Method and apparatus for measuring pressure with embedded non-intrusive fiber optics

• US 5,452,087 A
• Filed: 11/04/1993
• Issued: 09/19/1995
• Est. Priority Date: 11/04/1993
• Status: Expired due to Fees

• Current Assignee: American Gas Association
• Original Assignee: American Gas Association, Texas A&M University System
• Inventors: Beshouri, Gregory M., Gibler, William N., Taylor, Henry F., Atkins, Robert A., Swenson, Victor P., McCoy, James J., Spears, Matthew O., Lee, Chung-Eun, Oakland, Mark D.
• Primary Examiner(s): Turner, Samuel A.
• Assistant Examiner(s): MERLINO, AMANDA H
• Application Number:
  US08/147,830
• Time in Patent Office: 684 Days
• Field of Search: 356/345, 356/352, 356/35.5, 250/227.14, 250/227.19, 385/12, 385/14
• US Class Current: 356/480
• CPC Class Codes: G01L 11/025 using a pressure-sensitive optical fibre
• CPC Class Codes: G01L 23/16 by photoelectric means

Abstract

A method and apparatus is provided for measuring pressure in a pressure containing vessel with a non-intrusive, metal-embedded fiber optic pressure sensor. The pressure containing vessel may, for example, be the combustion chamber of an internal combustion engine. A Fabry-Perot Interferometer is arranged in a terminated, single mode fiber to function as a strain gauge. The fiber Fabry-Perot Interferometer (FFPI) is embedded in a metal part which may be disposed in a wall of the pressure containing vessel. The metal part and FFPI experience a longitudinal strain in response to the pressure in the vessel. In another aspect of the invention, a non-intrusive fiber containing the FFPI may be embedded along the axis of a metal bolt. The bolt may be used to attach a part or structure, which is directly exposed to the pressure, to the wall of the vessel. Consequently, the bolt and FFPI experience a longitudinal strain in response to the pressure on the part or structure. In this aspect, the part or structure exposed to the pressure may be, for example, a fuel injection valve that is attached by the bolt to a cylinder head of an internal combustion engine.

Claims

1. Apparatus for measuring pressure in a vessel containing a gas or liquid, comprising:

a first metallic member which is deployed in contact with an external wall of said vessel and exposed to said gas or liquid through an aperture in said wall;

a second metallic member having a first end attached to said wall of said vessel and contacting said first metallic member in such a manner as to hold said first metallic member in firm contact with said external wall of said vessel; and

a fiber optic sensor embedded in said second metallic member wherein one end of said fiber optic sensor terminates in said second metallic member, said fiber optic sensor operable to experience a strain responsive to a pressure in said vessel.

2. The apparatus of claim 1, wherein said fiber optic sensor includes a Fabry-Perot Interferometer.

3. The apparatus of claim 1, wherein said second metallic member comprises a metal bolt which is attached to said wall of said vessel by screwing into a threaded hole in said wall.

4. The apparatus of claim 1, wherein said vessel comprises a combustion chamber in a cylinder of an internal combustion engine.

5. The apparatus of claim 1, wherein said first metallic member comprises a fuel injector valve of an internal combustion engine.

6. The apparatus of claim 1, wherein said pressure comprises a negative pressure.

7. A method of measuring pressure in a pressure containing vessel, comprising the steps of:

positioning a first metallic member to cover and seal an aperture in a wall of said pressure containing vessel;

embedding a fiber optic sensor in a second metallic member wherein one end of said fiber optic sensor terminates in said second metallic member;

attaching a first end of said second metallic member to a wall of said pressure containing vessel, said second metallic member contacting said first metallic member in such a manner as to hold said first metallic member in firm contact with an exterior of said wall of said vessel;

sensing a strain in said fiber optic sensor responsive to a pressure in said pressure containing vessel; and

generating an optical signal responsive to said strain.

8. The method of claim 7, wherein the embedding and sensing steps further comprise the steps of:

embedding a fiber Fabry-Perot Interferometer in said second metallic member; and

sensing a strain in said fiber Fabry-Perot Interferometer responsive to a pressure in said pressure containing vessel.