FLOW MEASUREMENTS BY INDUCED VORTEX IN A CAVITY

A FLOW METERING TECHNIQUE IS PROPOSED BASED ON THE HYDRODYNAMIC PHENOMENON OF VORTEX FORMATION IN A FLOW CAVITY ADJACENT TO A FLOW BEND SUCH AS AN ELBOW. IT HAS BEEN DISCOVERED THAT WHEN A CIRCULAR CAVITY IS PROVIDED AT THE OUTER SIDE OF THE BEND CURVATURE OF THE FLOW BEND, A VORTEX WILL BE DEVELOPED IN THE CAVITY AND THE STRENGTH OF THE VORTEX INCREASES MONOTONICALLY WITH THE RATE OF THE BEND FLOW. THIS SUGGESTS THAT THE RATE OF THE BEND FLOW CAN BE DETERMINED BY THE VORTEX MOTION IN THE CAVITY. THE VORTEX STRENGTH IS DETERMINED BY A FREE ROTATABLE ROTOR IN THE CAVITY WITH ITS ROTATIONAL AXIS COINCIDENT WITH THE CIRCULAR CENTER OF THE CAVITY. THE ROTOR SO INSTALLED TURNSWITH THE VORTEX MOTION IN THE CAVITY AND ITS ROTATIONAL SPEED MEASURES THE VORTEX STRENGTH. THUS, THE BEND FLOW CANBE DETERMINED BY THE INDUCED ROTOR SPEED. THE PROPOSED FLOWMETERING TECHNIQUE MONITORS A SECONDARY FLOW TO DETERMINE THE MAIN FLOW RATE WHICH IS CONCEPTUALLY DIFFERENT FROM CONVENTIONAL FLOWMETERS WHICH MEASURE DIRECTLY THE MAIN FLOW AND CAUSE INTERFERENCE WITH THE MAIN FLOW FIELD AND NORMALLY A HIGH PRESSURE DROP. THE ADVANTAGE OF THE PROPOSED TECHNIQUE IS THAT THE FLOW METERING ELEMENT CAUSES LITTLE INTERFERENCE WITH THE MAIN FLOW FIELD. IN FACT, THE PRELIMINARY TEST SHOWS THAT THE INTRODUCTION OF A CAVITY AND A ROTOR TO AN ELBOW RESULTED IN A MORE FAVORABLE FLOW CONDITION AND A PRESSURE DROP REDUCTION FROM THE ORIGINAL ELBOW. THIS INDICATES THAT THE PROPOSED TECHNIQUE, WHEN SUCCESSFULLY DEVELOPED, CAN MEASURE FLOW WITHOUT CAUSING ANYADDITIONAL PRESSURE DROP TO THE PIPING SYSTEM OR EVEN A PRESSURE DROP REDUCTION.