摘要 |
Flow rate measurement system includes two measurement regions 14,16 located an average axial distance DeltaX apart along the pipe 12 , the first measurement region 14 having two unsteady pressure sensors 18,20 , located a distance X<SUB>1 </SUB>apart, and the second measurement region 16 , having two other unsteady pressure sensors 22,24 , located a distance X<SUB>2 </SUB>apart, each capable of measuring the unsteady pressure in the pipe 12 . Signals from each pair of pressure sensors 18,20 and 22,24 are differenced by summers 44,54 , respectively, to form spatial wavelength filters 33,35 , respectively. Each spatial filter 33,35 filters out acoustic pressure disturbances P<SUB>acoustic </SUB>and other long wavelength pressure disturbances in the pipe 12 and passes short-wavelength low-frequency vortical pressure disturbances P<SUB>vortical </SUB>associated with the vortical flow field 15 . The spatial filters 33,35 provide signals P<SUB>as1</SUB>,P<SUB>as2 </SUB>to band pass filters 46,56 that filter out high frequency signals. The P<SUB>vortical </SUB>-dominated filtered signals P<SUB>asf1</SUB>,P<SUB>asf2 </SUB>from the two regions 14,16 are cross-correlated by Cross-Correlation Logic 50 to determine a time delay tau between the two sensing locations 14,16 which is divided into the distance DeltaX to obtain a convection velocity U<SUB>c</SUB>(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 12 . 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.
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