Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~5~683 T. J. Fussell, Jr, 7
1 Back~round of the Invention
2 This invention relates to flowmetering equipment
3 and, in particular, to a flowmeter utilizing a diaphragm
4 sensor arrangement particularly suited to measure the
flowrate of hetero~eneous fluids, e.g,, fluids such as
6 steam having constituents in both vapor and liquid phases.
7 Various and sundry arrangements have been
8 proposed by those skilled in the art which exploit the
9 phenomenon of the Karman vortex street in order to-measure
fluid flowrates. More than a decade ago W, G. ~ird
11 (U.S. patent 3,116,639) devised an arrangement in which
12 a pivoted vane-like element was positioned downstream
13 of a vortex shedding body. Flowrate was measured by ~ -
14 detecting the frequency of pivotal oscillation of the
element. In general, the Bird arrangement, and others
16 like it, suffered from a basic problem: intermittent
17 vortex shedding. This problem perplexed the art until
18 A. E. Rodely (U,S.- patent 3,572,117) recognized that a
19 suitably dimensioned bluff body, havin~ a base surface
facing fluid flow and do~mstream surfaces to control
21 oscillatory flow, would produce vortex shedding free of
22 intermittency~ In this arrangement, a temperature sensitive
23 sensor situated outside the wake generated by the bluff
~4 body detects vortex shedding and produces electrical
pulses proportional to the flow rate. The sensor is
26 mounted separately in the pipeli~e wall and the probe-like
27 sensor is positioned in the low turbulence flow zone
28 outside of the wake~
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~S~683 T. J. Fussell, Jr. 7
1 Improved versions of the Rodely bluff body
2 flowmeter generally detect vortex shedding in the high
3 turbulence flow zone immediately downstream of the base
4 surface o~ the bluff body. Thus, in U.S. patent 3,732,731
a removable temperature sensor, on end of a rod-like
6 holder, is located at the intersection of two channels
7 in the bluff body. One channel extends between the down-
8 stream surfaces and the other, into which the holder and
9 sensor are inserted, extends along the long axis of the
body to the exterior of the conduit. In another arrangement
11 shown in U.S. patent 3,796,095 the two channels are in
12 nonfluid flow communication with one another, a cylindrical
13 body containing a ferromagnetic disc is situated in the
14 one channel which extends between the downstream surfaces,
and a magnetic detector is situated in the other channel.
16 As the disc moves, it interrupts a magnetic field causing
17 perturbations which result in an EMF related to the flow-
18 rate. Finally, in U.S. patent 3,823,610, the bluff body
19 has a pair of orifices proximate the downstream surfaces,
a cylindrically shaped chamber within the body, and a
21 shuttle ball free to move a relatively short distance
22 within the chamber along the long axis of the bluff body
23 in response to vortex induced pressure changes at the
24 orifices.
~hile the foregoing flowmeter arrangements
26 represent significant contributions to the state of the
27 art, none has generally been suitable for measuring the
28 flowrate of heterogeneous fluids: those containing
29 constituents in both vapor and liquid phases, especially
steam. In particular, the high temperature of steam,
31 often in the neighborhood of 500 degrees F., has deleterious
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T. J, Fussell, Jr, 7
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1 effects on ~lowmeters utilizing thermistor sensors,
