CA1190414A - Vortex flowmeter bluff body - Google Patents
Vortex flowmeter bluff bodyInfo
- Publication number
- CA1190414A CA1190414A CA000422619A CA422619A CA1190414A CA 1190414 A CA1190414 A CA 1190414A CA 000422619 A CA000422619 A CA 000422619A CA 422619 A CA422619 A CA 422619A CA 1190414 A CA1190414 A CA 1190414A
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- Prior art keywords
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- intermediate section
- flow
- bar
- Prior art date
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- 239000012530 fluid Substances 0.000 claims description 19
- 238000011144 upstream manufacturing Methods 0.000 claims description 12
- 230000015572 biosynthetic process Effects 0.000 claims description 8
- 238000000034 method Methods 0.000 claims 1
- 230000007704 transition Effects 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract 2
- 230000001419 dependent effect Effects 0.000 description 4
- 238000010276 construction Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000002730 additional effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 235000020004 porter Nutrition 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/20—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow
- G01F1/32—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow using swirl flowmeters
- G01F1/3209—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow using swirl flowmeters using Karman vortices
- G01F1/3218—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow using swirl flowmeters using Karman vortices bluff body design
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- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Volume Flow (AREA)
Abstract
VORTEX FLOWMETER BLUFF BODY
ABSTRACT OF THE DISCLOSURE
A vortex flowmeter utilizes a bluff body or bar which creates vortices that are sufficiently stable and of sufficient strength to provide for pressure signals that are easily sensed, and at the same time achieves satisfactory linearity between the frequency of the vortices and the rate of flow past the sensor. The flowmeter is designed so that the same sensor arrangement for sensing the frequency of vortex generation can be used for flowmeters designed for a wide range of pipe or line sizes. By utilizing the cross section geometry of the bluff body or bar disclosed herein, the section of the body that is used for mounting the sensor is the same width, which is the critical dimension for sensor mounting, for line sizes from two inches (5.08 cm) to eight inches (20.32 cm) inclusive and line sizes from one inch (2.54 cm) to one and one-half inches (3.81 cm) inclusive. The ability to have a standard sensor for a number of different meter sizes reduces inventories and manufacturing costs, and also makes service of sensors easier. The flowmeter of the present invention not only permits the interchangeability of sensors across a wide range of pipe sizes, but also has good linearity, is easy to manufacture, and continues to operate reliably after extensive usage.
ABSTRACT OF THE DISCLOSURE
A vortex flowmeter utilizes a bluff body or bar which creates vortices that are sufficiently stable and of sufficient strength to provide for pressure signals that are easily sensed, and at the same time achieves satisfactory linearity between the frequency of the vortices and the rate of flow past the sensor. The flowmeter is designed so that the same sensor arrangement for sensing the frequency of vortex generation can be used for flowmeters designed for a wide range of pipe or line sizes. By utilizing the cross section geometry of the bluff body or bar disclosed herein, the section of the body that is used for mounting the sensor is the same width, which is the critical dimension for sensor mounting, for line sizes from two inches (5.08 cm) to eight inches (20.32 cm) inclusive and line sizes from one inch (2.54 cm) to one and one-half inches (3.81 cm) inclusive. The ability to have a standard sensor for a number of different meter sizes reduces inventories and manufacturing costs, and also makes service of sensors easier. The flowmeter of the present invention not only permits the interchangeability of sensors across a wide range of pipe sizes, but also has good linearity, is easy to manufacture, and continues to operate reliably after extensive usage.
Description
VORTE~ FLOWMETER BLUFF BODY
BACKGQOUND OF TIIE INVENTION
1. Field of the Invention.
The present inven-tion relates to Flowmeters of the vortex sheddiny type, and more particularly to bluff body configurations for generating vortices in the flowmeter.
BACKGQOUND OF TIIE INVENTION
1. Field of the Invention.
The present inven-tion relates to Flowmeters of the vortex sheddiny type, and more particularly to bluff body configurations for generating vortices in the flowmeter.
2. Description of the Prior Art.
While the investigations of development of vortices in flow and the relationship of the frequency of formation of such vortices to the flow rate in a line date back many years, industrial quality vortex flowmeters were first introduced about in 1969. Vortex flowmeters use the phenomena of reyular and alternate generation and separation of vor-tices from opposite sides of a suitably shaped bluff body or bar that is inserted into the fluid stream.
The basis for obtaining accuracy is to insure that the vortices are formed in a stable manner, that is that there aren't any "skips" and that the vortex shedding ~requency is in fact proportional to the flow rate past the meter. In describing the vortex sheddin~J
behavioI~ of bluff bodies, it is usual to relate the shedding frequency, bar yeoMetry and ~low rate using ~5 two nondimensional parameters. Ttlese are the Strouhal number (S) which is a propor-tionality constant between the vortex shedding frequency (f), the fluid velocity (v), and the maximum cross sectional width of the bar ()-1) yiven by:
3û S = v Equation (1) and the Reynolds number (RH) relating the fluid velocity (V), the fluid density ( ~), the fluid viscosity (~) and the bar width (H) given by:
f RH ~ P vH Equation (2) The bluff bodies or bars that have a constant Strouhal number over a wide range of Reynolds numbers are considered good candidates for vortex flowmeters lû because their vortex shedding Frequency does vary linearly with flow rate.
Vortex flowmeter manufacturers commonly choose cross sections similar to the rectangle, square, triangle or T 9 since such bodies shed strong vortices.
Although these bars shed strong vortices, they must be linearized. Prior art devices have attempted to do this in various ways i.e., by changing the bar width (H) which affects the blockage such bar causes in the conduit or pipe. Linearity of vortex shedding to flow ~û ln the conduit remains a primary concern in using vortex shedding flowrneters for geome~ries that shed strong vortices.
In the prior art many cross sectional variations of blu~f bodles or bars have been advanced.
One early pa~ent that illustrates a variety o~ cross sectional geometries for a bluff body flowmeter is the patent to W. G. 3ird, U.S. Patent No. 3,116,6~9, issued January 7, 196~. The ef~ect of circular cross section bluff bodies mounted ahead of splitter plates or pivoting vanes is shown. Additionally, generally triangular shaped cross sections of bluff bodies and a modified diarrtond type shape body are shown in Figures 10 and 13 of this patent. The sensing of the frequency of vortex formation was done by the use of the downstrearn, pivoting splitter plate.
~ ., ~ 9~
U.S~ Patent No. 3,572,117, issued March 23, 1971 to A. E. Rodely illustrates bluff body flowmeters having generally triangular shaped crass sections, as well as variations of the triangular shape. Further, in Figure 4C and 6A of this patent, ~-r~ shape cross section bodies are illustrated, and a "cross shaped" cross section also is shown. Patent No.
While the investigations of development of vortices in flow and the relationship of the frequency of formation of such vortices to the flow rate in a line date back many years, industrial quality vortex flowmeters were first introduced about in 1969. Vortex flowmeters use the phenomena of reyular and alternate generation and separation of vor-tices from opposite sides of a suitably shaped bluff body or bar that is inserted into the fluid stream.
The basis for obtaining accuracy is to insure that the vortices are formed in a stable manner, that is that there aren't any "skips" and that the vortex shedding ~requency is in fact proportional to the flow rate past the meter. In describing the vortex sheddin~J
behavioI~ of bluff bodies, it is usual to relate the shedding frequency, bar yeoMetry and ~low rate using ~5 two nondimensional parameters. Ttlese are the Strouhal number (S) which is a propor-tionality constant between the vortex shedding frequency (f), the fluid velocity (v), and the maximum cross sectional width of the bar ()-1) yiven by:
3û S = v Equation (1) and the Reynolds number (RH) relating the fluid velocity (V), the fluid density ( ~), the fluid viscosity (~) and the bar width (H) given by:
f RH ~ P vH Equation (2) The bluff bodies or bars that have a constant Strouhal number over a wide range of Reynolds numbers are considered good candidates for vortex flowmeters lû because their vortex shedding Frequency does vary linearly with flow rate.
Vortex flowmeter manufacturers commonly choose cross sections similar to the rectangle, square, triangle or T 9 since such bodies shed strong vortices.
Although these bars shed strong vortices, they must be linearized. Prior art devices have attempted to do this in various ways i.e., by changing the bar width (H) which affects the blockage such bar causes in the conduit or pipe. Linearity of vortex shedding to flow ~û ln the conduit remains a primary concern in using vortex shedding flowrneters for geome~ries that shed strong vortices.
In the prior art many cross sectional variations of blu~f bodles or bars have been advanced.
One early pa~ent that illustrates a variety o~ cross sectional geometries for a bluff body flowmeter is the patent to W. G. 3ird, U.S. Patent No. 3,116,6~9, issued January 7, 196~. The ef~ect of circular cross section bluff bodies mounted ahead of splitter plates or pivoting vanes is shown. Additionally, generally triangular shaped cross sections of bluff bodies and a modified diarrtond type shape body are shown in Figures 10 and 13 of this patent. The sensing of the frequency of vortex formation was done by the use of the downstrearn, pivoting splitter plate.
