillation chamber, means in said oscillation chamber
for causing said jet of fluid to sweep back and forth within said
oscillation chamber, and a flexible fiber optic wave guide adapted
to lose light as a result of bending, means for mounting said fiber
optic wave guide in a flow path in said oscillation chamber subject
to oscillatory flow of said fluid, means for injecting light into
one end of said fiber optic wave guide and means for detecting the
loss of light from said fiber optic wave guide as a measure of fluid
flow through said oscillation chamber.
2. The fluidic flow sensor defined in claim 1 wherein said flexible
fiber optic waveguide is mounted at an upstream position in said
power nozzle.
3. The fluidic flow sensor defined in claim 1 wherein said fluidic
oscillator has at least one feedback passage and said flexible fiber
optic waveguide is mounted in said at least one feedback passage.
4. The fluidic flow sensor defined in claim 1 wherein said flexible
fiber optic waveguide has a light input end and a light output end,
a light source coupled to said light input end and a photodetector
coupled to said light output end and circuit means for measuring
fluctuation in light issuing from said light output end as the measure
of fluid flow through said oscillation chamber.
5. The fluidic flow sensor defined in claim 4 wherein said fluidic
oscillator has an upstream end and a downstream end and said flexible
fiber optic waveguide is adapted to seek the maximum velocity point
in said stream as fluid flow oscillates in said fluidic oscillator.
6. The fluidic flow sensor defined in claim 1 wherein said flexible
fiber optic wave guide is comprised of at least a pair of loops,
each loop having input and output ends, and a surface section adapted
to lose light on flexing, said surface section adapted to lose light
on bending, one of said loops being maintained at a predetermined
angle relative to the other of said surface section adapted to lose
light and form a reference for the other of said loops.
7. A fluidic flow sensor comprising a fluidic oscillator having
an oscillation chamber, a power nozzle for issuing a jet of fluid
into said oscillation chamber, an outlet for issuing fluid from
said oscillation chamber, means in said oscillation chamber for
causing said jet of fluid to sweep back and forth within said oscillation
chamber, and a flexible fiber optic wave guide having a light input
end and a light output end and a predetermined surface area which
is adapted to lose light as a result of flexing, means for mounting
said fiber optic wave guide in a flow path in said oscillation chamber
subject to oscillatory flow of said fluid, means for injecting light
into one end of said fiber optic wave guide and means for detecting
loss of light from said surface area due to oscillatory flow of
said fluid as a measure of fluid flow through said oscillation chamber.
8. A fluidic flow sensor comprising a fluidic oscillator having
an oscillation chamber, a power nozzle for issuing a jet of fluid
into said oscillation chamber, an outlet for issuing fluid from
said oscillation chamber, means in said oscillation chamber for
causing said jet of fluid to sweep back and forth within said oscillation
chamber, and a pair of flexible fiber optic loops, each loop having
a light input end and a light output end and a predetermined surface
area which is adapted to lose light as a result of flexing, said
predetermined surface area being at different angular orientations
on each of said loops, respectively, means for mounting said fiber
optic loops in a flow path in said oscillation chamber subject to
oscillatory flow of said fluid, means for injecting light into one
end of said fiber optic loop and means for detecting loss of light
from said surface areas due to oscillatory flow of said fluid as
a measure of fluid flow through said oscillation chamber.
Description BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION
It is well known that in a fluidic oscillator, the rate of oscillation
is a function of the fluid flow rate through the oscillator and
that by transducing pressure piezoelectrically or thermistor measured
temperature changes in a feedback flow path in the oscillator, the
rate of fluid flow can be converted to an electrical signal to perform
a control or monitoring function. In one commercial fluid flow meter,
a heated thermistor is located in a feedback passage. When feedback
flow is a maximum or minimum, the heat carried away at a corresponding
maximum or minimum and the rate of fluctuation is linear and directly
proportional to flow rate.
