EP2583066A1 - Capteur d'écoulement - Google Patents

Capteur d'écoulement

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Publication number
EP2583066A1
EP2583066A1 EP20100853563 EP10853563A EP2583066A1 EP 2583066 A1 EP2583066 A1 EP 2583066A1 EP 20100853563 EP20100853563 EP 20100853563 EP 10853563 A EP10853563 A EP 10853563A EP 2583066 A1 EP2583066 A1 EP 2583066A1
Authority
EP
European Patent Office
Prior art keywords
sensor
flow
vibration
velocity
connecting element
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.)
Withdrawn
Application number
EP20100853563
Other languages
German (de)
English (en)
Other versions
EP2583066A4 (fr
Inventor
Sami Lakka
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
KYTOLA INSTRUMENTS Oy
Original Assignee
Lakka Sami
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Lakka Sami filed Critical Lakka Sami
Publication of EP2583066A1 publication Critical patent/EP2583066A1/fr
Publication of EP2583066A4 publication Critical patent/EP2583066A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/20—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow
    • G01F1/32—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow using swirl flowmeters
    • 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
    • G01F1/325—Means for detecting quantities used as proxy variables for swirl
    • G01F1/3259—Means for detecting quantities used as proxy variables for swirl for detecting fluid pressure oscillations
    • G01F1/3266—Means for detecting quantities used as proxy variables for swirl for detecting fluid pressure oscillations by sensing mechanical vibrations
    • 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
    • G01F1/325—Means for detecting quantities used as proxy variables for swirl
    • G01F1/3282—Means for detecting quantities used as proxy variables for swirl for detecting variations in infrasonic, sonic or ultrasonic waves, due to modulation by passing through the swirling fluid
    • 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
    • G01F1/325—Means for detecting quantities used as proxy variables for swirl
    • G01F1/3287—Means for detecting quantities used as proxy variables for swirl circuits therefor

Definitions

  • the present invention relates to monitoring fluid flows.
  • Water flows in water distribution systems are typically monitored by using turbine sensors, which comprise a rotating turbine and a bearing.
  • the bearing may comprise parts made of e.g. sapphire. Deposition of dirt on the blades of the turbine may cause substantial errors in the measurement. Manufacturing of the turbine and the bearing is not trivial.
  • the turbine is exposed to water. Consequently, impurities in the water may severely disturb operation of the turbine sensor. Freezing of the water may permanently damage a turbine sensor at temperatures below 0 °C. It is known to monitor flow velocity based on the frequency of vortices created after a stationary bluff body positioned in a flow. The frequency is measured by a sensitive pressure sensor. However, this kind of a sensor is typically not suitable for measuring very small flow rates.
  • An object of the present invention is to provide a flow sensor for monitoring velocity and/or flow rate of a fluid flow.
  • An object of the present invention is also to provide a method for monitoring velocity and/or flow rate of a fluid flow.
  • a vibration sensor (40) arranged to provide a sensor signal (S 0 ), which depends on the frequency (f v ) of vibration of said body (1 0), and
  • a calculation unit (200) configured to determine a velocity (U F i) and/or a flow rate (Q) of the fluid flow (F1 ) based on said sensor signal (S 0 ),
  • the mass of the body (1 0) is smaller than 0.54 times the external volume of the body (1 0) multiplied by a density of 1 g/cm 3 .
  • the mass of the body (1 0) is smaller than 0.54 times the external volume of the body (1 0) multiplied by the density of the fluid of said fluid flow (F1 )
  • the body starts to vibrate in the transverse direction due to vortex generation.
  • the vibration frequency is proportional to the fluid flow velocity in a broad velocity range. Consequently, the velocity may be accurately determined based on the vibration frequency of the body.
  • the lower limit of the applicable velocity range may be smaller than or equal to a first velocity value, which corresponds a Reynolds number which is equal to e.g. 50.
  • the upper limit of the velocity range may be greater than or equal to a second velocity value, which corresponds a Reynolds number which is equal to e.g. 5000.
  • the flow sensor can also be used for measuring low flow velocities, because the body may vibrate already at flow velocities which correspond to laminar conditions.
  • the measurement may be based on monitoring the frequency of large- amplitude vibration of the body. Consequently the accuracy of the flow measurement can be high.
  • the flow sensor according to the invention may be mechanically very simple and robust. Consequently long operating life, reliable operation, and/or low manufacturing costs may be expected.
  • the use of wet bearing surfaces sliding against each other is not necessary. Consequently long operating life and/or reliable operation may be expected.
  • the flow sensor may withstand freezing of the fluid flow without being permanently damaged. Consequently, the flow sensor may be suitable e.g. for monitoring water flow in households, and water distribution systems, or for monitoring coolant flow in automobiles, aircrafts and marine applications.
  • the wetted parts of sensor may be rather easily made from application-specific materials.
  • the wetted parts of the sensor may be made of corrosion resistant and/or heat resistant materials.
  • the sensor may be applicable for monitoring hot and/or corrosive liquid flows in industrial processes.
  • Fig. 1 shows, in a side view, vortices generated by a bluff body
  • Fig. 2 shows, in a three-dimensional view, a flow sensor comprising a vibrating body
  • Fig. 3a shows, in a side view, the uppermost position of the vibrating body during vibration
  • Fig. 3b shows, in a side view, the lowermost position of the vibrating body during vibration
  • Fig. 4a shows frequency of vibration as a function of fluid velocity in case of a comparative example
  • Fig. 4b shows frequency of vibration as a function of fluid velocity in case of a light vibrating body
  • Fig. 5a shows, in a side view, dimensions associated with the flow sensor
  • Fig. 5b shows, in a top view, dimensions associated with the flow sensor
  • Fig. 6a shows, in a three-dimensional view, a flow sensor, which comprises connecting elements attached directly to a duct
  • Fig. 6b shows, in a top view, the flow sensor of Fig. 6a
  • Fig. 7a shows, in a three-dimensional view, a flow sensor comprising an asymmetrical holder for the connecting element
  • Fig. 7b shows, in a top view, the flow sensor of Fig. 7a
  • Fig. 8a shows, in a three-dimensional view, a flow sensor which comprises a connecting element attached directly to a duct,
  • Fig. 8b shows, in a top view, the flow sensor of Fig. 8a
  • Fig. 9a shows, in a three-dimensional view, capacitive detection of vibration
  • Fig. 9b shows an exploded view of a vibrating body, which comprises a conductive portion
  • Fig. 1 0 shows an equivalent electrical circuit for the set-up of Fig. 9a
  • Figs. 1 1 a-1 1 d show fastening a connecting element to a holder
  • Fig. 1 2a shows, in a three-dimensional view, electromagnetic detection of vibration by using a stationary coil
  • Fig. 1 2b shows, in a three-dimensional view, electromagnetic detection of vibration by using a moving coil
  • Fig. 1 3a shows, in a cross-sectional side view, piezoelectric detection of vibration
  • Fig. 1 3b shows, in a top view, optical detection of vibration
  • Fig. 1 3c shows, in a top view, optical detection of vibration
  • Fig. 14a shows, in a side view, a body having a circular cross-section
  • Fig. 14b shows, in a side view, a circular cross-section of the body, wherein the cross-section deviates from a perfect circle
  • Fig. 1 5a shows, in a side view, an elliptical cross section of the body
  • Fig. 1 5b shows, in a side view, an elliptical cross section of the body
  • Fig. 1 6a shows a circular cross-section of a connecting element
  • Fig. 1 6b shows a cross-section of a flat connecting element
  • Fig. 1 6c shows a cross-section of a flat connecting element.
