CA2259930C - Fluid flow measurement correcting system, and methods of constructing and utilizing same - Google Patents
Fluid flow measurement correcting system, and methods of constructing and utilizing same Download PDFInfo
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- CA2259930C CA2259930C CA 2259930 CA2259930A CA2259930C CA 2259930 C CA2259930 C CA 2259930C CA 2259930 CA2259930 CA 2259930 CA 2259930 A CA2259930 A CA 2259930A CA 2259930 C CA2259930 C CA 2259930C
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- fluid
- recited
- drawdown
- correcting
- fluid level
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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
- G01F1/002—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow wherein the flow is in an open channel
-
- 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
- G01F1/34—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 measuring pressure or differential pressure
-
- 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
- G01F1/66—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 measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
- G01F1/663—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 measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters by measuring Doppler frequency shift
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/14—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of pressure
- G01F23/16—Indicating, recording, or alarm devices being actuated by mechanical or fluid means, e.g. using gas, mercury, or a diaphragm as transmitting element, or by a column of liquid
- G01F23/165—Indicating, recording, or alarm devices being actuated by mechanical or fluid means, e.g. using gas, mercury, or a diaphragm as transmitting element, or by a column of liquid of bubbler type
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S239/00—Fluid sprinkling, spraying, and diffusing
- Y10S239/03—Fluid amplifier
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T137/00—Fluid handling
- Y10T137/7287—Liquid level responsive or maintaining systems
Abstract
An apparatus (1) for calculating fluid flow in a channel, comprising a probe member (1) which detects fluid depth (L) in the channel; a mechanism (4) for measuring average fluid velocity in the channel; a mechanism for correcting the detected fluid depth based upon the measured average fluid velocity in order to account for drawdown;
and a mechanism (2) for calculating average flow rate based upon the average fluid velocity measurement and the corrected fluid depth value.
and a mechanism (2) for calculating average flow rate based upon the average fluid velocity measurement and the corrected fluid depth value.
Description
WO ~8Jû3~3~ PCT/US97/12372 FLUID FLOW MEASUREMENT CORRECrlNG SYSTEM. AND METHODS OF
CONSTRUCI~NG AND UTlLIZING SAME
~ Bac~yloulld of the Invention 1. Field of Invention The present invention relates to a system for measuring parameters relating to fluid flow in a channel, and in particular to a system which provides an accurate measurement of average fluid flow rate which takes into account the effect of drawdown.
Flow of material through a partially filled rh~nnel or pipe is expressed by the equation Q = A * V, where Q represents the rate of flowable material through the ~h~nnel; V represents the average velocity of material in the channel; and A represents the cross-sectional area of material in the ch~nnel, or wetted cross-sectional area. For a channel or pipe having a subst~nti~lly circular cross-section, the wetted cross-sectional area may be expressed as A = R2 * cos-l((R - L)/R)- (R - L) * (2 * R * L- L2~5, where R represents the actual channel or pipe radius and L represents the depth of the flowable m~teri~l in the ch~nn~l (FIG. 3). It is noted that similar equations exist for calc~ ting the wetted cross-sectional area of channels having different cross-sectional shapes. As a result, an accurate m~Cl~rement of the depth of flowable material in the h~nnel is çsse-nti~l in dete~ g flow through a partially filled ~nnel Pressure sensitive devices exist which, when placed in a fluid rh~nn~l, determine fluid depth by me~cnring the pressure exerted on the device due to the fluid overhead.
Once the fluid pressure is me~cllred, fluid depth L may be c~ te-l as L = 27.681 * P, where P represents the measured pressure acting on the probe, in psi.
Pressure sensitive devices which me~cllre fluid depth in a channel are often placed in a stilling well - a calm, isolated area which is ~dj~cçnt a stream of flowing fluid and WO ~)8~38.33 PCT/US97/12372 which has a fluid level which is substantially the sarne as the fluid level in the stream.
In some instances, howt;ver, the pl~s~ule se~ e devices are placed directly into the stream of flowing fluid, in which case their f~uid depth me~c~lrements are affected by a phenomenon known as drawdown.
Drawdown is caused by the presence of objects in the stream of fluid flow.
Specifically, drawdown is an effect that occurs in nonhydrostatic conditions in which the pressure exerted on the probe by the flowing ~uid is actually less than the ambient pressure in the stream due to the stream lines of flow being disturbed by the probe. If the presence of the probe causes any disturbance in the stream lines of flow (FIG. 4), drawdown will occur regardless of the stre~mlined nature of the probe. With the pressure sensitive probe measuring fluid pressure that is less than the actual ambient pressure in the stream of fluid, fluid depth in the channel is under-represented, thereby le~fling to an in~ccllrate flow rate computation. The present invention is directed at substantially eli,l-i"~t;llg the in~cc~racies associated with fluid depth measurements by taking into con~ideration the effects of drawdown.
CONSTRUCI~NG AND UTlLIZING SAME
~ Bac~yloulld of the Invention 1. Field of Invention The present invention relates to a system for measuring parameters relating to fluid flow in a channel, and in particular to a system which provides an accurate measurement of average fluid flow rate which takes into account the effect of drawdown.
