Ultrasonic Flow Meter Accuracy thiab Flow Rate Correction Improvement

Yog tias koj tau siv sijhawm tiag tiag nrogultrasonic flowmeter, koj twb paub lub suab: tsis yog - ntxeem tau, tsis muaj qhov txav, ua haujlwm ntawm yuav luag txhua yam. Thiab saib, feem ntau yog qhov tseeb. Tab sis qhov tseeb kev sib tham? Qhov ntawd yog qhov uas tej yam txaus siab -thiab qee zaum ntxhov siab. Vim tias lub ntsuas ultrasonic uas yog qhov tseeb hauv chav kuaj tuaj yeem coj txawv txawv thaum koj ntsia nws mus rau hauv lub raj xa dej tiag tiag nrog lub luj tshib, qhov kub thiab txias, thiab lwm yam uas koj cov txheej txheem cuam tshuam rau nws.

Qhov no tsis yog txhais tau tias yuav ntshai koj tawm ntawm kev siv tshuab. Ultrasonic meters nyob twj ywm ib qho ntawm cov kev xaiv zoo tshaj plaws rau ntau daim ntawv thov. Lub ntsiab lus yog nkag siab txog dab tsi cuam tshuam rau lawv qhov raug thiab - tseem ceeb dua - koj tuaj yeem ua dab tsi txog nws.

Kev thauj mus los- lub sij hawm ultrasonic flow meter ua hauj lwm los ntawm kev xa cov suab paj nruag ntawm ob lub transducers -ib qho dej ntws, ib qho qis. Cov mem tes mus nrog cov ntws tuaj txog me ntsis nrawm dua li qhov sib ntaus sib tua. Lub sijhawm sib txawv ntawd, peb tab tom tham nanoseconds ntawm no, tau hloov mus rau hauv qhov nrawm nrawm.

Yooj yim txaus rau ntawm daim ntawv. Qhov teeb meem pib thaum koj paub tias kev ntsuas nrawm tshwm sim raws li ib txoj hauv kev (lossis tej zaum ob peb txoj hauv kev hauv cov meters fancier), tab sis qhov koj xav tau yog qhovnruab nrabnrawm hla tag nrho cov yeeb nkab hla -section. Cov kua dej tsis txav mus rau tib qhov ceev txhua qhov chaw. Nws qeeb qeeb ze ntawm phab ntsa, nrawm dua hauv nruab nrab. Qhov kev sib raug zoo ntawm qhov ntsuas pom thiab qhov tshwm sim tiag tiag yog nyob ntawm qee yam hu ua qhov nrawm nrawm- thiab qhov profile hloov pauv nrog Reynolds tus lej, cov yeeb nkab roughness, kev cuam tshuam ntawm cov dej ntws, thiab txog kaum kaum lwm yam.

Wb yuav blunt txog lub ntsiab qhov chaw ntawm kev ua yuam kev.

Ultrasonic Flow Meter Accuracy

Muab lub luj tshib ntawm koj lub 'meter' thiab koj nyuam qhuav tsim asymmetric ntws. Qhov kev faib tawm nrawm tau skewed, tej zaum swirling, thiab koj ib leeg - txoj kev ntsuas tam sim no sawv cev ... dab tsi tiag? Kev tshawb fawb tau pom qhov ua yuam kev txog li 15% los ntawm kev cuam tshuam txog dej ntws ib leeg thaum koj tsis suav rau lawv. Ntau-pab metres pab tau zoo heev-lawv ua piv txwv nrawm ntawm ob peb lub ntsiab lus hla cov yeeb nkab txoj kab uas hla thiab siv qhov hnyav nruab nrab-tab sis lawv tsis yog khawv koob. Ib qho profile uas cuam tshuam tsis zoo tseem tuaj yeem ua rau lawv mus.

Ntawm no yog ib yam dab tsi uas ntes cov neeg tawm tsam. Cov duab ntawm koj qhov profile nrawm tsis kho - nws hloov nrog Reynolds tus lej. Thaum qis ntws (laminar tsoom fwv, Re hauv qab txog 2300), koj tau txais ib qho profile parabolic. Qhov nruab nrab qhov nrawm yuav yog ob npaug ntawm qhov nruab nrab. Thaum siab ntws (turbulent, Re saum toj 4000), qhov profile flattens tawm considerably; nruab nrab tshaj tawm yog tej zaum 1.1 mus rau 1.2 npaug nruab nrab.