  • interaction between the fluid flow F1 and a bluff body 1 0 may cause periodic formation of vortices VX1 .
  • the flow F1 may be parallel to the direction SX.
  • the interaction may also cause vibration of the body 1 0 in a direction normal to the flow F1 , e.g. in the transverse direction SZ.
  • Vibration or oscillation refers herein to a periodic reciprocating movement of center of gravity of the body 1 0.
  • the "bluff" body may refer to a body having a "non- aerodynamic" and/or a "non-hydrodynamic" shape.
  • U F i denotes the free-stream velocity of the fluid flow F1 with respect to the body 1 0.
  • SVIB denotes the principal direction of vibration of the body 10 caused by the flow F1 .
  • SVIB may be substantially parallel to the direction SZ.
  • a flow sensor 1 00 may comprise a vibrating bluff body 1 0, a connecting element 20 arranged to support the body 1 0, and a vibration sensor 40 to detect vibration of the body 1 0.
  • the flow sensor 1 00 may optionally comprise a holder 30 for holding the connecting element 20, a duct 50 for defining a cross-section of the flow F1 , and/or a signal processing unit 200 for processing a sensor signal provided by the vibration sensor 40. Interaction between the flow F1 and the body 1 0 induces periodic vibration of the body 1 0 in the transverse direction SZ.
  • the mass of the body 1 0 should be substantially smaller than the mass of the fluid displaced by the body 1 0.
  • the body 1 0 may be e.g. a circular cylinder.
  • the body 1 0 may be a hollow circular cylinder having closed ends.
  • the body 1 0 may also be a sphere or an ellipsoid.
  • the body 1 0 and at least a portion of the connecting element 20 are immersed in the flow F1 .
  • the connecting element 20 is arranged to prevent the body 1 0 from moving out of the sensing range of the vibration sensor 40.
  • the connecting element 20 may prevent the body 1 0 from escaping with the flow F1 in the direction SX. Additionally, the connecting element 20 may prevent the body 1 0 from hitting the internal walls of the duct 50 during a flow measurement.
  • the connecting element 20 may be e.g. a resilient spring wire.
  • the body 1 0 may be mounted elastically.
  • the vibration sensor 40 is arranged to detect vibration of the body 1 0.
  • the vibration sensor 40 may be e.g. a capacitive plate, which is arranged to capacitively detect movements of the body 1 0 with respect to the sensor 40.
  • the capacitance between the body 1 0 and a capacitive plate 40 may vary at the vibration frequency of the body 1 0.
  • the periodic variation of the capacitance may be monitored by the signal processing unit 200.
  • a sensor signal S 0 provided by the vibration sensor 40 may be processed in the signal processing unit 200 in order to provide an output signal SOUT-
  • the output signal SOUT may be e.g. a digital signal determined based on the sensor signal S 0 .
  • the signal processing unit 200 of the flow sensor 1 00 may be configured to provide an output signal SOUT, which specifies a velocity and/or a flow rate of the fluid flow F1 based on a frequency determined by using the vibration sensor 40.
  • the frequency determined by using the vibration sensor 40 may be e.g. an integer multiple of the frequency of vibration f v of the body 1 0, i.e. the frequency determined by using the vibration sensor 40 may be e.g. equal to 1 x f v , 2 x f v , or 3 x f v .
  • the signal processing unit 200 may be calculation unit, which is configured to determine a velocity U F i and/or a flow rate Q of the fluid flow F1 based on the sensor signal S 0 provided by the vibration sensor 40.
  • the flow sensor 1 00 may comprise:
  • a vibration sensor 40 arranged to provide a sensor signal S 0 , which depends on the frequency f v of vibration of said body 1 0 in said transverse direction SZ, and
  • a calculation unit 200 configured to determine a velocity U F i and/or a flow rate Q of the fluid flow F1 based on said sensor signal S 0 ,
  • a method for monitoring velocity or flow rate may comprise:
  • the signal processing unit 200 may also be substantially remote from the vibration sensor 40.
  • the signal processing unit 200 i.e. calculation unit
  • the signal processing unit 200 may be implemented in a process control unit of an industrial facility.
  • the signal processing unit 200 may also be called as a calculation unit.
  • the output signal SOUT may be provided by using a calibration constant k C Au or kcAi_2 (see equations 5 and 6).
  • the body 1 0 and the connecting element 20 may be located in a duct 50, which has a predetermined cross-sectional area. Consequently, the flow sensor 100 may be used for measuring the flow rate Q of the fluid F1 .
  • the cross-section of the duct 50 may be e.g. rectangular (Fig. 2), or circular (Fig. 1 1 d).
  • the sensor 1 00 may still be used for measuring velocity U F i of the fluid F1 , e.g. for measuring the velocity of a boat with respect to water.
  • the connecting element 20 may be attached to the holder 30 at a point HP1 .
  • the holder 30 may, in turn, be fixed to the wall(s) of the duct 50.
  • the joint at the point HP1 may be rigid or pivoted.
  • the connecting element 20, or a portion of the connection element 20 may be flexible so as to allow vibration of the body 1 0 in the transverse direction SZ.
  • the body 1 0 may move along a curved path due to the finite length of the connecting element 20.
  • AX1 0 denotes the longitudinal axis of the body 1 0.
  • the body 1 0 may be e.g. a substantially circular cylinder, wherein the body 1 0 is circularly symmetrical with respect to the axis AX1 0.
  • Fig. 3a shows the body 1 0 at the uppermost position of the vibration
  • Fig. 3b shows the body 1 0 at the lowermost position of the vibration.
  • H1 denotes dimension of the body 1 0 in the direction SY (vertical dimension).
