Improvements in or relating to rotary meters for measuring mass flow of fluids

摘要

1,084,520. Rotary mass-flow meters. R. MAURER. May 22, 1964 [May 25, 1963], No.20957/63. Heading F1F. A rotary fluid mass-flow meter of paddle wheel type, comprising guide vane means for imparting a swirl to the fluid, means for measuring the torsional reaction of the fluid on the guide vane means, and a freely rotatable paddle wheel for determining the swirl velocity of the fluid, includes a by-pass by-passing the guide vane means and a mixing chamber upstream of the paddle wheel into which both the by-pass and the guide vane means discharge. As shown in Fig. 1, helical guide vanes 18 fixed to a shaft 17 are mounted within a sleeve 25 supported by axially extending vanes 28 within an enlarged diameter portion 12 of the meter casing to provide an outer annular by-pass chamber 27 whose inlet 31 is controlled by a valve member 29 movable in response to fluid flow by a rack and pinion (not shown) and a servomotor 30. The inlet 31 being closed when flow is a minimum and opened to its maximum when flow is a maximum. The shaft 17 upstream of the guide vanes 18 carries a torque meter 15 whose output is fed to a computer 35 and on a reduced diameter portion downstream thereof is a freely rotatable paddle wheel 21 whose speed is recorded by a pick-up 34 feeding signals to the computer 35 so that mass flow is measured by the quotient of the swirl velocity and torque reaction. The provision of the by-pass and the valve 29 controlling the flow therethrough is said to maintain the accuracy of the motor over a wide range of flow values. In a modified construction, the valve member 29, and servomotor 30 are removed and the sleeve 25 is replaced by a spring-loaded sleeve separated from the vanes 28. At low rates of flow the spring urges the sleeve into seating engagement with an annular projection on the meter casing to close the inlet 31. As the flow rate increases the sleeve is moved away from the projection to increase the flow through the by-pass.