FLUID FLOW VELOCITY AND TEMPERATURE MEASUREMENT

• US 20120279313A1
• Filed: 05/05/2011
• Published: 11/08/2012
• Est. Priority Date: 05/05/2011
• Status: Active Grant

• Current Assignee: Siemens Energy Incorporated (Siemens AG)
• Original Assignee: Siemens Energy Incorporated (Siemens AG)
• Inventors: Diatzikis, Evangelos V., Thompson, Edward D., Twerdochlib, Michael
• Granted Patent: US 8,687,175 B2
• Time in Patent Office: Days
• US Class Current: 73/861
• CPC Class Codes: G01F 1/28 by drag-force, e.g. vane type or impact flowmeter
• CPC Class Codes: G01F 1/661 using light
• CPC Class Codes: G01P 5/02 by measuring forces exerted by the fluid on solid bodies, e.g. anemometer

Abstract

A method is provided for monitoring velocity of a fluid flow through a predetermined fluid flow space. A fiber optic conductor includes a flow measurement portion defining an elongated dimension extending across a portion of the fluid flow space. The fluid flow in the fluid flow space causes the measurement portion of the fiber optic conductor to flex in a direction transverse to the elongated dimension. Optical radiation is supplied to the fiber optic conductor, and optical radiation is received from the fiber optic conductor after the supplied optical radiation has passed through the measurement portion. The received optical radiation is analyzed to effect a determination of a flow velocity of the fluid flow.

Claims

1. A method of monitoring velocity of a fluid flow through a predetermined fluid flow space, the method comprising:

supporting a fiber optic conductor having a flow measurement portion defining an elongated dimension extending across a portion of the fluid flow space;

the fluid flow in the fluid flow space causing the measurement portion of the fiber optic conductor to flex in a direction transverse to the elongated dimension;

supplying optical radiation to the fiber optic conductor;

receiving optical radiation from the fiber optic conductor after the supplied optical radiation has passed through at least a portion of the measurement portion; and

analyzing the received optical radiation to effect a determination of a flow velocity of the fluid flow.

2. The method of claim 1, wherein the flow measurement portion of the fiber optic conductor includes a Bragg grating having a characteristic optical wavelength, and the Bragg grating interacts with the supplied optical radiation to form the received optical radiation.

3. The method of claim 1, wherein a strain produced within the measurement portion of the fiber optic conductor produces a reflected wavelength, and a change in the received optical radiation results from a shift in wavelength from the characteristic wavelength corresponding to a flow velocity at the measurement portion.

4. The method of claim 3, wherein the fiber optic conductor includes a plurality of Bragg gratings, each Bragg grating defining a flow measurement portion comprising a unique characteristic wavelength, and including obtaining a flow velocity measurement corresponding to the location of each Bragg grating.

5. The method of claim 3, wherein the fiber optic conductor is at least partially enclosed within a conduit structure defining a loop, and the fluid flow passes through the loop generally transverse to a plane defined by the loop, the fluid flow causing the measurement portion of the fiber optic conductor to flex, in a direction transverse to the plane defined by the loop, between a pair of locations on the loop.

6. The method of claim 5, wherein the fiber optic conductor includes a plurality of measurement portions traversing between respective pairs of locations on the loop, each measurement portion including one or more of the Bragg gratings and providing flow velocity measurements at different locations along the fiber optic conductor.

7. The method of claim 5, including a second fiber optic conductor including one or more Bragg gratings and enclosed within the conduit structure, and including:

supplying optical radiation to the second fiber optic conductor;

receiving optical radiation from the second fiber optic conductor; and

determining a shift in wavelength from a characteristic wavelength to effect a determination of a temperature at the locations of the one or more Bragg gratings of the second fiber optic conductor.

8. The method of claim 7, including adjusting the determination of the flow velocity with reference to the determination of the temperature.

9. The method of claim 1, wherein the flow measurement portion of the fiber optic conductor includes a long period grating (LPG) structure, and the LPG structure effects a change in the supplied optical radiation to form the received optical radiation including cladding modes characteristic of an amount of flexing of the fiber optic conductor corresponding to the flow velocity of the fluid flow.

10. The method of claim 9, wherein a plurality of fiber optic conductors are provided, each fiber optic conductor having a base end supported on a base structure and a free end located in the fluid flow, each fiber being free to bend in the fluid flow and having an LPG structure and each LPG structure having a set of cladding modes characteristic of the bending of a respective fiber optic conductor.

11. The method of claim 10, including comparing cladding modes of two or more of the fiber optic conductors to determine a direction of fluid flow.

12. The method of claim 10, wherein the received optical radiation comprises optical radiation reflected off ends of the fiber optic conductors distal from the base end.

13. A system for monitoring velocity of a fluid flow through a predetermined fluid flow space, the system comprising:

a conduit structure comprising a hollow member extending in a loop to define a generally circular passage;

a fiber optic conductor extending within the conduit structure, the fiber optic conductor defining a flow measurement portion including a Bragg grating extending outside of the conduit structure across a portion of the fluid flow space within the generally circular passage;

an optical radiation source supplying optical radiation to the fiber optic conductor;

a processing unit adapted to receive and analyze optical radiation from the fiber optic conductor after the supplied optical radiation has passed through the measurement portion to effect a determination of a flow velocity of the fluid flow.

14. The system of claim 13, including a second fiber optic conductor connected to the optical radiation source and the processing unit and extending within the conduit structure, the second fiber optic conductor being fully contained within the conduit structure and including one or more Bragg gratings adapted to provide a temperature measurement at locations of the one or more Bragg gratings.

15. The system of claim 13, wherein the conduit structure defines a plurality of loops, each of the loops comprising one or more measurement portions.

16. A system for monitoring velocity of a fluid flow through a predetermined fluid flow space, the system comprising:

a base;

a fiber optic conductor including a base end supported on the base, the fiber optic conductor defining a flow measurement portion including a long period grating (LPG) structure extending across a portion of the fluid flow space;

an optical radiation source supplying optical radiation to the fiber optic conductor;

a processing unit adapted to receive and analyze optical radiation from the fiber optic conductor after the supplied optical radiation has passed through the measurement portion to effect a determination of a flow velocity of the fluid flow with reference to cladding modes formed by the LPG structure.

17. The system of claim 16, including a plurality of the fiber optic conductors supported on the base and each including a LPG structure, and including a supply fiber optic conductor extending from the optical radiation source and a splitter providing optical radiation from the supply fiber optic conductor to each of the fiber optic conductors.

18. The system of claim 17, wherein the plurality of fiber optic conductors are arranged in a plurality of rows supported on the base.

19. The system of claim 16, wherein the fiber optic conductor includes a reflective surface at an end distal from the base end for reflecting optical radiation including the cladding modes through the fiber optic conductor to the processing unit.