Danisch patent 5321257 discloses a fiber optic bending and positioning
sensor in which a fiber optic or light wave guide is attached to
a member to be bent or displaced and light is injected at one end
and detected at the other end. Bending of the fiber results in loss
of light through a surface strip or bend along one side of the fiber
and this loss is detected to produce an indication of the bending
or displacement.
The object of the present invention is to provide an improved fluid
flow metering system and method. A further object of the invention
is to provide a fluidic oscillator with a highly flexible fiber
optic wave guide which is adapted to flex with changes in fluid
flow and lose light on flexing, and a detector senses the oscillatory
loss of light as a measure of fluid flow through the oscillator
and produce an electrical signal for control and/or monitoring functions.
The device measures flow rates of all fluids either by the degree
to which a flexible fiber optic lead or light guide is bent or flexed
by the frequency of its oscillation. The device includes a fiber
optic or light guide loop treated in such a way as to lose light
into a light absorbing covering in a repeatable and predictable
manner when bent or flexed. When connected to the appropriate light
source and electronic circuitry, the device will provide an electrical
output having a frequency proportional to the rate of oscillation.
In oscillating chambers such as a fluidic,the light guide which
is located in the plane of the flow will maintain a position in
the center of the jet or stream. In the preferred embodiment, the
flexible fiber optic light guide will seek the maximum velocity
point in the stream. As the jet switches from side to side, the
light guide is compelled to switch also. Since the frequency of
oscillation of the jet and therefore the fiber optic is directly
proportional to the flow rate the output signal may be fed into
a frequency counter or totalizer to give an output related to flow
rate (Mode 1). In an alternate embodiment, the fiber optic is embedded
in a section of the fluidic oscillator where flow reverses direction
at a rate proportional to flow rate. In this case, when the flow
is in a direction towards the free end of the light guide, the light
guide will maintain a position in the center of the jet and will
cause a certain output level. When the flow is from the free end
of the fiber the flow forces the fiber towards the wall of the section,
inducing a bend or flexure and changing the output level (Mode 2).
A further operational mode (Mode 3) places the fiber in various
planes perpendicular to the flow. The fiber may be held at one clamping
location with the free end in the fluid flow or be held both at
the free end and second clamping location. In each of these locations
the fiber is used to detect the flow rate through its frequency
of oscillation. Modes 1-3 utilize the fluidic oscillation of the
fluid to compel the fiber to mirror the movement and hence generate
an output whose frequency is proportional to flow rate. A pair of
loops with light loss regions maintained at a 90.degree. relation
to each other can measure flow in multiple planes or three-dimensional
directions.
DESCRIPTION OF THE DRAWINGS
The above and other objects, advantages and features of the invention
will become more apparent when considered with the following specification
and accompanying drawings wherein:
FIG. 1A is a top plan view of a fluidic oscillator with a section
of the cover plate removed to expose the oscillator silhouette and
the fiber optic sensor in one position and condition of operation,
FIG. 1B is a top plan view similar to Fig. 1A but illustrating
the oscillator and fiber optic sensor position and condition during
a further portion of a cycle of oscillation,
FIGS. 2A and 2B are top plan views of a similar fluidic oscillator
showing the fiber optic sensor mounted in one of the feedback passages
thereof,
FIGS. 3A, 3B and 3C are top plan views of a similar fluidic oscillator
showing the fiber optic sensor mounted in one of the feedback passages
thereof,
FIG. 4 is a top plan view of a fluidic oscillator showing the fiber
optic sensor mounted in a further position in one of the feedback
passages,
FIG. 5 is a sectional view taken on lines A--A of Fig.4
FIGS. 6A and 6B are top plan views of a fluidic oscillator illustrating
a further modification of the invention,
FIGS. 7A, 7B and 7C illustrate the invention as applied to an island-type
oscillator,
FIGS. 8A, 8B and 8C illustrate various features of prior art fiber
optic sensors or detectors useful in the practice of the invention,
FIG. 9 illustrates the fiber optic loop coupled to an interface
box containing a light source or photoemitter and photodetector,
FIG. 10 illustrates the fiber optic measuring loop and an associated
reference fiber optic loop,
FIG. 11 is a sectional view crossing the outbound loop section
with cladding removed to form a light loss region and the inbound
loop section,
FIG. 12A illustrates an embodiment of the invention for measuring
flow, movements in multiple planes, FIG. 12B is a sectional view
on lines XX of FIG. 12A, and FIG. 12C illustrates the multiple sensing
plane.