~ ., ~ 9~
U.S~ Patent No. 3,572,117, issued March 23, 1971 to A. E. Rodely illustrates bluff body flowmeters having generally triangular shaped crass sections, as well as variations of the triangular shape. Further, in Figure 4C and 6A of this patent, ~-r~ shape cross section bodies are illustrated, and a "cross shaped" cross section also is shown. Patent No.
3,572,117 indicates that the upstream facing surface of the body should be flat or convex for increased rangeability.
In U.S. Patent No. 3,732,731 which is owned by the same company as Patent '117, a modified cross sectional shape having a rounded front face is illustrated, and in U.S. Patent No. 4,û69,708 which is also owned by this same company, a plate downstream of the bluff body is used to facilitate sensing of the shed vortices.
U.S. Paten-t No. 3,693,438, issued September 26, 1972 to Yamasaki et al. sho~s a variety of bluff body cross sectional shapes including a cylindrical body that has recesses along a portion of the leng-th on the sides khereof for purposes of enhanclng vortex formation. The bluff body response was to be free of the influences of changes in flow and ~5 eddy currents in the stream to maintain a linearity of the sensed frequency of the formation of Yortices with changing fluid flow. In particular, Figure 5 of Paten-t No. 3,693,438 shows recessed sides that form a type of a dimple in cross section9 while other forms sho~l flat parallel surfaces in the recessed sections.
Patent No. 3,948,097 also shows a Flo~
measuring device ~hich uses a rectangular cross section bluff body related in a particular manner to the diameter of the pipe in which it is used and also the patent emphasis tha-t the dimensions o-f the rectanyular cross section should oe related to each other for satisfac'cory operation.
r~any of the bluff bodies illustrated in the last two mentioned patents have passageways in the bodies to Facilitate the detection of vortices.
However the geometry of the disclosed bluff bodies had to be changed with changing flow line size, and this also influenced the selection of sensors to ~e used.
Thus different sensor construction and size would likely have to be supplied with the bluff bodies for each different size fluid flow pipe.
lû U.S. Patent Nos. 3 888,120; 3 9~6,60~;
In U.S. Patent No. 3,732,731 which is owned by the same company as Patent '117, a modified cross sectional shape having a rounded front face is illustrated, and in U.S. Patent No. 4,û69,708 which is also owned by this same company, a plate downstream of the bluff body is used to facilitate sensing of the shed vortices.
U.S. Paten-t No. 3,693,438, issued September 26, 1972 to Yamasaki et al. sho~s a variety of bluff body cross sectional shapes including a cylindrical body that has recesses along a portion of the leng-th on the sides khereof for purposes of enhanclng vortex formation. The bluff body response was to be free of the influences of changes in flow and ~5 eddy currents in the stream to maintain a linearity of the sensed frequency of the formation of Yortices with changing fluid flow. In particular, Figure 5 of Paten-t No. 3,693,438 shows recessed sides that form a type of a dimple in cross section9 while other forms sho~l flat parallel surfaces in the recessed sections.
Patent No. 3,948,097 also shows a Flo~
measuring device ~hich uses a rectangular cross section bluff body related in a particular manner to the diameter of the pipe in which it is used and also the patent emphasis tha-t the dimensions o-f the rectanyular cross section should oe related to each other for satisfac'cory operation.
r~any of the bluff bodies illustrated in the last two mentioned patents have passageways in the bodies to Facilitate the detection of vortices.
However the geometry of the disclosed bluff bodies had to be changed with changing flow line size, and this also influenced the selection of sensors to ~e used.
Thus different sensor construction and size would likely have to be supplied with the bluff bodies for each different size fluid flow pipe.
lû U.S. Patent Nos. 3 888,120; 3 9~6,60~;
4,003,251; 4,005,604; and ~,033,189 are typical of the devices placed on the market by Fischer & Porter Co. of Warminster, Pennsylvania, and show various bluff body members that have a trailing portion connected to the bluff body through the use o~ one or more beams or "stings". U.S. Patent No. 3 88~,120 shows various configurations for the upstream bluff body and the trailing rear section in Figures 1 5, 6 and 7 of that patent.
U.S. Patent No. 4,052,895 which is also owned by Fischer & Porter shows a bluff body having a traiLing "tail" assembly connected by an intermediate beam that has a very small cross section and does r-ot extend along the longitudinal axis oF the bluff body.
Tnus flow may interact in the space between the bluff body arld the tall.
Additional generally T cross section shapes of bluff bodies and their associated sensors are shown in U.S. Patent No. 3 972,232. The bluff bodies have head members with facing surfaces and a narrower body section extending downstream from the nead member. In this device~ the sensor is a member that moves under differential pressures that occur along the side surfaces of the downstream extending sensor bar. This patent discloses the general relationshi? of positioning of a sensor relative to an upstream head member for sensing pressure differentials on the body portion downstream from the head member, but does not -teach the unique geometry that permits the same sensor to be used in flowmeters for a wide range of pipe diameters.
Flowmeters similar to that shown in the last mentioned paten-t also are disclosed and discussed in U.S. Patent Nos. 4,085,614 and 4,088,020. Particular attention should be paid to the angular arrangement of the edges of the head member or upstream plate, as well as the transverse width of the plate in relation to the 1enrJth of the sensor bar that is used. The width of the sensor bar represented by the dimension r in drawings of l'atent No. 3,972,~32 changes with di~ferent pipe sizes as shown in Column 9 of that patent. This is also the case in Pa-tent No. ~,085,614 as disclosed in Column 9 of that patent.
While various typical cross sectional configurations are shown in the prior art the geometries of the cross sections of the pri.or bluff bodies do not provide fo-r the use of a body having a sensor mounting section tha-t remains substantially constant in its critica]. dimension so that the same sensor assemL~ly can be utilize~J for flowrneters used on different line sizes.
SUMMARY OF THE I~lVENTION
A bluff body or bar for Forming a vortex generating flowrneter comprising an upstream head rnember having a flo~r facing surface causing a disruption in flow of fluid in a line or pipe in which the bluff body is inserted; an intermediate section of less width than the flow facing surface connected to the head member and extendiny downstream relative thereto; and a tail section at the downstream end of said intermediate section of greater width than the intermediate section. The bar is configured to provide for the formation of strong vortices that are alternately and repeatably formed on the opposite sides of the intermediate section at a frequency dependent upon flow rate through the line or pipe. The intermediate section has a width that is constant for blufF bodies used across a substantial range of line sizes, so that the sensors utilized with the flowmeter (which are mounted in the intermediate section) can be standarized and yet the outputs of the flowmeters remain linear 0 and repeatable across a substantial flow range.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a sectional view through a line carrying fluid flow havinr~ a vor-tex flowmeter uslng a bluff body or bar made according to the present invention installed therein;
Figure 2 is a sectional view taken as on line 2--2 of Figure l;
Figure 3 is a transverse sectional view taken as on line 3--3 in Figure 2;
Figure 4 is an enlarged sectional view of the bluff body shown in the flowmeter of Figure 3 with illustrative dirnensions labeled on the figure;
Figures 5, 6, 7 and 8 are addi-tional embodimellts showing the cross sec-tional shape of bluff ~5 bodies made accordlng to the present invention and;
Figures 9, 10 and 11 disclose slir~ht variation in the front face configuration.
DETAILED DESORIPTION OF THE PREFERRED EMaODIMENTS
The basic equations for describing -the action and effect of nondimensional parameters on vortex shedding were set forth in the Oescription of the Prior Art and are well known.
Referring to Figure 1, a flow pipe 10 carries a fluid, the flow rate of which is to be rneasured.
Usually the Flows of liquids are measured but gases and steam can also be measured. The pipe 10 can be a meter section that is placed into an existing flow pipe or conduit, and generally the meter section will be fastened into the conduit with suitable flanges coupled to flanges on the conduit carrying the fluid.
Alternatively the meter section can be a spool piece held between the flanges by bolts or other conventional means. These flanges are not shown, but are well known in the art. Flow is in the direction of arrow 11 (Figure 2) through the pipe.
lû The vortex shedding flowmeter 13 made according to the present invention is shown installed on the interior of the pipe 10. The pipe wa]l has an opening 14 therethrough into which the bluff body or vortex shedding bar section of the flowmeter, indicated generally at 15, is inserted. The bar has a height dimension, which is measured along its longi-tudinal axis. Preferably bar 15 extends substan-kially across the en-tire diameter of the pipe 10. The pipe (internal) diameter is indica-ted by D in Figure 2. A
suitable mounting collar 16 surrounds the opening 14 in the wall of the pipe 10, and the vortex shedding flowmeter has a plug or head 17 that fits inside the sleeve 16. Sleeve 16 may nok be required as bar 15 can be rnechanically fixed in position by conventional means such as bolts through the pipe wall opposite from head 17. The head 17 has a surFace contoured on its bottom side to conForm to the curvature of the inside diameter of the pipe 10. Cap screws 20 are used for securing the bar or bluff body 15 -to the head 17. The head may be held in place in sleeve 16 in a suitable manner9 for e~.ample with clamps or with an open center nut that is threaded into collar 16. As can be seen, the head 17 has an 0-ring 21 on its exterior ~Jhich seals against the interior surface of the sleeve 16.