Flow of material through a partially filled rh~nnel or pipe is expressed by the equation Q = A * V, where Q represents the rate of flowable material through the ~h~nnel; V represents the average velocity of material in the channel; and A represents the cross-sectional area of material in the ch~nnel, or wetted cross-sectional area. For a channel or pipe having a subst~nti~lly circular cross-section, the wetted cross-sectional area may be expressed as A = R2 * cos-l((R - L)/R)- (R - L) * (2 * R * L- L2~5, where R represents the actual channel or pipe radius and L represents the depth of the flowable m~teri~l in the ch~nn~l (FIG. 3). It is noted that similar equations exist for calc~ ting the wetted cross-sectional area of channels having different cross-sectional shapes. As a result, an accurate m~Cl~rement of the depth of flowable material in the h~nnel is çsse-nti~l in dete~ g flow through a partially filled ~nnel Pressure sensitive devices exist which, when placed in a fluid rh~nn~l, determine fluid depth by me~cnring the pressure exerted on the device due to the fluid overhead.
Once the fluid pressure is me~cllred, fluid depth L may be c~ te-l as L = 27.681 * P, where P represents the measured pressure acting on the probe, in psi.
Pressure sensitive devices which me~cllre fluid depth in a channel are often placed in a stilling well - a calm, isolated area which is ~dj~cçnt a stream of flowing fluid and WO ~)8~38.33 PCT/US97/12372 which has a fluid level which is substantially the sarne as the fluid level in the stream.
In some instances, howt;ver, the pl~s~ule se~ e devices are placed directly into the stream of flowing fluid, in which case their f~uid depth me~c~lrements are affected by a phenomenon known as drawdown.
Drawdown is caused by the presence of objects in the stream of fluid flow.
Specifically, drawdown is an effect that occurs in nonhydrostatic conditions in which the pressure exerted on the probe by the flowing ~uid is actually less than the ambient pressure in the stream due to the stream lines of flow being disturbed by the probe. If the presence of the probe causes any disturbance in the stream lines of flow (FIG. 4), drawdown will occur regardless of the stre~mlined nature of the probe. With the pressure sensitive probe measuring fluid pressure that is less than the actual ambient pressure in the stream of fluid, fluid depth in the channel is under-represented, thereby le~fling to an in~ccllrate flow rate computation. The present invention is directed at substantially eli,l-i"~t;llg the in~cc~racies associated with fluid depth measurements by taking into con~ideration the effects of drawdown.
2. Description of the Relevant Art There are known probes which measure fluid flow. For example, U.S. Patent 5,506,791 discloses a multi-functional device having a pressure sensitive probe for measuring fluid depth in a channel.
The above-identified reference, however, fails to disclose or otherwise suggest a system for measuring fluid velocity in a channel which takes into account the effects of drawdown.
S~mm~ry of the Invention lhe present invention ~velcol~les the above-discussed shortcoings of prior fluidflow measuring devices and s~ti~fies a significant need for accurately registering fluid level by con~ide.ring the effects of drawdown acting on pressure se~,siLive devices.
Accordillg to the invention, there is provided a fluid flow rate measurement system, comprising a submerged probe member having a means for deterllli~ ing ~uid .. . . .... .. . ... . .
CA 022~9930 1999-01-11 depth in a rh~nnel; a means for measuring average fluid velocity in the channel; a means for correcting the fluid depth dete-rmin~tion to account for drawdown conditions acting on the probe member; and a means for calculating average fluid flow rate based upon ~ the fluid depth correction and the average fluid velocity measurement.
In use, the probe member is first analyzed in order to determine and record the extent of drawdown acting thereon over a range of fluid velocities. Next, the probe member is placed within the fluid channel and connected to the fluid depth dete~ ~ing means. Thereafter, the probe member measures fluid pressure and tr~n~mit~ the measured ~res~ule data to the dete~ il~ing means for computing fluid depth. The fluid velocity measuring means tr~n~mit~ average fluid velocity m~Cllrements to the fluid depth correcting means so that it computes a fluid depth value which accoul~ls for drawdown. The flow rate calcl-l~ting means then computes average fluid flow rate based upon the average fluid velocity m~ rement and the corrected fluid depth value.
It is an object of the present invention to provide a system which accurately measures fluid flow rate in a channel.
Another object of the present invention in to provide such a system which considers the effect of drawdown in me~llring average fluid flow rate.
It is another object of the present invention to provide a system which providesaccurate fluid flow rate me~Cllrement~ in real time.
Other objects, advantages and salient~features of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the ~nn~Yed drawi~ , disclose preferred embo~limçnt~ of the present invention.
Brief Description of the Drawin~s F~G. 1 is a perspective view of a probe member of the present system.
FIG. 2 is a perspective view of another probe member of the present system.
FIG. 3 is a crossffectional view of a closed ~h~nnçl in which fluid flow is to be measured.
CA 022~9930 1999-01-11 FIG. 4 is a side elev~tion~l view of a dosed ch~nnel having there a preferred embodiment of the present invention.
FIG. S is a flowchart depicting the correcting means of a preferred embodiment of the present invention.
FIG. 6 is a graph showving the relationship bet~,-veen m~cllred average fluid velocity and fluid level error due to drawdown, for a probe member of the present system.
FIG. 7 is a block diagram showing components of some of the preferred embo~limentc of the present invention.
Detailed Description of the Preferred Embodiments Referring to FIGS. 1-7, there is shown a fluid flow rate me~ ring system accordhlg to the preferred embo-limerlt~ of the present invention, co~ lising a submerged probe member; a means for measuring average fluid velocity in a ~ h~nnel;
a means for dete~ ~ing fluid depth in the channel; a means for correcting the determined fluid depth based upon the average fluid velocity me~ elllent in order to account for drawdown; and a means for calc~ tin~ fluid flow rate based upon the average fluid velocity measurement and the corrected fluid depth.