2 whereas the corrosive, errosive, non-lubricating
3 characteristics of steam tend to clog flo~lmeters utilizing
4 shuttle cylinders and shuttle balls,
It is therefore one object of my invention to
6 provide a flowmeter capable of measuring the ~lowrate
7 of heterogenous fluids,
8 It is ano-ther object o~ my invention to measure
9 the flowrate of corrosive, errosive, non-lubricating fluids,
10 It is yet another object of my invention to .
11 measure the ~lowrate of steam,
12 Other schemes, which however do not utilize
13 Rodely bluff bodies, have been suggested for controlling
14 the condition of vortex formation, In particular,
M, Tomota et al (U,S, patent 3,564,915) teach a rod-
16 shaped object for producing vortices, the object having
17 a transverse bore the ports of which open in the vicinity ;;
18 o~ the separation points of the boundary layers of the
19 fluid from the object, Various types o~ sensing elements
can be positioned in the bore. For example, in FIG. 7A,
21 a stainless steel diaphragm 22 lS used as a sensor, and
22 at column 9, lines 66-74 t it is sta~ed that ~low rate can
23 be measured by detecting "the vibration of the diaphragm
24 in the form of resistance varîation with a strain vauge
attached to the diaphragm or by convertin~ the vibration
26 of the diaphragm into an electric signal in the form
27 of an electrostatic capacity change or electromagnetic
28 change or by directly detectinv the vibration o~ the -
29 diaphragm,~ \
Jeneralized configurations such as -those shown
31 in the Tomota el al pa~tent fail, however, to address
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1 significant design problems which render flowmeters
2 practically useable in terms of measurement accuracy
3 as well as field serviceability, From the standpoint of
4 accuracy, these prior art proposals recogni~e neither
resonant frequency problems nor fluid drainage problems
6 associated with the sensor chamber, On the other hand,
7 when considering fluid serviceability, the latter prior
8 art proposals are not designed so that the most vulnerable
9 part, the sensor, is easily replaced in the field in
order to reduce flowmeter downtime,
11 - It is therefore still another object of my
12 invention to provide a Rodely-type flowmeter utilizin~
13 a diaphragm sensor arrangement in which accuracy of
14 measuring the flowrate of heterogeneous fluids such as
steam is enhanced by facilitating liquid drain-off from
16 the diaphragm,
-17 It is another object of my invention to provide
18 a Rodely-type flowmeter utilizing a diaphragm sensor
19 arran~ement in which the diaphragm chamber has no resonant
frequency near to the vortex shedding frequency.
21 It is also an object of my invention to provide
22 a Rodely-type flowmeter utilizing a diaphragm sensor
23 arrangement in which field serviceability is enhanced by
24 situating the diaphragm so that it is easily replaced in
25 the field. ,~
26 Summary of the Invention
27 The foregoin~ and other objects o~ my invention
28 are achieved in accordance with principles of my invention ',:
29 as disclosed in an illustrative embodiment of a pressure
fluctuation sensor assembly which advantageously is suitable
31 for use in measuring the flowrate of heterogeneous fluids,
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~5~83 T. J. Fussell, Jr. 7
1 especially steam. The assembly comprises means defining
2 a hollow interior and means bifurcating the interior
3 to define a pair of channels, the channels having port
4 means at a same end of the interior for admitting
pressure fluctuations into the channels. A diaphragm
6 having first and second opposite surfaces is mounted with
7 its first surface communicating with a first one of the
8 pair of channels and its second surface separatel~
9 communicating with a second one of the pair of channels
and thereby to cause the diaphragm to vibrate in response
11 to pressure fluctuations admitted to the channels. The
12 vibrations of the diaphragm are detected by a means
13 located proximately to the plane of vibration of the
14 diaphragm. The detecting means preferrably includes means
in nonpressure fluctuation communication with the pair of
16 interior channels for sensing vibrations of the diaphragm.
17 Another aspect is that the diaphragm comprises a ferro-
18 magnetic material on at least one of its surfaces and the
19 sensing means comprises a magnetic detector.
Another feature of the illustrative embodiment
21 is the provision of a pressure fluctuation sensor means
22 which is suitable for use with a variety of vortex shedding
23 bodies for flowmetering. According to principles of such
24 an embodiment, the sensor assembly is insertably mounted
within a means defining a hollow inner chamber, a portion
26 of which communicates with pressure fluctuations for a
27 first surface of a diaphragm. The sensor assembly comprises
28 wall means having an exterior sealing a portion of the
~9 inner chamber and an inner segment providing a hollow
interior. The assembly is equipped with means bifurcating
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~S1683 T.J. ~'ussell, Jr. 7
1 the interior into a pair of channels, each of which has
2 port means at a same end of the interior for admitting
3 and withdrawing pressure fluctuations therethrough
4 Assembly means provide an aperture between a first one
of the channels and the hollow inner chamber. A
6 diaphragm having first and second opposite surfaces is
7 vibratorily mounted for communication of pressure
8 fluctuations in a first one of the channels through the
9 aperture and the holloN inner chamber with the first
diaphragm surface, as well as, for separate communication
11 of pressure fluctuations in a second one of the channels
12 with a second diaphragm surface and thereby to cause the
13 diaphragm to vibrate in response to the communicating
14 pressure fluctuations,
My invention provides a flow sensor assembly
16 for use with a vortex shedding flowmeter which meter
17 comprises means for generatin~ streets of pressure fluc-
18 tuations in a fluid flow through a conduit. 'rhe assembly
19 comprises means deflning a hollow interior, means
bifurcating the interior into a pair of channels each of
21 which comprises port means at a same end of the interior
22 for communicating pressure fluctuations from an individual
23 one of the generated streets, a diaphragm havin~ first ~
24 and second opposite surfaces, and means mounting the -
2~ diaphra~m for communicating pressure fluctuations in a
26 first one of the channels with the first diaphragm surface
27 and for separately communicatin~ pressure fluctuations in
28 a second one of the channels with the second diaphragm
29 surface and thereby to cause the diaphragm to vibrate in
response -to the communicating pressure fluctuations and
31 at a frequency related to the flowra-te through the conduit.