- 35 As will be explained9 the sensing device for sensing the frequency of the vor-tices being formed on , opposite sides of the bar 15 is mounted on the interior of the bar 15 and a portlon of the connections are under a cap 22 that is mounted on the head 17. Leads 23 couples sensing circuitry of a desired form to the sensing device.
The vortex forming bar 15 is divided up into three distinct parts including a head section 25 having a Flow face 26; an intermediate body section 27 that is integral with and immedlately downstream from the head section 25; and a tail section 30 that is downstream of the intermediate body section 27 and integral with section 27.
As shown in Figure 4, the eleven linearly independent degrees of freedom that completely specify the meter geometry include the following:
The Pipe diameter = D (Figure 2) The Flow Face width = H
Bar Lengths . L, L1, L2~ L3, L4 and L5 ~ar Intermediate width = H1 The Tail widths = H2 and 113 Also the distances of` the bar face From the nearest upstrearn and (lf present) downstream disturbance may be drsignated L6 and L7 as represented schematically in Figure 3 which would bring the to~al number of linearly independent degrees of freedom to thirteen.
Angles ~ 2~ and ~3 whlch are shûwn in Figure 4, are dependent on some of the dimensions labeled above and are therefore not included as variables. The angles could, however, be substituted for some of the linear dimensions to form a new linearly independent set of parameters that also would completely describe the flo~rneter.
The 1~11 angles are angles of slope of surfaces joininy the portions of dlfferent widths in the f'rOSS section of the vortex shedding bar 15. The reference for measuring the angles is the longitudinal plane of the bar 15 parallel to the direction of flow.
Ul, is the slope ang],e of the back surfaces of head sectlon 25 between dimension H and Hl; 92 is the angle of the f'ront sur-faces of the tail section 3û, between Hl and H2; ~3 is the angle of trailing tapered surfaces of the -tail section bet~een H2 and H3.
There are a varlety of ways for obtaining linearly independent, nondimensional sets of parameters that describe the meter cross section geometry. Two of the more common nondimensional sets of parameters are shown in Table I below. Either set shown in Table I
may be used, depending on preference of the designer.
Note that set 1 includes only linear dimensions, while set two includes the angles ~ labeled on Figure 4.
TABLE I
Two nondimensionalized, linearly in-dependent sets of parameters describing 2û the geometry of the bar cross section of Fiqure ~.
Set 1: D (inches) ~cm); H/3; L1/H; L2/H;
L3/~ l; Is/~l; L/~
rl2/~ l3/H and, if' applicable, L6/H; L7/H;
Set 2: D (inches) (cm); H/D; L1/H; L3/H;
L/H; Hl/H; H2/H; H3/H; ~1;
42i ~3; L6/H; L7/H-The two nondimensional sets of parameters shown i~ rabl~ I are related by the equations:
L2 = Ll -~ 1/2(1 _ Hl) tan (90 ~ ~1) H l-l H
L~, = L3 + 1 ( H2 _ Hl ) tan (90 - a H H 2 ~ 2 L5 = L - 1 ~ H2 _ H3 ) tan (90 - a3) The utility of such sets of parameters is that once a set of values for the nondimensional parameters oF either set has been determined such that the Strouhal number is a constant over a suitably wide Reynolds number range, for example and values (dimensions) have been established for a flowmeter bluff body or bar that behaves linearly in a particular line size, the nondimensional sets defined above will have been established and in theory -to deterrnine the actual dimensions for a flowmeter in another line si~e one simply has to know -the pipe diameter, D 7 and perform the appropriate calculations to determine the remaining dirnensions usirlg the Set 1 or Set 2 rclatlorlships, then, based on actual performance data, the skilled designer may desire to alter certain pararneters to further enhance performance. The ratio Il/D is kept constant within a sui-table range and other parameters are kept within essentially predetermined ranges This also assumes, in the case of` a vor-tex flowmeter, that the Strouhal number vsO Reynolds number and Mach number relationships are constant oYer the flo~l range of interest. Wa-ter flow is usually Mach .005 maxlmum and airflow generally is no higher than Mach .1 although in isolated cases airFlows rnay oe as high as Mach .25.
The geometry of the bar cross section of Figure 4 can be designed for different line sizes (different values of D) in such a way that the intermediate body section width, ill remains constant (Hl/H increases with decreasing line size) without compromising the linearity of tne meter between D = two inches (5.08 cm) and D = eight inches (2û.32 cm).
Meters below D = two inches (5.08 cm) use a smaller Hl dlmension. ~hus for example, one inch (2.54 cm) and one and one-half inch (3.~1 cm) line size meters preferably have the same Hl dimension. The ability to keep Hl constant across such a wide range of pipe diameters can be accomplished by varying the remaining dimensions in the set of parameters being used.
The parameters L6/t-l and L7/H are not provided in that the meter preferably operates without obstruction upstream or downstrearn. tlowever, these obstructions may occur from small discontinuities in the pipe wall. For example, the meter assernbly may be in a short pipe sectiorl with end Flanges which is bolted and installed between two pipe sectiorls. The junctiorl lines along the pipe wall rnay Form discontinuities which have to be taken into consideratlon.
These meters will behave satisfactorily over the flow ranges 1.25 Ft/sec. (0.381 m/sec.) to 25 ft/sec. (7.62 m/sec.) in liquids and 10 ft/sec.
(3.048 m/sec.) to 250 ft/sec. (76.2 m/sec.) in gases and steam. The two inch (5.08 cm) through eight inch (20.32 cm) meters preferably have a value of tl1 = 0.223 inches (0.566 cm) while the 1 in.
(2.54 cm) and 1-1/2 inch (3.81 cm) meters preferably have til = 0.100 inches (0.254 cm). Hl can be any value less than H2 wherein Hl is irnperforate and precludes -fluid movement frc~ one side of the bar to the other and wherein Hl further provides sufficient spacing for hûusing means to sense the differential pressure caused by the vortex action.
The ranges of dimensions for a typical preferred meter relationship is as follows:
TABLE II
D = 1.049 inches t2.664 cm) to 7.981 inches (20.272 cm) H/D = û.2732 tThis may be established b~J test) ~11 = .1 to 0.3955 H
H2 = û 45û9 to 0-5045 H3 = û.1689 to 0.1692 H
Ll = û.û273 to 0.1181 L2 = 0.2169 to û.3342 3 = 0.7555 to l.OûO
Ll, = 0.860~ -to l.û32 15 = l.û9û to 1.26~
L = 1.3~4 to 1.432 l = 30 to 90-preferred 58 to 60 2 = 45 to 90-preferred 60 to 90 03 = 17 to 45-preferred 3û to 45 ~_ = 1.14û to 3.112 Hl 9(~
The fluctuating p~essure coefficients, Cp. are related to the fluctuating differential pressures p across the vortex flowmeters by the equation:
AP = cp pv2 sin 2 ft Where p = fluid density v = velocity of the flow f = shedding frequency These coefficients were measured at a flow velocity of approximately 1.5 ft/sec. (0.457 m/sec.~and indicate that strong vortices are being shed.
For optimum performance, it was found that the value of L/H is dependent on the angle 03. Thu , when 03 was 45, the meter having a ratio L/H o 1.33 to 1.38 generally performed best, but when 03 was 30, meters having L/H ratios of 1038 to 1.43 generally performed best. The best choice for L/H
appears to depend on other dimensions as well as 03.
Each meter made as shown in Figure 4 exhibits good linearity and with substantially the same Hl dimension, thus standardized sensor arrangernents are possible for a significant range of flow pipe diameters.
Referring now specifically to Figures 1 through 3, it can be seen that bar 15 has a diaphragm for sensing pressure indicated at 32 on the shown side thereof, and a like diaphragm preferably is positioned on the other side of the intermediate section 27 of the bar 15. As vortices are formed they switch from side to side on the bar and, hence, the pressure on each diaphragm changes. This causes the diaphragms to deflect and the diaphragms act on a sensor that senses differential pressure between the opposite sides of the intermediate section 27. A sensor that is constructed in a desired manner is shown in applicant's Canadian Patent Application No. 422~621, filed March 1 1983, entitled Differential Pressure Vortex Sensor~
One feature is that the width Hl can remain constant ~ 14 -across a wide range of pipe diameters, and -then the same sensor regardless of the type can be u-tilized for -the flowmeters used in such pipes, even though the various length (L, Ll, L2, L3 --) dimensions (L, Ll, L2, ...) may change, H may change, and H2 and H3 also may change. Thus the sensor ~ se may be a prior art sensor, for example the sensor shown in U.S.
