Thermocouple probe

Abstract

A thermocouple probe 10 suitable for use in a gas turbine engine comprises a thermocouple element 12 which is coaxially arranged inside a protective sheath 16. The thermocouple element 12 is resiliently supported by a helical member 18 which insulates the element 12 from deleterious vibrations induced in the sheath 16. In use, the thermocouple probe 10 projects through an aperture 30 in the casing 32 of a gas chamber 34. Vibrations in the probe 10 are further reduced by ensuring that the longitudinal axis AA of the probe is angularly offset from the central axis BB of the aperture 30, such that the outer periphery of the sheath 16 is in contact with the inner periphery of the aperture 30 in two diametrically opposite and axially offset locations.

We claim: 
     
       1. A method for mounting a sensing probe in a fluid chamber, said sensing probe being exposed to fluid flowing through said chamber, comprising the steps of: providing said sensing probe, said sensing probe comprising a rigid cylindrical body and a flange extending outwardly from said rigid cylindrical body;   providing an aperture in the casing of said chamber, said aperture being such that said flange is too big to pass therethrough;   inserting said sensing probe into said aperture such that said rigid cylindrical body projects into said chamber and such that said flange abuts against the outer surface of the casing of said chamber; and   positioning said sensing probe such that the longitudinal axis of said sensing probe and the central axis of said aperture are angularly offset, with the outer surface of said rigid cylindrical body in contact with the inner periphery of said aperture in . .only.!. two locations which are diametrically opposite and axially offset from one another.   
     
     
       2. A method according to claim 1 wherein the angular offset is such that the longitudinal axis of said sensing probe and the two points of contact between the outer surface of said rigid cylindrical body and the inner periphery of said aperture are contained in a plane which is inclined at an angle to a principal direction of flow of fluid through said chamber and which is a non-preferred plane of vibration for said sensing probe. 
     
     
       3. A method according to claim 2 wherein said angle between said plane and said principal direction of flow of fluid is 45°. 
     
     
       4. A method according to claim 2 or 3 wherein said sensing probe is positioned such that at least a component of any force exerted thereon by the fluid flowing through said chamber increases the contact pressure exerted by said rigid cylindrical body on the inner periphery of said aperture. 
     
     
       5. An assemblage consisting of a sensing probe mounted in a chamber, said chamber having a casing with an aperture therein for receiving said sensing probe, said sensing probe comprising a rigid cylindrical body and a flange extending outwardly from said rigid cylindrical body, said flange being too big to pass through said aperture, wherein said rigid cylindrical body projects into said chamber through said aperture with said flange having a mating face which abuts the outer surface of said casing, such that the longitudinal axis of said sensing probe and the central axis of said aperture are angularly offset, with the outer surface of said rigid cylindrical body in contact with the inner periphery of said aperture in . .only.!. two locations which are diametrically opposite and axially offset from one another. 
     
     
       6. An assemblage according to claim 5 wherein the central axis of said aperture is substantially perpendicular to the inner and outer surfaces of the casing of said chamber adjacent said aperture. 
     
     
       7. An assemblage according to claim 6 Wherein the normal to the mating face of the flange is inclined at an angle to the longitudinal axis of said sensing probe. 
     
     
       8. An assemblage according to claim 6 wherein the mating face of the flange has a stud-like protrusion, said stud-like protrusion being radially offset from the longitudinal axis of said sensing probe.