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1 The vibrator~ frequency is sensed by a detector which
2 advan-tageously is arrangeable in nonfluid communication
3 wi-th the bifurcated channels and which is selectably a
4 ,magnetic detector for detectin~ vibratory movement of a
ferromagnetic material of at least one of the diaphragm
.6 surfaces,.
7 A.nother feature is the provision of a fluidic
8 sensor comprising means defining a first hollow conduit, ';
9 means defining a second hollow conduit having a portion
thereof substantially parallel to the first conduit
11 defining means, the first and second conduits having
12 exterior ports substantially parallel toone another for ,
13 admitting pressure fluctuations into the conduits in the
14 same longitudinal direction, a diaphragm having first and
15 second surfaces, and means mounting the diaphragm for ~.
16 communicating pressure fluctuations in the first conduit ,-
17 with the first diaphragm surface and for separately
18 communicating pressure fluctuations in the second conduit,~,
19 with the second diaphragm su~ace. ~"
20 A.ccordingly, m~ invention is for use in a fluid ::
21 sensor having a diaphragm with first and second opposite
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22 surfaces mounted in a hollow inner chamber and comprises -:
23 means for bifurcating the inner chamber into two
24 channels for admitting pressure fluctuations in the same
25 longitudinal direction toward one of the diaphragm surfaces~.
26 and through the two channels and means cooperating with ,'
27 the bifurcating means for communicating pressure fluctuations
28 in a first one of the channels with a first diaphragm
2'9 surface and for separately communicating pressure
fluctuations in a second one of the channels with a second
31 diaphragm surface, '-
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105~683 T. J. Fu~sell, Jr. 7
1 In accordance with another specific illustrative
2 embodiment of my invention, a flo~rmeter comprises a
3 Rodely-type bluff body for producing vortex sheddin~
4 free of intermittency, The body has at one end a support
member for moun-ting in a conduit and has proximate its
6 downstream surfaces a pair of orifices. A diaphragm,
7 preferably ferromagnetic, is situated in a sensor chamber
8 within the support member, and a magnetic detector is
9 situated in proximity to the diaphragm for producing an
electrical signal when the diaphragm vibrates in response
11 to vortex shedding. Fluid in the conduit, and thus vortex
12 shedding, is coupled from the orifices through a pair of
13 channels, which are in nonfluid flow communication with
14 one another, to opposite sides of the diaphragm.
In a preferred embodiment, the bluff body has
16 in its end face near the support member a cavity which
17 extends inwardly along the long axis of the body and which
18 forms the orifices in its downstream surfaces. The ~-
19 diaphragm is mounted at one end of a cylindrical housing
20 the interior of which is bifurcated by a partition to form -
21 the two channels. Cut-outs in the housing wall at its
22 other end are in registry with the two orifices when the
23 housing is inserted into the cavity in the bluff body.
24 One of the channels couples fluid from one of the orifices
to the side of the diaphragm interior to the housing.
26 The other channel couples fluid from the other orifice
27 through an aperture in -the housing wall to the side of the
28 diaphragm exterior to the housing, i.e., to the sensor
29 chamber,
In order to enhance measurement accuracy, the
31 sensor chamber, as well as the two channels, are desi~ned
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~S~3 T. J. Fussell, Jr. 7
1 so that their resonant frequencies are remote from the
2 vortex shedding frequency. In addition, by positioning
3 the diaphragm out of the main stream of fluid flow, the
4 deleterious effects of corrosive, errosive, nonlubricating
fluid, such as steam, are considerably ameliorated.
6 Drainage problems associated with hetergeneous liquids,
7 such as steam, especially saturated steam, are alleviated
8 by the configuration of the sensor chamber and channels,
9 particularly when the bluff body is mounted vertically
with the sensor chamber at the top. To facilitate field
11 serviceability, the magnetic detector is situated in a
12 removable head cap which is secured to the support member
13 but which protrudes exterior to the conduit. Removal
14 of the head cap exposes the sensor chamber, and hence
the diaphragm for repair or replacement without requiring
16 significant flowmeter downtime.
