9 research outputs found
Improved flow measurement using EM flat probes in mixed flow conditions
One of the commonly used approaches, for the flow measurements in sewer systems, are velocity-area methods. Although, it is reported that the velocity sensors operate with high uncertainty, the popularity of these methods stem from the fact that they can be applied in wide range of hydraulic conditions including the mixed flow conditions. Uncertainties are related both to the applied instruments and properties of the measurement site. In order to overcome this issue, additional site-specific calibration procedure for flat EM sensors is presented in this paper. Concept of its application in the engineering practice example are presented
Improvement of EM flow meters accuracy through site-specific CFD calibration case study HPS Trebinje
Using CFD and real-magnetic field of EM probes to improve the accuracy of flow measurements in mixed flow conditions
Flow measurement in mixed flow conditions is a challenging task, which can be performed only by few techniques like ultrasonic and electromagnetic. Usually despite the flowmeterās special design, the systematic uncertainty of flow rate remains high. In order to overcome this issue, additional site-specific calibration procedure for flat EM sensors is presented in this paper. Procedure includes both a hydraulic and magnetic field analysis. Concept of its application in the engineering practice example are presented
Improved flow measurement using EM flat probes in mixed flow conditions
One of the commonly used approaches, for the flow measurements in sewer systems, are velocity-area methods. Although, it is reported that the velocity sensors operate with high uncertainty, the popularity of these methods stem from the fact that they can be applied in wide range of hydraulic conditions including the mixed flow conditions. Uncertainties are related both to the applied instruments and properties of the measurement site. In order to overcome this issue, additional site-specific calibration procedure for flat EM sensors is presented in this paper. Concept of its application in the engineering practice example are presented
Improvement of EM flow meters accuracy through site-specific CFD calibration case study HPS Trebinje
Merenje protoka vode u tunelima pri kombinovanim uslovima teÄenja: primer tunela Dabarsko Polje - FatniÄko polje
U opÅ”tem sluÄaju, metode za merenje protoka vode se mogu klasifikovati prema uslovima teÄenja na mernom mestu, pa se tako odreÄene metode koriste u sistemima pod pritiskom dok neÅ”to drugaÄije u sistemima gde se javlja teÄenje sa slobodnom povrÅ”inom. U odreÄenim sluÄajevima, na mernom mestu se može javiti i teÄenje pod pritiskom i sa slobodnom povrÅ”inom, odnosno tzv. kombinovani uslovi teÄenja. U ovom radu analiziran je jedan upravo takav sluÄaj, derivacioni tunel izmeÄu Dabarskog i FatniÄkog Polja u okviru sistema Hidroelektrane na TrebiÅ”njici (HET). Glavne karakteristike ovog tunela, pored kombinovanih uslova teÄenja, su i impozantne dimenzije, gde preÄnik varira od 5,0 m do oko 5,6 m, kao i bidirekcioni raspon protoka od -40 do ~55 m3/s. Za
potrebe merenja protoka projektovano je i izvedeno jedno merno mesto unutar tunela, neposredno uz izlazno/ulaznu graÄevinu u FatniÄkom polju, opremljeno sa Äetiri ravne EM sonde, dva logera pritiska i dve kontrolne EM sonde tipa āAjkulino kriloā. ImajuÄi u vidu karakteristike tunela kao i merne metode, neophodno je pažljivo uspostaviti korelaciju izmeÄu izmerene brzine i srednje profilske, odnosno lokalno kalibrisati ravne EM senzore brzine. U radu je analizirana moguÄnost lokalne kalibracije ravnih EM senzora brzine pomoÄu kontrolnih EM sondi āAjkulino kriloā. Dobijeni rezultati su uporeÄeni sa rezultatima āsuve kalibracijeā sprovedene koriÅ”Äenjem teorijskog rasporeda brzine i jednodimenzionalne težinske funkcije
UnapreÄenje metodologije merenja protoka pomoÄu ravnih elektromagnetnih senzora brzine
One of the commonly used approaches, for the flow measurements in open chanel hydraulic systems, is to measure one depth and use the stable Q-H relationship to compute the flow rate. If this method is inappropriate, the velocity-area method has to be used: both area (depth) and mean velocity are measured in order to compute the flow rate. Although, it is reported that the velocity sensors operate with high uncertainty, the popularity of these methods stem from the fact that they can be applied in wide range of hydraulic conditions including the mixed flow conditions. Uncertainties are related both to the applied instruments and properties of the measurement site. While Doppler probes are preffered nowadays in the hydraulic systems, electromagnetic probes have certain adventages which are found to be useful in the methodology presented in this paper. Here, so called flat EM velocity probes are analyzed, which can be used instead of Doppler probes for the flow measurements. Due to the more rigourous operating principle, particular weighting functions can be derived in order to define contributions from different parts of the flow to the measured