  • d fi MAx denotes maximum distance between the body 1 0 and the lower surface of the duct 50
  • d fjM iN denotes minimum distance between the body 10 and the lower surface of the duct 50.
  • the body 1 0 may have a neutral position.
  • the body may be periodically deflected from the neutral position upwards (Fig. 3a) and downwards (Fig. 3b).
  • the amplitude of vibration is equal to (d fiM Ax-df,MiN)/2.
  • the Reynolds number Re-m of the body 1 0 is calculated according to the following equation :
  • H1 denotes the vertical dimension of the body 1
  • U FI denotes the free-stream velocity of the fluid flow F1 before the fluid flow F1 impinges on the body 1
  • VFI denotes kinematic viscosity v of the fluid flow F1 (the unit of kinematic viscosity is m 2 /s).
  • the body 10 is free to vibrate, and it has a low mass. Comparative examples illustrate what happens when the body is not free to vibrate and when the body does have a low mass.
  • the position of the body 1 0 is fixed so that it cannot vibrate.
  • the bluff body 1 0 creates a Karman vortex street similar to the one shown in Fig. 1 .
  • H1 is equal to the diameter of the body 10.
  • St is approximately equal to 0.2.
  • the frequency f V x of formation of the vortices is proportional to the velocity U F i of the fluid flow F1 .
  • the vortices VX1 cause fluctuations of local pressure in the fluid.
  • the frequency f V x of formation of the vortices VX1 may be measured e.g. by using sensitive pressure sensors.
  • the frequency f V x can be reliably detected only when the Reynolds number Re-m is greater than 1000. Consequently, a flow sensor based on vortices created by an immobile body is not optimal for measuring low velocities.
  • the mass M 0 of the body 10 is smaller than 0.54 times the mass M F i of the fluid F1 displaced by the body.
  • Fig. 4a shows, as a second comparative example, the vibration frequency f v of the body 10 as a function of the flow velocity U F i when the mass M 0 of the body 10 is greater than 0.54 times the mass M F of the fluid F1 displaced by the body.
  • f v ,MiN denotes minimum detectable vibration frequency of the body 10.
  • fv.MAx denotes maximum detectable vibration frequency of the body 10.
  • UR denotes velocity of the fluid flow F1 .
  • U M IN denotes a minimum velocity, which causes detectable periodic vibration of the body 10.
  • UMAX denotes a maximum velocity which causes detectable periodic vibration of the body 10.
  • Ui denotes a lower limit of a synchronization regime.
  • U 3 denotes an upper limit of the synchronization regime in case of increasing velocity U F .
  • U 2 denotes a lower limit of the synchronization regime in case of decreasing velocity UR .
  • the vibrating body 1 0 interacts with the vortices VX1 .
  • the moving body creates vortices VX1 , and on the other hand, the body is moved by the vortices VX1 (See Fig. 1 ).
  • the vibration frequency f v of the body 10 may be substantially equal to the frequency f V x of formation of the vortices. In this regime, the vibration amplitude is typically small.
  • the vibration frequency f v of the body 10 is substantially independent of the velocity U1 of the fluid flow F1 .
  • This phenomenon is called synchronization (or frequency locking).
  • the synchronization phenomenon takes place because formation of the vortices VX1 is synchronized with a mechanical resonance frequency f RE s of the body 1 0.
  • the vibration frequency f v may even exhibit hysteresis in the range from U 2 to U 3 .
  • the upper limit of the synchronization regime may be U 2 in case of decreasing velocity U F i
  • the upper limit of the synchronization regime may be U 3 in case of increasing velocity U F i .
  • the vibration frequency f v of the body 10 may again be substantially equal to the frequency f V x of formation of the vortices.
  • the amplitude of vibration rapidly decreases with increasing velocity due to desynchronization.
  • Fig. 4b shows a linear relationship attained by using a light body 1 0.
  • the frequency f v of vibration of the body 1 0 may be proportional to the velocity U F i of the fluid flow F1 in the whole regime from U L ow to U H IGH-
  • the frequency f v may be linearly dependent on the velocity U F i in the whole regime from U L ow to U H IGH-
  • U L ow denotes lower limit of a substantially linear velocity range
  • U H IGH denotes an upper limit of said substantially linear velocity range.
  • the lower limit U L ow may be smaller than or equal to the minimum detectable velocity U M IN shown in Fig. 4a, and the upper limit U H IGH may be greater than or equal to the maximum detectable velocity UMAX shown in Fig. 4a (when the external dimensions of the body 10 according to Fig. 4b are equal to the dimensions of the body according to Fig. 4a and when the fluid F1 is the same).
  • the mass M 0 of the body 10 may be smaller than 0.54 times the mass M F i of the fluid F1 displaced by the body, i.e.
  • the mass M-m of the body 10 may be 0.54 times the mass of the fluid F1 displaced by the body, advantageously smaller than 0.50 times the mass of the fluid F1 displaced by the body, and preferably smaller 0.30 than times the mass of the fluid F1 displaced by the body.
  • the value 0.54 may be applicable for a body 10 which has a substantially circular cross section, and whose length L1 is substantially greater than the dimension H1 (See Fig. 14a).
  • the value 0.50 may guarantee linear operation also when the form of the cross section slightly deviates from a perfect circle (See e.g. Fig. 14b).
  • the value 0.30 may be applicable for various different shapes, including a substantially deformed circular cylinder.
  • the value 0.30 may also be applicable for a tethered sphere.
  • the mass M F i of the displaced fluid F1 is equal to the density of the fluid F1 multiplied by the external volume of the body 10.
  • the displaced mass MFI can be calculated as follows:
  • Un P*B (4) wherein p denotes density of the fluid F1 .
  • U H IGH may be e.g. greater than 30 times U L ow, or even greater than 1 00 times U L ow-
  • the body 1 0 may vibrate at high amplitude e.g. when RE 0 > 200, when Re-m > 1 00, or even when Re 0 > 50. Consequently, the relationship between the vibration frequency f v and U F i may be substantially linear e.g. at Reynolds numbers Re-m ranging from 1 00 to 3000. Throughout this range, the amplitude of vibration may substantially equal to the vertical dimension H 1 of the body 1 0. The behavior may be linear even at Reynolds numbers Re-m ranging from 50 to 5000.
  • the Reynolds number Re-io corresponding to the lower limit ULOW of the velocity range may be e.g. equal to 200, preferably equal to 1 00, or even equal to 50.
  • the lower limit U L ow of the substantially linear velocity range may be smaller than or equal to a first velocity value, which corresponds a Reynolds number which is equal to e.g. 50.
  • the upper limit U H IGH of the substantially linear velocity range may be greater than or equal to a second velocity value, which corresponds a Reynolds number which is equal to e.g. 3000.