Qhov no txhais li cas rau kev xyaum? Qhov kev kho qhov ntsuas koj qhov ntsuas tau siv ntawm ib tus nqi ntws yuav tsis raug ntawm lwm qhov. Feem ntau cov tuam txhab tsim hauv qee qhov nyiaj them, tab sis qhov kev xav tom qab nws yuav tsis phim koj cov xwm txheej tiag tiag.

Lub hwj chim- txoj cai nrawm nrawm tau siv los ua qauv rau ntau xyoo lawm. Nikuradse txoj hauj lwm los ntawm 1930s-yog, qhov qub- tseem ua lub hauv paus rau ntau qhov kev kho algorithms. Cov profile ua raws li qhov sib npaug u/u_max=(1 - r/R)^(1/n), qhov twg n txawv nrog Reynolds tus lej. Thaum n yog nyob ib ncig ntawm 7, koj tab tom saib ntawm ib qho chaw tiaj tus turbulent profile. Thaum n poob rau 4, tej yam tau taw qhia ntau dua. Qhov kev kho kom haum rau ib txoj hauv kev hauv nruab nrab tuaj yeem ua viav vias ntawm 0.75 txog 0.95 nyob ntawm seb muaj xwm txheej.

Ultrasonic Flow Meter Accuracy

Cov kav dej ntxhib ua rau qhov profile flatter. Cov kav dej tshiab tshiab piv rau cov qub qub tuaj yeem txhais tau tias qhov sib txawv ntawm 0.5 mus rau 1% ntawm kev nyeem ntawv dhau sijhawm -thiab tej zaum koj yuav tsis pom txog tias koj xav paub yog vim li cas koj lub meter drifted.

Qhov no tsim nyog nws cov ntu vim tias qhov kub thiab txias cuam tshuam rau kev ntsuas ultrasonic hauv txoj kev uas tsis pom tseeb tam sim ntawd.

Ua ntej, qhov ceev ntawm lub suab hauv koj cov kua hloov nrog qhov kub thiab txias. Hauv dej, lub suab nrawm nce li 2.4 m / s rau txhua qib Celsius nce. Lub 'meter' lub sij hawm thauj mus los suav hais tias muaj qee lub suab tshaj tawm; tau txais nws tsis ncaj ncees lawm thiab koj cov ntawv nyeem hloov pauv. Cov ntsuas niaj hnub no suav nrog ntsuas qhov ntsuas kub thiab ntsuas cov txheej txheem them nyiaj, thiab cov khoom zoo tuaj yeem txo qhov kub thiab txias - vim qhov yuam kev los ntawm 1.5% mus rau thaj tsam 0.2%. Tab sis pheej yig dua units nrog cov nyiaj them tsis zoo? Lawv yuav taug kev.

Thib ob-thiab qhov no yog qhov hloov maj mam- cov transducers lawv tus kheej hloov cov yam ntxwv nrog kub. Lawv electromechanical teb hloov. Lub sij hawm thaum lawv yeej tua hluav taws thaum lawv thov kom tua hluav taws. Yog tias koj cov khoom siv hluav taws xob sab saud thiab qis qis tsis sib haum xeeb (thiab lawv yeej tsis ua, txawm tias los ntawm tib lub chaw tsim khoom), koj tau txais kev tsis ncaj ncees uas txawv nrog qhov kub thiab txias. Qee cov ntaub ntawv qhia txog lub sijhawm hloov pauv hloov pauv ntawm qhov kev txiav txim ntawm picoseconds ib degree, uas suab tsis tseem ceeb kom txog rau thaum koj nco ntsoov koj ntsuas nanosecond - ntsuas qhov sib txawv.

Thib peb, cov yeeb nkab nws tus kheej nthuav dav thiab cog lus. Txoj kev ntev hloov. Cov nyhuv me me, feem ntau, tab sis nws sau nrog txhua yam.

Yog lawm, teeb meem txaus. Koj ua tau dab tsi?

