CA1097943A - Mass flow sensor and method - Google Patents
Mass flow sensor and methodInfo
- Publication number
- CA1097943A CA1097943A CA311,321A CA311321A CA1097943A CA 1097943 A CA1097943 A CA 1097943A CA 311321 A CA311321 A CA 311321A CA 1097943 A CA1097943 A CA 1097943A
- Authority
- CA
- Canada
- Prior art keywords
- mass flow
- density
- mass
- set forth
- conduit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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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
- G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
- G01F1/78—Direct mass flowmeters
-
- 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
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- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Volume Flow (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A true mass flow sensor utilizing a bluff body in the mass flow to generate period? vortices therein, in com-bination with method and apparatus for adjusting generation of the vortices such that the frequency thereof is indicative of the mass flow.
A true mass flow sensor utilizing a bluff body in the mass flow to generate period? vortices therein, in com-bination with method and apparatus for adjusting generation of the vortices such that the frequency thereof is indicative of the mass flow.
Description
BACKGROUND OF THE_INVENTION
This invention relates to flow sensors, and relates more particularly ~o a true mass flow sensor Prior art fluid flow measurement is most commonly performed by positive displacement meters, turbine meters, or restriction-type Elow meters. Positive displacement flow meters, turbine flow meters, anemometers, and blu~f body-type flow m~ters measure only volumetric flow rate. Measurement of mass ~low requires correction of such volumetric flow sig-nals for ~luid density changes which in a liquid ~low is afunction o the temperature of the liquid, while a gas flow density correction must be made as a function of both pressure and temperature of the fluid~
Restrictive type of prior art meters operate on a principle that a restric~ion in a fluid stream creates a pres-sure drop which i~ a function of mass flow rate for a given set of fluid parameters. For accurate measurement of flow, parameters such as pressure ratio, Reynold~s number, orifice con~iguration, and fluid compressibility must be measured acc~rately. Methods to automate such computations require use of eithex transducers and electronic computation or complex mechanical mechanisms which are undesirable for most industrial, military, and commercial applications.
True ma~s flow sen~ors presently available operate on the principle of 1uid inertia measurement, Such devices utilize measurement or coriolis Eorce~ gyroscopic e~fect, or angular momentum. ~owever, such prior art true mass flow sen-sors are both expensive and relatively unreliableO
Prior art volumetric flow meters of the blu~f body type are based upon the phenomenon of vortex-shedding behind a `~ '~'''';
bluff body disposed in the flow stream. ~or a wide range of Reynold's number, a regular patter~ of vortices is generated by such a bluff body in the flow stream~ The frequ~cy of these vortices is directly proportional to the stream ~elocity past the body. When installed in a moving stream~ a wide variety of bluff body shapes generate a wake consisting of a series of vortices. It is believed these vortices form in the boundary layer around the body and grow until they sepa~
rate and are shed into the flow stream. A regular pattern of alternating clockwise and counterclockwise vorti¢es are gener-ated from Reynold's number~ from about 60 to over 200,000. The frequency o~ the periodic vortices is directly proportional to the flow velocity past the body and inversely proportional to the characteristic dimension of the bluff body in a direction substantially perpendicular to the direction of fluid flow, More specificallyJ the volumetric flow rate multiplied by the Strouhal number and divided by the characteristic dimension is equal to the frequency of vortex shedding. For a particular shape of bluf~ body, such as the cylindrical body~ the Strouhal number is constant for Reynold's numbers greater than 600.
Accordingly within the appropriate Reynold's number range~ the frequency is determined by the stream velocity divided by the characteristic dimension and multiplied by a constant~ For determining mass flow in using such volumetric flow meters, separate sensing o the fluid temperature and/or presqure must also be accomplished to correct for density changes in the mass flow. Then, appropriate computation must be made of thsse sen-sed parameters in order to generate a mass flow sensor.
SUMMARY OF THE I~VENTION
, It is a primary object of the preeent invention to
This invention relates to flow sensors, and relates more particularly ~o a true mass flow sensor Prior art fluid flow measurement is most commonly performed by positive displacement meters, turbine meters, or restriction-type Elow meters. Positive displacement flow meters, turbine flow meters, anemometers, and blu~f body-type flow m~ters measure only volumetric flow rate. Measurement of mass ~low requires correction of such volumetric flow sig-nals for ~luid density changes which in a liquid ~low is afunction o the temperature of the liquid, while a gas flow density correction must be made as a function of both pressure and temperature of the fluid~
Restrictive type of prior art meters operate on a principle that a restric~ion in a fluid stream creates a pres-sure drop which i~ a function of mass flow rate for a given set of fluid parameters. For accurate measurement of flow, parameters such as pressure ratio, Reynold~s number, orifice con~iguration, and fluid compressibility must be measured acc~rately. Methods to automate such computations require use of eithex transducers and electronic computation or complex mechanical mechanisms which are undesirable for most industrial, military, and commercial applications.
True ma~s flow sen~ors presently available operate on the principle of 1uid inertia measurement, Such devices utilize measurement or coriolis Eorce~ gyroscopic e~fect, or angular momentum. ~owever, such prior art true mass flow sen-sors are both expensive and relatively unreliableO
Prior art volumetric flow meters of the blu~f body type are based upon the phenomenon of vortex-shedding behind a `~ '~'''';
bluff body disposed in the flow stream. ~or a wide range of Reynold's number, a regular patter~ of vortices is generated by such a bluff body in the flow stream~ The frequ~cy of these vortices is directly proportional to the stream ~elocity past the body. When installed in a moving stream~ a wide variety of bluff body shapes generate a wake consisting of a series of vortices. It is believed these vortices form in the boundary layer around the body and grow until they sepa~
rate and are shed into the flow stream. A regular pattern of alternating clockwise and counterclockwise vorti¢es are gener-ated from Reynold's number~ from about 60 to over 200,000. The frequency o~ the periodic vortices is directly proportional to the flow velocity past the body and inversely proportional to the characteristic dimension of the bluff body in a direction substantially perpendicular to the direction of fluid flow, More specificallyJ the volumetric flow rate multiplied by the Strouhal number and divided by the characteristic dimension is equal to the frequency of vortex shedding. For a particular shape of bluf~ body, such as the cylindrical body~ the Strouhal number is constant for Reynold's numbers greater than 600.