DETAILED DESCRIPTION OF THE INVENTION:
FIGS. 1A-6B illustrate a fluidic oscillator of the type in which
a power nozzle PN issues a jet of fluid into an oscillation chamber
OC having right and left side walls SWR, SWL, respectively, which
diverge and then converge to an outlet opening OO which issues a
jet of fluid, in this case to ambient. Initially, the jet travels
from power nozzle PN through the throat in a straight stream. The
power jet must expand sufficiently to fill the outlet throat before
interaction region and the oscillation feedback channels OFCR and
OFCL begin to fill. Vortices are formed on either side of the jet
of the fluidic oscillator, and since two of the vortices cannot
exist simultaneously with equal intensity, one vortex becomes dominant
and the power stream will be diverted against the opposite wall
and the oscillations begin. In the situation illustrated in FIG.
1A, for example, a dominant vortex is on the right-hand side of
the chamber diverting the power stream against the opposite wall
SWL. In the situation illustrated in Figure lB, the dominant vortex
is on the left-hand side with the power stream being diverted against
the opposite wall in this case, SWR.
In the oscillator illustrated in FIGS. 1A-6B, the dominant vortex,
in conjunction with the suction at the control port caused by the
jet issuing from the power nozzle, cause the flow in the oscillation
feedback channels OFCR and OFCL to reverse direction.
As the power stream flows along the wall, a portion of the fluid
is received into a feedback passage FL or FR. The fluid in the feedback
passages FL or FR is directed against the power stream entering
the oscillation chamber OC adjacent the power nozzle PN, forcing
the jet to the opposite side where a corresponding operation takes
place forcing it to the opposite side again thereby causing the
oscillation to ensue.
In the island-type oscillators shown in FIGS. 7A-7C, oscillation
is caused by oppositely rotating vortices, V1 and V2 being shed
off of opposite sides of the barrier or island 42.
Fiber optic sensors FO (primed in the later embodiments) useful
in the practice of the invention are disclosed in Danisch patents
5321257 and 4880971 incorporated herein by reference. FIGS.
8A, 8B and 8C disclose fiber optic light guides 10 having a light
emission surface 11 extending along one side of the fiber. Light
emission from surface 11 which can be treated as at 12 increase
when the fiber is bent or flexed in one direction and decrease when
the fiber is bent or flexed in the opposite direction. The fiber
optic light guide can be in the form of a simple strand or plural
fiber strands. As shown in FIG. 9 one end 14 of the fiber optic
light guide can be coupled to a light source or photoemitter LS
and the opposite end coupled to photodetector PD which are part
of an electronic circuit 16 which measures the difference in intensity
between light emitted by source LS and detector PD. Optionally,
a second fiber optic light guide loop 20 (FIG. 10) made of the same
length and material, but without the light emission surface, may
be provided as a reference or standard. Reference fiber optic light
guide loop 20 is coupled to a second source LS.sub.2 and detector
PD.sub.2.
FIGS. 8A, 8B and 8C illustrate serrated SE corrugated CU and notched
NO regions of surface treatments to show various ways in which light
loss in a selected surface area can be achieved. In FIG. 9 the
loop has a light input end LIE coupled to a light source LS. Light
loss region or surface area RC is positioned where flex or bend
of the fiber optic light guide occur due to changes in flow direction.
