GB473139A - Improvements in or relating to fluid flow meters - Google Patents

Abstract

473,139. Flow meters. RICARDO, H. R., and ALCOCK, J. F. April 6, 1936, No. 10090. [Class 69 (i)] A fluid-flow meter, particularly for measuring the mean rate of a pulsating flow, comprises a passage containing a viscous resistance element A3, Fig. 1, offering a frictional resistance to the flow, a manometer C connected to the passage at each side of the element A<3>, and a viscous resistance element D in one or both of the manometer connections. The element A<3> comprises one or more long narrow passages offering a resistance substantially proportional to the rate of flow, and the subsidiary resistance elements D enable a steady manometer reading to be obtained, whilst offering such frictional resistance as to render negligible any kinetic non-linear resistance in the connecting-tubes ; the manometer readings are therefore proportional to the mean rate of the pulsating flow. The main resistance element may be formed of alternate layers of corrugated and plain strip material comprising, for example, separate sheets pressed together or two elongated strips placed together face to face and rolled to form a cylindrical element. In either case the corrugations form passages of triangular section which, in the case of a meter to deal with an air flow of about 30 feet per second, may be 0À017 inch high and 3 inches long. The elements D may be of felt. To eliminate the effect on the manometer of pressures produced by kinetic effects, which pressures are non- linear in relation to the flow, the connections to the manometer are such that the kinetic energy of the flow modifies the pressures in them so as to counterbalance the pressure difference set up by it on the two sides of the element A<3>. For example, the openings B<3> of the downstream connection B<2> may face upstream ; or, the opening B<1> of the upstream connection B may be arranged in a Venturi inlet A<1>; or both means may be employed together. To secure the desired correction, the end of the tube B<2> may be rotatable to vary the direction in which the orifices B<3> face, and the tube B may be longitudinally adjustable in the Venturi inlet. The adjustments may be made by trial and error, by passing air at constant known rates of flow through the apparatus, and adjusting the parts until the manometer readings are correct for all the rates in the range to be measured. Fig. 2 shows a meter suitable for connection to the induction pipe of an internal-combustion engine, in which the air enters through an annular filter F and passes through a resistance element E<1> formed of a pack of plain and corrugated sheets. The manometer connections G, K contain felt subsidiary resistance elements G<2>, K<2>, the former having an aperture G<1> in its end and the latter, which is rotatably mounted, apertures K<1> in its side. By longitudinal adjustment of the tube G and angular adjustment of the tube K, as described above, the kinetic pressure effects may be compensated.