Accordingly within the appropriate Reynold's number range~ the frequency is determined by the stream velocity divided by the characteristic dimension and multiplied by a constant~ For determining mass flow in using such volumetric flow meters, separate sensing o the fluid temperature and/or presqure must also be accomplished to correct for density changes in the mass flow. Then, appropriate computation must be made of thsse sen-sed parameters in order to generate a mass flow sensor.
SUMMARY OF THE I~VENTION
, It is a primary object of the preeent invention to
2--provide a true mass flow sensox based upon the blu ff body, vortex~shedding principle. More particularly, it is an impor-tant object o~ ~he present inven~ion to provide a vortex-shedding type flow sensor which generates vor~ices at a ~re-quency which is a ~unction of mass flow rather than volumetric flow rate.
Another important object o~ the pre ent invention is to provide apparatus and method for accomplishing the object set orth in preceding paragraph, which includes the intrinsic compensation of the vortex shedding in relation to the density of the mass El~w being measured.
Accordingly, the present invention contemplates an improved mass flow sensor and method of extreme simplicity, economy and greater reliability of operation in comparison to previous mass flow sensors. ~ore particularly, the present invention contemplates a bluff body type of ~low me~er operat-ing on the relationships set forth previously~ Consid0ring that mass flow i5 determined by density times volumetric ~low, and that volumetric flow in turn is a function o~ the cross-sectional flow area times the stream velocity, it c~n be seen that the freque~cy of the generated periodic vortices is in-versely proportional to the product quantity of the cross-sectional area times the charactexistic dimension of the bluf~
body. The present invention contemplates structure and method which varies the product quantity of cross-sectional area A
times the characteristic dimension d, i.e. A x d, in inverse proportion to the density o~ the mass flow. The fre~uency o~
the vortices then become a direct function of the mass flow rather than the stream ~elocity past the bluf~ body.
To accomplish this, the present invention contemplates method and apparatus for varying either the characteristic dimension d, or the corss-sectional area A, or both, such that the product quantity A x d is in inverse proportion to the den-sity of the mass flow. In preferred arrangem2nts, this is accomplished by expanding the bluEf body characteristic dimen-sion d through US8 of a bellows which expands and contracts both in response to changes in pressure and/or temperature of ~he mass Elow, or by use of a bimetallic Plement that expands and contracts in response to changes in temperature of the mass flowO In another arrangement the bellows or bimetallic element acts as a driving mechanism for adjusting the ~ross-sectional area A in response to changes of temperature and/or pr0~sure~
Thesa and other more particular objects and advantages in the present invention are specifically set forth in or will become apparent from the following detailed description of preferred forms of the invention when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a front elevational view of the mass ~low sensor constructed in accordance with the principles of the present invention;
Fig. 2 is a cross-sectional elevational view taken along the lines of 2-2 of Fig. l;
Fig. 3 is a cross-sectional view in enlarged Eorm taXen along the lines of 3-3 of Fig. 2 and showing the expanding bluff body and driving element associated therewith;
Fig. 4 is an enlarged, plan cros~-sectional view along the lines of 4-4 of th~ expandable bluff body;
~ ig. 5 is a view similar to Fig. 4 but showing the bluff body in a more expanded state;
~aS_ Fig. 6 is a cross-sectional elevational view of another form ~f the invention;
Fig. 7 is an enlarged view of a portion of the bluff body of Fig. 6 with portions broken away -to reveal internal detail~ o~ constructionl Fig. 8 is a cross-sectional view o the bluEf body of Fig. 6 tak~n along lines 8-8 of Fig. 6;
Fig. 9 is a partial cross-sectional-.elevational view o~ another modif~ed form of the invention; and Fig. 10 is a partial cr~ss-sectional view of yet another form o th~ invention.
DETAILEI) DESC~IPTIO~ OF TEIE PRE~ERRED EMBODIMENTS
Re~erring now more particularly to the Figs. 1-5 of the drawings, there is illustrated a mass flow sensor as con~
templated by the present invention generally denoted by the ~umeral 20. The sensor includes a housing 22 which may be com prised of several different components as illustrated in Fig. 2, which housing defines an internal conduit opening 24 therewithin having appropriate fittings 25 at opposite ends connactable with an existing mass flow transmitting conduit. The ¢onduit 24 has a reduce diameter, rectangular cr~ss-sectional æection 26.
Disposed within section 26 is a bluff body 28 having a pair of spaced sidewalls 30, 32 de~ining a distance d there~
between in a direction substantially perpendicular to the direc-tion of fluid flow through section 26~ The bluff body 28 coop-erates with section 26 to define a fluid flow transmitting area A between the sidewalls 30, 32 and the periphery o~ the section 26. Pxeferably, the bluff body i~ arranged such that the width of section 26 in the direction of the distance d, is at least three times the length o~ distance d, At the rearward end of bluff body 28 relative to th~ direction of mass flow, the bluEf body includes a pair of vertical sensor tubes 34 inter-secured such as by weld joint 38. Each of the walls 30, 32 are attachad to the associated sensor tubes 36 in cantilever arrangement.
The sensor tubes 34 have openings 36 therein for receiving vorticas shed from the bluf~ body, and as illustratad in Fig. 2 the sensor tubes 36 extend downwardly through housing 22 to a transducer arrangement which may include a ~luidic stack 40 that is operable ~o amplify the pxessure fluctuations sensed by tubes 34. The sensed pre sure fluctuations are trans-mitted through a passage 42 to a piezo ceramic transducex 44 that is operable to generate an electrical voltage o-ltput whose frequency is responsive to the frequ~ncy o the pressure fluc-tuations sensed by tubes 34. Through an appropriate electrical outlet 46 the sensed electrical ~requency signal may be trans-mitt~d to a desired readout, control, or other utilization device. The fluidic stack 40 and piezo ceramic transducer 44 are shown only in outline form, it being understood that such transducers are generally widely available and are known to those skilled in the art.
The invention further contemplates movable means in the form of a density compensatox element which includes a bellow~ 50 di~posed within a chamber ~8 of housing 22~ The flexible walls of bellows 50 coopera~e with end plates 54, 56 thereof to define an enclosed interior 58 of the -b~llows. If desired, a spring or other biasing mechanism 62 may also be incorporatPd within the bellows. Upper plate 54 rests again~t or is secured to a stop 60 which is adjustable by rotation of an adjusting nut 61 disposed eæteriorly of the housing 22~
7~3 Secured to lower plate 56 are a pair of parallel compensating struts 68 and 70 which extend downwardly between s.idewalls 30, 32 of bluff body 28. The low0r ends of struts 68 and 70 are held rigidly by housing 22. Accordingly, in response to expan-sion and contraction of bellows 5U, the c~mpensator struts 70 and 68 shift vertically as illus~rated in Fig. 3 so that their central bowed portions between walls 30, 32 will shift in a aorresponding hori~ontal directi~n and thereby expand and con-tract the cantilevered sidewalls 30, 32 to alter the character-istic dimension d of the bluff body. The interior 58 of bellows50 is sealed and filled with fluid hav.ing the same temperature and pressure characteristic~ of the fluid flow in conduit 24.
