GB856204A - Improvements in or relating to mass flow meters - Google Patents

Abstract

856,204. Flow-meters. BOPP & REUTHER G.m.b.H. June 14, 1957 [June 14, 1956; Aug. 23, 1956; Sept. 1, 1956; Oct. 17, 1956], No. 18833/57. Class 40 (1). [Also in Group XXIX] A mass flow-meter comprises a rotor 2 (Fig. 2), running at a constant speed, arranged to be subjected to the flow of the medium to be measured in a direction perpendicular to its axis of rotation and means for deriving a measurement of the force, or a measurement proportional to the force, tending to move the rotor in a direction perpendicular to its rotational axis and the fluid flow. As shown in Fig. 2, the rotor is arranged in a cylindrical housing 1 and the fluid passes from a branch 5 to flow tangentially over a rotor 2 housed in an annular space 7, the fluid being discharged through a branch 6. The rotor 2 causes a velocity difference and consequent pressure difference in the upper and lower parts of the annular space 7. A gauge 12 records this pressure difference which is proportional to # V Un where # is the density of the medium to be measured, V is the flow velocity of the medium and Un is the peripheral velocity of the rotor. Since the speed of the rotor is maintained constant the pressure difference will be proportional to the mass flow. The surface of the rotor may be roughened by sand blasting to increase its friction and thereby enhance the velocity difference above and below the rotor. Alternatively the outer surface of the rotor may have blades extending parallel to the rotational axis or the rotor may have radially-extending annular discs mounted on its periphery. In other modifications the unsymmetrical pressure distribution is transmitted mechanically to a bellows and the pressure difference measured by a moving weight controlled by an opposing compressedair pressure source actuated by a turbine or by an electric motor. In a further modification shown in Fig. 7, the mass flow is derived electrically from a mercury differential pressure gauge 12 provided with teletransmitter resistances 34 and a tachometer generator 31 mounted on the rotor shaft. To regulate the mass flow the flow-meter is combined with a regulating valve 44 (Fig. 8). A differential pressure transmitter 40 actuates the valve 44 to regulate the flow in the whole duct 42, 43. The speed of rotation of the rotor 2 is controlled by variable gearing 41. The transmission of the variable gearing may be effected through a second mass meter and transmitter. If the two mass flows are thereafter combined, the entire installation acts as a mixture regulator. It is thus possible to regulate a flowing medium to a constant density.