CA1051683A - Diaphragm pressure fluctuation sensor - Google Patents

Abstract

Abstract of the Disclosure A fluid flowmeter includes a bluff body for producing vortex shedding free of intermittency. The body has at one end a support member for mounting in a conduit and has proximate its downstream surfaces a pair of orifices. A diaphragm, preferably ferromagnetic, is situated in a sensor chamber within the support member for vibrating in response to received pressure fluctuations.
A magnetic detector is situated in proximity to the diaphragm for producing an electrical signal when the diaphragm vibrates in response to vortex shedding. Fluid in the conduit, and thus vortex shedding, is coupled from the orifices through a pair of channels, which are in nonfluid flow communication with one another, to opposite sides of the diaphragm.

Description

~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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- 1 - ~ '. , ~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 ~; `', T. J, Fussell, Jr, 7 ~0516g33 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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.. . . ~ ,. ,, .' ~. J. Fussell, Jr. 7 ~51~iil 33 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, - 4 ~

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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 -~? . ., ~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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~OS1~83 T. J. Fussell, Jr, 7 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 .i , 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, '-. 7 ~'.

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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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'. , ~ 6~3 T. J. Fussell/ Jr. 7 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 . ' ' ' ' ,, . . : ''' . . , ~ '' : ' ' 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 ;

~ ` ~ , :' . . '` ' :, ~ 5~3 . J. Fussell, Jr. 7 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 ~ a , . l 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 - 14 _ .. :.

~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.

~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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Claims (21)

What is claimed is:

1. A pressure fluctuation sensor assembly comprising means defining a hollow interior, means bifurcating said interior to define a pair of channels in nonfluid communication with one another, a diaphragm having first and second opposite surfaces, said channels having port means at a same end of said interior for admitting and withdrawing pressure fluctuations into said channels for communication in a same longitudinal direction toward said diaphragm, and means mounting said diaphragm with said first and second surfaces normal to said longitudinal direction and with said first surface communicating with a first one of said pair of channels and said second surface separately communicating with a second one of said pair of channels and thereby to cause said diaphragm to vibrate in response to pressure fluctuations in said channels.

2. The invention of claim 1 wherein said first and second surfaces of said diaphragm comprise upper and lower surfaces thereof, and said bifurcating means is L-shaped for separately communicating admitted pressure fluctuations in said first one of said pair of channels to said upper diaphragm surface and admitted pressure fluctuations in said second one of said pair of channels to said lower diaphragm surface and thereby to cause said diaphragm to vibrate in response to said pressure fluctuations.

3. The invention of claim 1 further comprising means for detecting vibrations of said diaphragm and including means in nonpressure fluctuation communication with said pair of channels for sensing vibrations of said diaphragm in response to admitted pressure fluctuations in said pair of channels.

4. The invention of claim 3 wherein said diaphragm comprises a ferromagnetic material, and said sensing means comprises a magnetic detector.

5. Pressure fluctuation sensor means comprising means defining a hollow inner chamber, a sensor assembly for insertable mounting in said chamber and including wall means having an exterior sealing a portion of said chamber and an inner segment defining a hollow interior, means bifurcating said interior into a pair of channels, each of said channels having port means at a same end of said interior for admitting and withdrawing pressure fluctuations therethrough, a diaphragm having first and second opposite surfaces, means providing an aperture between a first one of said channels and said hollow inner chamber, and means mounting said diaphragm for communication of pressure fluctuations in said first one of said channels through said aperture, said hollow inner chamber with said first diaphragm surface and for separate communication of pressure fluctuation in a second one of said channels with said second diaphragm surface and thereby to vibrate said diaphragm in response to said communicating pressure fluctuations.

6. For use with a vortex shedding flowmeter having means for generating streets of pressure fluctuations in a fluid flow through a conduit, the invention comprising a flow sensor assembly having means defining a hollow inner chamber, means bifurcating said interior into a pair of channels, each of said channels having port means at a same end of said interior for communicating pressure fluctuations from an individual one of the generated streets of pressure fluctuations, a diaphragm having first and second opposite surfaces, means mounting said diaphragm for cooperating with said bifurcating means for providing nonfluid communication between said channels and for communicating pressure fluctuations in a first one of said channels individually with said first diaphragm surface and for separately communicating pressure fluctuations in a second one of said channels individually with said second diaphragm surface and thereby to cause said diaphragm to vibrate in response to communicating pressure fluctuations and at a frequency related to the flowrate through said conduit, and means in nonfluid communication with said first and second channels for sensing vibrations of said diaphragm.