Tau txais koj lub installation txoj cai

Cov lus teb tho txawv, tab sis feem ntau cuam tshuam. Ncaj yeeb nkab khiav teeb meem. Txoj cai qub ntawm tus ntiv tes xoo yog 10-20 yeeb nkab txoj kab uas hla ntawm lub 'meter', 5 downstream. Qhov ntawd yog qhov tsim nyog rau ib qho - txoj kab meters; ntau- txoj kev tsim kev zam txim ntau dua tab sis tseem tau txais txiaj ntsig los ntawm kev ntws huv. Yog tias koj tsis tuaj yeem ua tiav qhov kev khiav ncaj nraim, cov cua txias tuaj yeem pab tau - cov hlua khi, cov phaj perforated, cov khoom siv vane. Lawv hlais qhov kev cuam tshuam ntawm qhov profile thiab muab sijhawm rau rov tsim dua.

Ntawm 2 yeeb nkab diameters downstream los ntawm kev cuam tshuam, ib txoj kev tshawb nrhiav pom ultrasonic meters tuaj yeem tawm los ntawm 15% nrog 21% tsis paub meej. Los ntawm 10 diameters, uas shrinks dramatically. Los ntawm 50 txoj kab uas hla, koj nyob ntawm qhov zoo tagnrho. Feem ntau cov kev teeb tsa tiag tiag poob rau qhov chaw nruab nrab, yog li cov lus nug siv tau dhau los: qhov ua yuam kev ntau npaum li cas koj tuaj yeem zam tau, thiab koj tuaj yeem faib cov yeeb nkab ntev npaum li cas?

Siv Cov Txheej Txheem Kho kom raug

Yog tias koj paub Reynolds tus naj npawb ntawm koj cov dej ntws (thiab koj yuav tsum muaj peev xwm xam nws los ntawm kev tshaj tawm, txoj kab uas hla, thiab kinematic viscosity), koj tuaj yeem siv qhov kev kho qhov profile. Rau ib txoj kab diametral, qhov kho qhov tseem ceeb K hais txog txoj kev - nruab nrab tshaj tawm mus hla -section- nruab nrab tshaj tawm. K txawv ntawm tej zaum 0.75 nyob rau hauv laminar ntws mus rau ib ncig ntawm 0.94 nyob rau hauv tag nrho tsim turbulent flow.

Qee cov ntsuas tshiab ua qhov no cia li siv ua - hauv algorithms. Lwm tus muab rau koj los kho qhov xwm txheej manually. Tseem muaj lwm tus xav tias tus nqi ruaj khov uas yog "ze txaus" rau lawv qhov kev cia siab ua haujlwm. Paub yam koj muaj.

Rau kev cuam tshuam qhov chaw uas qhov profile yog asymmetric, kev tsis ncaj ncees - kho qhov sib npaug tau tsim. Lawv nyob ntawm hom kev cuam tshuam (ib lub luj tshib, ob lub luj tshib tawm - ntawm - dav hlau, valve, thiab lwm yam) thiab nyob deb ntawm nws. Cov no tsis zoo tag nrho-lawv nyob ntawm qhov nruab nrab qhov kev sim cov ntaub ntawv-tab sis siv lawv yeej tsis quav ntsej qhov teeb meem.

Ntau-Txoj kev teeb tsa

Mus los ntawm ib txoj kev ultrasonic mus rau plaub los yog tsib dramatically txhim kho qhov tseeb nyob rau hauv tiag tiag tej yam kev mob. Txoj hauv kev tau muab tso rau ntawm qhov kev ncua deb ntawm cov yeeb nkab chaw, hnyav raws li kev sib koom ua ke (Gaussian quadrature thiab cov txheej txheem zoo sib xws) uas kwv yees qhov tseeb hla -sectional averaging.

British Gas tau tshaj tawm 4- txoj kab geometry rov qab rau hnub uas tau dhau los siv dav hauv kev saib xyuas cov ntawv thov hloov chaw. Nws ua tiav qhov tseeb hauv 0.2% ntawm qhov tseeb ntws tsis hais txog kev taw qhia profile- tsawg kawg yog thaum qhov profile ua raws li cov qauv xav tau. Muab piv rau ib leeg-txoj kev ntsuas uas yuav viav vias 1.4% tsuas yog los ntawm kev tig lub dav hlau ntsuas txheeb ze rau kev cuam tshuam. Qhov sib txawv loj rau kev ntsuas nyiaj txiag.

