DK144716B - APPARATUS FOR MEASURING THE FLOW SPEED OF A FLUID - Google Patents

APPARATUS FOR MEASURING THE FLOW SPEED OF A FLUID Download PDF

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Publication number
DK144716B
DK144716B DK544968AA DK544968A DK144716B DK 144716 B DK144716 B DK 144716B DK 544968A A DK544968A A DK 544968AA DK 544968 A DK544968 A DK 544968A DK 144716 B DK144716 B DK 144716B
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light
fluid
frequency
measuring
bundle
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DK544968AA
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Danish (da)
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DK144716C (en
Inventor
P A Egelstaff
T P J W D A Bourke
D A Jackson
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United Kingdon Atomic Energy
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Publication of DK144716C publication Critical patent/DK144716C/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/36—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light
    • G01P3/366—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light by using diffraction of light
    • 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
    • G01F1/661—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 using light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/26—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50—Systems of measurement based on relative movement of target
    • G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G01S13/585—Velocity or trajectory determination systems; Sense-of-movement determination systems processing the video signal in order to evaluate or display the velocity value
    • G01S13/587—Velocity or trajectory determination systems; Sense-of-movement determination systems processing the video signal in order to evaluate or display the velocity value using optical means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/50—Systems of measurement based on relative movement of target
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/083—Ring lasers
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/30—Assessment of water resources

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Plasma & Fusion (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Multimedia (AREA)
  • Optics & Photonics (AREA)
  • Fluid Mechanics (AREA)
  • Power Engineering (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Optical Radar Systems And Details Thereof (AREA)
  • Measuring Volume Flow (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Description

144716144716

Opfindelsen angår et apparat til måling af et fluidums strømningshastighed under anvendelse af den frekvensændring, der beroende på Doppler-effekten opstår ved spredning af lys fra diskontinuiteter i fluidet, 5 hvilket apparat omfatter midler til frembringelse af to bundter af kohærent lys, hvoraf det ene udgør et målebundt og det andet et referencebundt, midler til at føre målebundtet gennem det fluidum, hvis strømningshastighed skal måles, midler til at føre referencebundtet ad 10 en bane uden om fluidet, og midler til at modtage det i fluidet fra målebundtet spredte lys kombineret med referencebundtet og analyse af det heraf resulterende Dopp-ler-stødfrekvensspektrum.BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an apparatus for measuring the flow rate of a fluid using the frequency change due to the Doppler effect of scattering light from discontinuities in the fluid, comprising means for producing two bundles of coherent light, one of which constitutes a measurement bundle and the other a reference bundle, means for passing the measuring bundle through the fluid whose flow rate is to be measured, means for passing the reference bundle along an orbit around the fluid, and means for receiving the light scattered in the fluid from the measuring bundle combined with the reference bundle. and analysis of the resulting Doppler clay frequency spectrum.

Der kendes målemetoder, hvor der anvendes ét enkelt 15 lysbundt, og hvor en del af bundtet føres gennem fluidet og spredes af diskontinuiteter i dette fluidum, medens den resterende del af bundtet anvendes som reference til måling af den på Doppler-effekten i fluidet beroende frekvensændring .Measurement methods are known in which a single bundle of light is used and where a portion of the bundle is passed through the fluid and spread by discontinuities in that fluid, while the remaining portion of the bundle is used as a reference for measuring the frequency change dependent on the Doppler effect in the fluid. .

20 Disse målemetoder har den ulempe, at der fås et dårligt signal/støj-forhold som følge af, at det lys, der spredes fra bundtet, spredes diskontinuerligt af en-keltpartikler, der bevæger sig uafhængigt af hinanden, hvorved der indføres støj såvel i referencebundtdelen 25 som det spredte lys.These measurement methods have the disadvantage that a poor signal-to-noise ratio is obtained because the light scattered from the bundle is discontinuously scattered by single particles moving independently of one another, thereby introducing noise into the the reference bottom portion 25 as the scattered light.

Opfindelsen tager sigte på at afhjælpe denne ulempe og giver anvisning på et apparat, som sikrer et bedre signal/støj-forhold end opnåeligt ved de kendte metoder.The invention aims to remedy this disadvantage and provides an apparatus which ensures a better signal-to-noise ratio than obtainable by the known methods.

30 Med henblik herpå er apparatet ifølge opfindelsen ejendommeligt ved midler til at bibringe referencebundtet en styrke af i det væsentlige samme størrelse som målebundtets styrke.To this end, the apparatus according to the invention is characterized by means for imparting the reference bundle a strength of substantially the same size as the strength of the measuring bundle.

