Flow rate measurement for industrial sensing applications using unsteady pressures
View Patent ↗Flow rate measurement system includes two measurement regions 14,16 located an average axial distance ΔX apart along the pipe 12 , the first measurement region 14 having two unsteady pressure sensors 18,20 , located a distance X 1 apart, and the second measurement region 16 , having two other unsteady pressure sensors 22,24 , located a distance X 2 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 acoustic and other long wavelength pressure disturbances in the pipe 12 and passes short-wavelength low-frequency vortical pressure disturbances P vortical associated with the vortical flow field 15 . The spatial filters 33,35 provide signals P as1 ,P as2 to band pass filters 46,56 that filter out high frequency signals. The P vortical -dominated filtered signals P asf1 ,P asf2 from the two regions 14,16 are cross-correlated by Cross-Correlation Logic 50 to determine a time delay τ between the two sensing locations 14,16 which is divided into the distance ΔX to obtain a convection velocity U c (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.
1. An apparatus for use in an industrial process for measuring a velocity of a fluid moving in a pipe, comprising:
a plurality of pressure sensors attached to the outside of the pipe for measuring the inhomogeneous pressure disturbances at a plurality of axial locations along the pipe, each sensor providing a pressure signal;
a processor, responsive to at least two of the plurality of pressure signals, which provides a velocity signal indicative of the velocity of the fluid in the pipe; and
a controller that provides a control signal, in response to the velocity signal, to a flow device that controls the velocity of the fluid.
2. The apparatus of claim 1 , wherein the inhomogeneous pressure disturbances are naturally occurring within the fluid.
3. The apparatus of claim 1 , wherein the in inhomogeneous pressure disturbances are stochastic within the fluid.
4. The apparatus of claim 1 , wherein the inhomogeneous pressure disturbances comprise vortices.
5. The apparatus of claim 1 , wherein the fluid comprises a fluid mixture.
6. The apparatus of claim 5 , wherein the velocity signal relates to the velocity of a constituent in the fluid mixture.
7. The apparatus of claim 1 , wherein the fluid comprises of any combination of oil, gas and water.
8. The apparatus of claim 1 , wherein the plurality of sensors is configured to filter out wavelengths above a predetermined wavelength.
9. The apparatus of claim 1 , wherein at least one of the pressure sensors is a strain gauge.
10. The apparatus of claim 9 , wherein the strain gauge is selected from the group consisting of a piezoelectric strain gauge, a capacitive strain gauge, a piezoresistive strain gauge, and an accelerometer.
11. The apparatus of claim 1 , wherein the processor comprises a cross-correlator, and wherein the plurality of pressure signals are in communication with the cross-correlator, and wherein the cross-correlator computes a time delay between at least two of the plurality of pressure signals.
12. The apparatus of claim 1 , wherein the flow device is one of at least a valve, a pump and a throttle.
13. The apparatus of claim 1 further comprising a volumetric flow meter wherein said signal processor provides a flow signal indicative of the volumetric flow rate of said fluid flowing in said pipe.
14. A method for use in an industrial process for measuring a velocity of a fluid moving in a pipe, the method comprising:
attaching a plurality of axially-spaced pressure sensors to the outside of the pipe;
detecting inhomogeneous pressure disturbances in the fluid at each pressure sensor, each pressure sensor providing a pressure signal;
processing at least two of the plurality of pressure signals to provide a velocity signal indicative of the velocity of the fluid in the pipe; and
providing a control signal, in response to the calculated velocity, to a flow device that controls the velocity of the fluid.
15. The method of claim 14 , wherein the inhomogeneous pressure disturbances are naturally occurring within the fluid.
16. The method of claim 14 , wherein the fluid comprises a fluid mixture.
17. The method of claim 14 , wherein the plurality of sensors is configured to filter out wavelengths above a predetermined wavelength.
18. The method of claim 14 , wherein at least one of the pressure sensors is a strain gauge.
19. The method of claim 18 , wherein the strain gauge is selected from the group consisting of a piezoelectric strain gauge, a capacitive strain gauge, a piezoresistive strain gauge, and an accelerometer.
20. The method of claim 14 , wherein the flow device is one of at least a valve, a pump and a throttle.