Patent No. 3,796,095.
It can be seen in Figure 3 that vortices are generated as the flow separates along the face 26, to create alternate swi-tching of high to low pressure along the sides of -the intermediate section 27 and thus the differential pressure also changes.
The cross section of the preFerred vortex forrning bar includes a head portion 25 having a face width 26 that is selected in size as a function oF the diameter of the pipe in which the flowmeter is used.
Once the ratio H/D has been established, Hl kept at a reasonable standard for a wide range of pipe diameters, the length L may be selected and also H2, L~ and H3 selected to insure that the vortices are strongly formed, repeatable, and that linearity is establishcd for the flowmeter.
In all cases, the tai] section la-teral wid-t ll2 Is greater tilan the width Hl of the intermediate bar section 27, and both of these dimensions (Hl and H2) are kept less than tne face width H of the surface 26.
Norrnally the face surface 26 is a plane surface perpendicular to the flow, although concave or convex surfaces or other protuberances are acceptable.
The modified emboditnents of the bar cross section shown in Figures 5, 6 and 7 are embodiments which exhibit acceptable linearity. It can be seen that the width of the intermediate bar section can oe maintained constant for flowmeters of these conflgurations, but dimensions such as the Ll and H2 dimensions vary substantially as the pipe diameter is changed. Further, it has been found that the Ll dimension can, if desired, be formed to be a sharp edge without subs-tantially affecting the per-formance of the flowmeter but this may affect the long term stability due to the erosion of this thin edge.
For example in Figure 5, the vortex forming bar indicated at 40 has a cross section as shown and includes a head section 42 with a face surface 41 that is generally perpendicular to the direction of flow indicated by the arrows. The head section 42 has a smoothly curved rear or downstream facing surface 43.
The intermediate bar section 44 has a transverse width lil that is sufficient -to accept a standard sensor therein for a wide range of pipe diameters. The side surfaces of intermediate bar section 44 are smoothly curved as shown, but a local area of the surfaces will be made flat (For example, with a spot face or a boss) when d:iaphragins are used for sensing pressure so the diaphragms are planar. The rest of the side surfaces may be curved as shown.
The bar 40 includes a tail section 45 at the trailing edge of the intermediate section 44. The tail section 45 as shown has a widtil H2 across its maximum dimension that is greater than the width Hl of intermediate section 44, but less than the width H of the face surface 41.
Linearity is acceptable across the desired range of fluid flows and the intermediate section 40 has a width that remains substantially constant across a substantial range of pipe diameters so that the sensor construction can be standardized.
In Figure 6 a greater difference between dimensions such as L4 and L5 is shown so that the tail section is reduced in length. In this particular embodiment the bluff body or vortex forming bar 5û has a head section 52 having an upstream face 51 that is generally perpendicular to the direction of flow as indicated. ~lead mernber 52 has straight sides for a lû distance Ll. The straight sides join concave rear surfaces 5~ leading to the intermediate bar section 54. The intermediate section as shown in Figure 6 has sligntly curved (concave) side surfaces joining the tail section 55 -that has a width H2 that is less than the width of the face 51 but greater than -the width (Hl) of the intermediate section 54. In this particular instance, the trailing side surfaces of the tail section S5 are planar surfaces that are formed at an angle ~3 as desired. Again~ if diaphragms are 2û used For sensing diF-Ferential pressures, the side sur-Faces of the intermediate bar section will be formed to hold the diaphragms planar. This can be a spot Face or a rourld boss the size oF the diaphragm l'he rest of the surface will be curvecl as shown.
In Fiyure 7, the cross sectlon oF a further embocl1nlent of' a blufF body or vortex sheddiny bar 6û is snown and the bar includes a head section 62 having a forwardly facing face 61. Head member 62 has a tapered rear (downstream facing) surface 6} which is joined to an intermediate section 64. The tail section 65 in this particular flowmeter has an H2 dimension which is at the low end of -the ratio given in Table II for H2/Hl .
Meters having bluff bodies or vortex shedding bars sho~"n herein operated at Flow rates between approxim2tely .5 ft/sec. (û.152 m/sec.)and 25 -Ft/sec.
( 7 . 62 m/sec.) in a nominal four inch (10.16 cm) ID pipe carrying water and performed with linearity errors under one percent. In fact, the forms shown in Figures 4, 5 and 7 showed llnearity errors of under .5 percent.
The ratio of the face width (~) to pipe diameter (D), (H/D), of the bluff bodies or bars in these meters was nominally in the range of û.2732.
The form of the cross section in Figure 8 includes a bar 70 having a head member 71 with a face surface 72. The head member is joined to an intermediate section 74 and a tail section 75 is also provided at the trailing end of intermedlate section 74.
The head member has a pair of protuberances lS 73 at the side edges of the head member 71 which face upstream and may aid in forming vortices. The front face thus does not have to be planar, but may be concave as shown, or a concave curved surface, or have irregularities such as those disclosed in U.S. Patent 20 No. 4,17~,643.
In Figure 9, a bluff body or bar 7B has a head member 79 with a concave front face 80 forrned by two shallow planar surfaces 81 taperlng inwar-JIy from the sides of the head member.
The bluff body or bar B4 shown in Figure 10 has a head 85 with a curved concave forward fare 86.
In Figure 11 a bluff body 90 has a nead mernber 91 with a convex face 92. The convex surface is not a deeply convex surface. The bluff bodies or bars 30 of Figures 9, 10 and 11 each have intermediate body portions and tail sections as shown to provide s-trong vortices as previously disclosed. The front face thus does not have to be planar to work satisfactorily.
Suitable sensors will be used for sensing the vibration ~5 of the bar caused by vortex formation.
A11 forrns o-f the invention have bars which include a head section having a upstream facing surface wi-th a width selected as a function of pipe diameter and with an intermediate bar section that ls substantially smaller in width than the face width.
It has been found tnat when maintaining a constant intermediate section width for di-Fferent line sizes bars having a T confiyuration and having a rather abrupt increase in size between the intermediate section and the tail section tend to shed stronger vortices and provide more linear response across a wider range of flows than can be achieved witnout the wider tail section. The gen-tly curved section of Figure 6 for example also gives good linearity.
Again tne preferred ratio of the length to the face width, that is H/D, is not substantially different from the quantity H/D = 0.2732.
Although the present invention has been described with reference to preferred embodiments workers skilled in the art will recognize that cnanges may be made in form and detail without departing From the spirit and scope of the invention.
U.S. Patent No. 4,052,895 which is also owned by Fischer & Porter shows a bluff body having a traiLing "tail" assembly connected by an intermediate beam that has a very small cross section and does r-ot extend along the longitudinal axis oF the bluff body.
Tnus flow may interact in the space between the bluff body arld the tall.
Additional generally T cross section shapes of bluff bodies and their associated sensors are shown in U.S. Patent No. 3 972,232. The bluff bodies have head members with facing surfaces and a narrower body section extending downstream from the nead member. In this device~ the sensor is a member that moves under differential pressures that occur along the side surfaces of the downstream extending sensor bar. This patent discloses the general relationshi? of positioning of a sensor relative to an upstream head member for sensing pressure differentials on the body portion downstream from the head member, but does not -teach the unique geometry that permits the same sensor to be used in flowmeters for a wide range of pipe diameters.
Flowmeters similar to that shown in the last mentioned paten-t also are disclosed and discussed in U.S. Patent Nos. 4,085,614 and 4,088,020. Particular attention should be paid to the angular arrangement of the edges of the head member or upstream plate, as well as the transverse width of the plate in relation to the 1enrJth of the sensor bar that is used. The width of the sensor bar represented by the dimension r in drawings of l'atent No. 3,972,~32 changes with di~ferent pipe sizes as shown in Column 9 of that patent. This is also the case in Pa-tent No. ~,085,614 as disclosed in Column 9 of that patent.
While various typical cross sectional configurations are shown in the prior art the geometries of the cross sections of the pri.or bluff bodies do not provide fo-r the use of a body having a sensor mounting section tha-t remains substantially constant in its critica]. dimension so that the same sensor assemL~ly can be utilize~J for flowrneters used on different line sizes.
