Flow rate measurement for industrial sensing applications using unsteady pressures

Abstract

Flow rate measurement system includes two measurement regionslocated an average axial distance ΔX apart along the pipe, the first measurement regionhaving two unsteady pressure sensors, located a distance Xapart, and the second measurement region, having two other unsteady pressure sensors, located a distance Xapart, each capable of measuring the unsteady pressure in the pipe. Signals from each pair of pressure sensorsandare differenced by summers, respectively, to form spatial wavelength filters, respectively. Each spatial filterfilters out acoustic pressure disturbances Pand other long wavelength pressure disturbances in the pipeand passes short-wavelength low-frequency vortical pressure disturbances Passociated with the vortical flow field. The spatial filtersprovide signals P,Pto band pass filtersthat filter out high frequency signals. The P-dominated filtered signals P,Pfrom the two regionsare cross-correlated by Cross-Correlation Logicto determine a time delay τ between the two sensing locationswhich is divided into the distance ΔX to obtain a convection velocity U(t) that is related to an average flow rate of the fluid (i.e., one or more liquids and/or gases) flowing in the pipe. The invention may also be configured to detect the velocity of any desired inhomogeneous pressure field in the flow. The invention may also be combined with an instrument, an opto-electronic converter and a controller in an industrial process control system.