17 Brief Description of the Drawing
_ _
18 These and other objects of my invention,
19 together with its various features and advantages, can
be readily understood from the following more detailed
21 description taken in conjunction with the accompanying
22 drawing, in which:
23 FIG. 1 shows schematically the flow zones
24 created by a Rodely~type bluff body in a conduit;
FIG. 2 shows a basic structure illustrating
26 principles of my invention; ~;
27 FIG. 3 is a cut-away view, partially in section,
28 of a diaphragm housing in accordance with one embodiment
29 of my invention;
FIG. 4 is a side view taken along lines 4-4 of
31 FIG. 3;
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1 FIG. 5 is a cut-away view of a flowmeter in
2 accordance with an illustrative embodiment of my invention
3 with the diaphragm housing in plac:e;
4 FIG. 6 is similar to FIG. 3 with the diaphragm
housing in section to show the direction of fluid flow
6 in the channels and in the sensor chamber;
7 FIG. 7 is an end view taken along line 7-7 of
8 FIG. 6; and
9 FIG. 8 is an exploded pictorial view showing
how the diaphragm housing fits into the bluff body.
11 Detailed Description
12 Before discussing my invention in detail, it
13 will be helpful to review briefly the manner in which
14 a Rodely bluff body interacts with fluid flowing in a
conduit. As shown in FIG. 1, a bluff body 5 having a
16 triangular cross-section is mounted along a diameter of
17 pipe 1. A facing surface or base 6 of body 5 interacts
18 with fluid flowing in the pipe 1 to produce separate
19 streets of pressure fluctuations about and downstream
of body 5. Thus, an oscillating wake; i.e., that region
21 bounded by and including the shear layers which separate
22 the periodic, high turbulence flow zone behind body 5
23 from the periodic, low turbulence flow zone outside thereof.
24 The wake zone commences proximate the sharp edged corners
9 and 10 of body 5 and spreads downstream from body 5 until
26 it fills the entire pipe 1. In the upstream direction from
27 body 5, the signals detectable in front of body 5 get
28 progressively weaker upstream and become almost completely
29 buried in the turbulent flow fluctuations at approximately
30 one bluff body length upstream from body 5. In Rodely -
31 patent 3,572,117 a probe-like sensor is typically mounted
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10$1683 T J, Fussell, Jr. 7
1 in the pipe wall at location 18 in the periodic, low
2 turbulence flow zone outside o~ the wake,
3 To achieve nonintermi-ttency in the oscilla-ting
4 fluid ~10VJ the Rodely patent teaches that the ratio of the
axial length of bluff body 5 to the h~ight o~ base 6 is
6 advantageously between 1 and 2, and the ratio o~ the
7 height of 'oase 6 to the inner diameter of pipe 1 is
8 advantageously between 0,15 and 0.4, Moreover, a dimensional
9 length between a ~rontmost surface of the base 6 to its
10 sharp corner edges with respect to that of the height - .
11 of the base is of a ratio of 0,3 or less,
12 These criteria are advantageously satisfied
13 in my invention, a P~odely-type ~lowme-ter incorporating a
14 diaphragm sensor arrangement shown in FI~S, 3-8~ .
Before discussing the specific exemplary Rodely-
16 type flowmeter-diaphragm sensor, it is desirable to explain
17 fundamental principles of my invention with respect to a
18 basic pressure ~luctuation sensor structure as depicted
19 in FIG. 2 by way of example, FIG, 2 shows an assembly 2Ql
20 comprising wall means 202 definin~ a hollow interior ..
21 chamber 203, A. diaphragm 204, illustratively of a
22 ferromagnetic material, is squipped with first and second
23 opposite surfaces 20~ and 206. A. partition member 2Q7
24 bifurcates the interior chamber 203 into two channels
208 and.209. Diaphragm 204 is illustratively mounted by
26 .a means 210 and with respect to the bi~urcating partition
27 member 207 so that pressure ~luctuation in the ~irst
28 channel 208 communicates exclusively with the first
29 diaphragm surface 205 and pressure fluctuations in the
second channel 209 communicate exclusively with the
31 second diaphragm sur~ace 206) Pressure ~luc-tuations from
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105~83 T, J. Fussell, Jr, 7
1 first and second vortex stree-ts produced by a vortex
2 generating body of any type, Rodely or otherwise, enter
3 the first and second channels 208 and 209 through port
4 devices 211 and 212 and, advantageous in a same longitudinal
and parallel direction toward diaphragm surface 206, A.n
6 aperture 213 enables admitted pressure fluctuations in
7 channel 208 to communicate with the diaphragm surface 205.