Ved at anvende to separate bundter og ved at sørge 35 for, at de indbyrdes har sådanne intensiteter, at intensiteten af det af en detektor modtagne, fra referencebundtet hidrørende lys styrkemæssigt er af samme størrelse som intensiteten af det spredte lys, opnås den til- 144716 2 sigtede forbedring af signal/støj-forholdet.By using two separate bundles and by ensuring that they have mutual intensities such that the intensity of the light received by a detector derived from the reference bundle is of the same magnitude as the intensity of the scattered light, it is obtained. 2 term improvement of signal-to-noise ratio.

Når lys udsendt fra en stationær kilde absorberes og genudsendes af en bevægende partikel f.eks. spredes af partiklen, vil en stillestående iagttager konstatere, 5 at frekvensen af det spredte lys afviger fra frekvensen af det lys, der iagttages direkte fra kilden, hvilken frekvensændring kendes som Doppler-frekvensforskydning.When light emitted from a stationary source is absorbed and emitted by a moving particle e.g. scattered by the particle, a stationary observer will observe that the frequency of the scattered light differs from the frequency of the light observed directly from the source, which frequency change is known as Doppler frequency shift.

Ved måling af en væskestrømning er det nødvendigt, at de partikler, der forårsager en spredning af lyset, ligger 10 tæt op til hinanden i forhold til lysets bølgelængde, men dette er den normale tilstand, når der anvendes synligt lys. Under disse betingelser afhænger frekvensforskydningen mere af den generelle væskehastighed end af hastigheden af de enkelte spredende partikler.When measuring a fluid flow, it is necessary that the particles causing the light to scatter are 10 close to each other relative to the wavelength of light, but this is the normal state when visible light is used. Under these conditions, the frequency shift depends more on the overall fluid velocity than on the velocity of the individual scattering particles.

15 Ved en indfaldende lysstråle med en bølgevektor k = hvor n er brydningsindekset, der af en gen stand, som bevæger sig med en hastighed v og med en vinkel α til en given retning K, hvor K = k - k', idet strålen spredes i en retning k' med en vinkel Θ 20 til K, angives Doppler-frekvensforskydningen Δω = 2πΔμ ved Δω = v · K (1)At an incident light beam with a wave vector k = where n is the index of refraction of an object moving at a velocity v and at an angle α to a given direction K, where K = k - k ', the beam being scattered in a direction k 'with an angle Θ 20 to K, the Doppler frequency offset Δω = 2πΔµ is indicated by Δω = v · K (1)

Denne formel kan skrives 0 0 Δμ = —— sin ^ cos a = Av sin ^ oos α (2) 25 hvor A er en konstant, forudsat at J k I ~ I k' I og v << c I det særlige tilfælde, hvor laserlyset er parallelt med den i bevægelse værende genstand, og hvor det spredte lys iagttages fra en retning vinkelret herpå 30 har man _ 1 9 “ 2 α = 0 og ligningen (2) reduceres til Δμ = ψ-^2 (3) 35 I det tilfælde, hvor fluidet er vand, og hvor der anvendes en helium/neonlaser har man n = 1,3 λ = 6328 Å 3 144716 og hvis v = 3cm/sek opnår man Δμ = 100 kHz = 105 Hz.This formula can be written 0 0 Δμ = —— sin ^ cos a = Av sin ^ oos α (2) 25 where A is a constant, provided that J k I ~ I k 'I and v << c In the particular case, where the laser light is parallel to the moving object and where the scattered light is observed from a direction perpendicular thereto, one has _ 1 9 "2 α = 0 and the equation (2) is reduced to Δμ = ψ- ^ 2 (3) 35 In the case where the fluid is water and where a helium / neon laser is used, one has n = 1.3 λ = 6328 Å 3 144716 and if v = 3cm / sec one obtains Δμ = 100 kHz = 105 Hz.

Da den til λ = 6328 Å svarende laserfrekvens er ca. 1014 Hz, kan det være vanskeligt at måle en frekvens-5 ændring af denne størrelsesorden.Since the laser frequency corresponding to λ = 6328 Å is approx. 1014 Hz, it can be difficult to measure a frequency-5 change of this magnitude.

Frekvensændringen kan dog måles ved heterodynvirk-ning, men det er dog mere hensigtsmæssigt at vælge værdierne Θ = 30° 10 α = 0 og at blande det spredte lys med en del af det oprindelige lys under anvendelse af et fotorør, der har en kvadrerende virkning.However, the frequency change can be measured by heterodynamic effect, but it is more appropriate to select the values Θ = 30 ° 10 α = 0 and to mix the scattered light with a portion of the original light using a photo tube having a squaring effect. .