In the embodiment illustrated in FIG. 9 the outbound leg OL of
the fiber optic loop is selected as having the light loss region
RC (see FIG. 11). The inbound or return leg has its end RIE coupled
to a photodetector PD and a signal processing circuit SPC is coupled
to the photodetector PD.
As shown in FIG. 11 the fiber optic light guide is comprised of
a fiber optic core FOC, fiber optic cladding FC, a portion of the
cladding being removed as at RC to form a light loss or treated
region. A light absorbing sheath LAS may be provided to reduce stray
light effects. As shown in FIGS. 8A, 8B and 8C, various methods
of causing light loss upon flexure or bending of the sensor include
serration SE, corrugation CU and notching NO, or other roughening
treatments.
A pair of fiber optic waveguide loops 30 31 in which the outbound
and inbound portions are maintained in a fixed relation to each
other is shown in FIGS. 12A and 12B. Loop 30 has a light loss region
or treated section 32 (facing in a given direction (right in FIG.
12B) and the fiber optic loop 31 has a treated light loss or treated
region 33 facing in a direction 90.degree. relative to the facing
direction of treated section 32 (e.g., down in FIG. 12B). Thus,
since the loops are maintained in fixed relation, any direction
and degree of flex or bend of the combined loops can be detected
and measured.
The invention can be applied to measure flow rates wherever there
is an oscillatory movement of fluid flow that is proportional to
flow rate. While several forms of fluidic oscillators are disclosed
herein, the invention is believed to be applicable to all forms
of fluidic oscillators or systems where there is oscillatory fluid
flow.
Referring now to FIGS. 1A to 7C, the device measures flow rates
of all fluids by the frequency of oscillation of the fiber optic
lead or light guide. The device includes a fiber optic or light
guide loop treated in such a way as to lose light into a light absorbing
covering in a repeatable and predictable manner when bent. When
connected to the appropriate electronic circuitry and light source,
the device will provide an output proportional to the degree of
bending. In oscillating chambers such as a fluidic (FIGS. 1A and
1B), the light guide which is located in the plane of the flow will
maintain a position in the center of the jet or stream. As the jet
switches from side to side, the light guide is compelled to switch
also. Since the frequency of oscillation of the jet and therefore
the fiber optic is directly proportional to the flow rate the output
signal may be fed into a frequency counter or totalizer to give
an output related to flow rate (Mode 1). In an alternate embodiment,
the fiber optic element is embedded in a section of the fluidic
oscillator where flow reverses direction at a rate proportional
to flow rate (FIGS. 2A and 2B). In this case, when the flow is in
a direction towards the free end of the light guide (FIG. 2A), the
light guide will maintain a position in the center of the jet and
will cause a certain output level. When the flow is from the free
end of the fiber (FIG. 2B) the flow forces the fiber towards the
wall of the section, inducing a bend or flexure and changing the
output level (Mode 2). A further operational mode (Mode 3) places
the fiber in various planes perpendicular to the flow (FIGS. 3-6).
The fiber may be held at one clamping location with the free end
in the fluid flow (FIGS. 3-5) or be held in two clamping location
(FIG. 6). In each of these locations the fiber is used to detect
the flow rate through its frequency of oscillation. Modes 1-3 utilize
the fluidic oscillation of the fluid to compel the fiber to mirror
the movement and hence generate an output whose frequency is proportional
to flow rate. An island oscillator 40 of the type shown in Stouffer
patents 4151955 and 5099753 is shown in FIGS. 7A-7C. In this
case, the fiber optic loop 43 is mounted at the apex 41 of island
42.
While there has been shown and described various preferred embodiments
of the invention, it will be appreciated that various other embodiments,
modifications and adaptations of the invention will become readily
apparent to those skilled in the art. It is intended that such other
obvious adaptations and modifications be incorporated within the
true spirit and scope of the claims appended hereto. |