Probe member 1 preferably comprises a pressure sensilive device, such as a bubbler-type probe (FIG. 2) in which the probe housing is isolated from the fluid flow and tubing is connected between the housing and the cll~nnel in which fluid flows for me~ ring fluid pressure there~olll; or a pressure transducer probe (FIG. 1) which is directly placed into the fluid stream. Alternatively, probe member 1 may suitably comprise other submerged measuring devices which measure fluid levels in a channel.
In a preferred embo-liment of the present invention, probe member 1 is sized and25 shaped in order to ,i,~i",i,e any disturbance in fluid flowing in the ch~nnel. As shown in FIGS. 1, 2 and 4, probe member 1 is preferably elongated having a curved end lA
which faces upstream when placed within the ch~nnel. Probe member 1 measures fluid ~ressure acting thereon and transmits the me~cllrement to the fluid depth determining WO 98~'03839 PCT/US97/12372 means. Wire end lB rYtçntl~ from probe member 1 in order to provide electrical col.~."~ ication to the deterrnining means.
The present invention preferably but not necessarily includes collll)ulillg means for performing arithmetic operations relating to calc~ sine fluid depth, average fluid S velocity, average flow rate and drawdown effects on fluid depth. As shown in FIG. 7, the COlll~u~illg means preferably but not necessarily comprises microprocessor 2 having, among other things, an arithmetic logic unit for pel Lorll~ing ~trithmetic and boolean logic operations; memory 3 for storing both data and program instructions, coll.~lising both random access memory (RAM) and read only memory (ROM); and interface and control10 cill;uiLly for suitably connecting microprocessor 2 to fluid level measuring devices, fluid velocity m~cllring devices, signal procec~ing circuitry, etc. Alternatively, the computing means of the present comprise other arithmetic processing devices.
The fluid depth detelll h~ g means receives electrical signals from probe member1 corresponding to the me~cllred fluid pressure in the channel, and calculates fluid depth 15 L using the equation identified above. In a preferred embodiment of the present invention, the fluid depth detell,,init-e means col,ll,-ises software stored in memory 3 which cooperates with microprocessor 2 in tr~nsl~tine measured fluid pressure to fluid depth, as shown in FIG. 7. The fluid depth dete~ ing means preferably calculates fluid depth in real time, but alternatively the fluid depth detel.nil~ g means stores the raw 20 fluid pressure measurements in memory 3 for processing at a later time.
According to a preferred embodiment of the present invention, the fluid velocitymeasuring means measures the average velocity of the fluid flowing in the channel. As shown in FIG. 7, the velocity me~Cl1ring means preferably but not nrces~ . ily colll~lises software stored in memory 3 which suitably cooperates with rnicroprocessor 2; and 25 sensing unit 4 which is suitably cormected to microprocessor 2.
Sensing unit 4 of the fluid velocity measuring means preferably but not necessarily conl~lises one or more piezoelectric tr~n~d~lcers which lrallsll,il and receive high frequency ~ign~lc, such as ultrasonic ~ign~l~; and signal proces~ing cil~uill~, operably .
.
CA 022~9930 1999-01-11 WO 98~ PCT/US97112372 associated with microprocessor 2, for controlling the tr~ncd-lcers and measuring the Doppler fre~uency shift between the l~ itted and received sign~lc, including amplifiers, mixing circuits, filters, and a spectrum analyzer. Microprocessor 2 and memory 3 preferably cooperate with the signal processing circuitry in recording and 5 calclll~ting the average fluid velocity in the channel. Alternatively, sensing unit 4 comprises circuitry which utilizes principles other than Doppler principles in me~cl~ring average fluid velocity. In a preferred embodiment of the present invention, the fluid velocity me~cllring means me~cllres average fluid velocity subst~n~i~lly in real time.
The flow rate calc~ ting means preferably computes average flow rate in the 10 charmel according to the equation:
Average Flow Rate = Average Velocity x A
where A is the wetted cross-sectional area which is dependent upon fluid depth and channel geometry information as described above. In a prefe,led embodiment of the present invention, the flow rate calc~llating incl~le~ software stored in memory 3 which 15 utilizes microprocessor 2, memory 3 and associated control and interface circuitry in calc~ ting average flow rate. In a preferred embodiment of the present invention, the flow rate c~ ting means computes average flow rate in real time.
According to the preferred embodiments of the present invention, the flow rate measuring system includes a means for correcting m.o~cllred fluid depth in order to 20 account for the drawdown effect. The correcting means preferably but not necessarily comprises a correcting factor which adjusts or offsets the raw fluid depth measurement so as to account for drawdown.
Since the effect of drawdown on an object varies depending upon fluid velocity in the stream, the correcting means in a preferred embodiment of the present invention 25 adjusts the raw fluid depth m~cllrement as a function of the average fluid velocity measurement. Once corrected, the adjusted fluid depth value, together with the measured average fluid velocity value, is used to calculate flow rate in the channel, using the equation for average flow rate indicated above.
CA 022~9930 1999-01-11 In a preferred embo~lim~nt of the present invention, the correcting means adds a correction factor to offset the raw fluid depth me~cllrement The correcting means preferably but not necessarily comprises an equation that represents the drawdown effect for the particular probe member 1 that is used to measure fluid depth. The correcting means preferably colllplises system software which cooperates with rnicroprocessor 2, memory 3 and necessary control and/or interface ch-;ui~ so that the drawdown correction equation is accessed from memory 3, the fluid depth offset value is calc~ te~l based upon the me~cllred average fluid velocity value, and the offset fluid depth value is thereafter added to the raw fluid depth value. The correcting means preferably but not necessarily adjusts the raw fluid depth value subst~nti~lly in real time.