signal. Reduction of the uncertainty can be obtained through combination of the weighting functions with site-specific velocity fields computed with CFD simulations, In order to overcome the high uncertainty issue, additional site-specific calibration procedure for flat EM sensors is presented in this paper. Concept of its application in the engineering practice example are presented.NajÄeÅ”Äe koriÅ”Äen naÄin merenja protoka u hidrotehniÄkim sistemima sa otvorenim tokom je preko merenja jedne dubine i preraÄunavanjem u protok koriÅ”Äenjem Q-H krive. U uslovima kada nije moguÄe jednoznaÄno uspostaviti Q-H vezu, neophodno je koristiti metodu Brzina-Proticajni presek, gde se odvojeno mere (srednja) proticajna brzina i dubina. Iako su dosadaÅ”nja istraživanja pokazala da senzori brzine Äesto rade sa visokom mernom neodreÄenoÅ”Äu, ovaj pristup je popularan zbog moguÄnosti primene u Å”irokom spektru hidrauliÄkih problema. Merna neodreÄenost u obraÄunatom protoku ima dvojaki karakter i rezultat je neodreÄenosti samog merenja brzine i dubine, kao i doprinosa usled nestandardnih uslova na mernom mestu. Iako se u hidrauliÄkim sistemima u poslednje vreme preferiraju ultrazvuÄne Dopler sonde, elekromagnetne (EM) sonde poseduju prednosti u realnim uslovima rada posebno u sistemima sa otpadnim vodama. U ovom radu, analizirane su ravne EM sonde za brzinu, koje se mogu koristiti umesto Dopler sondi za merenje protoka. Zbog jasnijeg principa rada EM sondi, moguÄe je definisati posebne težinske funkcije kojima se opisuje koliko koji deo polja brzina utiÄe na izlazni signal ureÄaja. KoristeÄi težinske funkcije u kombinaciji sa modeliranim realnim strujnim poljem, dobijenim pomoÄu prostornih numeriÄkih simulacija turbulentnog toka, moguÄe je smanjiti mernu neodreÄenost ureÄaja. Predložena metodologija je klasifikovana kao naknadna kalibracija EM ureÄaja prema uslovima na mernom mestu. Koncept njene primene je prikazan kroz praktiÄan primer
UnapreÄenje metodologije merenja protoka pomoÄu ravnih elektromagnetnih senzora brzine
One of the commonly used approaches, for the flow measurements in open chanel hydraulic systems, is to measure one depth and use the stable Q-H relationship to compute the flow rate. If this method is inappropriate, the velocity-area method has to be used: both area (depth) and mean velocity are measured in order to compute the flow rate. Although, it is reported that the velocity sensors operate with high uncertainty, the popularity of these methods stem from the fact that they can be applied in wide range of hydraulic conditions including the mixed flow conditions. Uncertainties are related both to the applied instruments and properties of the measurement site. While Doppler probes are preffered nowadays in the hydraulic systems, electromagnetic probes have certain adventages which are found to be useful in the methodology presented in this paper. Here, so called flat EM velocity probes are analyzed, which can be used instead of Doppler probes for the flow measurements. Due to the more rigourous operating principle, particular weighting functions can be derived in order to define contributions from different parts of the flow to the measured signal. Reduction of the uncertainty can be obtained through combination of the weighting functions with site-specific velocity fields computed with CFD simulations, In order to overcome the high uncertainty issue, additional site-specific calibration procedure for flat EM sensors is presented in this paper. Concept of its application in the engineering practice example are presented.NajÄeÅ”Äe koriÅ”Äen naÄin merenja protoka u hidrotehniÄkim sistemima sa otvorenim tokom je preko merenja jedne dubine i preraÄunavanjem u protok koriÅ”Äenjem Q-H krive. U uslovima kada nije moguÄe jednoznaÄno uspostaviti Q-H vezu, neophodno je koristiti metodu Brzina-Proticajni presek, gde se odvojeno mere (srednja) proticajna brzina i dubina. Iako su dosadaÅ”nja istraživanja pokazala da senzori brzine Äesto rade sa visokom mernom neodreÄenoÅ”Äu, ovaj pristup je popularan zbog moguÄnosti primene u Å”irokom spektru hidrauliÄkih problema. Merna neodreÄenost u obraÄunatom protoku ima dvojaki karakter i rezultat je neodreÄenosti samog merenja brzine i dubine, kao i doprinosa usled nestandardnih uslova na mernom mestu. Iako se u hidrauliÄkim sistemima u poslednje vreme preferiraju ultrazvuÄne Dopler sonde, elekromagnetne (EM) sonde poseduju prednosti u realnim uslovima rada posebno u sistemima sa otpadnim vodama. U ovom radu, analizirane su ravne EM sonde za brzinu, koje se mogu koristiti umesto Dopler sondi za merenje protoka. Zbog jasnijeg principa rada EM sondi, moguÄe je definisati posebne težinske funkcije kojima se opisuje koliko koji deo polja brzina utiÄe na izlazni signal ureÄaja. KoristeÄi težinske funkcije u kombinaciji sa modeliranim realnim strujnim poljem, dobijenim pomoÄu prostornih numeriÄkih simulacija turbulentnog toka, moguÄe je smanjiti mernu neodreÄenost ureÄaja. Predložena metodologija je klasifikovana kao naknadna kalibracija EM ureÄaja prema uslovima na mernom mestu. Koncept njene primene je prikazan kroz praktiÄan primer