Det skal forstås, at frekvensen ved de sædvanlige 15 lasere ikke er konstant, men varierer over et frekvensbånd, der tilnærmelsesvis er centreret på laserlysets nominelle frekvens- I praksis har det vist sig, at dette ikke har nogen betydning, eftersom frekvensvariationerne er betydeligt højere end enhver frekvensændring, der 20 skyldes partikelbevægelsens hastighed.It should be understood that the frequency of the usual 15 lasers is not constant, but varies over a frequency band that is centered approximately on the nominal frequency of the laser light. any frequency change due to the rate of particle movement.

Opfindelsen forklares nærmere i det følgende under henvisning til tegningen, der viser en udførelsesform for apparatet ifølge opfindelsen til måling af væskestrømning.The invention will be explained in more detail below with reference to the drawing, which shows an embodiment of the apparatus for measuring fluid flow.

25 Apparatet omfatter et rør 10, f.eks. glasrør af en diameter på 1,3 cm, hvori vand strømmer i den ved en pil 11 angivne retning med en hastighed på ca. 50 cm pr. sek. For at sikre en passende lysspredning er der til vandet tilsat nogle få dråber mælk.The apparatus comprises a tube 10, e.g. 1.3 cm diameter glass tubes in which water flows in the direction indicated by an arrow 11 at a rate of approx. 50 cm per SEC. A few drops of milk have been added to the water to ensure a suitable light distribution.

30 Som lyskilde anvendes en helium-neon-laser 12 med en udgangseffekt på 50 mW ved en frekvens på 1014 Hz.30 As a light source, a helium-neon laser 12 with an output power of 50 mW is used at a frequency of 1014 Hz.

Lyset fra laserkilden opdeles i to stråler ved hjælp af en stråleopdeler 13, der udgøres af en tynd plade af glas, der med strålen danner en vinkel på 30°, således 35 at der tilvejebringes en reflekteret referencestråle a, der derefter føres gennem et neutralt tæthedsfilter 14.The light from the laser source is divided into two rays by means of a beam splitter 13 formed by a thin plate of glass forming with the beam an angle of 30 °, so as to provide a reflected reference beam a, which is then passed through a neutral density filter 14th

De to divergerende stråler reflekteres derefter ved hjælp af to parallelt med stråleopdeleren beliggende 144716 4 plane spejl 15 og 16, hvorefter hver stråle fokuseres til dannelse af to lyspletter af en diameter på 2 mm ved hjælp af to linser 17 og 18 med en fokallængde på 30 cm. Hovedstrålen b føres gennem glasrøret 10 un-5 der en vinkel på 60° i forhold til glasrørets akse, medens referencestrålen a føres bag røret 10 under en modsat lige stor vinkel i forhold til aksen, hvorefter strålen rammer et fotorør 19. Lyset fra hovedstrålen b spredes af vandet i en retning parallel med 10 referencestrålen og føres også til fotorøret 19. For at begrænse et uønsket spredt lys i at nå fotorøret, er der i rørets akse i en afstand på 10 cm foran røret anbragt et diafragm 20 med en åbning på 0,2 mm. Hovedstrålen b absorberes i en strålefælde 21.The two divergent beams are then reflected by two parallel mirrors 15 and 16 located parallel to the beam divider, after which each beam is focused to form two 2 mm diameter light spots by two lenses 17 and 18 having a focal length of 30 cm. The main beam b is passed through the glass tube 10 at an angle of 60 ° to the axis of the glass tube, while the reference beam a is passed behind the tube 10 at an opposite equal angle to the axis, after which the beam strikes a photo tube 19. The light from the main beam b is spread by the water in a direction parallel to the reference beam and is also fed to the photo tube 19. In order to limit an undesirable scattered light in reaching the photo tube, a diaphragm 20 with an aperture of 10 cm is arranged in the axis of the tube at a distance of 10 cm. 0.2 mm. The main beam b is absorbed in a beam trap 21.