  • the lower limit U L ow of the substantially linear velocity range may be smaller than or equal to a first velocity value, which corresponds to a Reynolds number which is equal to e.g. 1 00.
  • the upper limit U H IGH of the substantially linear velocity range may be greater than or equal to a second velocity value, which corresponds to a Reynolds number which is equal to e.g. 3000.
  • the lower limit U L ow of the substantially linear velocity range may be smaller than or equal to a first velocity value, which corresponds to a Reynolds number which is equal to e.g. 50.
  • the upper limit U H IGH of the substantially linear velocity range may be greater than or equal to a second velocity value, which corresponds to a Reynolds number which is equal to e.g. 5000.
  • the lower limit U L ow of the substantially linear velocity range may be smaller than or equal to a first velocity value, which corresponds to a Reynolds number which is equal to e.g. 100.
  • the upper limit U H IGH of the substantially linear velocity range may be greater than or equal to a second velocity value, which corresponds to a Reynolds number which is equal to e.g. 5000.
  • at least the structural strength of the body 10 and the structural strength of the connecting element 20 are expected to limit the maximum allowed velocity of the flow F1 .
  • the amplitude of vibration may substantially equal to the vertical dimension H1 of the body 10, i.e. it is not necessary to detect small-amplitude vibration.
  • the unit of the velocity U F i may be e.g. meters/second (m/s).
  • the unit of the flow rate Q may be e.g. liters/second (l/s) or kilograms/second (kg/s).
  • the body 1 0 may be elastically supported by the connecting element 20.
  • the body 1 0 may have a mechanical resonance frequency f RE s-
  • the light body 1 0 may start to vibrate when Re-m is greater than or equal to a predetermined value and the frequency f V x of formation of the vortices VX1 (Eq. 2) is greater than or equal to the mechanical resonance frequency f RE s-
  • the body 1 0 may be arranged to vibrate in a linear range having a lower limit U M IN when:
  • the lower limit U M IN and/or the dimension H 1 is selected such that Re-m corresponding to U M IN is greater than or equal to a predetermined Reynolds number
  • the lower limit U M IN may substantially correspond to the minimum velocity ULOW, which causes detectable periodic vibrations.
  • the lower limit U M IN may also correspond to the minimum vibration frequency f v ,MiN-
  • a velocity U F i of the fluid corresponding to a predetermined Reynolds number may be solved from eq. (1 ), i.e. by using the following equation: ⁇ j _ v Re io , m
  • the frequency f V x of vortices corresponding to a predetermined Reynolds number Re-m may be calculated from eq. (2) by using the velocity value obtained from eq. (8).
  • the frequency f V x of vortices may be estimated by using the following equation: f - H ⁇ v Re io (Q)
  • the frequency fvx corresponding to the Reynolds number may be approximately equal to 2-10 "5 m 2 s "1 (H1 ) "2 .
  • H1 10 mm
  • the velocity corresponding to is 10 mm/s
  • the corresponding f V x is approximately equal to 0.2 Hz.
  • the velocity corresponding to is 2 mm/s, and the corresponding f V x is approximately equal to 5 Hz. If the response of the flow sensor 100 should be linear starting from the flow velocity 2 mm/s, the mechanical resonance frequency fREs of the body 10 should be smaller than or equal to 5 Hz.
  • the minimum vibration frequency .MIN is a vibration frequency attained at the minimum detectable velocity UMIN-
  • the resonance frequency fREs of the combination of the body 10 may be selected to be smaller than the minimum vibration frequency .MIN in order to make the relationship between vibration frequency .MIN and the velocity UFI as linear as possible.
  • a low mechanical resonance frequency fREs may be implemented by selecting a small spring rate and/or a high mass.
  • the connecting element 20 may create a restoring force, which tends to move the body 10 back to a neutral position.
  • the body 10 supported by the connecting element 20 has a mechanical resonance frequency fREs given by: where k 20 denotes the spring rate (spring coefficient) of the connecting element 20.
  • the unit of k 20 may be e.g. N/m.
  • M 0 denotes the mass of the body 1 0.
  • k 20 may refer to the sum of the spring rates of the individual connecting elements 20a, 20b.
  • the connecting element 20 may be a spring element, which is fixed to a holder 30 or to the duct 50 without a pivoting hinge.
  • the spring constant k 2 o is determined by the material, the length L2, and the cross- sectional dimensions of the element 20.
  • the connecting element 20 may also be arranged such that the spring rate k 20 is substantially equal to zero.
  • the connecting element 20 may be a hinged lever, whose movement range is limited by mechanical stoppers.
  • the connecting elements 20, 20a, 20b may even be made from flexible thread or flexible plastic foil whose spring rate is very low or substantially equal to zero.
  • the spring rate k 20 is very small, the average position of the vibrating body 1 0 may be stabilized e.g. by buoyancy forces (when flow direction SX is opposite the direction of gravity).
  • the body 1 0 has a tendency to float, as the mass of the body 1 0 is smaller smaller than the mass of the displaced fluid.
  • the spring rate k 2 o is very small, the average position of the vibrating body 1 0 may also be stabilized by an average drag force created by the flow F1 . If the flow direction SX is not opposite the direction of gravity, the buoyancy of the body 1 0 may slightly disturb operation of the sensor at low velocities.
  • Fig. 5a shows a few dimensions associated with a flow sensor 1 00.
  • H1 denotes height of the body 1 0 in the direction SZ.
  • H2 denotes inner height of the duct 50 in the direction SZ.
  • L2 denotes length of the connecting element 20.
  • d f denotes distance between the body 1 0 and the lower inner wall of the duct 50 in the direction SZ.
  • d9 denotes the dimension of the holder 30 in the direction SZ.
  • d9 may be e.g. smaller than 1 0% of H1 so as to minimize the effect of vortices created by the holder 30.
  • the cross-sectional shape of the holder 30 may be selected so as to minimize creation of vortices by the holder 30.
  • Fig. 5b shows a few dimensions associated with a flow sensor 1 00.
  • W2 denotes the inner width of the duct 50 in the direction SY.
  • W9 denotes the width of the holder 30 in the direction SY.
  • W1 denotes the width of the body 10 in the direction SY.
  • W s denotes distance between the body 10 and the inner side wall(s) of the duct 50.
  • the dimensions of the duct 50 and/or the dimensions of the body 1 0 may be selected such that the horizontal clearance W s between the body 1 0 and the duct 50 is greater than or equal to 1 .5 times the vertical dimension H1 of the body 1 0.