8 A.ccordin~ly, pressure fluctuations in channels 208 and
9 209 cause the diaphragm 204 to vibrate at a frequency
related to the flowrate of a fluid producing the fluctuations,
11 Such vibrations are detected in accordance with my arrangement ~ :
12 by a detector means (not shown in FIG, 2) which
13 advantageously is in nonfluid communication wi-th both
14 channels 208 and 209 and is illustratively a magnetic ;~
detector,
16 Turning now to a Rodely-type flowmeter9 a
17 specific exemplary diaphragm sensor assembly therefor `.
18 is shown in FIGS~ 3-8. A. Rodely bluff body 11 as sho~
19 in FI~. 6 and 7 has a support member 12 and is mounted
along a d1ameter of a conduit (not shown) and between
21 the walls thereof, Preferably the bluff body 11 comprises
22 a base surface 13 disposed normal to the direction of
23 fluid flow in the conduit and a pair of convergin~ down-
24 stream surfaces 1~ and 17, The cross section of bluff
25 body 11 there~ore, as shown in FIGS. 6 and 7, is sub- . .
26 stantially triangular. In order to detect oscillatory
27 fluid motion (vortex shedding) produced by the bluff body, -
28 my flowmeter is provided with a diaphragm sensor arrangement,
29 More specifically, the sensor arrangement ~
30 comprises a cylindrical diaphragm housing 19 havin~ a ..
31 diaphragm 21 mounted at one end thereof as shown in
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1 FIG. 3. The hollow interior of the housing 19 is
2 bifurcated by an L-shaped partition 23 which forms a pair
3 of fluid channels 25 and 27 in nonfluid flow communication
4 with one another. At the other end of the housing 19
there are a pair of rectangular cutouts 29 and 31 which,
6 as will be described hereinafter, permit fluid flow into
7 channels 25 and 27, respectively. At the end of the housing
8 19 which carries the diaphragm 21 there is an aperture 33
9 which, as will be described hereinafter, places channel 25
in fluid flow communication with the side of diaphragm 21
11 exterior to housing 19. Channel 27, on the other hand,
12 is in fluid flow communication with the side of diaphragm
13 21 interior to housing 19. Note that the foot 23.1 of
14 L-shaped partition 23 is affixed to the housing wall at
a point above aperture so that fluid flowing in channel
16 25 cannot reach the side of diaphragm 21 interior to
17 housing 19.
18 In an illustrative example, the diaphragm housing
19 19 is manufactured of stainless steel. The diaphragm 21
is ferromagnetic KEARFLEX #100 manufactured by Kearflex
21 Corporation of Warwick, Rhode Island, and is electron beam
22 welded to a head cap 35 which is welded in the same manner
23 to the cylindrical walls of the housing. Typical dimensions
24 in inches are as follows: overall housing length 1.15,
25 housing inside diameter 0.64, cutouts 29 and 31 measure ;`
26 0.20 by 0.47, and aperture 33 measures 0.19 by 0.64.
27 As shown in FIG. 8, diaphragm housing 19 fits
28 snuggly into a cavity 37 by drilling a bore into one end
29 face 39 of bluff body 11. The bore breaks through each
of the downstream surfaces 15 and 17 to form a pair of
31 rectangular orifices 41 and 43, respectively. When housing 19
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105~683 T, J, ~ussell, Jr. 7
1 is inserted into cavity 37, rectan~ular cu-touts 29 and 31
2 are substan-tially in registration with orifices 41 and 43.
3 Moreover, the bottom 45 of the leg 23,2 of partition 23
4 is flush with the end of housin~ 19, so that when the
housin7~ is inserted into cavity 37 the bottom 45 of the
6 partition abuts the bottom surface of cavity 37, ''
7 In an illustrative example, the outside diameter
8 o~ support member 12 is about 1,86 in,, the end ~ace
9 (cross-section) of the bluf~ body 11 measures about 1.75
in. at its base and 0,31 inD at its apex. The bore
11 used to form cavity 37 is about 0.75 in. in diameter.