Chamber 48 ommunicates with mass fluid flow in conduit 24 via a port 64 and a passageway 66 i.n the housing.
In operation, mass fluid flow passes through conduit 24 and the section 26 in a left to right direction as viewed in Fig. 2. Within the desired opexating range of the mass flow sensor, section 26 is sized such that the ~eynold'~ number re-mains above 600. In flowing past bluff body 28, Karmann vortex sheets shed off of the bluff body, and the pressure fluctuations created by the periodically shedding vortices are sensed through openings 36 in sensor tubes 34. These pressure Eluctuations are then amplified by fluidic amplifier 40, and transmitted to drive the pieZG ceramic transducer 44. The pressure fluctuations acting upon the piezo ceramic transducer generate a voltage a~ss the piezo ceramic transducer so that an electric~ output signal rom connection 46 is cxeated who~e frequency is indica-tîve of the frequency of vortices shed by bluff body 28~
Bellows 50 compensates for changes in density of the mass ~low by correspondingly contracting and expanding to respectively drive the sidewalls 30, 32 toward and away from one another to ther~by ch~nge the characteristic dimension d of the blu.EE body 28. In this manner the frequency of the periodic vortices is varied ln response to changes in d~nsity such that the sensed frequency of the vortices is indicative of tha mass flow itsel~ through section 26. For instance, as-suming the mass- fluid flow through conduit 2~ to be a substan-tially incompressible liquid mass ~low, th~ density of such liquid flow is responsive substan~ially only to changes in tem-pe.rature of thi.s liquid. Upon an increase of temperature of a mass flow, which accordingly red~uces density of the liquid, in~reased temperature in chamber 48 causes expansion of liquid trapped within interior 58 of the bellows causing the bellows to expand. This causes the bowed sections o:f the s-truts 68t 70 to expand and move the sidewalls 30~ 32 farther away from one another toward a configuration as illustrated in Fig. 5, In this manner a decrease in density of the liquid flow increases the characteristic dimension d such that the Erequency of the shed periodic vortices i.s indicative of the mass fluid flow.
If the conduit 24 is carrying a relatively compres-sible gaseous fluid flow, the density of this gas flow is a function of both changes in pressure and temperature. A trapped volume of gas having temperature and pressure characteri~tics like that of the gas flow in conduit 24, and preferably tha same yas as in conduit 24, is then contained in the interior of sealed bellows 50~ The trapped volum0 of gas in int~rior 58 of the bellows causes expansion and contraction of the bellows both in response to changes in pressure of the gas flow as well as change~ in temperature of the gas delivered through passage-way 66 to chamber 48~ Temperature increase in chamber 48 causes ~$~
expansion oE the bellows to increase d in respo~se to the reduction in density, and pressure incxease in chamber 4~
(indicative of increased density) causes contraction of the bellows to reduce dimension d. Thus, similarly to the discus-sion above with respect to a liquid Elow, the change in density of the gas flow causes a corresponding expansion or contraction of bellows 50 and resulting change in the characteristic dimen-sion d of ~he bluff body such that the frequency of the periodic vortices is indicative of the mass flow itself.
More specifically, the frequency of the peri~dic vor-tices being shed by the blu:EE body 28 is determined by the following equation:
t 1 ) where:
f is the vortex shedding frequency;
V is the stream flow velocity past the bluff body;
d is the characteristic dimension of the bluf body;
K is a constant related to the Strouhal number.
The stream ~elocity and the mass flow rate are defined by -~he following well known equations (constants be.ing delet d):
~2) V ~ ~ , (31 m = pQ , where-Q is th~ volumetric flow rate of the fluid;
A is the duct cross-sectional area;
m is the mass flow rate;
p is the fluid density.
Straight~orward substitution oE the second equation into the first equation provides the following relat.ionship:
(4) f = KQ
g ~
Accordingly it is seen that the frequency of the periodic vor-tices is an inverse function of the product quanti ty A x d .
The pxesent invention includes th~ compensator in the form of bellows 50 in order to vary the quantity product A x d in inverse proportional proport.ion to the fluid density p:
(5~ Ad By then substituting equation 5 into equation 4, the following res~lts (6) f ~ XpQ .
By comparing equations 3 and 6 it is seen that:
(7) f = Km .
Thus, the frequency of the periodic vortices devel-oped in the present invention is indicative of the mass flow rateO It will be noted by reference to Figs. 3 and 4 that upon change o~ the characteristic dimension d by expansion and con-traction of the walls 30 and 32, a slight change in area A also results. Accordingly, the bellows 50 and associated actuating structure is arranged such that the product quantity A x d changes in inverse proportion to the density p. By arranging the bluEf body 28 relative to section 26 in an appropriate manner, such as by assuxing that the width of the section ~6 in the direction of dimension d is approximately three times the length of dimension d, the percentage change of area A as a result of change in characteristic dimension d, is relatively small in comparison to the percentage change of dimension d it-self. In this manner, for instance, the density compensator is arranged such that the characteristic dimension d is changed at a rate slightly greater than being simply inver~ely propor-tional to the change in density, in order to compensate for the ~mall decrease in area A, all such that the resulting relation-ship is that the produc~ quantity A x d is inversely propor-tional to the change in density.
Figs. 6-8 illustrate an alternate embodiment oE the present inventlon wherein only the cross-~ectional area A is varied in order to provide density compensation. More parti-cularly this arrangement includes a housing 80 defininy an in-terior conduit opening 82 carrying the mass fluid ~low, and a cylindrical bluff body 84 disposad within conduit 82 such tha t the characteristic dimension d of bluff body 84 is in a vertical direction as illustrated in Fig. 6~ A density compensating bellows 86 is included which along with rigid end walls 88 and 90 define an enclosed, trapped volume which contains fluid having like pressure and temperature characteristics as the ~luid in conduit 82. Surrounding the bellows is a chamber 93 which communicates with the mass flow in conduit 82 via passage~
way 32. Associated with bluff body 84 is a piston-~ype arrange-ment presenting a barrier element 94. The integral bluff body 84 and barrier 94 are movably mounted in housing 80 and inter-connected with end wall 88 to b~ responsive to changes in mass 10w density.
