CORIOLIS MASS-FLOW MEASUREMENT OF GAS UNDER NORMAL CONDITIONS

This paper presents a new method of directly measuring the mass flow o f gas using the well-known Coriolis principle, which has proved succes sful for mass flow measurement of liquids. The prototype consists of t wo U-shaped tubes, forming a device resembling very much a tuning fork , which is stimulated by electromagnetic actuators to perform autonomo us bending oscillations. By this means the fluid is subjected to a rad ial velocity that, in combination with the axial velocity of the flow, induces harmonic Coriolis forces of the same frequency. This causes t he U-shaped tube to perform torsional oscillations that superimpose on the bending oscillations. Both oscillations can be detected via elect romagnetic transducers. The amplitude of the torsional oscillation ind uced by the Coriolis forces is very small as the density of gas is ver y low. It can be amplified by tuning the eigenfrequencies of torsion a nd bending in a control loop. This results in an amplification of the torsional amplitude by a factor of 10(2), allowing the mass flow of ga s to be measured under normal conditions.