  • the dimensions of the duct 50 and/or the dimensions of the body 10 may be selected such that the (minimum) vertical clearance d f between the body 1 0 and the duct 50 is greater than or equal to two times the vertical dimension H1 of the body 1 0. If the clearances W s , d f are too small, this may suppress or completely prevent the vibrations of the body 1 0.
  • Fig. 6a shows a flow sensor 1 00 comprising two connecting elements 20a, 20b, which are directly attached to the walls of the duct 50 at the points HP1 , HP2.
  • Fig. 2 shows a bridging holder 30 (Fig. 2) or to a protruding holder 30 (Fig. 7a).
  • Fig. 6b shows, in a top view, a first connecting element 20a attached to a first side of the duct 50 at a point HP1 , and a second connecting element 20b attached to a second side of the duct 50 at a point HP2.
  • the body 1 0 may be substantially narrower than the duct 50, and the connecting elements 20a, 20b may be inclined with respect to the fluid flow F1 .
  • an angle ⁇ between the orientation of a connecting element 20a and the direction SX may be substantially greater than zero.
  • Fig. 7a shows a connecting element 20 attached to a protruding holder 30. In Fig. 7a, only one end of the protruding holder 30 is attached to the duct 50.
  • Fig. 7b shows, in a top view, the protruding holder 30 of Fig. 7a.
  • Figs. 8a and 8b show a body 1 0, which is supported by only one connecting element 20, wherein the connecting element 20 is directly attached to the wall of the duct 50 at the point HP1 .
  • the connecting element 20 may be e.g. a resilient spring element.
  • the body 1 0 may comprise a portion, which is electrically conductive.
  • the whole body 1 0 may be made of an electrically conductive material e.g. made of metal or conductive polymer.
  • the body 1 0 may comprise an electrically conductive coating, e.g. a vacuum deposited layer of aluminum or gold.
  • the electrically conductive portion of the body 1 0 may be further covered with an electrically insulating structure, e.g. with an electrically insulating polymer, e.g. polyvinylidene fluoride (PVDF).
  • PVDF polyvinylidene fluoride
  • the insulation may be useful e.g. in order to prevent galvanic corrosion and/or in order to reduce noise of an electric signal generated by the vibrating body 1 0.
  • the electrically conductive portion of the body 1 0 may be electrically connected to a first terminal T1 .
  • the vibration sensor 40a may be e.g. a capacitive plate, which is electrically connected to a second terminal T2.
  • the distance H x between the body 1 0 and the plate 1 0 varies at the vibration frequency f v . Consequently, the capacitance C x of a capacitor formed by the conductive portion and the plate 40a varies at the vibration frequency f v .
  • the capacitance Cx is inversely proportional to the distance H x .
  • the frequency f v may be determined based on the varying capacitance C x .
  • the capacitance C x may be measured or at least monitored e.g. by charging and/or discharging the capacitor at a predetermined current, and by monitoring the resulting change of voltage per unit time (voltage derivative).
  • the capacitance C x may be monitored by applying a substantially constant voltage between the conductive portion and the plate 40a, and by measuring the resulting change of charging/discharging current per unit time (current derivative) flowing via a terminal T1 or via a terminal TO.
  • the conductive portion of the body 1 0 may be electrically connected to the terminal T1 , which is outside the duct 50.
  • the connection may be provided e.g. via the connecting element 20, the holder 30, and a pressure-resistant electrical feedthrough CONN1 .
  • the feedthrough CONN1 may be a galvanic feedthrough, e.g. a metal wire insulated by glass or epoxy.
  • the feedthrough CONN1 may be a capacitive feedthrough, e.g. a polymer plate between to conductive plates.
  • the electrical signal S 0 may be coupled from the internal pressure to the external pressure by the feedthrough CONN1 .
  • the pressure-resistant electrical feedthrough CONN1 may be deeded because the pressure inside the duct 50 is typically substantially different from the pressure outside the duct 50.
  • the plate 40a may be electrically connected to the reference terminal TO.
  • the duct 50 When using the capacitive detection, at least a portion of the duct 50 should be made of an electrically insulating material.
  • the plate 40a is preferably positioned outside the duct 50 in order to galvanically isolate the plate 40a from the fluid F1 .
  • the plate 40a may also be inside the duct 50 if the fluid F1 is electrically insulating (e.g. oil, alcohol, distilled water). However, in that case an additional feedthrough would also be needed for connecting the plate 40 inside the duct 50 to the external terminal TO outside the duct 50.
  • electrically insulating e.g. oil, alcohol, distilled water
  • the flow sensor 1 00 may comprise a second capacitive plate 40b for implementing a differential capacitive measurement.
  • a first capacitor may be formed between the conductive portion of the body 1 0 and the first capacitive plate 40a.
  • a second capacitor may be formed between the conductive portion of the body 1 0 and the second capacitive plate 40b.
  • the distance H x between the body 1 0 and the first capacitor plate 40a increases, the distance H Y between the body 1 0 and the second capacitor plate 40b decreases, respectively. Consequently, the when the capacitance C x formed by the conductive portion and the first plate 40a decreases, the capacitance formed by the conductive portion and the first plate 40a increases, respectively.
  • the differential measurement set-up may reduce sensitivity to common-mode electrical noise.
  • the second plate 40b may be electrically connected to a second terminal T2.
  • the flow sensor 1 00 may comprise a Faraday cage for suppressing electrical noise.
  • the Faraday cage may enclose the capacitive sensors 40a, 40b and the body 1 0.
  • a conductive portion 1 0c may be embedded in the body 10 e.g. by stacking a piece of conductive sheet 1 0c between a first part 1 0a and a second part 10b.
  • the parts 1 0a, 1 0b may be half-cylinders (i.e. the parts 1 0a, 1 0b may be hemicylindrical).
  • the material of the parts 1 0a, 1 0b may be e.g. polymer foam or porous ceramic.
  • the material of the parts 1 0a, 10b may be electrically insulating. 1 0a.
  • the parts 1 0a, 1 0b may be joined together e.g. by using adhesive or by welding.
  • the connecting element 20 may be joined to the conductive portion 10c e.g. by welding or soldering prior to joining the parts 10a, 1 0b together.
  • a combination of the connecting element 20 and the portion 1 0c may be cut from a metal sheet as a single piece so that there is no need to join them together.
  • lightweight insulating material may be molded around the portion 1 0c so that the conductive portion 1 0c is embedded in the body 1 0.
  • Fig. 1 0 shows an equivalent circuit for the capacitive measurement set-up shown in Fig. 9a.
  • the terminals TO, T1 and T2 may be connected to inputs of a signal processing unit 200.
  • the signal processing unit 200 may comprise e.g. a voltage waveform generator or a current waveform generator for monitoring changes in the capacitance C x .