In addition, the correcting means preferably but not necessarily in~lll(les system software and nececs~ry control circuitry to retrieve the raw fluid depth value from either memory 3 or the fluid depth detellllil~ing means and to check to see if the fluid velocity m~ llring means is connected into the system. If the fluid velocity m~ ring means in not conn~cted so that an average fluid velocity measurement is unavailable, then the correcting means does not calculate or apply an offset fluid depth value in order for the flow rate calclll~ting means to calculate average flow rate. A flowchart representing the operation of the correcting means is shown in FIG. S.
The fluid depth offset equation representing the drawdown effect is preferably but not necessarily derived from an analysis of the particular probe member 1 used in the system. The particular probe member 1 is analyzed at a plurality of fluid velocities so that an accurate drawdown profile for the probe member is obtained. The test results are then curve fitted, such as by using a least squares a~l~roxi~ tion~ in order to derive a drawdown equation from the test data points. In one preferred embodiment of the present invention, the offset fluid depth equation is a second order equation. A graph showing the fluid depth offset cune as a function of fluid velocity for a probe member 1 is shown in FIG. 6.
In an alternative embodiment, the fluid depth offset values are stored directly in CA 022~9930 1999-01-11 WO ~ .3&39 PCT/US97/12372 memory 3 rather than an equation being derived therefrom and stored in memory 3 instead. In this way, the measured average velocity value is used as the address polnter for the al,prol)liate fluid depth offset value when the correcting means adjusts the measured fluid depth value.
S Inst~ tion and operation of the system is as follows. First, probe member 1 is placed into position in the t~h~nnel, Next, probe member 1 is connected to microprocessor 2 and/ormemory 3 via interface I h ~ y in order to co. ~ icate with the fluid depth dete~ i,.illg software. Sensing unit 4 of the fluid velocity measuring means is inserted into the channel and is connected to microprocessor 2 and/ormemory 3 via interface circuitry so that it can cnl"",--l-icate with the fluid level correcting means software and the flow rate calclll~ting means software.
Once the system is installed, probe member 1 m~cllres fluid pressure acting thereon and transmits the me~cllred data to microprocessor 2 and/ormemory 3; and the fluid depth dete~ g sof~w~re computes fluid depth, based upon this data.
Concurrently, sensing unit 4 me~c~lres average fluid velocity and llallsll~ils the mea ured data to microprocessor 2 and/ormemory 3. Thereafter, the flow rate correcting software computes the fluid level offset value based upon the average fluid velocity m~cllrement and adjusts the fluid depth measurement accordingly. Next, the flow rate calc~ ting soLlware computes average flow rate in the channel based upon the average fluid velocity me~cllrement and the adjusted fluid depth value.
Prior to being used in the system, probe member 1 is initially analyzed by measuring for drawdown at a plurality of different velocities and by deriving a formula representing the relationship between fluid level error due to drawdown and fluid velocity.
2~ Although there have been described what are ~;ullelllly considered to be the preferred embo(limeTItc of the present invention, it will be understood that the invention can be embodied in other specific forms without departing from the spirit or es~çnti~l characteristics thereof.
WO 98/03839 PCTIUS971123~2 The described embotliment~ are, therefore, to be considered in all aspects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description.
The above-identified reference, however, fails to disclose or otherwise suggest a system for measuring fluid velocity in a channel which takes into account the effects of drawdown.
S~mm~ry of the Invention lhe present invention ~velcol~les the above-discussed shortcoings of prior fluidflow measuring devices and s~ti~fies a significant need for accurately registering fluid level by con~ide.ring the effects of drawdown acting on pressure se~,siLive devices.
Accordillg to the invention, there is provided a fluid flow rate measurement system, comprising a submerged probe member having a means for deterllli~ ing ~uid .. . . .... .. . ... . .
CA 022~9930 1999-01-11 depth in a rh~nnel; a means for measuring average fluid velocity in the channel; a means for correcting the fluid depth dete-rmin~tion to account for drawdown conditions acting on the probe member; and a means for calculating average fluid flow rate based upon ~ the fluid depth correction and the average fluid velocity measurement.
In use, the probe member is first analyzed in order to determine and record the extent of drawdown acting thereon over a range of fluid velocities. Next, the probe member is placed within the fluid channel and connected to the fluid depth dete~ ~ing means. Thereafter, the probe member measures fluid pressure and tr~n~mit~ the measured ~res~ule data to the dete~ il~ing means for computing fluid depth. The fluid velocity measuring means tr~n~mit~ average fluid velocity m~Cllrements to the fluid depth correcting means so that it computes a fluid depth value which accoul~ls for drawdown. The flow rate calcl-l~ting means then computes average fluid flow rate based upon the average fluid velocity m~ rement and the corrected fluid depth value.
It is an object of the present invention to provide a system which accurately measures fluid flow rate in a channel.
Another object of the present invention in to provide such a system which considers the effect of drawdown in me~llring average fluid flow rate.
It is another object of the present invention to provide a system which providesaccurate fluid flow rate me~Cllrement~ in real time.
Other objects, advantages and salient~features of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the ~nn~Yed drawi~ , disclose preferred embo~limçnt~ of the present invention.
Brief Description of the Drawin~s F~G. 1 is a perspective view of a probe member of the present system.
FIG. 2 is a perspective view of another probe member of the present system.
FIG. 3 is a crossffectional view of a closed ~h~nnçl in which fluid flow is to be measured.
CA 022~9930 1999-01-11 FIG. 4 is a side elev~tion~l view of a dosed ch~nnel having there a preferred embodiment of the present invention.
FIG. S is a flowchart depicting the correcting means of a preferred embodiment of the present invention.
