Relating to flow measurement

• US 6,345,539 B1
• Filed: 04/19/1999
• Issued: 02/12/2002
• Est. Priority Date: 10/19/1996
• Status: Expired due to Fees

• Current Assignee: Cranfield University
• Original Assignee: Cranfield University
• Inventors: Rawes, William Leslie Hodges, Sanderson, Michael Langley
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US09/294,645
• Time in Patent Office: 1,030 Days
• Field of Search: 738/612.7, 738/611.8, 738/612.9, 731/94
• US Class Current: 73/861.27
• CPC Class Codes: G01F 1/662 Constructional details
• CPC Class Codes: G01F 15/185 Connecting means, e.g. bypass conduits
• CPC Class Codes: G01P 5/245 by measuring transit time of acoustical waves measuring propagation velocity of acoustical waves per se G01H5/00

Abstract

An ultrasonic insertion flowmeter (100) is disclosed having a probe (101) which is adapted to be inserted into a duct, the probe having at least first and second ultrasonic transducer means, the probe (101) being adapted to measure the transit time difference of an ultrasonic pulse along a first path and a second path, the difference in transit time for signals along the two paths enabling the flow rate to be measured. Preferably, the probe takes measurements in both the forward and reverse directions along each path, and is adapted to rotate after initial insertion from an insertion position to a measurement position, whereafter the probe (101) may be drawn up against a wall of the duct so that alignment of the probe within the duct is readily achieved.

Claims

1. An ultrasonic insertion flow meter, comprising a probe for insertion into a duct, the probe having ultrasound transducers and being arranged to perform at a single site of introduction into the duct a first ultrasonic path interrogation having a component of travel of ultrasound in a first axial direction relative to a region of the duct where the probe is inserted and to perform a second ultrasound path interrogation having a component of travel of ultrasound in a second axial direction opposite to the first axial direction, the transducers being arranged such that a comparison of a signal associated with ultrasound travel in the first axial direction with a signal associated with ultrasound travel in the second axial direction enables the flow rate of fluid in the duct to be estimated, said ultrasonic transducers including a first spaced-apart emitter and receiver pair and a second spaced-apart emitter and receiver pair, and variable spacing means for altering the spacing between the emitters and their respective receivers.

2. An ultrasonic insertion flow meter according to claim 1 further comprising signal processing means for processing output signals from the transducers and for monitoring transit times for ultrasonic signals passing along the first and second ultrasound paths.

3. An ultrasonic insertion flow meter according to claim 2 wherein the signal processing means compares the transit times of signals passing in forward and reverse directions along the duct.

4. An ultrasonic insertion flow meter according to claim 3 wherein the probe measures the transit time difference of an ultrasonic pulse in the forward and reverse directions of the first interrogation path and also the transit time difference in the forward and reverse directions of the second interrogation path.

5. An ultrasonic insertion flow meter according to claim 1 wherein the transducers include at least one ultrasound emitter and one ultrasound detector.

6. An ultrasonic insertion flow meter according to claim 1 wherein the ultrasonic transducers include at least one transducer which can act as an emitter and a detector.

7. An ultrasonic insertion flow meter according to claim 1 wherein at least one of said ultrasonic transducers is provided on a first transducer mounting and at least one of said ultrasonic transducers is provided on a second transducer mounting spaced apart from the first transducer mounting so that the first and second pairs of transducers may communicate along said first and second interrogation paths.

8. An ultrasonic insertion flow meter according to claim 1 wherein the insertion flow meter uses at least one reflection of ultrasound off a side wall of the duct to perform at least one of the ultrasonic path interrogations.

9. An ultrasonic insertion flow meter according to claim 1 wherein the ultrasonic paths are beams of ultrasound.

10. An ultrasonic insertion flow meter according to claim 1 wherein the insertion flow meter performs the first and second ultrasonic path interrogations while the insertion flow meter is stationary.

11. An ultrasonic insertion flow meter according to claim 1 wherein the duct has a central longitudinal axis, the first emitter/receiver pair is configured to be spaced axially of the duct in use in a direction parallel to the central longitudinal axis of the duct and the second emitter/receiver pair is configured to be spaced axially of the duct in use in a direction that is parallel to the central longitudinal axis of the duct.