  • V 0 i denotes a (voltage) signal between the terminals TO and T1 .
  • V1 2 denotes a (voltage) signal between the terminals T1 and T2.
  • the signal processing unit 200 may provide an output signal SOUT, which depends on the vibration frequency f v of the body 1 0.
  • the output signal SOUT may also be provided based on electric currents flowing through the terminals TO, T1 and/or T2.
  • the output signal SOUT may comprise information specifying vibration frequency of the body 1 0.
  • the output signal SOUT may be e.g. a digital number, a 4-20 mA current loop signal, or a 1 -bit digital signal whose frequency or duty cycle depends on the vibration frequency f v of the body 1 0.
  • the output signal SOUT may comprise information indicative of the velocity U F i and/or flow rate Q of the fluid F1 .
  • Figs. 1 1 a-1 1 d show, by way of example, a possible mechanical construction of a flow sensor 1 00.
  • Fig 1 1 a shows two holder portions, which together form a holder 30 for the connecting element 20.
  • Fig. 1 1 b is a side view of a flow sensor 100
  • Fig. 1 1 c is a cross-sectional view of the flow sensor 1 00
  • Fig. 1 1 d is an end view of the flow sensor 1 00.
  • the connecting element 20 may be a piece of spring wire.
  • the body 1 0 may be attached to a connecting element 20 by a hook 21 , which is secured to a groove 1 1 of the body 1 0.
  • the other end of the connecting element 20 may be bent to form a transverse portion 22.
  • a first holder portion 30b may have a groove 32, which matches the shape of the transverse portion 22 and the longitudinal portion of the connecting element 20.
  • a second holder portion 30a may form a cover for the groove 32 so as to clamp the transverse portion 22 of the connecting element 20 securely in the groove 32.
  • the holder portions 30a, 30b may be attached to rim portions 31 a, 31 b, respectively.
  • the rim portions 31 a, 31 b may be positioned in a recess of the duct 50 so as to keep the holder portions 30a, 30b firmly together.
  • the vibration sensors 40a, 40b may be curved plates, which have been attached on the outer surface of the duct 50 e.g. by an adhesive.
  • the vibration sensors may also be implemented e.g. by using conductive paint or vacuum deposited metal (e.g. aluminium).
  • vibration of the body 1 0 may be detected electromagnetically.
  • the body 1 0 may comprise magnet 41 , which creates a magnetic field MF.
  • the vibration sensor 40 may be a coil or a Hall magnetic field sensor (i.e. a Hall element). Movement of the magnet 41 with respect to the stationary coil 40 may induce a voltage between terminals TO, T1 of the coil 40.
  • An advantage associated with the set-up of Fig. 1 2a is that it is not necessary to couple electricity to the body 1 0, i.e. it is not necessary to use an electrical feedthrough in order to couple electricity through the wall of the duct 50.
  • the presence of the magnet 41 may increase weight of the body 1 0.
  • the signal provided by the coil may oscillate at a frequency, which is e.g. equal to two times the vibration frequency of the body 1 0.
  • the body 1 0 may comprise a sensor coil or a Hall sensor 40, which detects a movement of the body with respect to an external magnet 41 .
  • the coil 40 may be galvanically connected to terminals TO, T1 , which are located outside the duct 50. Electricity may be connected from the terminal T1 to the coil 40 through the wall of the duct 50 e.g. via a feedthrough CONN1 (the duct is not shown in Fig. 1 2b).
  • Insulated wires may be positioned inside the connecting element 20. In particular a pair of insulated wires may be used as connecting elements 20a, 20b (See e.g. Fig. 6a).
  • movements of the body 1 0 may be detected by a piezoelectric sensor PZ1 .
  • the piezoelectric sensor PZ1 may be covered with an insulating layer 26.
  • the piezoelectric sensor PZ1 may be optionally connected to the body 1 0 by an arm 25.
  • the piezoelectric sensor PZ1 may also be directly attached to the body 1 0 without the additional arm 25.
  • vibration of the body 1 0 may be detected optically.
  • an optical fiber 44 may be used as a vibration detector.
  • Radiation B0 may be coupled into the fiber 44 from a radiation source 45.
  • the radiation B0 may be visible light or infrared light.
  • Radiation transmitted through the fiber 44 may be coupled out of the fiber 44 to a radiation detector 46.
  • Periodic bending of the fiber caused by vibration of the body 1 0 may cause modulation of at least one property of the transmitted radiation B1 .
  • the modulated property may be e.g. transmitted power, divergence, or spectral composition.
  • the modulation frequency of the property may be e.g. equal to the vibration frequency, or equal to two times the vibration frequency.
  • the fiber 44 may be disposed inside connecting elements 20a, 20b.
  • one or more portions of an optical fiber may be used as a connecting element.
  • the optical fiber 44 has a protective layer, e.g. a cladding, then contamination of the external surface of the fiber does not make optical detection of the vibration more difficult. In that case, dirt deposited on the fiber does not affect optical transmission through the fiber 44.
  • radiation BO may be coupled into the fiber 44 from a radiation unit 45.
  • the radiation BO may be visible light or infrared light.
  • Radiation propagating in the fiber 44 may be reflected from a reflector 47.
  • the reflector 47 may be e.g. a mirror or a diffraction grating.
  • the reflector 47 may be a Bragg grating.
  • Radiation reflected by the reflector 47 is coupled out of the fiber 47 to the radiation unit 45.
  • Periodic bending of the fiber and/or periodic mending of the reflector 47 caused by vibration of the body 1 0 may cause modulation of at least one property of the reflected radiation B1 .
  • the modulated property may be e.g. transmitted power, divergence, or spectral composition.
  • the modulation frequency of the property may be e.g. equal to the vibration frequency, or equal to two times the vibration frequency.
  • the fiber 44 may be disposed inside connecting elements 20a, 20b.
  • one or more portions of an optical fiber may be used as a connecting element.
  • the optical fiber 44 and the reflector 47 are covered with a protective layer, e.g. a cladding, then contamination of the external surface of the fiber does not make optical detection of the vibration more difficult. In that case, dirt deposited on the fiber does not affect optical transmission through the fiber 44.
  • a protective layer e.g. a cladding
  • Vibration of the body may also be detected e.g. by using a laser detector or an ultrasonic detector (not shown in Figs).
  • the ideal cross-sectional shape of the bluff body 1 0 is expected to be a perfect circle. This form is expected to provide the largest vibration amplitude at both low and high flow velocities.
  • the cross-sectional shape of the bluff body 1 0 may slightly deviate from the perfect circle due to manufacturing tolerances.
