Primeri primene ravnih elektromagnetnih sondi za merenje protoka u kolektorima

Abstract

Merenje protoka u kolektorima sa otvorenim tokom, kao i kanalizacionim sistemima predstavlja izazov jer ne postoji jedna najbolja metoda, već je neophodno dobro poznavati radne uslove i shodno njima izabrati optimalnu mernu metodu. U ovom radu je prikazana elektromagnetna (EM) metoda koja koristi ravne sonde, prilagođene ugradnji u kanalizacione sisteme. Ravne EM sonde su robusne, mogu da mere izuzetno male brzine (pri usporu) kao i velike brzine tokom kišnih epizoda, mogu da rade sa jako malim dubinama a i otporne su na nanos i prljavštinu koja može da se na njima nataloži. Kod većih proticajnih profila je moguće više ravnih EM sondi povezati u jedan integrisani sistem, čime se dobija bolja prostorna integracija brzina a ukupna cena sistema ostaje relativno mala. U radu su dati rezultati detaljnih ispitivanja sondi sprovedenih na Građevinskom fakultetu: snimanja 3D magnetnog polja radi definisanja kontrolne zapremine i težinskog vektora u realnim radnim uslovima, rad ravnih EM sondi pod nanosom i korekciju merenja u takvim uslovima, kao i metodologija primene CFD radi analize uticaja realnih uslova tečenja. Na kraju rada su dati i primeri upotrebe ravnih EM sondi na nekoliko sistema.

Flow measurement in trunks with open flow and in sewer systems is still a challenge: there is no one “the best” method which can solve all requests, but user has to optimize the selection of equipment to fulfill the existing flow and working conditions. One of the possibilities is to use the flat electromagnetic (EM) probes, presented in this paper. Flat EM probe is designed to suit the needs of sewer systems, i.e. they are robust, can operate with low velocities of few cm/s and at the same time can measure high velocities during heavy storms, can work with shallow water and even will operate if covered with sludge and sediments of reasonable height. In large flow profiles, user can easily integrate more flat EM probes into one system, improving the spatial integration of measured velocities and at the same time keeping the low overall costs. Results of laboratory investigation at Faculty of Civil Engineering in Belgrade are presented in the paper: mapping of 3D magnetic field to delineate the control volume and calculate the weighting function in real conditions, operation of probe under the heavy sediment load of different height and usage of CFD to analyze the influence of real flow filed. Few examples of flat EM probe applications are presented at the end of the paper.