FIG. 6 is a graph showving the relationship bet~,-veen m~cllred average fluid velocity and fluid level error due to drawdown, for a probe member of the present system.
FIG. 7 is a block diagram showing components of some of the preferred embo~limentc of the present invention.
Detailed Description of the Preferred Embodiments Referring to FIGS. 1-7, there is shown a fluid flow rate me~ ring system accordhlg to the preferred embo-limerlt~ of the present invention, co~ lising a submerged probe member; a means for measuring average fluid velocity in a ~ h~nnel;
a means for dete~ ~ing fluid depth in the channel; a means for correcting the determined fluid depth based upon the average fluid velocity me~ elllent in order to account for drawdown; and a means for calc~ tin~ fluid flow rate based upon the average fluid velocity measurement and the corrected fluid depth.
Probe member 1 preferably comprises a pressure sensilive device, such as a bubbler-type probe (FIG. 2) in which the probe housing is isolated from the fluid flow and tubing is connected between the housing and the cll~nnel in which fluid flows for me~ ring fluid pressure there~olll; or a pressure transducer probe (FIG. 1) which is directly placed into the fluid stream. Alternatively, probe member 1 may suitably comprise other submerged measuring devices which measure fluid levels in a channel.
In a preferred embo-liment of the present invention, probe member 1 is sized and25 shaped in order to ,i,~i",i,e any disturbance in fluid flowing in the ch~nnel. As shown in FIGS. 1, 2 and 4, probe member 1 is preferably elongated having a curved end lA
which faces upstream when placed within the ch~nnel. Probe member 1 measures fluid ~ressure acting thereon and transmits the me~cllrement to the fluid depth determining WO 98~'03839 PCT/US97/12372 means. Wire end lB rYtçntl~ from probe member 1 in order to provide electrical col.~."~ ication to the deterrnining means.
The present invention preferably but not necessarily includes collll)ulillg means for performing arithmetic operations relating to calc~ sine fluid depth, average fluid S velocity, average flow rate and drawdown effects on fluid depth. As shown in FIG. 7, the COlll~u~illg means preferably but not necessarily comprises microprocessor 2 having, among other things, an arithmetic logic unit for pel Lorll~ing ~trithmetic and boolean logic operations; memory 3 for storing both data and program instructions, coll.~lising both random access memory (RAM) and read only memory (ROM); and interface and control10 cill;uiLly for suitably connecting microprocessor 2 to fluid level measuring devices, fluid velocity m~cllring devices, signal procec~ing circuitry, etc. Alternatively, the computing means of the present comprise other arithmetic processing devices.
The fluid depth detelll h~ g means receives electrical signals from probe member1 corresponding to the me~cllred fluid pressure in the channel, and calculates fluid depth 15 L using the equation identified above. In a preferred embodiment of the present invention, the fluid depth detell,,init-e means col,ll,-ises software stored in memory 3 which cooperates with microprocessor 2 in tr~nsl~tine measured fluid pressure to fluid depth, as shown in FIG. 7. The fluid depth dete~ ing means preferably calculates fluid depth in real time, but alternatively the fluid depth detel.nil~ g means stores the raw 20 fluid pressure measurements in memory 3 for processing at a later time.
According to a preferred embodiment of the present invention, the fluid velocitymeasuring means measures the average velocity of the fluid flowing in the channel. As shown in FIG. 7, the velocity me~Cl1ring means preferably but not nrces~ . ily colll~lises software stored in memory 3 which suitably cooperates with rnicroprocessor 2; and 25 sensing unit 4 which is suitably cormected to microprocessor 2.
Sensing unit 4 of the fluid velocity measuring means preferably but not necessarily conl~lises one or more piezoelectric tr~n~d~lcers which lrallsll,il and receive high frequency ~ign~lc, such as ultrasonic ~ign~l~; and signal proces~ing cil~uill~, operably .
.
CA 022~9930 1999-01-11 WO 98~ PCT/US97112372 associated with microprocessor 2, for controlling the tr~ncd-lcers and measuring the Doppler fre~uency shift between the l~ itted and received sign~lc, including amplifiers, mixing circuits, filters, and a spectrum analyzer. Microprocessor 2 and memory 3 preferably cooperate with the signal processing circuitry in recording and 5 calclll~ting the average fluid velocity in the channel. Alternatively, sensing unit 4 comprises circuitry which utilizes principles other than Doppler principles in me~cl~ring average fluid velocity. In a preferred embodiment of the present invention, the fluid velocity me~cllring means me~cllres average fluid velocity subst~n~i~lly in real time.
The flow rate calc~ ting means preferably computes average flow rate in the 10 charmel according to the equation:
Average Flow Rate = Average Velocity x A
where A is the wetted cross-sectional area which is dependent upon fluid depth and channel geometry information as described above. In a prefe,led embodiment of the present invention, the flow rate calc~llating incl~le~ software stored in memory 3 which 15 utilizes microprocessor 2, memory 3 and associated control and interface circuitry in calc~ ting average flow rate. In a preferred embodiment of the present invention, the flow rate c~ ting means computes average flow rate in real time.
According to the preferred embodiments of the present invention, the flow rate measuring system includes a means for correcting m.o~cllred fluid depth in order to 20 account for the drawdown effect. The correcting means preferably but not necessarily comprises a correcting factor which adjusts or offsets the raw fluid depth measurement so as to account for drawdown.
Since the effect of drawdown on an object varies depending upon fluid velocity in the stream, the correcting means in a preferred embodiment of the present invention 25 adjusts the raw fluid depth m~cllrement as a function of the average fluid velocity measurement. Once corrected, the adjusted fluid depth value, together with the measured average fluid velocity value, is used to calculate flow rate in the channel, using the equation for average flow rate indicated above.