  • the deviation AR may be e.g. smaller than 1 0% of the height H1 of the body 1 0, i.e. the perimeter of the cross-section may fit between an inner circle and an outer circle so that the radius of the inner circle is greater than 0.90 times the radius of the outer circle.
  • the cross-sectional shape of the bluff body 1 0 may be substantially elliptical.
  • the length L1 of the cross- section may be greater than 0.75 times the height H 1
  • the length L1 of the cross-section may be smaller than 1 .3 times the height H1 .
  • the circle is a special case of an ellipse.
  • the circular form of Figs. 14a, 14b is a special case of the elliptical form.
  • the length L1 of the body 1 0 may be e.g. smaller than 20 times the dimension H1 in order to ensure that both ends of the body 1 0 are in the same phase of vibration, i.e. both ends of the longitudinal body should be at the lowermost position at the same time.
  • the length L1 may be e.g. greater than or equal to 2 x H1
  • L1 may be e.g. smaller than 1 0 x H1 .
  • the value of the parameter of the right hand side of eq. (3) may depend on the cross-sectional shape of the bluff body 1 0.
  • the maximum value of said parameter may be determined experimentally or by computer simulation such that linear behavior is provided in the desired velocity range.
  • an upper limit for the mass of the body 1 0 may be determined based on the cross- sectional shape such that linear behavior is provided in the desired velocity range.
  • the parameter may be e.g. equal to 0.30, 0.50, or 0.54.
  • the parameter may be e.g. equal to 0.30 or 0.50.
  • the value 0.30 is expected to be applicable also for shapes which substantially deviate from the circular form (e.g. in case of Fig. 15a or 1 5b).
  • the body 1 0 may be a hollow component, e.g. a tube having closed ends.
  • the circular end pieces may be joined to the tube e.g. by electron beam welding, ultrasonic welding, or by using an adhesive. Alternatively, open ends of a tube may be crimped or squeezed so as to close them.
  • the body 1 0 may comprise foam, e.g. metal foam or closed cell polymer foam.
  • the body 1 0 may comprise syntactic foam (e.g. metal, polymer or ceramic filled with microballoons).
  • the foam may be coated with a sealing layer.
  • the cross-sectional shape of the connecting element may be e.g. circular (Fig. 1 6a) or flat (Figs. 1 6b and 1 6c).
  • the cross-sectional dimension of the connecting element 20 in the direction SY is substantially greater than the cross-sectional dimension of the connecting element 20 in the direction SY.
  • the cross-sectional dimension of the connecting element 20 in the direction SY is substantially smaller than the cross-sectional dimension of the connecting element 20 in the direction SY.
  • the element 20 of Fig. 1 6c disturbs the flow F1 less than the element 20 of Fig. 1 6b.
  • the element 20 of Fig. 1 6b may provide better stabilization of the body 1 0 in the direction SY than the element 20 of Fig. 1 6c.
  • the connecting element 20, 20a, 20b of the flow sensor 1 00 prevents the body 1 0 from escaping away from the sensing region of the vibration sensor 40, 40a, 40b.
  • the connecting element 20, 20a, 20b also preferably prevents the body 1 0 from hitting the inner walls of the duct 50 in normal operation.
  • the connecting element 20, 20a, 20b may also be called e.g. as a retainer or as a restraining element.
  • the one or more connecting elements 20, 20a, 20b are arranged to allow vibration of the body 1 0 in a first transverse direction SZ.
  • the body 1 0 may be arranged to vibrate primarily in only one transverse direction, e.g. in the direction SZ.
  • the one or more connecting elements 20, 20a, 20b may be arranged to suppress or prevent oscillation in the other transverse direction SY.
  • One or more connecting elements 20, 20a, 20b may stabilize the angular orientation of the body 1 0 so that the longitudinal axis AX1 0 of the body 1 0 remains substantially parallel to the direction SY (Fig. 2).
  • the connecting element 20, 20a, 20b may be e.g. a flexible shaft.
  • the one or more connecting elements 20, 20a, 20b may stabilize the orientation of the body 1 0 so that the average orientation of the longitudinal axis AX1 0 of the body 1 0 is substantially parallel to the direction SY, wherein the vibration sensor 40, 40a, 40b is arranged to detect vibration in the perpendicular direction SZ.
  • One or more connecting elements 20, 20a, 20b may stabilize the horizontal position of the body 1 0 so that the gaps W s between the body 10 and the sides of the duct 50 remain substantially constant (Fig. 5b)
  • the one or more connecting elements 20, 20a, 20b may stabilize the orientation of the body 1 0 so that the body 1 0 oscillates primarily in a direction (SZ), which maximizes the amplitude of a signal provided by the vibration sensor 40, 40a, 40b.
  • the body may also be a tethered body 1 0, which is free to vibrate in the direction SZ and also in the direction SY.
  • the body may be e.g. a sphere.
  • the direction of the vibration SVIB may be random.
  • the spherical body may vibrate in the horizontal direction SY, in the vertical direction SZ, or in some intermediate direction between SY and SZ.
  • Two or more vibration sensors may be arranged to detect the vibration of the body 1 0.
  • a first vibration sensor 40 may be arranged to detect vibration e.g. in the direction SY, and a second vibration sensor 40 may be arranged to detect vibration e.g. in the direction SZ.
  • the connecting element 20, 20a, 20b may be made of e.g. carbon steel, chrome vanadium steel, stainless spring steel, brass, phosphor bronze, Inconel 600 (registered trademark of Special Metals Corporation), Hastelloy C-276 (registered trademark name of Haynes International, Inc.).
  • Hastelloy C-276 may retain its (reversibly) resilient properties to temperatures up to 400 °C.
  • the sensor 50 may be suitable for monitoring the flow velocity of e.g. molten metal.
  • the sensor 50 may be suitable for monitoring the flow velocity of a corrosive liquid, e.g. hot nitric acid or sulphuric acid in industrial processes.
  • an average vibration frequency is expected to be e.g. 200 Hz, and if the target is to attain an operating lifetime of 20 years of continuous operation, the expected total number of oscillations may exceed e.g. 1 0 11 cycles.
  • the material and dimensions of the connecting element 20 may be selected so as to minimize the risk of structural damage due to material fatigue.
  • the flow sensor 1 00 may comprise a sieve for catching the body 1 0 in a situation where the connecting element is broken.
  • the connecting element 20 is attached to the holder 30 or to the duct 50 by a hinge, then the connecting element 20 does not need to have resilient properties.
  • the hinge may mechanically define a range of angles where the combination of the connecting element 20 and the body 1 0 may vibrate.