7. The invention of claim 6 wherein said diaphragm comprises a ferromagnetic material, and said sensing means comprises a magnetic detector.

8. A fluidic sensor comprising means defining a first hollow conduit, means defining a second hollow conduit having a longitudinal portion thereof substantially parallel to said first conduit defining means, a diaphragm having first and second surfaces, said first and second conduits having exterior ports substantially parallel to one another for admitting pressure fluctuations into said conduits in the same direction toward said diaphragm, and means mounting said diaphragm with said surfaces substantially normal to said longitudinal portion of said second hollow conduit and for communicating pressure fluctuations in said first conduit with said first diaphragm surface and for separately communicating pressure fluctuations in said second conduit with said second diaphragm surface.

9. For use in a fluidic sensor having a diaphragm with first and second opposite surfaces mounted in a hollow inner chamber, the invention comprising means bifurcating the inner chamber into two channels having longitudinal portions substantially parallel to each other and normal to said diaphragm surfaces and for admitting pressure fluctuations into said channels in a same longitudinal direction toward one of said diaphragm surfaces, and means cooperating with said bifurcating means for communicating pressure fluctuations in a first one of said channels with said first diaphragm surface and for separately communicating pressure fluctuations in a second one of said channels with said second diaphragm surface.

10. The invention of claim 1 in combination with apparatus for measuring the flowrate of fluid in a conduit comprising an elongated vortex shedding body having a base surface disposed substantially normal to the direction of fluid flow and a pair of downstream surfaces extending downstream from said base surfaces and meeting said base surface along a pair of edges, said base and downstream surfaces being mutually adapted so that the boundary layers of said fluid separate from said body at said edges and so that vortex shedding is free of intermittency, and means including said sensor assembly responsive to said vortex shedding for producing an electrical signal related to the flowrate of said fluid, CHARACTERIZED IN THAT, said body includes a support member at one end thereof for mounting said body in said conduit, said support member having a sensor chamber therein, said sensor assembly disposed within said chamber, and detector means exterior to said chamber but proximate thereto for producing said electrical signal when said diaphragm vibrates, said body has a pair of orifices, one of said orifices located in each of said downstream surfaces near to said one end, and said bifurcating means being disposed within said member and forming said pair of channels in nonfluid flow communication with one another, said channels connecting said orifices in fluid flow communication with opposite sides of said diaphragm, thereby to cause said diaphragm to vibrate in response to said vortex shedding.

11. The apparatus of claim 10 wherein said forming means comprises a cylindrical housing having a hollow interior, said diaphragm being mounted at one end of said housing, a partition within said housing which bifurcates said interior and forms said pair of channels so that only one said channel is in fluid flow communication with the side of said diaphragm interior to said housing, said housing having a first aperture which places the other of said channels in fluid flow communication with said chamber and the side of said diaphragm exterior to said housing.

12. The apparatus of claim 11 wherein said vortex shedding body has a cavity in one end face thereof which is in fluid flow communication with said orifices, the other end of said housing being removably situated in said cavity, said housing having at said other end second and third of apertures in substantial registration with said orifices.

13. The apparatus of claim 12 wherein said support member comprises a cylindrical first portion connected to said body and having a bore therein, said housing being removably situated in said bore, said first portion being insertable through a hole in the wall of said conduit, a cylindrical second portion adjacent said first portion and having a larger diameter than said first portion, said second portion being situated exterior to said conduit, said sensor chamber being located in at least said second portion, a removable head cap engaging said second portion and arranged so that when removed said diaphragm is exposed, said head cap having said detection means incorporated therein.

14. The apparatus of claim 13 wherein said diaphragm comprises a ferromagnetic material, and said detector means comprises a magnetic detector.

15. The apparatus of claim 12 wherein said partition is L-shaped with the foot of the L affixed near to said diaphragm so that said first aperture and the other of said channels are separated from the side of said diaphragm interior to said housing, and the leg of the L extending parallel to the walls of the housing and extending flush with said other end of said housing and abutting the bottom of said cavity of said vortex shedding body.

16. The apparatus of claim 15 wherein said cavity is formed in said body by a bore which extends through said downstream surfaces to form said orifices of rectangular shape and said second and third apertures are rectangular cutouts in said other end of said housing.