12 Turning now to FIGS, 4 and 5, it can be seen
13 that support mernber 12 has a first portion 12.1 to which ~,,
14 bluff body 11 is attached and a larger diameter second
15 portion 12.2 which is situated exterior to the conduit ~ '
16 (not shown). An O-ring 46 provides a fluid ti,~ht seal between
17 portion 12,1 and the conduit, First portion 12,1 has a
18 bore into which housing 19 fits snu~gly.-Second portion
19 12.2 has a,sensor chamber 47 into which the housin~ 19 ~, '
20 extends so that diaphragm 21 is disposed in the chamber 47, -
. . .
21 Aperture 33 couples chamber 47 in fluid flow communication
22 with channel 25.
23 Chamber 47 ~s closed via a head cap 49, O-rin~ , ' '
24 51 provides a fluid tight seal between the two, Head cap
49 has a threaded, stepped opening 53 into which a magnetic
26 pick-up (not shown) is inserted. ~he sensitive portion
27 of the detector is positioned in a recess 55 so that it
28 is as close to the (~erroma~netic) diaphargm 21 as practical,
29 In an illustrative example, the bottom of the ~
30 head cap 49 is separated from the top of diaphragm,21 by ,,
31 only 0,10 in, Other typical dimensions in inches are:
32 outside diameter of head cap 49 and portion 12.1 about 1.88
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~5~683 r ~. ~ussell, Jr. 7
1 and inside diameter of chamber 47 about 1.32.
2 It is to be understood that the illustrative
3 examples given above for various components are taken
4 from a single flowmeter designed in accordance with one
-5 embodiment of m~ invention and are not intended to limit
6 the scope thereof. The resonant frequency associated
7 with sensor chamber 47 and channels 25 and 27, having
8 the dimensions given above is outside the typical range
9 of vortex shedding frequencies of steam flowing in a
conduit.
11 The operation of my invention will now be described
12 with reference to FIG. 6. Fluid, such as saturated steam ;~
13 at 500 degrees F and 100 psig, flows in a direction out
14 of the paper, that is, generally normal to the base surface
of bluff body 11. Vortex shedding results, as described
16 in Rodely patent 3,572,117, at the edges of the base surface
17 and spreads along the downstream surfaces 15 and 17 and
18 hence into orifices 41 and 43. Thus, as shown by arrows
19 57 and 59, fluid flows through orifices 41 and 43 and
channels 25 and 27, respectively, to opposite sides of
21 diaphragm 21. In particular, fluid flows into orifice 41,
22 through channel 25 and aperture 33, into chamber 47 to the
23 side of diaphragm 21 exterior to housing 19. On the other
24 hand, as shown by arrows 59, fluid also flows into
orifice 43, through channel 27 to the side of diaphragm 21
26 interior to housing 19.
27 Vortex induced pressure changes in the fluid
28 on opposite sides of the ferromagnetic diaphragm 21 cause
29 it to vibrate at a frequency related to the flow rate of
the fluid. This vibration of the diaphragm perturbs
31 a magnetic field of the detector which generates an EMF
32 proportional to the flowrate.
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~05~683 T. J~ ~ussell, Jr, 7
1 I have found that my flowmeter is particularly
2 suited to measuring the flowrate of steam, especially
3 saturated steam which has a considerable liquid content,
4 ~rom the standpoint of measurement accuracy, liquid
~ accumulation on the diaphragm would be detrimental, However,
6 if my flowmeter is mounted vertically, with the diaphragm
7 at the top, then the design o~ the chamber and channels
8 facilitates drainage of li~uid (water) which would interfere
9 with signal detection. ~qoreover, in my flowmeter the
diaphragm is located outside the main stream of fluid flow
11 to reduce the corrosive, errosive effects of steam, From
12 the standpoint o~ field serviceability, the diaphragm 21
13 is readily replaced in the field by merely unscrewing head
14 cap 49 and removing housing 19, This feature is also made
15 possible because there is no need to hermetically seal -
16 the diaphragm, mechanical force and the ~ring ~1 are sufficient,
17 It is to be understood that the above-described
18 arrangements are merely illustrative of the many possible
19 specific embodiments which can be devised to represent
application of the principles of my invention, Numerous
21 and varied other arrangements can be devised in accordance
22 with these principles by those skilled in the art withou-t
23 departing from the spirit and scope of the invention. In
24 particular~ the diaphragm may be attached to its head cap
by brazing as well as welding or it may be restrained by
26 a snap ring or spring, Alternatively, -the diaphragm may
27 be mounted between resilient 0-rings or an elastomeric
28 ring may be molded to a stiff disk, Moreover, an elastomeric l~ '
29 membrane with an encapsulated metal exciter may be used
in lieu of a ferromagnetic diaphragm,
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