CA 022~9930 1999-01-11 In a preferred embo~lim~nt of the present invention, the correcting means adds a correction factor to offset the raw fluid depth me~cllrement The correcting means preferably but not necessarily comprises an equation that represents the drawdown effect for the particular probe member 1 that is used to measure fluid depth. The correcting means preferably colllplises system software which cooperates with rnicroprocessor 2, memory 3 and necessary control and/or interface ch-;ui~ so that the drawdown correction equation is accessed from memory 3, the fluid depth offset value is calc~ te~l based upon the me~cllred average fluid velocity value, and the offset fluid depth value is thereafter added to the raw fluid depth value. The correcting means preferably but not necessarily adjusts the raw fluid depth value subst~nti~lly in real time.
In addition, the correcting means preferably but not necessarily in~lll(les system software and nececs~ry control circuitry to retrieve the raw fluid depth value from either memory 3 or the fluid depth detellllil~ing means and to check to see if the fluid velocity m~ llring means is connected into the system. If the fluid velocity m~ ring means in not conn~cted so that an average fluid velocity measurement is unavailable, then the correcting means does not calculate or apply an offset fluid depth value in order for the flow rate calclll~ting means to calculate average flow rate. A flowchart representing the operation of the correcting means is shown in FIG. S.
The fluid depth offset equation representing the drawdown effect is preferably but not necessarily derived from an analysis of the particular probe member 1 used in the system. The particular probe member 1 is analyzed at a plurality of fluid velocities so that an accurate drawdown profile for the probe member is obtained. The test results are then curve fitted, such as by using a least squares a~l~roxi~ tion~ in order to derive a drawdown equation from the test data points. In one preferred embodiment of the present invention, the offset fluid depth equation is a second order equation. A graph showing the fluid depth offset cune as a function of fluid velocity for a probe member 1 is shown in FIG. 6.
In an alternative embodiment, the fluid depth offset values are stored directly in CA 022~9930 1999-01-11 WO ~ .3&39 PCT/US97/12372 memory 3 rather than an equation being derived therefrom and stored in memory 3 instead. In this way, the measured average velocity value is used as the address polnter for the al,prol)liate fluid depth offset value when the correcting means adjusts the measured fluid depth value.
S Inst~ tion and operation of the system is as follows. First, probe member 1 is placed into position in the t~h~nnel, Next, probe member 1 is connected to microprocessor 2 and/ormemory 3 via interface I h ~ y in order to co. ~ icate with the fluid depth dete~ i,.illg software. Sensing unit 4 of the fluid velocity measuring means is inserted into the channel and is connected to microprocessor 2 and/ormemory 3 via interface circuitry so that it can cnl"",--l-icate with the fluid level correcting means software and the flow rate calclll~ting means software.
Once the system is installed, probe member 1 m~cllres fluid pressure acting thereon and transmits the me~cllred data to microprocessor 2 and/ormemory 3; and the fluid depth dete~ g sof~w~re computes fluid depth, based upon this data.
Concurrently, sensing unit 4 me~c~lres average fluid velocity and llallsll~ils the mea ured data to microprocessor 2 and/ormemory 3. Thereafter, the flow rate correcting software computes the fluid level offset value based upon the average fluid velocity m~cllrement and adjusts the fluid depth measurement accordingly. Next, the flow rate calc~ ting soLlware computes average flow rate in the channel based upon the average fluid velocity me~cllrement and the adjusted fluid depth value.
Prior to being used in the system, probe member 1 is initially analyzed by measuring for drawdown at a plurality of different velocities and by deriving a formula representing the relationship between fluid level error due to drawdown and fluid velocity.
2~ Although there have been described what are ~;ullelllly considered to be the preferred embo(limeTItc of the present invention, it will be understood that the invention can be embodied in other specific forms without departing from the spirit or es~çnti~l characteristics thereof.
WO 98/03839 PCTIUS971123~2 The described embotliment~ are, therefore, to be considered in all aspects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description.
Claims
-1-A method for measuring fluid flow in a channel, comprising the steps of:
obtaining a probe;
obtaining a computing means having stored therein drawdown data for said probe;
placing said probe in a channel where fluid flow is to be measured;
determining fluid depth in said channel with said probe;
correcting said fluid depth determination based upon said drawdown data using said computing means; and calculating fluid flow rate based upon said corrected fluid depth determination using said computing means.
A method as recited in claim 1, including the steps of:
measuring drawdown effects for said probe at a plurality of fluid velocities; and storing said drawdown effect measurements for said probe in said computing means.
A method as recited in claim 2, wherein:
said drawdown storing step comprises the steps of curve fitting said drawdown measurements and storing an equation representing said curve fitted drawdown measurements in said computing means.
A method as recited in claim 3, including the steps of:
measuring average fluid velocity in the channel; and recording said fluid velocity measurements in said computing means.
A method as recited in claim 1, wherein:
said correcting step occurs in real time following said fluid depth determining step.
A method as recited in claim 3, wherein:
said curve fitting step utilizes a least squares approximation.
A method as recited in claim 4, wherein:
said drawdown equation provides fluid level error as a function of fluid velocity;
and said correcting step comprises the step of providing said fluid level error as an offset to said fluid depth determination.
A method as recited in claim 4, further including the step of:
verifying that said fluid velocity measurement and said fluid velocity recording step have been completed before executing said correcting step.
A method as recited in claim 4, wherein:
said fluid depth correcting step and said flow rate calculating step execute substantially in real time.