Ntau- kab ntsuas kab kuj tseem muab ua - hauv kev kuaj mob. Koj tuaj yeem sib piv cov nrawm ntawm txoj kev sib txawv. Yog tias txoj kev tshaj tawm tsis sib xws hauv qhov kev xav tau, ib yam dab tsi tsis ncaj ncees lawm nrog cov dej ntws profile, thiab koj paub tshawb xyuas.

Temperature Compensation Ua Tau Zoo

Tsis txhob cia siab rau ib qho ntsuas kub ntawm qhov ntsuas qhov ntsuas. Ntsuas ntsuas kub ntawm lossis ze ntawm cov transducers. Siv qhov ntsuas kub los ntsuas qhov nrawm ntawm lub suab yog tias koj lub ntsuas ntsuas tsis ua nws tau. Rau cov kua uas paub cov khoom, cov ntxhuav muaj nyob; rau cov kua dej kev cai, koj yuav xav tau cov ntaub ntawv tus cwj pwm.

Rau siab - daim ntawv thov precision, transducer nyiaj tau txais kev koom tes ntau dua. Txoj hauv kev suav nrog ntsuas lub sijhawm oscillation ntawm cov cim tau txais thiab siv ob lub sijhawm thiab qhov kub thiab txias raws li kev nkag mus rau ob -point linear them algorithm. Nws suab nyuaj vim tias nws yog, tab sis IC cov tuam txhab tau pib tsim qhov no rau hauv lub sijhawm tshwj xeeb- rau - digital converter chips.

Clamp-Rau Cov Teeb Meem Tshwj Xeeb

Clamp- ntawm meters ntxiv lwm txheej ntawm complexity: cov yeeb nkab phab ntsa. Suab mus los ntawm phab ntsa, refracts ntawm interfaces, thiab tuaj tos qeeb. Kev ntsuas phab ntsa tuab yog qhov tseem ceeb heev - siv cov thickness ntsuas cais, nyob rau ntawm qhov chaw, nrog cov gel txuas. Corrosion los yog scale deposits pov tawm ob phab ntsa thickness thiab internal txoj kab uas hla. Ib txoj kev tshawb fawb xyoo 2016 tau soj ntsuam cuaj lub tshuab nqa tau yooj yim- ntawm cov meters pom qhov ua yuam kev nruab nrab ntawm -12.8% mus rau +1.2%, nrog rau feem ntau underestimating ntws. Yim ntawm cuaj meters nyeem qis.

Lub sijhawm sib txawv ntawm qhov koj tab tom sim ntsuas yuav yog kaum ntawm nanoseconds. Extracting uas los ntawm cov suab nrov yuav tsum tau zoo algorithms.

Zero-Kev kuaj pom hla yog txoj hauv kev ib txwm muaj: nrhiav qhov twg qhov tau txais waveform hla xoom amplitude, siv lub sijhawm ntawd. Yooj yim thiab ceev, tab sis rhiab rau lub suab nrov thiab amplitude variations.

Hla -kev sib raug zoo muaj kev tiv thaiv suab nrov zoo dua. Nws muab piv rau tag nrho cov dej ntws thiab cov dej ntws qis, nrhiav lub sijhawm ua haujlwm uas ua rau lawv qhov kev sib raug zoo. Cov lej yog hnyav dua, tab sis FPGAs tau yooj yim tam sim no. Qee qhov kev siv tau ua tiav sub-nanosecond daws teeb meem.

Tsis ntev los no, cov kev kawm tob tau pom cov lus cog tseg rau kev kwv yees tus nqi ntws hauv cov xwm txheej nyuaj. Qhia lub network neural ntawm CFD-simulated flow fields thiab lawv cov npe ultrasonic sib raug; cia nws kawm cov qauv uas tib neeg yuav nco. Tseem sim hauv cov khoom lag luam, tab sis cov ntaub ntawv kawm tau txhawb nqa.

Ultrasonic Flow Meter Accuracy

Factory calibration siv cov xwm txheej zoo: cov kav dej ntev ntev, ruaj khov, cov kua dej paub, tswj qhov kub thiab txias. Koj lub installation tsis muaj qhov no. Qhov ntawd tsis ua rau qhov ntsuas ntsuas tsis muaj txiaj ntsig, tab sis nws txhais tau hais tias qhov tseeb (feem ntau ± 0.5% rau ± 1% ntawm kev nyeem ntawv) yog qhov zoo tshaj plaws - rooj plaub ua haujlwm.

