Apparatus for measuring the velocity of a fluid flowing in a conduit

• US 5,908,990 A
• Filed: 04/18/1997
• Issued: 06/01/1999
• Est. Priority Date: 04/19/1996
• Status: Expired due to Fees

• Current Assignee: AURA Environmental Limited
• Original Assignee: AURA Environmental Limited
• Inventors: Cummings, Derek Philip
• Primary Examiner(s): Patel, Harshad
• Application Number:
  US08/844,324
• Time in Patent Office: 774 Days
• Field of Search: 73/861.21, 73/861.22, 73/861.42, 73/861.52
• US Class Current: 73/861.22
• CPC Class Codes: G01F 1/3218 bluff body design
• CPC Class Codes: G01F 1/40 Details of construction of the flow constriction devices
• CPC Class Codes: G01F 1/46 Pitot tubes

Abstract

An apparatus for measuring the velocity of a fluid flowing in a conduit 13 comprises a differential pressure generator including first and second bluff bodies 6a, 6b which are positioned in the conduit to create a differential pressure that is a function of the velocity of the fluid. First and second pressure sampling apertures 4a'"'"', 4b'"'"'are located downstream of the first and second bluff bodies respectively, and a differential pressure sensor 9a provides an electrical signal which is a function of the difference between the pressures at the apertures.

Claims

1. An apparatus for measuring the velocity of a fluid flowing in a conduit, comprising a differential pressure generator including first and second bluff bodies which are positioned in the conduit to create a differential pressure that is a function of the velocity of the fluid, first and second pressure sampling apertures which are located downstream of the first and second bluff bodies respectively, and a differential pressure sensor for providing an electrical signal which is a function of the difference between the pressures at the apertures, wherein the first and second bluff bodies are located in a substantially constant cross-section portion of the conduit with the first bluff body immediately upstream of and at least approximately in line with the second bluff body in a direction parallel to the axis of the conduit, and wherein the maximum cross-sectional area of the first bluff body taken on a plane perpendicular to the axis of the conduit is substantially less than the maximum cross-sectional area of the second bluff body.

2. An apparatus as claimed in claim 1, wherein the first pressure sampling aperture emerges in the wake of the first bluff body at least approximately centrally in front of the second bluff body, and the second pressure sampling aperture emerges in the wake of the downstream bluff body.

3. An apparatus as claimed in claim 1, wherein the maximum cross-sectional area of the first bluff body taken on a plane perpendicular to the axis of the conduit is less than 1/4 the maximum cross-sectional area of the second bluff body.

4. An apparatus as claimed in claim 1, wherein the bluff bodies are supported away from the internal surface of the conduit by respective tubes extending from a side of the conduit, the tubes communicating through the respective bodies with the first and second pressure sampling apertures and serving to transmit the sampled pressures to the differential pressure sensor.

5. An apparatus as claimed in claim 4, wherein tile bluff bodies comprise respective cones arranged at least approximately on a common axes parallel to the axis of the conduit and having broad upstream-facing surfaces arranged at least approximately normal to the axis of the conduit.

6. An apparatus as claimed in claim 5, wherein the first bluff body comprises a ninety degree cone with a base diameter of approximately 1/12 of the conduit internal diameter and the second bluff body comprises a ninety degree cone with a base diameter of approximately 1/4 of the conduit internal diameter.

7. An apparatus as claimed in claims 1, wherein the bluff bodies are mounted along the internal surface of the conduit.

8. An apparatus as claimed in claim 7, wherein the bluff bodies comprise respective half-cones arranged at least approximately on a common axis parallel to the axis of the conduit and having broad upstream-facing surfaces arranged at least approximately normal to the axis of the conduit.

9. An apparatus as claimed in claim 8, wherein the first bluff body comprises a half ninety degree cone with a base diameter of approximately 1/12 of the conduit internal diameter and the second bluff body comprises a half ninety degree cone with a base diameter of approximately 1/4 of the conduit internal diameter.

10. A system for monitoring and controlling an arrangement in which a particulate material is transported through a conduit entrained in a fluid, the system comprising a first apparatus and a second apparatus,

the first apparatus comprising a differential pressure generator including first and second bluff bodies which are positioned in the conduit to create a differential pressure that is a function of the velocity of the fluid, first and second pressure sampling apertures which are located downstream of the first and second bluff bodies respectively and a differential pressure sensor for providing an electrical signal which is a function of the difference between the pressures at the apertures, wherein the first and second bluff bodies are located in a substantially constant cross-section portion of the conduit with the first bluff body immediately upstream of and at least approximately in line with the second bluff body in a direction parallel to the axis of the conduit, and wherein the maximum cross-sectional area of the first bluff body taken on a plane perpendicular to the axis of the conduit is substantially less than the maximum cross-sectional area of the second bluff body, the first apparatus being positioned relative to the conduit such that the bluff bodies are located in a region of the conduit at least generally free of particulate material, and

the second apparatus comprising means for producing a further electrical signal which is a function of the difference between the pressures at relatively widely spaced locations along the conduit,

the system further including means for automatically controlling at least one flow parameter as a function of the first and further electrical signals.