SUMMARY OF THE I~lVENTION
A bluff body or bar for Forming a vortex generating flowrneter comprising an upstream head rnember having a flo~r facing surface causing a disruption in flow of fluid in a line or pipe in which the bluff body is inserted; an intermediate section of less width than the flow facing surface connected to the head member and extendiny downstream relative thereto; and a tail section at the downstream end of said intermediate section of greater width than the intermediate section. The bar is configured to provide for the formation of strong vortices that are alternately and repeatably formed on the opposite sides of the intermediate section at a frequency dependent upon flow rate through the line or pipe. The intermediate section has a width that is constant for blufF bodies used across a substantial range of line sizes, so that the sensors utilized with the flowmeter (which are mounted in the intermediate section) can be standarized and yet the outputs of the flowmeters remain linear 0 and repeatable across a substantial flow range.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a sectional view through a line carrying fluid flow havinr~ a vor-tex flowmeter uslng a bluff body or bar made according to the present invention installed therein;
Figure 2 is a sectional view taken as on line 2--2 of Figure l;
Figure 3 is a transverse sectional view taken as on line 3--3 in Figure 2;
Figure 4 is an enlarged sectional view of the bluff body shown in the flowmeter of Figure 3 with illustrative dirnensions labeled on the figure;
Figures 5, 6, 7 and 8 are addi-tional embodimellts showing the cross sec-tional shape of bluff ~5 bodies made accordlng to the present invention and;
Figures 9, 10 and 11 disclose slir~ht variation in the front face configuration.
DETAILED DESORIPTION OF THE PREFERRED EMaODIMENTS
The basic equations for describing -the action and effect of nondimensional parameters on vortex shedding were set forth in the Oescription of the Prior Art and are well known.
Referring to Figure 1, a flow pipe 10 carries a fluid, the flow rate of which is to be rneasured.
Usually the Flows of liquids are measured but gases and steam can also be measured. The pipe 10 can be a meter section that is placed into an existing flow pipe or conduit, and generally the meter section will be fastened into the conduit with suitable flanges coupled to flanges on the conduit carrying the fluid.
Alternatively the meter section can be a spool piece held between the flanges by bolts or other conventional means. These flanges are not shown, but are well known in the art. Flow is in the direction of arrow 11 (Figure 2) through the pipe.
lû The vortex shedding flowmeter 13 made according to the present invention is shown installed on the interior of the pipe 10. The pipe wa]l has an opening 14 therethrough into which the bluff body or vortex shedding bar section of the flowmeter, indicated generally at 15, is inserted. The bar has a height dimension, which is measured along its longi-tudinal axis. Preferably bar 15 extends substan-kially across the en-tire diameter of the pipe 10. The pipe (internal) diameter is indica-ted by D in Figure 2. A
suitable mounting collar 16 surrounds the opening 14 in the wall of the pipe 10, and the vortex shedding flowmeter has a plug or head 17 that fits inside the sleeve 16. Sleeve 16 may nok be required as bar 15 can be rnechanically fixed in position by conventional means such as bolts through the pipe wall opposite from head 17. The head 17 has a surFace contoured on its bottom side to conForm to the curvature of the inside diameter of the pipe 10. Cap screws 20 are used for securing the bar or bluff body 15 -to the head 17. The head may be held in place in sleeve 16 in a suitable manner9 for e~.ample with clamps or with an open center nut that is threaded into collar 16. As can be seen, the head 17 has an 0-ring 21 on its exterior ~Jhich seals against the interior surface of the sleeve 16.
- 35 As will be explained9 the sensing device for sensing the frequency of the vor-tices being formed on , opposite sides of the bar 15 is mounted on the interior of the bar 15 and a portlon of the connections are under a cap 22 that is mounted on the head 17. Leads 23 couples sensing circuitry of a desired form to the sensing device.
The vortex forming bar 15 is divided up into three distinct parts including a head section 25 having a Flow face 26; an intermediate body section 27 that is integral with and immedlately downstream from the head section 25; and a tail section 30 that is downstream of the intermediate body section 27 and integral with section 27.
As shown in Figure 4, the eleven linearly independent degrees of freedom that completely specify the meter geometry include the following:
The Pipe diameter = D (Figure 2) The Flow Face width = H
Bar Lengths . L, L1, L2~ L3, L4 and L5 ~ar Intermediate width = H1 The Tail widths = H2 and 113 Also the distances of` the bar face From the nearest upstrearn and (lf present) downstream disturbance may be drsignated L6 and L7 as represented schematically in Figure 3 which would bring the to~al number of linearly independent degrees of freedom to thirteen.
Angles ~ 2~ and ~3 whlch are shûwn in Figure 4, are dependent on some of the dimensions labeled above and are therefore not included as variables. The angles could, however, be substituted for some of the linear dimensions to form a new linearly independent set of parameters that also would completely describe the flo~rneter.
The 1~11 angles are angles of slope of surfaces joininy the portions of dlfferent widths in the f'rOSS section of the vortex shedding bar 15. The reference for measuring the angles is the longitudinal plane of the bar 15 parallel to the direction of flow.
Ul, is the slope ang],e of the back surfaces of head sectlon 25 between dimension H and Hl; 92 is the angle of the f'ront sur-faces of the tail section 3û, between Hl and H2; ~3 is the angle of trailing tapered surfaces of the -tail section bet~een H2 and H3.
There are a varlety of ways for obtaining linearly independent, nondimensional sets of parameters that describe the meter cross section geometry. Two of the more common nondimensional sets of parameters are shown in Table I below. Either set shown in Table I
may be used, depending on preference of the designer.
Note that set 1 includes only linear dimensions, while set two includes the angles ~ labeled on Figure 4.
TABLE I
Two nondimensionalized, linearly in-dependent sets of parameters describing 2û the geometry of the bar cross section of Fiqure ~.
Set 1: D (inches) ~cm); H/3; L1/H; L2/H;
L3/~ l; Is/~l; L/~
rl2/~ l3/H and, if' applicable, L6/H; L7/H;
Set 2: D (inches) (cm); H/D; L1/H; L3/H;
L/H; Hl/H; H2/H; H3/H; ~1;
42i ~3; L6/H; L7/H-The two nondimensional sets of parameters shown i~ rabl~ I are related by the equations:
L2 = Ll -~ 1/2(1 _ Hl) tan (90 ~ ~1) H l-l H
L~, = L3 + 1 ( H2 _ Hl ) tan (90 - a H H 2 ~ 2 L5 = L - 1 ~ H2 _ H3 ) tan (90 - a3) The utility of such sets of parameters is that once a set of values for the nondimensional parameters oF either set has been determined such that the Strouhal number is a constant over a suitably wide Reynolds number range, for example and values (dimensions) have been established for a flowmeter bluff body or bar that behaves linearly in a particular line size, the nondimensional sets defined above will have been established and in theory -to deterrnine the actual dimensions for a flowmeter in another line si~e one simply has to know -the pipe diameter, D 7 and perform the appropriate calculations to determine the remaining dirnensions usirlg the Set 1 or Set 2 rclatlorlships, then, based on actual performance data, the skilled designer may desire to alter certain pararneters to further enhance performance. The ratio Il/D is kept constant within a sui-table range and other parameters are kept within essentially predetermined ranges This also assumes, in the case of` a vor-tex flowmeter, that the Strouhal number vsO Reynolds number and Mach number relationships are constant oYer the flo~l range of interest. Wa-ter flow is usually Mach .005 maxlmum and airflow generally is no higher than Mach .1 although in isolated cases airFlows rnay oe as high as Mach .25.
The geometry of the bar cross section of Figure 4 can be designed for different line sizes (different values of D) in such a way that the intermediate body section width, ill remains constant (Hl/H increases with decreasing line size) without compromising the linearity of tne meter between D = two inches (5.08 cm) and D = eight inches (2û.32 cm).
Meters below D = two inches (5.08 cm) use a smaller Hl dlmension. ~hus for example, one inch (2.54 cm) and one and one-half inch (3.~1 cm) line size meters preferably have the same Hl dimension. The ability to keep Hl constant across such a wide range of pipe diameters can be accomplished by varying the remaining dimensions in the set of parameters being used.
The parameters L6/t-l and L7/H are not provided in that the meter preferably operates without obstruction upstream or downstrearn. tlowever, these obstructions may occur from small discontinuities in the pipe wall. For example, the meter assernbly may be in a short pipe sectiorl with end Flanges which is bolted and installed between two pipe sectiorls. The junctiorl lines along the pipe wall rnay Form discontinuities which have to be taken into consideratlon.
These meters will behave satisfactorily over the flow ranges 1.25 Ft/sec. (0.381 m/sec.) to 25 ft/sec. (7.62 m/sec.) in liquids and 10 ft/sec.
(3.048 m/sec.) to 250 ft/sec. (76.2 m/sec.) in gases and steam. The two inch (5.08 cm) through eight inch (20.32 cm) meters preferably have a value of tl1 = 0.223 inches (0.566 cm) while the 1 in.
(2.54 cm) and 1-1/2 inch (3.81 cm) meters preferably have til = 0.100 inches (0.254 cm). Hl can be any value less than H2 wherein Hl is irnperforate and precludes -fluid movement frc~ one side of the bar to the other and wherein Hl further provides sufficient spacing for hûusing means to sense the differential pressure caused by the vortex action.