  • the vibration sensor 40 may provide a sensor signal S 0 , whose frequency depends on the velocity U F i of the fluid flow F1 in a known manner
  • the relationship between the velocity U F i and frequency of the sensor signal S 0 may be established e.g. by calibration or simulation.
  • the duct 50 has a predetermined geometry and cross-sectional area. Consequently, the flow rate through the duct 50 can be determined by using the sensor signal S 0 or the output signal SOUT provided by the flow sensor 1 00
  • the amplitude of the sensor signal S 0 may be used for evaluating the reliability of measurement. For example, if the amplitude associated with a predetermined frequency range is lower than a predetermined limit, this may indicate an erroneous condition. This may indicate e.g. that additional material has been stuck to the body 1 0.
  • the fluid F1 may be e.g. a liquid.
  • the fluid F1 may be a multi-phase flow comprising e.g. a mixture of liquid and gas bubbles.
  • the fluid F1 may be a multi-phase flow comprising e.g. a mixture of liquid and non-sticky solid particles, whose size is substantially smaller than H1 .
  • Vibration of the body 1 0 and the connecting element 20 may reduce deposition of dirt on the surfaces of the body 1 0 and the connecting element 20. Vibration of the body 1 0 and the connecting element 20 may remove dirt from the surfaces of the body 1 0 and the connecting element 20.
  • the same sensor 1 00 may be used e.g. to detect high flow rates during peak consumption, and to detect small flows in case of a small leak in the pipeline system.
  • a minimum flow rate in a normal household should at least occasionally be equal to zero. If the monitored flow rate does not reach zero during a predetermined monitoring, e.g. during 1 2 hours, this may indicate a leak in the pipeline system.
  • the sensor is suitable for use in a leak detecting system.
  • a leak detection system may comprise a flow sensor 1 00.
  • a method for detecting a leak may comprise: monitoring flow rate during a predetermined observation period, and indicating whether the flow rate attains or does not attain a substantially zero level during the predetermined observation period. The length of the observation period may be e.g.
  • a method for detecting a leak may comprise: monitoring flow rate, and indicating whether the flow rate is at least momentarily below a predetermined minimum level during the predetermined observation period.
  • the predetermined minimum level may be e.g. equal to the minimum detectable flow rate of the flow sensor 1 00.
  • the flow sensor 1 00 may be used to monitor water flow delivered e.g. to and/or from a house, agricultural facility or industrial facility.
  • the flow sensor 100 may be used to monitor a liquid flow e.g. in chemical industry or food industry.
  • the liquid may be e.g. milk, cream, olive oil, beer, or alcohol.
  • the flow sensor 1 00 may be used to monitor fuel flow in a gasoline/petrol station.
  • the flow sensor 1 00 may be used e.g. to monitor liquid coolant flow in an automobile, motorcycle, marine vessel, aircraft, or machinery.
  • the flow sensor 1 00 may be used e.g. to monitor lubricant flow and/or fuel flow in an automobile, motorcycle, marine vessel, aircraft, or machinery.
  • the flow sensor 1 00 may be a part of an automobile, motorcycle, marine vessel, aircraft, or machinery.
  • the flow sensor 100 may be used to monitor flow of e.g. water, milk, beer, gasoline, kerosene, ethanol, or liquefied natural gas, for example.
  • the density of the fluid F1 is substantially equal to 1 g/cm 3 .
  • the density of e.g. milk and beer is also approximately 1 g/cm 3 .
  • the density of gasoline may be e.g. approximately 0.71 g/cm 3 .
  • the density of kerosene may be e.g. approximately 0.82.
  • the density of ethanol is approximately 0.78 g/cm 3 .
  • the density of liquefied natural gas may be e.g. 0.41 g/cm 3 .
  • the senor may be made of plastics and vacuum- deposited aluminum in order to implement a low-cost disposable flow sensor.
  • a flow sensor for biomedical applications may be made of sterilizable materials and/or of biocompatible materials.
  • flow sensor may be used for monitoring blood flow.
  • the flow sensor may be implanted in a human body in order to monitor blood flow.

Landscapes

  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)

Abstract

Selon l'invention, la vitesse (UF1) et/ou le débit (Q) d'un écoulement de fluide (F1) sont surveillés au moyen d'un corps vibrant (10), qui est soutenu par au moins un élément de raccord (20) de sorte que le corps (10) est libre de vibrer dans une direction (DZ), qui est transversale à l'écoulement de fluide (F1). Le procédé comprend l'étape consistant à - provoquer une vibration périodique du corps (10) par l'écoulement de fluide (F1), - fournir d'un signal de capteur (SO), qui dépend de la fréquence (fv) de vibration dudit corps (10) dans ladite direction transversale (SZ), et - la détermination d'une vitesse (UF1) et/ou d'un débit (Q) de l'écoulement de fluide (F1) sur la base dudit signal de capteur (S0), la masse du corps (10) étant inférieure à 0,54 fois le volume externe du corps (10) multiplié par la masse volumique du fluide (F1).
EP10853563.4A 2010-06-21 2010-06-21 Capteur d'écoulement Withdrawn EP2583066A4 (fr)

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DE102011119981B4 (de) * 2011-12-02 2014-02-27 Krohne Messtechnik Gmbh Vortex-Durchflussmessgerät
JP6099240B2 (ja) * 2012-06-26 2017-03-22 学校法人日本大学 複数の振動子を備えたエネルギー変換装置およびその製造方法
DE102013113365A1 (de) * 2013-12-03 2015-06-03 Endress + Hauser Wetzer Gmbh + Co Kg Verfahren zum Betreiben eines Messvorrichtung
US10564303B2 (en) 2016-07-26 2020-02-18 International Business Machines Corporation Parallel dipole line trap seismometer and vibration sensor
DE102019117831A1 (de) * 2019-07-02 2021-01-07 Krohne Messtechnik Gmbh Wirbeldurchflussmessgerät und Verfahren zum Betreiben eines Wirbeldurchflussmessgeräts
CN113267642B (zh) * 2021-05-25 2022-11-29 海南赛沐科技有限公司 一种全海深海流分布的监测方法及系统

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GB1327751A (en) * 1969-08-20 1973-08-22 Kent Instruments Ltd Devices for measuring fluid velocities
US3698245A (en) * 1970-04-14 1972-10-17 Foxboro Co Fluid oscillator flowmeter
US3823610A (en) * 1973-01-05 1974-07-16 Eastech Bluff body flowmeter utilizing a moveable shutter ball responsive to vortex shedding
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GB8915994D0 (en) * 1989-07-12 1989-08-31 Schlumberger Ind Ltd Vortex flowmeters
JP2610590B2 (ja) * 1994-04-26 1997-05-14 有限会社エーディ 流量計
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