More particularly a change in the mass flow density causes contraction or expansion of bellows 86 in the same manner as bellows 50 of the,Fig. 1 arrangement. In response to move-ment of the bellows, the barrier 94 shift to adju t the cross-sec~ional area A of the conduit which is carrying the mass flow past the bluff body 8~. Barrier 94 is appropriately shaped so that the cross-sectional area A changes in inverse proportion to chan~es in density of the mass ~low. The characteristic dimension d of the bluff body remains unchanged, and therefore the product quantity A x d is varied in inverse proportion to the density of the mass flow. As a result the frequency of the shed periodic vortices whose pressure fluctuations are sensed by openings 98 on the downstream side of the bluff body and transmitted through sensing tubes 96 to an appropriate trans-ducer, are propoxtional to mass flow.
Fig. 9 ilLustrates another alternate for~ of density compensator in combination with a bluEf body substantially simi-lar to that illustrated in Fig. 1. The Fig. 9 arrangement in-cludes a housing 100 defining an internal, rectangular, mass flow carrying conduit 102, and a bluff body generally similar to configura~ion to that illustrated in Fig. 1 is disposed in conduit 102. ~ore specifically, the bluff body has spaced sidewalls 106 defining the characteristic dimension d thexe-between along with bowing compensator struts 104 therebetween having one or both opposite ends thereof affixed to the housing 100 .
In contrast to the compensator-type bellows of the Fig. 1 arrangementt the Fig. 9 structure includes compensator struts 104 which are composed of a bimetallic, thermally res-ponsive material. The compensator struts are responsive tochanges in temperature of the fluid in conduit 102, r~spectively bow.ing .inwardly and outwardly in response to decrease and in-cxease of temperatu.re of mass flow. Again, the compensator arrangement is such that the product quan~ity A x d is varied in inverse proportion to the changes in density such that the shedding frequency from the bluff body is indicative of the mass flow rate through the conduit. The Fig. 9 arrangement is parti-cularly useful in sen~ing the mass flow rate of a substantially incompressible l.iquid whose density changes substantially only in response to changes in temperature of the liquid.
~L~7~
Fig. 10 illustrates a further arrangement contem-plated by the present invention which includes a housing 110 defining an internal conduit 112 carrying the ma~s fluid flow, with a bluEf body 114 extending across the conduit 112. Parti-cularly for applications wherein the bluff body may be substan~
tially smaller than the size of the flow carrying conduit, the Fig. 10 arrangement is useful in that bluff body 114 has only a portion 116 thereof which changes in size in ~elation to changes in density o the mass flow. To prevent interference by end effects from the bluff body itself upon the frequency of the vortices, the length of the expandable section 116 in a horizontal direction as illustrated in ~ig. 10, it is prefer-ably approximately at least six times the diameter of the sen-sing opening 118. The Fig. 10 arrangement is constructed in order to operate along the principles discussed previously.
From the Fig. 10 arrangement it will be apparent therefore that the entire length of the bluff body need not be expandable, but rather only a sufficient portion thereof to avoid end effects.
It will be apparent that the present invention pro-vides an improved method of sensing mass flow which includesstep of producing periodic vortices in the mass flow that are at a frequency which is indicative of the mass flow, along with the step of sensing the frequency of the~e periodic vortices.
Den~ity compensation is a part of the step of producing the desired periodic vortices, and may be accomplished by emplacing a bluff body in the mass flow and then varying the characteris~
tic dimension d of the bluEf body in relation to the density of the mass flow. Alternately, density compensation is accom-lished by varying the cross-sectional flow area A in relation to the density of the mass flow.
Various alterations and modifications to the fore-going will be apparent to those skilled in the art. Accordingly, the foregoing detailed description of preferred arrangements of the present invention should be considered exemplary in nature and not as limiting to the scope and spixit of the invention as set forth in the appended claims.
Another important object o~ the pre ent invention is to provide apparatus and method for accomplishing the object set orth in preceding paragraph, which includes the intrinsic compensation of the vortex shedding in relation to the density of the mass El~w being measured.
Accordingly, the present invention contemplates an improved mass flow sensor and method of extreme simplicity, economy and greater reliability of operation in comparison to previous mass flow sensors. ~ore particularly, the present invention contemplates a bluff body type of ~low me~er operat-ing on the relationships set forth previously~ Consid0ring that mass flow i5 determined by density times volumetric ~low, and that volumetric flow in turn is a function o~ the cross-sectional flow area times the stream velocity, it c~n be seen that the freque~cy of the generated periodic vortices is in-versely proportional to the product quantity of the cross-sectional area times the charactexistic dimension of the bluf~
body. The present invention contemplates structure and method which varies the product quantity of cross-sectional area A
times the characteristic dimension d, i.e. A x d, in inverse proportion to the density o~ the mass flow. The fre~uency o~
the vortices then become a direct function of the mass flow rather than the stream ~elocity past the bluf~ body.
To accomplish this, the present invention contemplates method and apparatus for varying either the characteristic dimension d, or the corss-sectional area A, or both, such that the product quantity A x d is in inverse proportion to the den-sity of the mass flow. In preferred arrangem2nts, this is accomplished by expanding the bluEf body characteristic dimen-sion d through US8 of a bellows which expands and contracts both in response to changes in pressure and/or temperature of ~he mass Elow, or by use of a bimetallic Plement that expands and contracts in response to changes in temperature of the mass flowO In another arrangement the bellows or bimetallic element acts as a driving mechanism for adjusting the ~ross-sectional area A in response to changes of temperature and/or pr0~sure~
Thesa and other more particular objects and advantages in the present invention are specifically set forth in or will become apparent from the following detailed description of preferred forms of the invention when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a front elevational view of the mass ~low sensor constructed in accordance with the principles of the present invention;
Fig. 2 is a cross-sectional elevational view taken along the lines of 2-2 of Fig. l;
Fig. 3 is a cross-sectional view in enlarged Eorm taXen along the lines of 3-3 of Fig. 2 and showing the expanding bluff body and driving element associated therewith;
Fig. 4 is an enlarged, plan cros~-sectional view along the lines of 4-4 of th~ expandable bluff body;
~ ig. 5 is a view similar to Fig. 4 but showing the bluff body in a more expanded state;
~aS_ Fig. 6 is a cross-sectional elevational view of another form ~f the invention;
Fig. 7 is an enlarged view of a portion of the bluff body of Fig. 6 with portions broken away -to reveal internal detail~ o~ constructionl Fig. 8 is a cross-sectional view o the bluEf body of Fig. 6 tak~n along lines 8-8 of Fig. 6;
Fig. 9 is a partial cross-sectional-.elevational view o~ another modif~ed form of the invention; and Fig. 10 is a partial cr~ss-sectional view of yet another form o th~ invention.