The ranges of dimensions for a typical preferred meter relationship is as follows:
TABLE II
D = 1.049 inches t2.664 cm) to 7.981 inches (20.272 cm) H/D = û.2732 tThis may be established b~J test) ~11 = .1 to 0.3955 H
H2 = û 45û9 to 0-5045 H3 = û.1689 to 0.1692 H
Ll = û.û273 to 0.1181 L2 = 0.2169 to û.3342 3 = 0.7555 to l.OûO
Ll, = 0.860~ -to l.û32 15 = l.û9û to 1.26~
L = 1.3~4 to 1.432 l = 30 to 90-preferred 58 to 60 2 = 45 to 90-preferred 60 to 90 03 = 17 to 45-preferred 3û to 45 ~_ = 1.14û to 3.112 Hl 9(~
The fluctuating p~essure coefficients, Cp. are related to the fluctuating differential pressures p across the vortex flowmeters by the equation:
AP = cp pv2 sin 2 ft Where p = fluid density v = velocity of the flow f = shedding frequency These coefficients were measured at a flow velocity of approximately 1.5 ft/sec. (0.457 m/sec.~and indicate that strong vortices are being shed.
For optimum performance, it was found that the value of L/H is dependent on the angle 03. Thu , when 03 was 45, the meter having a ratio L/H o 1.33 to 1.38 generally performed best, but when 03 was 30, meters having L/H ratios of 1038 to 1.43 generally performed best. The best choice for L/H
appears to depend on other dimensions as well as 03.
Each meter made as shown in Figure 4 exhibits good linearity and with substantially the same Hl dimension, thus standardized sensor arrangernents are possible for a significant range of flow pipe diameters.
Referring now specifically to Figures 1 through 3, it can be seen that bar 15 has a diaphragm for sensing pressure indicated at 32 on the shown side thereof, and a like diaphragm preferably is positioned on the other side of the intermediate section 27 of the bar 15. As vortices are formed they switch from side to side on the bar and, hence, the pressure on each diaphragm changes. This causes the diaphragms to deflect and the diaphragms act on a sensor that senses differential pressure between the opposite sides of the intermediate section 27. A sensor that is constructed in a desired manner is shown in applicant's Canadian Patent Application No. 422~621, filed March 1 1983, entitled Differential Pressure Vortex Sensor~
One feature is that the width Hl can remain constant ~ 14 -across a wide range of pipe diameters, and -then the same sensor regardless of the type can be u-tilized for -the flowmeters used in such pipes, even though the various length (L, Ll, L2, L3 --) dimensions (L, Ll, L2, ...) may change, H may change, and H2 and H3 also may change. Thus the sensor ~ se may be a prior art sensor, for example the sensor shown in U.S.
Patent No. 3,796,095.
It can be seen in Figure 3 that vortices are generated as the flow separates along the face 26, to create alternate swi-tching of high to low pressure along the sides of -the intermediate section 27 and thus the differential pressure also changes.
The cross section of the preFerred vortex forrning bar includes a head portion 25 having a face width 26 that is selected in size as a function oF the diameter of the pipe in which the flowmeter is used.
Once the ratio H/D has been established, Hl kept at a reasonable standard for a wide range of pipe diameters, the length L may be selected and also H2, L~ and H3 selected to insure that the vortices are strongly formed, repeatable, and that linearity is establishcd for the flowmeter.
In all cases, the tai] section la-teral wid-t ll2 Is greater tilan the width Hl of the intermediate bar section 27, and both of these dimensions (Hl and H2) are kept less than tne face width H of the surface 26.
Norrnally the face surface 26 is a plane surface perpendicular to the flow, although concave or convex surfaces or other protuberances are acceptable.
The modified emboditnents of the bar cross section shown in Figures 5, 6 and 7 are embodiments which exhibit acceptable linearity. It can be seen that the width of the intermediate bar section can oe maintained constant for flowmeters of these conflgurations, but dimensions such as the Ll and H2 dimensions vary substantially as the pipe diameter is changed. Further, it has been found that the Ll dimension can, if desired, be formed to be a sharp edge without subs-tantially affecting the per-formance of the flowmeter but this may affect the long term stability due to the erosion of this thin edge.
For example in Figure 5, the vortex forming bar indicated at 40 has a cross section as shown and includes a head section 42 with a face surface 41 that is generally perpendicular to the direction of flow indicated by the arrows. The head section 42 has a smoothly curved rear or downstream facing surface 43.
The intermediate bar section 44 has a transverse width lil that is sufficient -to accept a standard sensor therein for a wide range of pipe diameters. The side surfaces of intermediate bar section 44 are smoothly curved as shown, but a local area of the surfaces will be made flat (For example, with a spot face or a boss) when d:iaphragins are used for sensing pressure so the diaphragms are planar. The rest of the side surfaces may be curved as shown.
The bar 40 includes a tail section 45 at the trailing edge of the intermediate section 44. The tail section 45 as shown has a widtil H2 across its maximum dimension that is greater than the width Hl of intermediate section 44, but less than the width H of the face surface 41.
Linearity is acceptable across the desired range of fluid flows and the intermediate section 40 has a width that remains substantially constant across a substantial range of pipe diameters so that the sensor construction can be standardized.
In Figure 6 a greater difference between dimensions such as L4 and L5 is shown so that the tail section is reduced in length. In this particular embodiment the bluff body or vortex forming bar 5û has a head section 52 having an upstream face 51 that is generally perpendicular to the direction of flow as indicated. ~lead mernber 52 has straight sides for a lû distance Ll. The straight sides join concave rear surfaces 5~ leading to the intermediate bar section 54. The intermediate section as shown in Figure 6 has sligntly curved (concave) side surfaces joining the tail section 55 -that has a width H2 that is less than the width of the face 51 but greater than -the width (Hl) of the intermediate section 54. In this particular instance, the trailing side surfaces of the tail section S5 are planar surfaces that are formed at an angle ~3 as desired. Again~ if diaphragms are 2û used For sensing diF-Ferential pressures, the side sur-Faces of the intermediate bar section will be formed to hold the diaphragms planar. This can be a spot Face or a rourld boss the size oF the diaphragm l'he rest of the surface will be curvecl as shown.
In Fiyure 7, the cross sectlon oF a further embocl1nlent of' a blufF body or vortex sheddiny bar 6û is snown and the bar includes a head section 62 having a forwardly facing face 61. Head member 62 has a tapered rear (downstream facing) surface 6} which is joined to an intermediate section 64. The tail section 65 in this particular flowmeter has an H2 dimension which is at the low end of -the ratio given in Table II for H2/Hl .
Meters having bluff bodies or vortex shedding bars sho~"n herein operated at Flow rates between approxim2tely .5 ft/sec. (û.152 m/sec.)and 25 -Ft/sec.
( 7 . 62 m/sec.) in a nominal four inch (10.16 cm) ID pipe carrying water and performed with linearity errors under one percent. In fact, the forms shown in Figures 4, 5 and 7 showed llnearity errors of under .5 percent.
The ratio of the face width (~) to pipe diameter (D), (H/D), of the bluff bodies or bars in these meters was nominally in the range of û.2732.
The form of the cross section in Figure 8 includes a bar 70 having a head member 71 with a face surface 72. The head member is joined to an intermediate section 74 and a tail section 75 is also provided at the trailing end of intermedlate section 74.
The head member has a pair of protuberances lS 73 at the side edges of the head member 71 which face upstream and may aid in forming vortices. The front face thus does not have to be planar, but may be concave as shown, or a concave curved surface, or have irregularities such as those disclosed in U.S. Patent 20 No. 4,17~,643.
In Figure 9, a bluff body or bar 7B has a head member 79 with a concave front face 80 forrned by two shallow planar surfaces 81 taperlng inwar-JIy from the sides of the head member.
The bluff body or bar B4 shown in Figure 10 has a head 85 with a curved concave forward fare 86.
In Figure 11 a bluff body 90 has a nead mernber 91 with a convex face 92. The convex surface is not a deeply convex surface. The bluff bodies or bars 30 of Figures 9, 10 and 11 each have intermediate body portions and tail sections as shown to provide s-trong vortices as previously disclosed. The front face thus does not have to be planar to work satisfactorily.
Suitable sensors will be used for sensing the vibration ~5 of the bar caused by vortex formation.
A11 forrns o-f the invention have bars which include a head section having a upstream facing surface wi-th a width selected as a function of pipe diameter and with an intermediate bar section that ls substantially smaller in width than the face width.
It has been found tnat when maintaining a constant intermediate section width for di-Fferent line sizes bars having a T confiyuration and having a rather abrupt increase in size between the intermediate section and the tail section tend to shed stronger vortices and provide more linear response across a wider range of flows than can be achieved witnout the wider tail section. The gen-tly curved section of Figure 6 for example also gives good linearity.
Again tne preferred ratio of the length to the face width, that is H/D, is not substantially different from the quantity H/D = 0.2732.
Although the present invention has been described with reference to preferred embodiments workers skilled in the art will recognize that cnanges may be made in form and detail without departing From the spirit and scope of the invention.
