Effect of a concentrated mass on coriolis flowmetering

Abstract

Usually a Coriolis mass flowmeter consists of a fluid conveying vibrating pipe segment with a reflection symmetry, on which the time delay Δτ is measured between the vibrations of two symmetrically situated cross sections. For a homogeneous pipe segment, the proportionality factorKc between Δτ and the mass flowrate\(\dot Q_m\), i.e. the calibration factor of the instrument, is independent of the nature of the flowing fluid. Fixing a concentrated massmc at the middle of the pipe segment — as required e.g. for the purpose of a symmetric excitation of the vibration — brings about a dependence of the factorKc on the fluid density. In the present paper the influence of the massmc on the vibration spectrum and on flowmetering is investigated in detail for an instrument working with a straight pipe segment. It turns out that, whereas the frequency of the fundamental vibration mode is strongly influenced bymc, the calibration factorKc is practically independent of the massmc, up to fairly high values compared to the mass of the fluid filled pipe segment.