DETAILEI) DESC~IPTIO~ OF TEIE PRE~ERRED EMBODIMENTS
Re~erring now more particularly to the Figs. 1-5 of the drawings, there is illustrated a mass flow sensor as con~
templated by the present invention generally denoted by the ~umeral 20. The sensor includes a housing 22 which may be com prised of several different components as illustrated in Fig. 2, which housing defines an internal conduit opening 24 therewithin having appropriate fittings 25 at opposite ends connactable with an existing mass flow transmitting conduit. The ¢onduit 24 has a reduce diameter, rectangular cr~ss-sectional æection 26.
Disposed within section 26 is a bluff body 28 having a pair of spaced sidewalls 30, 32 de~ining a distance d there~
between in a direction substantially perpendicular to the direc-tion of fluid flow through section 26~ The bluff body 28 coop-erates with section 26 to define a fluid flow transmitting area A between the sidewalls 30, 32 and the periphery o~ the section 26. Pxeferably, the bluff body i~ arranged such that the width of section 26 in the direction of the distance d, is at least three times the length o~ distance d, At the rearward end of bluff body 28 relative to th~ direction of mass flow, the bluEf body includes a pair of vertical sensor tubes 34 inter-secured such as by weld joint 38. Each of the walls 30, 32 are attachad to the associated sensor tubes 36 in cantilever arrangement.
The sensor tubes 34 have openings 36 therein for receiving vorticas shed from the bluf~ body, and as illustratad in Fig. 2 the sensor tubes 36 extend downwardly through housing 22 to a transducer arrangement which may include a ~luidic stack 40 that is operable ~o amplify the pxessure fluctuations sensed by tubes 34. The sensed pre sure fluctuations are trans-mitted through a passage 42 to a piezo ceramic transducex 44 that is operable to generate an electrical voltage o-ltput whose frequency is responsive to the frequ~ncy o the pressure fluc-tuations sensed by tubes 34. Through an appropriate electrical outlet 46 the sensed electrical ~requency signal may be trans-mitt~d to a desired readout, control, or other utilization device. The fluidic stack 40 and piezo ceramic transducer 44 are shown only in outline form, it being understood that such transducers are generally widely available and are known to those skilled in the art.
The invention further contemplates movable means in the form of a density compensatox element which includes a bellow~ 50 di~posed within a chamber ~8 of housing 22~ The flexible walls of bellows 50 coopera~e with end plates 54, 56 thereof to define an enclosed interior 58 of the -b~llows. If desired, a spring or other biasing mechanism 62 may also be incorporatPd within the bellows. Upper plate 54 rests again~t or is secured to a stop 60 which is adjustable by rotation of an adjusting nut 61 disposed eæteriorly of the housing 22~
7~3 Secured to lower plate 56 are a pair of parallel compensating struts 68 and 70 which extend downwardly between s.idewalls 30, 32 of bluff body 28. The low0r ends of struts 68 and 70 are held rigidly by housing 22. Accordingly, in response to expan-sion and contraction of bellows 5U, the c~mpensator struts 70 and 68 shift vertically as illus~rated in Fig. 3 so that their central bowed portions between walls 30, 32 will shift in a aorresponding hori~ontal directi~n and thereby expand and con-tract the cantilevered sidewalls 30, 32 to alter the character-istic dimension d of the bluff body. The interior 58 of bellows50 is sealed and filled with fluid hav.ing the same temperature and pressure characteristic~ of the fluid flow in conduit 24.
Chamber 48 ommunicates with mass fluid flow in conduit 24 via a port 64 and a passageway 66 i.n the housing.
In operation, mass fluid flow passes through conduit 24 and the section 26 in a left to right direction as viewed in Fig. 2. Within the desired opexating range of the mass flow sensor, section 26 is sized such that the ~eynold'~ number re-mains above 600. In flowing past bluff body 28, Karmann vortex sheets shed off of the bluff body, and the pressure fluctuations created by the periodically shedding vortices are sensed through openings 36 in sensor tubes 34. These pressure Eluctuations are then amplified by fluidic amplifier 40, and transmitted to drive the pieZG ceramic transducer 44. The pressure fluctuations acting upon the piezo ceramic transducer generate a voltage a~ss the piezo ceramic transducer so that an electric~ output signal rom connection 46 is cxeated who~e frequency is indica-tîve of the frequency of vortices shed by bluff body 28~
Bellows 50 compensates for changes in density of the mass ~low by correspondingly contracting and expanding to respectively drive the sidewalls 30, 32 toward and away from one another to ther~by ch~nge the characteristic dimension d of the blu.EE body 28. In this manner the frequency of the periodic vortices is varied ln response to changes in d~nsity such that the sensed frequency of the vortices is indicative of tha mass flow itsel~ through section 26. For instance, as-suming the mass- fluid flow through conduit 2~ to be a substan-tially incompressible liquid mass ~low, th~ density of such liquid flow is responsive substan~ially only to changes in tem-pe.rature of thi.s liquid. Upon an increase of temperature of a mass flow, which accordingly red~uces density of the liquid, in~reased temperature in chamber 48 causes expansion of liquid trapped within interior 58 of the bellows causing the bellows to expand. This causes the bowed sections o:f the s-truts 68t 70 to expand and move the sidewalls 30~ 32 farther away from one another toward a configuration as illustrated in Fig. 5, In this manner a decrease in density of the liquid flow increases the characteristic dimension d such that the Erequency of the shed periodic vortices i.s indicative of the mass fluid flow.
