Clearance and wear determination apparatus
Apparatus is provided for determining the clearance between a member and a casing surface over and relative to which the member moves, e.g. in a gas turbine engine. The apparatus includes a main waveguide and a reference element that is provided at a position intermediate the proximal and distal ends, or at the distal end, of the waveguide. The transmitter/receiver is arranged to transmit an electromagnetic signal through the main waveguide and receive (i) a first portion of the electromagnetic signal reflected from the reference element, (ii) a second portion of the electromagnetic signal reflected from the casing surface, and (iii) a third portion of the electromagnetic signal reflected from the member, allowing the relative positioning of the reference element, the casing surface and the member to be simultaneously determined.
1. Apparatus for determining the clearance between a member and a casing surface over and relative to which the member moves, comprising:
a main waveguide, the waveguide having a proximal end and a distal end, the distal end being adjacent the casing surface and the proximal end being at a position recessed in the casing;
a transmitter/receiver, provided at the proximal end of the main waveguide, and
a reference element at a position intermediate the proximal and distal ends of the waveguide or at the distal end of the waveguide;
wherein the transmitter receiver is arranged to transmit an electromagnetic signal through the main waveguide and receive:
(i) a first portion of the electromagnetic signal reflected from the reference element;
(ii) a second portion of the electromagnetic signal reflected from the casing surface, and
(iii) a third portion of the electromagnetic signal reflected from the member.
2. The apparatus of claim 1 , wherein the casing comprises a liner, the outer surface of the liner providing the casing surface.
3. The apparatus of claim 2 , wherein the liner covers an opening at the distal end of the main waveguide.
4. The apparatus of claim 2 , wherein the reference element is provided by the inner surface of the liner.
5. The apparatus of claim 1 , wherein the reference element is intermediate the proximal and distal ends of the waveguide.
6. The apparatus of claim 5 , wherein the transmitter is arranged to receive a fourth portion of the electromagnetic signal reflected from the inner surface of the liner.
7. The apparatus of claim 5 , wherein the reference element is provided by an interface between different materials in the main waveguide.
8. The apparatus of claim 5 , wherein the reference element is provided by a change in width of the main waveguide.
9. The apparatus of claim 5 , wherein the reference element is provided by a change in the direction of extension of the main waveguide.
10. The apparatus of claim 1 , wherein the electromagnetic signal is a microwave signal.
11. The apparatus of claim 1 , wherein the electromagnetic signal is a visible or ultraviolet light signal.
12. The apparatus of claim 1 , wherein a reference waveguide having a proximal end and a distal end is provided, adjacent the main waveguide, for determining any change in length of the main waveguide.
13. The apparatus of claim 12 , wherein the reference waveguide is the same length as the main waveguide.
14. The apparatus of claim 12 , wherein the transmitter/receiver is arranged to receive a fifth portion of the electromagnetic signal reflected from the distal end of the reference waveguide.
15. The apparatus of claim 1 , comprising a signal processing means connected to the transmitter/receiver.
16. The apparatus of claim 15 , wherein the signal processing means is arranged to determine the relative positioning of the casing surface and the member, from the second and third portions of the electromagnetic signal, to calculate the clearance between the casing surface and the member.
17. The apparatus of claim 15 , wherein the signal processing means is arranged to determine the relative positioning of the reference element and the casing surface, from the first and second portions of the electromagnetic signal, to calculate the thickness of the liner.
18. The apparatus of claim 15 , wherein the signal processing means is arranged to determine the relative positioning of the casing surface and the inner surface of the liner, from the second and fourth portions of the electromagnetic signal, to calculate the thickness of the liner.
19. The apparatus of claim 15 , wherein the signal processing means is arranged to determine the relative positioning of the reference element and the member, from the first and third portions of the electromagnetic signal, to calculate any changes in the positioning of the member relative to the casing.
20. The apparatus of claim 15 , wherein the signal processing means is arranged to determine the relative positioning of the member and the inner surface of the liner, from the third and fourth portions of the electromagnetic signal, to calculate any changes in the positioning of the member relative to the casing.