12. An ultrasonic insertion flow meter according to claim 5 wherein the ultrasound emitter is configured to be adjacent a wall of the duct in use.

13. An ultrasonic insertion flow meter according to claim 5 wherein the ultrasound detector is configured to be adjacent a wall of the duct in use.

14. An ultrasonic insertion flow meter according to claim 1 wherein the duct has a first wall region, each receiver and each emitter are configured to be adjacent said first wall region and in which the emitter/receiver of the first pair is spaced emitter-to-receiver in one axial direction and the emitter/receiver of the second pair is spaced emitter-to-receiver in the opposite direction.

15. An ultrasonic insertion flow meter according to claim 9 wherein a first beam of ultrasound when viewed along an axis of the duct in a direction has reflections having a clockwise sense of rotation about the axis, and a second beam when viewed along the axis and the direction has reflections in an anticlockwise sense of rotation about the axis.

16. An ultrasonic flow meter according to claim 1 further comprising an insertion device supporting the probe for movement in use relative to the duct between a first position in which said probe can be inserted into the duct and a second position in which flow measurements can be made.

17. An ultrasonic insertion flow meter according to claim 16 wherein the probe has a greater dimension parallel to an axis of the duct in its second position than it does in its first position.

18. An ultrasonic insertion flow meter according to claim 16 wherein in the first position the probe is oriented so that the first and second emitter and receiver pairs are spaced apart substantially orthogonal to the axis of the duct and in the second position the probe is oriented so that the first and second emitter and receiver pairs are spaced apart substantially axially along the duct.

19. An ultrasonic insertion flow meter according to claim 16 wherein the probe is supported on the insertion device to swing from its first position to its second position.

20. An ultrasonic insertion flow meter according to claim 16 wherein the probe is hingedly attached to the insertion device so that the probe can be moved angularly between the first position and the second position.

21. An ultrasonic insertion flow meter according to claim 20 wherein the probe is joined by a hinge to the insertion device.

22. An ultrasonic insertion flow meter according to claim 16 wherein the transducers are arranged so that in the second position of the probe, the signals along each path are reflected twice from the wall of the duct, so that, when viewed along the axis of the duct, an angle of about 60 degrees is subtended between signals incident upon and signals reflected from a point of reflection.

23. An ultrasonic insertion flow meter according to claim 1 wherein the probe comprises first and second transducers which are mounted back to back between and spaced apart from a pair of spaced-apart conic reflectors which reflect signals from the first transducer to the second transducer and signals from the second transducer to the first transducer.

24. An ultrasonic insertion flow meter according to claim 23 wherein the spacing of the reflectors relative to the transducers is adjustable.

25. An ultrasonic flow meter according to claim 23 wherein the spacing between the reflectors and the transducers is fixed.

26. A method of measuring the flow rate of a fluid in a duct having a diameter and a longitudinal axis, comprising the steps of providing an insertion flow meter having spaced-apart transducers;

adjusting the spacing of the transducers in accordance with the diameter of the duct;

inserting the insertion flow meter into the duct;

conducting a forward direction ultrasonic transit time test with a component of travel of an ultrasound signal in an axial direction of flow of the fluid in the duct;

conducting a reverse direction ultrasonic transit time test with a component of travel of an ultrasound signal in a direction opposite to the axial direction of flow of fluid in the duct; and

comparing the results of the forward and reverse transit time tests to give a result indicative of the fluid flow rate.

27. The method according to claim 26 wherein the steps of conducting the forward test and the reverse test are conducted between a pair of transducers which act as emitter/receiver for the forward test and receiver/emitter for the reverse test.

28. The method according to claim 26 further comprising the steps of conducting a second forward direction test performed along a different ultrasound travel path than the first forward direction test, and comparing the result from the second test with that of the first travel path test to give a figure indicative of swirl of the fluid in the duct.

29. The method according to claim 26 wherein the steps of conducting the transit time tests are conducted with the transducers stationary.

30. The method according to claim 29 wherein the steps of conducting the transit time tests are conducted with the transducers adjacent a wall of the duct.