If the conduit 24 is carrying a relatively compres-sible gaseous fluid flow, the density of this gas flow is a function of both changes in pressure and temperature. A trapped volume of gas having temperature and pressure characteri~tics like that of the gas flow in conduit 24, and preferably tha same yas as in conduit 24, is then contained in the interior of sealed bellows 50~ The trapped volum0 of gas in int~rior 58 of the bellows causes expansion and contraction of the bellows both in response to changes in pressure of the gas flow as well as change~ in temperature of the gas delivered through passage-way 66 to chamber 48~ Temperature increase in chamber 48 causes ~$~
expansion oE the bellows to increase d in respo~se to the reduction in density, and pressure incxease in chamber 4~
(indicative of increased density) causes contraction of the bellows to reduce dimension d. Thus, similarly to the discus-sion above with respect to a liquid Elow, the change in density of the gas flow causes a corresponding expansion or contraction of bellows 50 and resulting change in the characteristic dimen-sion d of ~he bluff body such that the frequency of the periodic vortices is indicative of the mass flow itself.
More specifically, the frequency of the peri~dic vor-tices being shed by the blu:EE body 28 is determined by the following equation:
t 1 ) where:
f is the vortex shedding frequency;
V is the stream flow velocity past the bluff body;
d is the characteristic dimension of the bluf body;
K is a constant related to the Strouhal number.
The stream ~elocity and the mass flow rate are defined by -~he following well known equations (constants be.ing delet d):
~2) V ~ ~ , (31 m = pQ , where-Q is th~ volumetric flow rate of the fluid;
A is the duct cross-sectional area;
m is the mass flow rate;
p is the fluid density.
Straight~orward substitution oE the second equation into the first equation provides the following relat.ionship:
(4) f = KQ
g ~
Accordingly it is seen that the frequency of the periodic vor-tices is an inverse function of the product quanti ty A x d .
The pxesent invention includes th~ compensator in the form of bellows 50 in order to vary the quantity product A x d in inverse proportional proport.ion to the fluid density p:
(5~ Ad By then substituting equation 5 into equation 4, the following res~lts (6) f ~ XpQ .
By comparing equations 3 and 6 it is seen that:
(7) f = Km .
Thus, the frequency of the periodic vortices devel-oped in the present invention is indicative of the mass flow rateO It will be noted by reference to Figs. 3 and 4 that upon change o~ the characteristic dimension d by expansion and con-traction of the walls 30 and 32, a slight change in area A also results. Accordingly, the bellows 50 and associated actuating structure is arranged such that the product quantity A x d changes in inverse proportion to the density p. By arranging the bluEf body 28 relative to section 26 in an appropriate manner, such as by assuxing that the width of the section ~6 in the direction of dimension d is approximately three times the length of dimension d, the percentage change of area A as a result of change in characteristic dimension d, is relatively small in comparison to the percentage change of dimension d it-self. In this manner, for instance, the density compensator is arranged such that the characteristic dimension d is changed at a rate slightly greater than being simply inver~ely propor-tional to the change in density, in order to compensate for the ~mall decrease in area A, all such that the resulting relation-ship is that the produc~ quantity A x d is inversely propor-tional to the change in density.
Figs. 6-8 illustrate an alternate embodiment oE the present inventlon wherein only the cross-~ectional area A is varied in order to provide density compensation. More parti-cularly this arrangement includes a housing 80 defininy an in-terior conduit opening 82 carrying the mass fluid ~low, and a cylindrical bluff body 84 disposad within conduit 82 such tha t the characteristic dimension d of bluff body 84 is in a vertical direction as illustrated in Fig. 6~ A density compensating bellows 86 is included which along with rigid end walls 88 and 90 define an enclosed, trapped volume which contains fluid having like pressure and temperature characteristics as the ~luid in conduit 82. Surrounding the bellows is a chamber 93 which communicates with the mass flow in conduit 82 via passage~
way 32. Associated with bluff body 84 is a piston-~ype arrange-ment presenting a barrier element 94. The integral bluff body 84 and barrier 94 are movably mounted in housing 80 and inter-connected with end wall 88 to b~ responsive to changes in mass 10w density.
More particularly a change in the mass flow density causes contraction or expansion of bellows 86 in the same manner as bellows 50 of the,Fig. 1 arrangement. In response to move-ment of the bellows, the barrier 94 shift to adju t the cross-sec~ional area A of the conduit which is carrying the mass flow past the bluff body 8~. Barrier 94 is appropriately shaped so that the cross-sectional area A changes in inverse proportion to chan~es in density of the mass ~low. The characteristic dimension d of the bluff body remains unchanged, and therefore the product quantity A x d is varied in inverse proportion to the density of the mass flow. As a result the frequency of the shed periodic vortices whose pressure fluctuations are sensed by openings 98 on the downstream side of the bluff body and transmitted through sensing tubes 96 to an appropriate trans-ducer, are propoxtional to mass flow.
Fig. 9 ilLustrates another alternate for~ of density compensator in combination with a bluEf body substantially simi-lar to that illustrated in Fig. 1. The Fig. 9 arrangement in-cludes a housing 100 defining an internal, rectangular, mass flow carrying conduit 102, and a bluff body generally similar to configura~ion to that illustrated in Fig. 1 is disposed in conduit 102. ~ore specifically, the bluff body has spaced sidewalls 106 defining the characteristic dimension d thexe-between along with bowing compensator struts 104 therebetween having one or both opposite ends thereof affixed to the housing 100 .
In contrast to the compensator-type bellows of the Fig. 1 arrangementt the Fig. 9 structure includes compensator struts 104 which are composed of a bimetallic, thermally res-ponsive material. The compensator struts are responsive tochanges in temperature of the fluid in conduit 102, r~spectively bow.ing .inwardly and outwardly in response to decrease and in-cxease of temperatu.re of mass flow. Again, the compensator arrangement is such that the product quan~ity A x d is varied in inverse proportion to the changes in density such that the shedding frequency from the bluff body is indicative of the mass flow rate through the conduit. The Fig. 9 arrangement is parti-cularly useful in sen~ing the mass flow rate of a substantially incompressible l.iquid whose density changes substantially only in response to changes in temperature of the liquid.
~L~7~
Fig. 10 illustrates a further arrangement contem-plated by the present invention which includes a housing 110 defining an internal conduit 112 carrying the ma~s fluid flow, with a bluEf body 114 extending across the conduit 112. Parti-cularly for applications wherein the bluff body may be substan~
tially smaller than the size of the flow carrying conduit, the Fig. 10 arrangement is useful in that bluff body 114 has only a portion 116 thereof which changes in size in ~elation to changes in density o the mass flow. To prevent interference by end effects from the bluff body itself upon the frequency of the vortices, the length of the expandable section 116 in a horizontal direction as illustrated in ~ig. 10, it is prefer-ably approximately at least six times the diameter of the sen-sing opening 118. The Fig. 10 arrangement is constructed in order to operate along the principles discussed previously.