17. Apparatus for measuring the flowrate of steam in a conduit comprising an elongated vortex shedding body having a planar base surface disposed substantially normal to the direction of fluid flow and a pair of downstream surfaces extending downstream from said base surface and meeting said base surface along a pair of edges, said base and downstream surfaces being mutually adapted so that the boundary layers of said fluid separate from said body at said edges and so that vortex shedding is free of intermittency, and means responsive to said vortex shedding for producing an electrical signal related to the flowrate of said fluid, CHARACTERIZED IN THAT, said body has at one end thereof a cavity which extends inwardly along the long axis of said body and forms in each of said downstream surfaces an orifice, said responsive means comprises a support member for mounting said one end of said body in said conduit, said member including a sensor chamber, a diaphragm, a sensor housing having said diaphragm mounted at one end thereof which is disposed in said chamber, said sensor housing having a hollow interior bifurcated into separate channels in nonfluid flow communication with one another and opening to the other end of said housing, said housing having said other end thereof disposed in said cavity of said body so that said channels are in fluid flow communication with separate ones of said orifices, said housing having therein an aperture which places one of said channels in fluid flow communication with said chamber so that fluid in said conduit entering said orifices passes through said channels and thence to opposite sides of said diaphragm, and detector means responsive to the vibration of said diaphragm for producing said electrical signal.

18. The apparatus of claim 17 wherein said body is oriented vertically in said conduit with said chamber at the top and said channels oriented vertically to facilitate drainage of condensed steam therefrom.

19. The apparatus of claim 17 wherein said diaphragm comprises a ferromagnetic material, and said detector means comprises a magnetic detector.

20. Apparatus for measuring the flowrate of steam in a conduit comprising an elongated vortex shedding body having a planar base surface disposed substantially normal to the direction of fluid flow and a pair of downstream planar surfaces extending downstream from said base surface and meeting said base surface along a pair of edges, said base and downstream surfaces being mutually adapted so that the boundary layers of fluid separate from said body at said edges and so that vortex shedding is free of intermittency, and means responsive to said vortex shedding for producing an electrical signal related to the flowrate of said fluid, CHARACTERIZED IN THAT, said body includes a support member at one end thereof for mounting said body in said conduit, said support member comprising a cylindrical first portion connected to said body and having a bore therein, said first portion being insertable through a hole in the wall of said conduit, a cylindrical second portion adjacent said first portion and having a larger diameter than said first portion, said second portion being situated exterior to said conduit, a sensor chamber located in at least said second portion, a removable head cap engaging said second portion and arranged so that when removed said chamber is exposed, said responsive means includes a ferromagnetic diaphragm disposed within said chamber and a magnetic detector incorporated in said head cap, said body has a cavity in one end face thereof and a pair of rectangular orifices located in said down-stream surfaces and in fluid flow communication with said cavity, and means disposed within said support member forming a pair of channels in nonfluid flow communication with one another, said channels connecting said orifices in fluid flow communication with opposite sides of said diaphragm, thereby to cause said diaphragm to vibrate in response to said vortex shedding, said forming means comprising a cylindrical housing having a hollow interior, said housing being removably situated in said bore of said first portion of said support member, said diaphragm being mounted at one end of said housing, the other end of said housing being removably situated in said cavity and having a pair of rectangular cutouts in substantial registration with said rectangular orifices of said body, an L-shaped partition within said housing which bifurcates said interior and forms said pair of channels, said housing having a first aperture near to said diaphragm which places one of said channels in fluid flow communication with said chamber and the side of said diaphragm exterior to said housing, the foot of said L-shaped partition being affixed near to said diaphragm so that said first aperture and said one channel are separated from the side of said diaphragm interior to said housing, the leg of said L-shaped partition extending parallel to the walls of said housing and extending flush with said other end of said housing and abutting the bottom of said cavity.

21. A pressure fluctuation sensor in apparatus for measuring the flowrate of fluid in a conduit comprising an elongated vortex shedding body spanning substantially the entire inner diameter of said conduit and having a base surface disposed substantially normal to the direction of fluid flow and a pair of downstream surfaces extending downstream from said base surface and meeting the base surface along a pair of edges, the base and downstream surfaces being mutually adapted so that boundary layers of the fluid separate and vortex shed from the body at the edges, and said assembly being responsive to the vortex shedding for producing an electrical signal related to the flowrate of the fluid, CHARACTERIZED IN THAT, said body including a pair of orifices adjacent the downstream surfaces, and said assembly having a housing including means defining a first hollow conduit, means defining a second hollow conduit having a longitudinal portion thereof substantially parallel to said first hollow conduit, a vibratory sensor having first and second surfaces, said first and second conduits having exterior ports substantially parallel to one another for admitting pressure fluctuations from said orifices into said conduits in the same direction toward the sensor, and said sensor being mounted in said surfaces substantially normal to the longitudinal portion of said second hollow conduit and for communicating pressure fluctuations in said first conduit to said first sensor surface and for separately communicating pressure fluctuations in second conduit to said second sensor surface.