Hauv -situ calibration lossis verification tiv thaiv ib qho kev ntsuas ntsuas pab tsim kom muaj kev ua tau zoo hauv ntiaj teb-. Coriolis meters ua cov ntaub ntawv zoo heev yog tias koj tuaj yeem nruab ib qho; lawv tiv thaiv rau feem ntau ntawm cov teebmeem profile uas teeb meem ultrasonics. Qee qhov kev ua haujlwm siv tus tswv ultrasonic meter nrog qhov raug ntau dua (ntau txoj hauv kev, ua haujlwm zoo dua) los xyuas cov chav ua haujlwm.

Calibration ntawm ntau tus nqi ntws thoob plaws koj qhov kev ua haujlwm xav tau yog tsim nyog rau kev siv zog. Lub 'meter' tej zaum yuav yog qhov chaw - ntawm 50% muaj peev xwm tab sis drift ntawm 10% lossis 90%. Tau txais cov ntaub ntawv cov ntsiab lus, haum rau qhov kho qhov nkhaus yog tias xav tau.

Hais lus ncaj ncees: qee zaum ib lub tshuab ntsuas sib txawv ua rau muaj kev nkag siab ntau dua. Yog tias koj xav tau 0.1% qhov tseeb thiab tuaj yeem them tus nqi, Coriolis meters yeej. Lawv ntsuas huab hwm coj ncaj qha, tsis quav ntsej qhov nrawm nrawm, thiab feem ntau tsis cuam tshuam los ntawm qhov kub thiab txias. Qhov downside yog tus nqi, qhov loj me, thiab siab poob -tab sis rau kev saib xyuas kev hloov pauv ntawm cov khoom muaj txiaj ntsig siab, lawv them rau lawv tus kheej.

Rau cov kua dej conductive uas muaj kev cuam tshuam loj heev, cov khoom sib nqus flowmeters yuav ua tau zoo dua ultrasonics. Lawv insensitive rau profile zoo li ntev raws li qhov profile yog axisymmetric (uas lub luj tshib thiab li qub tuaj yeem cuam tshuam, tab sis tsawg dua nrog ultrasonics).

Tab sis rau cov kav dej loj, kev siv roj av, kev teeb tsa rov qab uas koj tsis tuaj yeem txiav cov yeeb nkab, lossis cov xwm txheej uas qhov kev poob siab tsis tuaj yeem txais tau -ultrasonics feem ntau tseem yog tib txoj kev xaiv. Paub lawv cov kev txwv thiab ua haujlwm nyob ib puag ncig lawv.

Ultrasonic flow meter raug nyob rau hauv lub ntiaj teb tiag tiag nyob ntawm kev nkag siab qhov sib txawv ntawm qhov chaw kuaj mob thiab koj qhov kev teeb tsa tiag tiag. Kev cuam tshuam qhov nrawm nrawm, qhov kub thiab txias hloov pauv, cov yam ntxwv ntawm cov transducer, cov yeeb nkab tej yam kev mob -lawv txhua tus pab. Qhov tseeb ntawm ± 1% yuav dhau los ua ± 3% lossis phem dua yog tias koj tsis quav ntsej txog cov xwm txheej no.

Qhov xwm zoo: feem ntau ntawm cov teeb meem no tau paub cov kev daws teeb meem lossis tsawg kawg paub txog kev daws teeb meem. Kev txhim kho kom zoo, kho qhov tsim nyog, kev them nyiaj kub zoo, ntau- txoj hauv kev tsim cov peev nyiaj tso cai, thiab kev ntsuas qhov tseeb raws li qhov tseeb tuaj yeem coj tau tiag tiag - ntiaj teb kev ua tau zoo dua los ze rau qhov kev txwv.

Tsis txhob ntseeg daim ntawv spec blindly. Nkag siab txog dab tsi cuam tshuam rau koj lub ntsuas, ntsuas qhov koj tuaj yeem ua tau, kho qhov koj paub, thiab tswj cov npoo tsis paub tseeb rau qhov uas tseem tsis tau paub. Qhov ntawd tsis yog pessimism -nws yog metrology.

Thiab yog tias ib tug neeg nug seb koj lub ntsuas ultrasonic puas yog, cov lus teb ncaj ncees yog: nws nyob ntawm. Tab sis tam sim no koj paub txog dab tsi.