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 industrial process control system for controlling a velocity of a fluid moving in a pipe of an industrial process, said system comprising:
a first filter which measures a vortical pressure field at a first axial location along the pipe and provides a first pressure signal indicative of said vortical pressure field; and
a second filter which measures said vortical pressure field at a second axial location along the pipe and provides a second pressure signal indicative of said vortical pressure field;
a processor, responsive to said first and said second pressure signals, which provides a velocity signal indicative of a velocity of the said vortical pressure field moving 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 control system of claim 1 wherein said velocity signal is related to a velocity of said fluid moving in said pipe.
3. The control system of claim 1 wherein said velocity signal is indicative of the velocity of said fluid moving in said pipe.
4. The control system 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.
5. The control system of claim 1 , wherein said first and said second filters filter out wavelengths associated with an acoustic pressure field and passes wavelengths associated with said vortical pressure field.
6. The control system of claim 5 , wherein said first filter comprises a first spatial filter; and said second filter comprises a second spatial filter.
7. The control system of claim 6 , wherein:
said first spatial filter comprises at least a first and a second unsteady pressure sensors disposed a predetermined first distance apart from each other; and
said second spatial filter comprises at least a third and a fourth unsteady pressure sensors disposed a predetermined second distance apart from each other.
8. The control system of claim 7 wherein said at least one of said pressure sensors comprises a fiber optic pressure sensor.
9. The control system of claim 1 wherein said processor comprises logic which calculates a cross-correlation between said first and said second pressure signals and provides a time delay signal indicative of the time it takes for said vortical pressure field to move from said first location to said second location.
10. The control system of claim 9 wherein said processor comprises logic responsive to said time delay signal which provides an inhomogeneous velocity signal indicative of the velocity of said vortical pressure field moving in said pipe.
11. The control system of claim 9 wherein said processor comprises logic responsive to said time delay signal which provides said velocity signal indicative of the velocity of said fluid moving in said pipe.
12. The control system of claim 1 , wherein the flow device is one of at least a valve, a pump and a throttle.
13. The control system of claim 1 , wherein at least one of the vortical pressure field is inhomogeneous.
14. A method for controlling a velocity of a fluid moving in a pipe of an industrial process, the method comprising:
a) measuring a vortical pressure field at a first location along the pipe and providing a first vortical pressure signal indicative of said vortical pressure field;
b) measuring said vortical pressure field at a second location along the pipe and providing a second vortical pressure signal indicative of said vortical pressure field, said first and said second locations being an axial distance apart;
c) calculating the velocity using said first and said second vortical pressure signals; and
d) 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 said calculating step (c) comprises:
e) calculating a cross-correlation of said first and said second pressure signals to obtain a time delay signal indicative of the time it takes for said vortical pressure field to move from said first location to said second location.
16. The method of claim 15 , wherein said calculating step (d) comprises:
f) calculating a velocity signal from said time delay signal.
17. The method of claim 16 , wherein said calculating step (e) comprises:
g) dividing said axial distance between said measurement locations by said time delay signal.
18. The method of claim 14 wherein:
said measuring step (a) comprises:
measuring a first unsteady pressure and a second unsteady pressure;
subtracting said second unsteady pressure from said first unsteady pressure to form said first vortical pressure signal; and
said measuring step (b) comprises:
measuring a third unsteady pressure and a fourth unsteady pressure; and
subtracting said fourth unsteady pressure from said third unsteady pressure to form said second vortical pressure signal.
19. The method of claim 14 wherein:
said first vortical pressure signal is indicative of wavelengths associated with a vortical pressure field and not associated with an acoustic pressure field at said first location; and
said second vortical pressure signal is indicative of wavelengths associated with said vortical pressure field and not associated with an acoustic pressure field at said second location.
20. The method of claim 14 , wherein the flow device is one of at least a valve, a pump and a throttle.