31. The method according to claim 26 further comprising the steps of moving the transducers in the duct after each of a succession of transit time tests, comparing the results of the succession of tests, and moving the transducers to a selected position in which one of a desired signal and or a comparison of signals is received.

32. The method according to claim 26 wherein the transducers are provided on a probe, the insertion step comprises the steps of inserting the probe into the duct with the probe having a smaller projected length axially of the duct in comparison to its length axially of the duct in a position of use, and moving the probe to the position of use prior to conducting the tests.

33. The method according to claim 26 wherein the insertion flow meter includes an ultrasonic probe having at least one first ultrasonic transducer and at least one second ultrasonic transducer spaced apart from the first transducer, the insertion step comprises the steps of placing the first and second transducers in a first position in which they are spaced apart substantially orthogonal to the duct axis and thereafter moving the probe from the first position to a second position in which the first and second transducers are spaced apart substantially along an axis of the duct, the steps of the transit time tests are conducted for pulses of ultrasound transmitted between the first and second transducers along one or more paths, and the comparing step comprises comparing the transit times for pulses propagating between the first and the second transducers to transit times for pulses propagating between the second and the first transducers to obtain a result indicative of the rate of flow of fluid in the duct.

34. The method according to claim 33 wherein the step of moving the probe between the first and second positions comprises rotating the probe between the first and second positions.

35. The method according to claim 26 wherein the step of providing an insertion flow meter comprises providing a pair of first transducers and a pair of second transducers on said insertion flow meter.

36. The method according to claim 35 wherein the step of providing the first and second pairs of transducers on said insertion flow meter comprises providing said first and second pairs of transducers such that they communicate along two different paths.

37. The method according to claim 26 wherein the insertion step comprises moving the transducers into contact with the surface of the duct adjacent an entry hole in the duct through which the transducers are inserted.

38. The method according to claim 26 further comprising the step of comparing transit times for signals propagating along each of two paths in order to measure the swirl of fluid in the duct.

39. The method according to claim 26 further comprising the step of monitoring one of a transit time and a signal amplitude, which is dependent on duct internal diameter and speed of sound in the fluid, in order to obtain accurate data indicative of the duct diameter and of transducer alignment.

40. A method of checking a fixed flow meter in a conduit comprising the steps of providing an ultrasonic insertion flow meter having a probe adapted to be inserted into a duct, the probe having ultrasound transducers and being operable to perform at a single site of introduction into the duct a first ultrasonic path interrogation having a component of travel of ultrasound in a first axial direction relative to a region of the duct where the probe is inserted and also to perform a second ultrasound path interrogation having a component of travel of ultrasound in a second axial direction opposite to the first axial direction, the transducers being arranged such that a comparison of a signal associated with ultrasound travel in the first axial direction with a signal associated with ultrasound travel in the second axial direction enables the flow rate of fluid in the duct to be estimated, said ultrasonic transducers including a first emitter and receiver pair spaced apart by a variable spacing and a second emitter and receiver pair which are spaced apart by a variable spacing, varying the spacing between the emitters and their respective receivers, determining a rate of flow of fluid in the conduit using the insertion flow meter, and comparing the rate of flow of fluid determined using the insertion flow meter with rate of flow of fluid measured using the fixed flow meter.

41. A method of measuring the flow rate of a fluid in a duct, comprising the steps of inserting an insertion flow meter into a duct;

conducting a first forward direction ultrasonic transit time test with a component of travel of the ultrasound in an axial direction of flow of the fluid in the duct;

conducting a first reverse direction ultrasonic transit time test with a component of travel of the ultrasound in a direction opposite to the axial direction of flow of fluid in the duct;

comparing the results of the forward and reverse transit time tests to give a result indicative of the fluid flow rate;

conducting at least one of a second forward direction test and a second reverse direction test along a different ultrasound travel path than the first forward direction and reverse direction tests;

comparing a result from said at least one of a second forward direction test and a second reverse direction test with the results of the first travel path tests to obtain a result indicative of swirl of the fluid in the duct, comparing a transit time for signals along the first travel path with a transit time for signals along the second travel path, and adjusting the alignment of the insertion flow meter in the duct until the transit times of the two paths are the same to the order of a few microseconds so as to fine-tune the alignment of the insertion flow meter along the duct axis.