Claims (16)
1. A flow measuring apparatus comprising a bluff body vortex generating element forming a bar having a longitudinal axis and having a cross section taken along a plane generally parallel to the direction of flow and perpendicular to the longitudinal axis, and being adapted to be rigidly mounted on at least one end in a stream of flowing fluid; said bar having:
a face situated to face toward and generally perpendicular to the direction of flow and having a first width in said plane perpendicular to the flow direction;
an intermediate section downstream of said face and of substantially reduced width measured in the same direction as the width of the face;
a tail section immediately downstream of said intermediate section and having a width measured in the same direction as the width of the face greater than the width of said intermediate section and less than the first width and extending outwardly from both edges of said intermediate section a desired amount;
the intermediate section being substantially imperforate and substantially co-extensive with the face and tail section in direction along the longitudinal axis; and means mounted in said intermediate section to sense the frequency of formation of vortices which flow past the intermediate section.
a face situated to face toward and generally perpendicular to the direction of flow and having a first width in said plane perpendicular to the flow direction;
an intermediate section downstream of said face and of substantially reduced width measured in the same direction as the width of the face;
a tail section immediately downstream of said intermediate section and having a width measured in the same direction as the width of the face greater than the width of said intermediate section and less than the first width and extending outwardly from both edges of said intermediate section a desired amount;
the intermediate section being substantially imperforate and substantially co-extensive with the face and tail section in direction along the longitudinal axis; and means mounted in said intermediate section to sense the frequency of formation of vortices which flow past the intermediate section.
2. The flow measuring apparatus of Claim 1 wherein said face is formed on a head section of said bar, said head section having side edges of a desired length extending in the direction of flow.
3. The flow measuring apparatus of Claim 1 wherein the face and tail configurations change dimension for bars used in different diameter fluid streams, and the width of the intermediate section remains substantially constant across a range of different size bars for different diameter fluid streams with which the flow measuring apparatus is utilized.
4. The flow measuring apparatus of Claim 1 wherein said flow measuring apparatus is inserted in a pipe having a diameter D, and the bar longitudinal axis extends substantially across the diameter, said first width being designated as H and selected so that the ratio H/D is substantially in the range of 0.2732.
5. The flow measuring apparatus of Claim 4 wherein the intermediate section has a width designated H1, and the maximum width of the tail section is designated H2, and the ratio of H2/H1 is at least 1.14.
6. The flow measuring apparatus of Claim 4 wherein the ratio of H1/H is within the range of 0.1 to 0.3955.
7. The flow measuring apparatus of Claim 1 wherein the bar cross section is substantially uniform along the entire bar longitudinal axis and the longitudinal axis extends across the diameter of a pipe in which the flow measuring apparatus is mounted, and wherein the bar includes a head section which extends from the face to the intermediate section and which has a length in direction of flow of L2, the intermediate section having a length to position where it joins the tail section of L3 when measured from the face, and wherein the tail section abruptly expands in width downstream from the end of the dimension L3 to the tail section maximum width.
8. The flow measuring device of Claim 6 wherein the cross section of the bar has substantially straight sides along the intermediate section of the bar, and the straight sides form generally planar surfaces parallel to the longitudinal axis of the bar.
9. A flow measuring device using the principles of vortex formation which comprises:
a vortex generating body elongated along its longitudinal axis and adapted to be mounted on one end and to project into a fluid stream, said body having a cross section taken generally perpendicular its longitudinal axis which includes a head member having a substantial cross section width transverse to the direction of flow past the body, a substantially imperforate intermediate section fixed to said head member and extending downstream therefrom, said intermediate section having a cross section width transverse to the longitudinal axis substantally less than the width of the head member, and a tail section having a cross section width transverse to the longitudinal axis greater than the width of the intermediate section but substantially less than the width of the head member, the head member, intermediate section and tail section being substantially co-extensive in length along the longitudinal axis and the intermediate section being fixed to the head member and tail section, respectively, along the entire length of the head member and tail section in direction of the longitudinal axis;
means mounted on the intermediate section for sensing differential pressure on opposite sides of said intermediate section; and the head member and the tail section being varied in width and length for different ranges of pipe diameter in which the flow is to be measured while the intermediate section is maintained at a substantially constant dimension to provide interchangeability of the means for sensing differential pressure in the intermediate section.
a vortex generating body elongated along its longitudinal axis and adapted to be mounted on one end and to project into a fluid stream, said body having a cross section taken generally perpendicular its longitudinal axis which includes a head member having a substantial cross section width transverse to the direction of flow past the body, a substantially imperforate intermediate section fixed to said head member and extending downstream therefrom, said intermediate section having a cross section width transverse to the longitudinal axis substantally less than the width of the head member, and a tail section having a cross section width transverse to the longitudinal axis greater than the width of the intermediate section but substantially less than the width of the head member, the head member, intermediate section and tail section being substantially co-extensive in length along the longitudinal axis and the intermediate section being fixed to the head member and tail section, respectively, along the entire length of the head member and tail section in direction of the longitudinal axis;
means mounted on the intermediate section for sensing differential pressure on opposite sides of said intermediate section; and the head member and the tail section being varied in width and length for different ranges of pipe diameter in which the flow is to be measured while the intermediate section is maintained at a substantially constant dimension to provide interchangeability of the means for sensing differential pressure in the intermediate section.
10. The device of Claim 9 wherein said tail section and the intermediate section are joined by a transition portion extending outwardly on opposite sides of said intermediate section at a selected angle greater than 30° as a minimum included angle with respect to the plane of the adjacent surface of the intermediate section.
11. The device of Claim 9 wherein the flowmeter has dimensions corresponding to those set forth in Figure 4 of the drawing and is constructed with the ratios substantially in accordance with Table II of the present specification.
12. The device of Claim 9 wherein said head member has a face surface facing upstream and extending transverse to the direction of flow, and a pair of protuberances on opposite edges of the head member and extending in direction from the face opposite from the flow direction.
13. The device of Claim 9 wherein the intermediate section comprises curved concave surfaces along the sides thereof when viewed in transverse cross section across the bar.
14. The device of Claim 9 wherein said head member has a concave face surface facing upstream and extending transverse to the direction of flow.
15. The device of Claim 9 wherein said head member has a convex face surface facing upstream and extending transverse to the direction of flow.
16. A method of constructing flow measuring devices for use in pipes carrying flow which are of different diameters, comprising the steps of:
forming vortex generating bars of different lengths for mounting in corresponding selected pipe sizes, each vortex generating bar being formed to be elongated along its longitudinal axis and adapted to be mounted at one end thereof within a pipe, and to project into a fluid stream in the pipe, each bar comprising a body being formed to have a cross-section taken generally perpendicular to its longitudinal axis which includes a head member having substantial cross-section width transverse to the direction of flow past the body, and a substantially imperforate intermediate section fixed to said head member and extending downstream therefrom, said intermediate section having a cross-section width transverse to the longitudinal axis substantially less than the width of the head member, and a tail section having a cross section width transverse to the longitudinal axis greater than the intermediate section width, but substantially less than the width of the head member, the head member, intermediate section and tail section being substantially co-extensive in length along the longitudinal axis and the intermediate section being fixed with the head member and tail section, respectively, along the entire length of the head member and tail section in direction of the longitudinal axis;
varying the head member and tail section in width and length for different bodies used in measuring the flow of respective different diameter pipes, and maintaining the intermediate section at a substantially constant width dimension for each such different body; and sensing differential in pressure on opposite sides of the intermediate section on each body using a standard differential pressure sensor that mounts in an opening in the intermediate section of each such body and which extends across the width of such intermediate section to thereby standardize the differential pressure sensor for a number of different bars used for measuring flow in different size pipes.