From the Fig. 10 arrangement it will be apparent therefore that the entire length of the bluff body need not be expandable, but rather only a sufficient portion thereof to avoid end effects.
It will be apparent that the present invention pro-vides an improved method of sensing mass flow which includesstep of producing periodic vortices in the mass flow that are at a frequency which is indicative of the mass flow, along with the step of sensing the frequency of the~e periodic vortices.
Den~ity compensation is a part of the step of producing the desired periodic vortices, and may be accomplished by emplacing a bluff body in the mass flow and then varying the characteris~
tic dimension d of the bluEf body in relation to the density of the mass flow. Alternately, density compensation is accom-lished by varying the cross-sectional flow area A in relation to the density of the mass flow.
Various alterations and modifications to the fore-going will be apparent to those skilled in the art. Accordingly, the foregoing detailed description of preferred arrangements of the present invention should be considered exemplary in nature and not as limiting to the scope and spixit of the invention as set forth in the appended claims.
Claims (36)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A mass flow sensor comprising:
a conduit for carrying mass fluid flow to be sensed;
a bluff body disposed in said conduit for producing periodic vortices, said body and conduit defining a flow cross-sectional area A therebetween, said body having a characteristic dimension d in a direction substantially perpendicular to the direction of mass flow through the conduit whereby the frequency of said vortices is a function of the product A x d;
means for adjusting the product A x d in relation to the density of said mass flow whereby said frequency is indicative of said mass flow; and means for sensing said frequency.
a conduit for carrying mass fluid flow to be sensed;
a bluff body disposed in said conduit for producing periodic vortices, said body and conduit defining a flow cross-sectional area A therebetween, said body having a characteristic dimension d in a direction substantially perpendicular to the direction of mass flow through the conduit whereby the frequency of said vortices is a function of the product A x d;
means for adjusting the product A x d in relation to the density of said mass flow whereby said frequency is indicative of said mass flow; and means for sensing said frequency.
2. A mass flow sensor as set forth in Claim 1, wherein said adjusting means includes means for varying said characteristic dimension d.
3. A mass flow sensor as set forth in Claim 1, wherein said adjusting means includes means for varying said cross-sectional area A.
4. A mass flow sensor as set forth in Claim 3, wherein said means for varying said cross-sectional area A is operable to vary said cross-sectional area A in substantially inverse proportion to changes in said density of the mass flow.
5. A mass flow sensor as set forth in Claim 1, wherein said adjusting means includes movable means operably exposed to said mass flow and movable in relation to changes in said density thereof.
6. A mass flow sensor as set forth in Claim 5, wherein said movable means includes an element movable in relation to changes in temperature of said mass flow.
7. A mass flow sensor as set forth in Claim 6, wherein said element includes a bimetallic element exposed to said mass flow and movable in response to said changes in temperature.
8. A mass flow sensor as set forth in Claim 5, wherein said movable means includes an element movable in relation to changes in temperature and pressure of said mass flow.
9. A mass flow sensor as set forth in Claim 8, wherein said element includes a hollowed bellows disposed in a surrounding chamber communicating with said mass flow, whereby said bellows expands and contracts in response to changes in said density of the mass flow.
10. A mass flow sensor as set forth in Claim 9, wherein said adjusting means includes flexible expansion means responsive to expansion and contraction of said bellows, said bluff body having a pair of spaced walls defining said characteristic dimension d therebetween, said expansion means operably accociated with said spaced walls to vary the spacing therebetween in response to movement of said bellows.
11. A mass flow sensor as set forth in Claim 10, wherein said spaced walls are interconnected at first ends thereof in cantilever arrangement.
12. A mass flow sensor as set forth in Claim 11, wherein said sensing means includes a sensing tube at said first ends interconnecting said spaced walls, said sensing tube having an opening therein exposed to mass flow downstream of said bluff body for receiving said periodic vortices.
13. A mass flow sensor as set forth in Claim 9, wherein said adjusting means includes a piston driven by said bellows, and a barrier carried by said piston movable across said conduit for varying said cross-sectional area A in substantially inverse proportion to changes in said density.
14. A mass flow sensor as set forth in Claim 1, wherein said sensing means includes at least one sensing tube having an opening therein exposed to said mass fluid flow downstream of said bluff body for receiving said periodic vortices in a manner generating a pressure signal in said tube fluctuating in response to said frequency of the periodic vortices.
15. A mass flow sensor as set forth in Claim 14, wherein at least a portion of said bluff body has said characteristic dimension d, the length of said portion being at least approximately six times the diameter of said opening.
16. A mass flow sensor as set forth in Claim 14, wherein said sensing means further includes a piezo-ceramic transducer responsive to said fluctuating pressure signal to produce an electrical output signal having a frequency indicative of said mass flow rate.
17. A mass flow sensor as set forth in Claim 16, wherein said sensing means further includes fluidic amplifier means between said sensing tube and said transducer for amplifying the magnitude of said fluctuating pressure signal.
18. In combination:
a conduit for carrying mass fluid flow;
a bluff body disposed in said conduit to define a flow area A between said body and said conduit, said body having a characteristic dimension d in a direction substantially perpendicular to the direction of mass fluid flow through said conduit; and means for adjusting the value of the product quantity A x d in relation to the density of said mass fluid flow.
a conduit for carrying mass fluid flow;
a bluff body disposed in said conduit to define a flow area A between said body and said conduit, said body having a characteristic dimension d in a direction substantially perpendicular to the direction of mass fluid flow through said conduit; and means for adjusting the value of the product quantity A x d in relation to the density of said mass fluid flow.
19. A combination as set forth in Claim 18, wherein said adjusting means includes means for varying said characteristic dimension d.
20. A combination as set forth in Claim 18, wherein said adjusting means includes means for varying said cross-sectional area A.
21. In a mass flow sensor including a conduit for carrying mass fluid flow to be sensed, and means disposed in said conduit for producing periodic vortices, wherein the improvement comprises:
means for altering the frequency of said periodic vortices in relation to the density of said mass fluid flow.
means for altering the frequency of said periodic vortices in relation to the density of said mass fluid flow.
22. In combination with a conduit for carrying a variable density mass fluid flow, a mass flow sensor comprising:
means operably associated with said conduit and responsive to the density of said mass fluid flow for producing periodic vortices in said mass fluid flow whose frequency is indicative of said mass fluid flow regardless of variations in said density; and means for sensing said frequency of the periodic vortices.
means operably associated with said conduit and responsive to the density of said mass fluid flow for producing periodic vortices in said mass fluid flow whose frequency is indicative of said mass fluid flow regardless of variations in said density; and means for sensing said frequency of the periodic vortices.