An apparatus for calculating fluid flow in a channel, comprising:
a probe member having means for detecting a fluid level in the channel;
means for measuring fluid velocity in the channel;
means for correcting said fluid level detection to account for drawdown conditions acting on said probe member; and means for calculating average fluid flow rate based upon said fluid velocity measurement and said corrected fluid level.
An apparatus as recited in claim 10, wherein:
said correcting means provides an offset fluid level value based upon said fluidvelocity measurement.
An apparatus as recited in claim 10, wherein:
said correcting means corrects said fluid level detection substantially in real time.
An apparatus as recited in claim 11, wherein:
said apparatus includes computing means and associated memory; and said correcting means comprises an equation stored in said memory, wherein said equation represents said offset fluid level value as a function of said fluid velocity as measured by said velocity measuring means.
An apparatus as recited in claim 11, wherein:
said apparatus includes computing means and associated memory;
said correcting means comprises a plurality of offset fluid level values being stored in said memory; and said fluid velocity measurement is used to point to one of said offset fluid level values in said memory for correction of said fluid level detection.
An apparatus as recited in claim 10, wherein:
said probe member comprises a pressure transducer.
A device for measuring fluid parameters in a channel, comprising:
means for measuring a fluid level in the channel;
memory means for storing drawdown data pertaining to said fluid level measuring means;
means for correcting said fluid level measurement based upon said drawdown data; and means for calculating fluid flow rate based upon said corrected fluid level measurement.
A device as recited in claim 16, wherein:
said memory means stores drawdown data pertaining to said fluid level measuring means at a plurality of fluid velocities.
A device as recited in claim 17, further including means for measuring fluid velocity in the channel; and wherein said correcting means corrects said measured fluid level based upon fluid velocity measured by said velocity measuring means.
A device as recited in claim 18, wherein:
said drawdown data comprises an equation for calculating a fluid level offset value based upon measured fluid velocity; and said fluid level offset value is added to said measured fluid level by said correcting means.
A device as recited in claim 16, wherein:
said correcting means and said flow rate calculating means occur substantially in real time following said fluid level measurement.
obtaining a probe;
obtaining a computing means having stored therein drawdown data for said probe;
placing said probe in a channel where fluid flow is to be measured;
determining fluid depth in said channel with said probe;
correcting said fluid depth determination based upon said drawdown data using said computing means; and calculating fluid flow rate based upon said corrected fluid depth determination using said computing means.
A method as recited in claim 1, including the steps of:
measuring drawdown effects for said probe at a plurality of fluid velocities; and storing said drawdown effect measurements for said probe in said computing means.
A method as recited in claim 2, wherein:
said drawdown storing step comprises the steps of curve fitting said drawdown measurements and storing an equation representing said curve fitted drawdown measurements in said computing means.
A method as recited in claim 3, including the steps of:
measuring average fluid velocity in the channel; and recording said fluid velocity measurements in said computing means.
A method as recited in claim 1, wherein:
said correcting step occurs in real time following said fluid depth determining step.
A method as recited in claim 3, wherein:
said curve fitting step utilizes a least squares approximation.
A method as recited in claim 4, wherein:
said drawdown equation provides fluid level error as a function of fluid velocity;
and said correcting step comprises the step of providing said fluid level error as an offset to said fluid depth determination.
A method as recited in claim 4, further including the step of:
verifying that said fluid velocity measurement and said fluid velocity recording step have been completed before executing said correcting step.
A method as recited in claim 4, wherein:
said fluid depth correcting step and said flow rate calculating step execute substantially in real time.
An apparatus for calculating fluid flow in a channel, comprising:
a probe member having means for detecting a fluid level in the channel;
means for measuring fluid velocity in the channel;
means for correcting said fluid level detection to account for drawdown conditions acting on said probe member; and means for calculating average fluid flow rate based upon said fluid velocity measurement and said corrected fluid level.
An apparatus as recited in claim 10, wherein:
said correcting means provides an offset fluid level value based upon said fluidvelocity measurement.
An apparatus as recited in claim 10, wherein:
said correcting means corrects said fluid level detection substantially in real time.
An apparatus as recited in claim 11, wherein:
said apparatus includes computing means and associated memory; and said correcting means comprises an equation stored in said memory, wherein said equation represents said offset fluid level value as a function of said fluid velocity as measured by said velocity measuring means.
An apparatus as recited in claim 11, wherein:
said apparatus includes computing means and associated memory;
said correcting means comprises a plurality of offset fluid level values being stored in said memory; and said fluid velocity measurement is used to point to one of said offset fluid level values in said memory for correction of said fluid level detection.
An apparatus as recited in claim 10, wherein:
said probe member comprises a pressure transducer.
A device for measuring fluid parameters in a channel, comprising:
means for measuring a fluid level in the channel;
memory means for storing drawdown data pertaining to said fluid level measuring means;
means for correcting said fluid level measurement based upon said drawdown data; and means for calculating fluid flow rate based upon said corrected fluid level measurement.
A device as recited in claim 16, wherein:
said memory means stores drawdown data pertaining to said fluid level measuring means at a plurality of fluid velocities.
A device as recited in claim 17, further including means for measuring fluid velocity in the channel; and wherein said correcting means corrects said measured fluid level based upon fluid velocity measured by said velocity measuring means.
A device as recited in claim 18, wherein:
said drawdown data comprises an equation for calculating a fluid level offset value based upon measured fluid velocity; and said fluid level offset value is added to said measured fluid level by said correcting means.