forming vortex generating bars of different lengths for mounting in corresponding selected pipe sizes, each vortex generating bar being formed to be elongated along its longitudinal axis and adapted to be mounted at one end thereof within a pipe, and to project into a fluid stream in the pipe, each bar comprising a body being formed to have a cross-section taken generally perpendicular to its longitudinal axis which includes a head member having substantial cross-section width transverse to the direction of flow past the body, and a substantially imperforate intermediate section fixed to said head member and extending downstream therefrom, said intermediate section having a cross-section width transverse to the longitudinal axis substantially less than the width of the head member, and a tail section having a cross section width transverse to the longitudinal axis greater than the intermediate section width, but substantially less than the width of the head member, the head member, intermediate section and tail section being substantially co-extensive in length along the longitudinal axis and the intermediate section being fixed with the head member and tail section, respectively, along the entire length of the head member and tail section in direction of the longitudinal axis;
varying the head member and tail section in width and length for different bodies used in measuring the flow of respective different diameter pipes, and maintaining the intermediate section at a substantially constant width dimension for each such different body; and sensing differential in pressure on opposite sides of the intermediate section on each body using a standard differential pressure sensor that mounts in an opening in the intermediate section of each such body and which extends across the width of such intermediate section to thereby standardize the differential pressure sensor for a number of different bars used for measuring flow in different size pipes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/357,465 US4464939A (en) | 1982-03-12 | 1982-03-12 | Vortex flowmeter bluff body |
| US357,465 | 1982-03-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1190414A true CA1190414A (en) | 1985-07-16 |
Family
ID=23405721
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000422619A Expired CA1190414A (en) | 1982-03-12 | 1983-03-01 | Vortex flowmeter bluff body |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4464939A (en) |
| EP (1) | EP0103625B1 (en) |
| JP (1) | JPS59500388A (en) |
| CA (1) | CA1190414A (en) |
| DE (1) | DE3374431D1 (en) |
| WO (1) | WO1983003299A1 (en) |
Families Citing this family (26)
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| US4445388A (en) * | 1983-09-26 | 1984-05-01 | Fischer & Porter Company | Dual-body vortex-shedding flowmeter |
| US4862750A (en) * | 1987-02-11 | 1989-09-05 | Nice Gerald J | Vortex shedding fluid velocity meter |
| US4926532A (en) * | 1987-06-03 | 1990-05-22 | Phipps Jackie M | Method of manufacturing a flow meter |
| US4854177A (en) * | 1987-06-03 | 1989-08-08 | Phipps Jackie M | Piezoelectric vortex flow meter |
| US4926695A (en) * | 1987-09-15 | 1990-05-22 | Rosemount Inc. | Rocking beam vortex sensor |
| US5343762A (en) * | 1992-10-05 | 1994-09-06 | Rosemount Inc. | Vortex flowmeter |
| US5351559A (en) * | 1993-08-31 | 1994-10-04 | National Science Council | T-shape vortex shedder wherein the bluff body extends across the diameter of a circular pipe and has a length to width ratio between 1.56 and 2.0 |
| US5561249A (en) * | 1993-12-23 | 1996-10-01 | Nice; Gerald J. | Insertable flow meter with dual sensors |
| DE19620655C2 (en) * | 1996-05-22 | 1998-07-23 | Kem Kueppers Elektromech Gmbh | Transducer for a vortex flow meter |
| US7224077B2 (en) * | 2004-01-14 | 2007-05-29 | Ocean Power Technologies, Inc. | Bluff body energy converter |
| US7073394B2 (en) * | 2004-04-05 | 2006-07-11 | Rosemount Inc. | Scalable averaging insertion vortex flow meter |
| US7208845B2 (en) * | 2004-04-15 | 2007-04-24 | Halliburton Energy Services, Inc. | Vibration based power generator |
| US6973841B2 (en) * | 2004-04-16 | 2005-12-13 | Rosemount Inc. | High pressure retention vortex flow meter with reinforced flexure |
| WO2006085869A1 (en) * | 2005-02-08 | 2006-08-17 | Welldynamics, Inc. | Downhole electrical power generator |
| EP1848875B1 (en) * | 2005-02-08 | 2012-01-18 | Welldynamics, Inc. | Flow regulator for use in a subterranean well |
| CA2610365A1 (en) * | 2005-05-31 | 2006-12-07 | Welldynamics, Inc. | Downhole ram pump |
| EP1915509B1 (en) * | 2005-08-15 | 2016-05-18 | Welldynamics, Inc. | Pulse width modulated downhole flow control |
| GB0525989D0 (en) * | 2005-12-21 | 2006-02-01 | Qinetiq Ltd | Generation of electrical power from fluid flows |
| NO333810B1 (en) * | 2008-04-02 | 2013-09-23 | Well Technology As | Downhole energy generation device and method |
| WO2011016813A1 (en) * | 2009-08-07 | 2011-02-10 | Halliburton Energy Services, Inc. | Annulus vortex flowmeter |
| JP5394506B2 (en) | 2009-12-24 | 2014-01-22 | ローズマウント インコーポレイテッド | Vortex flowmeter with vortex vibration sensor plate |
| US9016138B2 (en) * | 2013-03-13 | 2015-04-28 | Rosemount Inc. | Flanged reducer vortex flowmeter |
| US9599493B2 (en) * | 2014-10-31 | 2017-03-21 | Invensys Systems, Inc. | Split flow vortex flowmeter |
| WO2018016984A1 (en) | 2016-07-21 | 2018-01-25 | Rosemount Inc. | Vortex flowmeter with reduced process intrusion |
| US10101184B2 (en) | 2016-11-04 | 2018-10-16 | Schneider Electric Systems Usa, Inc. | Vortex flowmeter for use in harsh environments |
| CN112525272A (en) * | 2019-09-17 | 2021-03-19 | Abb瑞士股份有限公司 | Vortex street flowmeter |
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| US3116639A (en) * | 1960-03-28 | 1964-01-07 | Savage & Parsons Ltd | Apparatus for the measurement and integration of fluid-velocities |
| US3572117A (en) * | 1968-05-27 | 1971-03-23 | Eastech | Bluff body flowmeter |
| US3589185A (en) * | 1969-09-04 | 1971-06-29 | Fischer & Porter Co | Vortex type flowmeter |
| JPS5113428B1 (en) * | 1970-05-09 | 1976-04-28 | ||
| US3732731A (en) * | 1971-02-02 | 1973-05-15 | Eastech | Bluff body flowmeter with internal sensor |
| GB1430062A (en) * | 1972-03-22 | 1976-03-31 | Kent Instruments Ltd | Flowmeters |
| US3888120A (en) * | 1973-04-26 | 1975-06-10 | Fischer & Porter Co | Vortex type flowmeter with strain gauge sensor |
| JPS5046155A (en) * | 1973-08-28 | 1975-04-24 | ||
| US3946608A (en) * | 1974-02-26 | 1976-03-30 | Fischer & Porter Company | Vortex flowmeter with external sensor |
| DE2458901C3 (en) * | 1974-04-23 | 1986-07-10 | The Foxboro Co., Foxboro, Mass. | Flow meter |
| US3972232A (en) * | 1974-04-24 | 1976-08-03 | The Foxboro Company | Vortex flow meter apparatus |
| US4005604A (en) * | 1975-09-30 | 1977-02-01 | Fischer & Porter Co. | Non-contact sensor for vortex-type flowmeter |
| US4069708A (en) * | 1975-11-12 | 1978-01-24 | Neptune Eastech, Inc. | Flowmeter plate and sensing apparatus |
| US4003251A (en) * | 1976-03-19 | 1977-01-18 | Fischer & Porter Co. | Acceleration-proof vortex-type flowmeter |
| US4033189A (en) * | 1976-03-26 | 1977-07-05 | Fischer & Porter Co. | External-sensor vortex-type flowmeter |
| US4030355A (en) * | 1976-06-18 | 1977-06-21 | Fischer & Porter Co. | Obstacle assembly for vortex type flowmeter |
| GB1584353A (en) * | 1976-09-18 | 1981-02-11 | Plessey Co Ltd | Fuel injection system for an engine |
| US4052895A (en) * | 1977-01-12 | 1977-10-11 | Fischer & Porter Co. | Obstacle assembly for vortex-type flowmeter |
| US4088020A (en) * | 1977-03-14 | 1978-05-09 | The Foxboro Company | Vortex flowmeter apparatus |
| US4257276A (en) * | 1978-05-29 | 1981-03-24 | Nissan Motor Company, Limited | Probe unit of fluid flow rate measuring apparatus |
| DE2831823A1 (en) * | 1978-07-19 | 1980-01-31 | Siemens Ag | FLOW MEASURING DEVICE ACCORDING TO THE PRINCIPLE OF THE KARMAN'S VESSEL ROAD |
| DE2832142C2 (en) * | 1978-07-21 | 1983-02-10 | Siemens AG, 1000 Berlin und 8000 München | Flow measuring device based on the principle of the Kármán vortex street |
| JPS5536933A (en) * | 1978-09-06 | 1980-03-14 | Toshiba Corp | Manufacturing of infrared detection array element |
-
1982
- 1982-03-12 US US06/357,465 patent/US4464939A/en not_active Expired - Lifetime
-
1983
- 1983-02-22 WO PCT/US1983/000255 patent/WO1983003299A1/en active IP Right Grant
- 1983-02-22 EP EP83901275A patent/EP0103625B1/en not_active Expired
- 1983-02-22 DE DE8383901275T patent/DE3374431D1/en not_active Expired
- 1983-02-22 JP JP58501267A patent/JPS59500388A/en active Granted
- 1983-03-01 CA CA000422619A patent/CA1190414A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59500388A (en) | 1984-03-08 |
| EP0103625A1 (en) | 1984-03-28 |
| EP0103625A4 (en) | 1984-11-07 |
| EP0103625B1 (en) | 1987-11-11 |
| WO1983003299A1 (en) | 1983-09-29 |
| US4464939A (en) | 1984-08-14 |
| JPH0554045B2 (en) | 1993-08-11 |
| DE3374431D1 (en) | 1987-12-17 |
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