23. A device for sensing the mass flow of a fluid varying in density comprising:
means for producing periodic vortices in the mass flow at a frequency indicative of said mass flow regardless of variations in said density; and means for sensing said frequency of the periodic vortices.
means for producing periodic vortices in the mass flow at a frequency indicative of said mass flow regardless of variations in said density; and means for sensing said frequency of the periodic vortices.
24. A method of sensing mass flow comprising the steps of:
allowing the density of the mass flow to vary;
producing periodic vortices in the mass flow at a frequency indicative of the mass flow regardless of variations in the density thereof; and sensing the frequency of the periodic vortices.
allowing the density of the mass flow to vary;
producing periodic vortices in the mass flow at a frequency indicative of the mass flow regardless of variations in the density thereof; and sensing the frequency of the periodic vortices.
25. A method of sensing mass flow comprising the steps of:
producing periodic vortices in the mass flow at a frequency indicative of the mass flow; and sensing the frequency of the periodic vortices, said producing step including emplacing in said mass flow a bluff body having a characteristic dimension d in a direction substantially perpendicular to the direction of mass flow, and varying said characteristic dimension d in relation to the density of said mass flow.
producing periodic vortices in the mass flow at a frequency indicative of the mass flow; and sensing the frequency of the periodic vortices, said producing step including emplacing in said mass flow a bluff body having a characteristic dimension d in a direction substantially perpendicular to the direction of mass flow, and varying said characteristic dimension d in relation to the density of said mass flow.
26. A method of sensing mass flow comprising the steps of:
producing periodic vortices in the mass flow at a frequency indicative of the mass flow; and sensing the frequency of the periodic vortices, said producing step including emplacing a bluff body in a conduit carrying said mass flow to define a cross-sectional flow area A between said conduit and said body, and varying said cross-sectional flow area A in relation to the density of said mass flow.
producing periodic vortices in the mass flow at a frequency indicative of the mass flow; and sensing the frequency of the periodic vortices, said producing step including emplacing a bluff body in a conduit carrying said mass flow to define a cross-sectional flow area A between said conduit and said body, and varying said cross-sectional flow area A in relation to the density of said mass flow.
27. A method of sensing mass flow, comprising the steps of:
producing periodic vortices in the mass flow;
sensing density of the mass flow; and altering the frequency of the periodic vortices in relation to the sensed density.
producing periodic vortices in the mass flow;
sensing density of the mass flow; and altering the frequency of the periodic vortices in relation to the sensed density.
28. A mass flow sensor comprising:
means for producing periodic vortices in the mass flow; and means for altering the frequency of said periodic vortices in relation to the density of said mass flow.
means for producing periodic vortices in the mass flow; and means for altering the frequency of said periodic vortices in relation to the density of said mass flow.
29. In combination:
a conduit for carrying mass fluid flow;
means for sensing a preselected parameter of said mass fluid flow;
a bluff body disposed in said conduit to define a flow area A between said body and said conduit, said body having a characteristic dimension d in a direction substantially perpendicular to the direction of mass fluid flow through said conduit; and means for adjusting the value of the product quantity A x d in relation to variations in said sensed parameter.
a conduit for carrying mass fluid flow;
means for sensing a preselected parameter of said mass fluid flow;
a bluff body disposed in said conduit to define a flow area A between said body and said conduit, said body having a characteristic dimension d in a direction substantially perpendicular to the direction of mass fluid flow through said conduit; and means for adjusting the value of the product quantity A x d in relation to variations in said sensed parameter.
30. A mass flow sensor as set forth in Claim 9, wherein said hollowed bellows is sealed and filled with a fluid having temperature characteristics like the fluid of said mass flow.
31. A mass flow sensor as set forth in Claim 30, wherein said hollowed bellows is filled with said fluid of the mass flow.
32, A mass flow sensor as set forth in Claim 1, wherein said adjusting means is operable to vary said product A x d in substantially inverse proportion to changes in said density of the mass flow.
33. A mass flow sensor as set forth in Claim 2, wherein said means for varying said characteristic dimension d is operable to vary said characteristic dimension d whereby said product A x d varies in substantially inverse proportion to changes in said density of the mass flow.
34. A combination as set forth in Claim 18, wherein said adjusting means is operable to vary said product A x d in substantially inverse proportion to changes in said density of the mass flow.
35. A method as set forth in Claim 25, wherein said bluff body is emplaced in a conduit carrying said mass flow to define a cross-sectional flow area A between said conduit and said body, said varying step operable to vary the product quantity A x d in inverse relation to said density of the mass flow.
36. A method as set forth in Claim 26, wherein said cross-sectional flow area A is varied inversely to the density of said mass flow.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US860,549 | 1977-12-14 | ||
| US05/860,549 US4116060A (en) | 1976-12-02 | 1977-12-14 | Mass flow sensor and method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1097943A true CA1097943A (en) | 1981-03-24 |
Family
ID=25333479
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA311,321A Expired CA1097943A (en) | 1977-12-14 | 1978-09-14 | Mass flow sensor and method |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5491367A (en) |
| CA (1) | CA1097943A (en) |
| FR (1) | FR2412059A2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3480566A1 (en) * | 2017-11-07 | 2019-05-08 | Bosch Termoteknik Isitma ve Klima Sanayi Ticaret Anonim Sirketi | A flow heater with flow meter |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3965730A (en) * | 1975-04-28 | 1976-06-29 | Ford Motor Company | Vortex shedding device for use in measuring air flow rate into an internal combustion engine |
| SE7713507L (en) * | 1976-12-02 | 1978-06-03 | Garrett Corp | SET AND DEVICE FOR DETERMINING A MASS FLOW |
-
1978
- 1978-09-14 CA CA311,321A patent/CA1097943A/en not_active Expired
- 1978-09-21 FR FR7827049A patent/FR2412059A2/en active Granted
- 1978-09-25 JP JP11674278A patent/JPS5491367A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3480566A1 (en) * | 2017-11-07 | 2019-05-08 | Bosch Termoteknik Isitma ve Klima Sanayi Ticaret Anonim Sirketi | A flow heater with flow meter |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2412059B2 (en) | 1983-02-11 |
| FR2412059A2 (en) | 1979-07-13 |
| JPS5491367A (en) | 1979-07-19 |
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