15 Det neutrale tæthedsfilter 14 nedsætter styrken af referencestrålen a i forhold til hovedstrålen b, således at det lys i referencestrålen a, der rammer fotorøret 19 tilnærmelsesvis har samme styrke som det lys, der spredes fra hovedstrålen b og rammer fotorø-20 ret 19. Uden filteret 14 ville styrken i reference-strålen a være flere størrelsesordner større end styrken af det lys, der spredes fra hovedstrålen, og ville således føre til et meget dårligt signal/støj-forhold.The neutral density filter 14 decreases the strength of the reference beam a in relation to the main beam b, such that the light in the reference beam a which strikes the photo tube 19 has approximately the same strength as the light scattered from the main beam b and strikes the phototube 19. Without the filter 14, the magnitude of the reference beam a would be several orders of magnitude greater than the magnitude of the light scattered from the main beam, and would thus result in a very poor signal-to-noise ratio.

Med filteret 14 kan man opnå et signal/støj-forhold 25 på 1 og dermed en god detektering af Doppler-stødfre-kvensspektret.With the filter 14, a signal-to-noise ratio 25 of 1 can be obtained and thus a good detection of the Doppler shock frequency spectrum.

Signalet fra fotorøret føres til en spekteranalysa-tor, der viser frekvensen som funktion af amplituden.The signal from the phototube is fed to a spectrum analyzer which shows the frequency as a function of the amplitude.

Såfremt der ikke er nogen Doppler-forskydning, afgiver 30 den iagttagne frekvens på ca. 10 Hz ingen signaler, men i praksis kan der iagttages et antal frekvenser, der angiver omfanget af de iagttagen hvirvelstrømmehastigheder. I tilfældet af en ensartet strømning iagttages der en enkelt spids i spektret.If there is no Doppler offset, 30 gives the observed frequency of approx. 10 Hz no signals, but in practice a number of frequencies can be observed indicating the range of the observed eddy current rates. In the case of a uniform flow, a single peak is observed in the spectrum.

35 Man har i praksis konstateret, at alle væsker inde holder et tilstrækkeligt stort antal spredende partikler til, at den foreliggende opfindelse kan anvendes uden tilsætning af yderligere spredende partikler. DogIn practice, it has been found that all liquids contain a sufficient number of dispersing particles for the present invention to be applied without the addition of additional dispersing particles. However

DK544968A 1967-11-10 1968-11-08 APPARATUS FOR MEASURING THE FLOW SPEED OF A FLUID DK144716C (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DK398974A DK136380B (en) 1967-11-10 1974-07-24 Method for detecting an eddy current in a fluid.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB5137167 1967-11-10
GB5137167 1967-11-10
GB00757/68A GB1242063A (en) 1967-11-10 1967-11-10 Improvements in or relating to the detection and measurement of movement
GB1075768 1968-03-05

Publications (2)

Publication Number Publication Date
DK144716B true DK144716B (en) 1982-05-17
DK144716C DK144716C (en) 1982-11-15

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DK544968A DK144716C (en) 1967-11-10 1968-11-08 APPARATUS FOR MEASURING THE FLOW SPEED OF A FLUID

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DE (1) DE1808162C3 (en)
DK (1) DK144716C (en)
FR (1) FR1592220A (en)
GB (1) GB1242063A (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2454102A1 (en) * 1979-02-27 1980-11-07 Anvar METHOD AND DEVICE FOR THE SIMULTANEOUS MEASUREMENT OF SPEEDS, FLUCTUATIONS OF SPEEDS AND DIAMETERS OF SUBMICRONIC PARTICLES IN A FLUID
DE3033250A1 (en) * 1980-09-04 1982-04-08 Stahl Gmbh & Co Maschinenfabrik, 7140 Ludwigsburg Gear wheel drive for shafts and rollers - is used in folding machines and has element damping mechanical oscillations located inside each gear wheel
DE3153109C2 (en) * 1981-03-27 1986-02-13 Jagenberg AG, 4000 Düsseldorf Noise-damped machine element
FR2527334B1 (en) * 1982-05-21 1985-03-01 Inst Nat Sante Rech Med FOCUSLESS LASER ELECTROPHORESIS APPARATUS
GB2215050B (en) * 1988-02-03 1991-09-04 Schlumberger Ind Ltd Systems for detecting magnetic particles in fluids
DE3936950C2 (en) * 1988-07-08 1996-12-19 Deutsch Franz Forsch Inst Laser Doppler anemometer
DE102012001703A1 (en) 2012-01-31 2013-08-01 Astrium Gmbh gear

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Publication number Publication date
FR1592220A (en) 1970-05-11
DK144716C (en) 1982-11-15
DE1808162B2 (en) 1978-10-26
DE1808162C3 (en) 1982-02-04
DE1808162A1 (en) 1969-07-24
GB1242063A (en) 1971-08-11

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