A device as recited in claim 16, wherein:
said correcting means and said flow rate calculating means occur substantially in real time following said fluid level measurement.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/685,502 US5691914A (en) | 1996-07-24 | 1996-07-24 | Fluid flow measurement correcting system, and methods of constructing and utilizing same |
| US08/685,502 | 1996-07-24 | ||
| PCT/US1997/012372 WO1998003839A1 (en) | 1996-07-24 | 1997-07-21 | Fluid flow measurement correcting system, and methods of constructing and utilizing same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2259930A1 CA2259930A1 (en) | 1998-01-29 |
| CA2259930C true CA2259930C (en) | 2001-11-06 |
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|---|---|---|---|
| CA 2259930 Expired - Fee Related CA2259930C (en) | 1996-07-24 | 1997-07-21 | Fluid flow measurement correcting system, and methods of constructing and utilizing same |
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| US (2) | US5691914A (en) |
| EP (1) | EP0914591A4 (en) |
| AU (1) | AU712632B2 (en) |
| CA (1) | CA2259930C (en) |
| WO (1) | WO1998003839A1 (en) |
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| US5691914A (en) * | 1996-07-24 | 1997-11-25 | American Sigma, Inc. | Fluid flow measurement correcting system, and methods of constructing and utilizing same |
| US6085588A (en) * | 1998-05-12 | 2000-07-11 | Therm-O-Disc, Incorporated | Flow rate sensor |
| US8958917B2 (en) | 1998-12-17 | 2015-02-17 | Hach Company | Method and system for remote monitoring of fluid quality and treatment |
| US7454295B2 (en) | 1998-12-17 | 2008-11-18 | The Watereye Corporation | Anti-terrorism water quality monitoring system |
| US9056783B2 (en) | 1998-12-17 | 2015-06-16 | Hach Company | System for monitoring discharges into a waste water collection system |
| US20100332149A1 (en) * | 1998-12-17 | 2010-12-30 | Hach Company | Method and system for remote monitoring of fluid quality and treatment |
| KR100326144B1 (en) * | 1999-02-09 | 2002-03-13 | 구자홍 | Method and apparatus for creating search information of recorded digital data streams and searching the recorded streams by using the search information |
| US8920619B2 (en) | 2003-03-19 | 2014-12-30 | Hach Company | Carbon nanotube sensor |
| US7286945B2 (en) * | 2003-11-19 | 2007-10-23 | Honeywell International Inc. | Apparatus and method for identifying possible defect indicators for a valve |
| US7274995B2 (en) * | 2003-11-19 | 2007-09-25 | Honeywell International Inc. | Apparatus and method for identifying possible defect indicators for a valve |
| US7419598B2 (en) * | 2005-03-08 | 2008-09-02 | Teledyne Isco, Inc. | Chromatographic solvent monitor |
| US7257501B2 (en) * | 2005-11-17 | 2007-08-14 | Honeywell International Inc. | Apparatus and method for identifying informative data in a process control environment |
| US7421374B2 (en) * | 2005-11-17 | 2008-09-02 | Honeywell International Inc. | Apparatus and method for analyzing model quality in a process control environment |
| US7532992B2 (en) * | 2006-01-20 | 2009-05-12 | Teledyne Isco, Inc. | Measuring apparatuses and methods of using them |
| US7721600B1 (en) | 2006-03-17 | 2010-05-25 | Eastech Flow Controls, Inc. | Flow measurement apparatus and method |
| US7894473B2 (en) * | 2006-04-12 | 2011-02-22 | Honeywell International Inc. | System and method for monitoring valve status and performance in a process control system |
| US9618037B2 (en) | 2008-08-01 | 2017-04-11 | Honeywell International Inc. | Apparatus and method for identifying health indicators for rolling element bearings |
| US8958995B2 (en) | 2009-04-02 | 2015-02-17 | Honeywell International Inc. | System and method for monitoring rotating and reciprocating machinery |
| US8620622B2 (en) * | 2009-04-02 | 2013-12-31 | Honeywell International Inc. | System and method for determining health indicators for impellers |
| US7945397B2 (en) * | 2009-04-02 | 2011-05-17 | Honeywell International Inc. | System and method for gearbox health monitoring |
| US8447533B1 (en) | 2009-10-13 | 2013-05-21 | Eastech Flow Controls, Inc. | Method of wastewater flow measurement, system analysis, and improvement |
| US8473252B2 (en) | 2010-06-09 | 2013-06-25 | Honeywell International Inc. | System and method for conflict resolution to support simultaneous monitoring of multiple subsystems |
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| US5691914A (en) * | 1996-07-24 | 1997-11-25 | American Sigma, Inc. | Fluid flow measurement correcting system, and methods of constructing and utilizing same |
-
1996
- 1996-07-24 US US08/685,502 patent/US5691914A/en not_active Expired - Lifetime
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1997
- 1997-07-21 WO PCT/US1997/012372 patent/WO1998003839A1/en active Application Filing
- 1997-07-21 EP EP97936077A patent/EP0914591A4/en not_active Withdrawn
- 1997-07-21 CA CA 2259930 patent/CA2259930C/en not_active Expired - Fee Related
- 1997-07-21 AU AU38834/97A patent/AU712632B2/en not_active Ceased
- 1997-11-19 US US08/974,027 patent/US6208943B1/en not_active Expired - Lifetime
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| AU3883497A (en) | 1998-02-10 |
| WO1998003839A1 (en) | 1998-01-29 |
| EP0914591A4 (en) | 2002-09-04 |
| CA2259930A1 (en) | 1998-01-29 |
| US5691914A (en) | 1997-11-25 |
| EP0914591A1 (en) | 1999-05-12 |
| US6208943B1 (en) | 2001-03-27 |
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