Optical systems and methods for measuring turbine blade tip clearance

Patent metadata

Field	Value
Publication number	US-12060865-B2
Application number	US-202117483087-A
Country	US
Kind code	B2
Filing date	Sep 23, 2021
Priority date	Sep 24, 2020
Publication date	Aug 13, 2024
Grant date	Aug 13, 2024

Abstract

A blade tip measurement system includes a case and a blade that rotates within the case, the blade having an outer blade tip surface that has a clearance distance from an inner surface of the case. A light source emits light along an optical path that is directed toward the outer blade tip surface by a lens, and the outer blade tip surface reflects the light back along the optical path. An optical interferometer generates an interference pattern using the reflected light, and a photoreceiver receives the interference pattern. A complex logic device determines the clearance distance of the blade tip surface from the inner surface of the case based on the interference pattern. The interferometer may be a Fabry-Perot optical interferometer formed using a window positioned between the lens and the blade tip surface, or a Michelson interferometer formed using a reference optical path. The system may alternatively include an optical time of flight measurement of the blade tip clearance. The system further may include an abradable substrate having an optical fiber array of optical fibers at different depths, whereby the blade tip clearance is determinable based on which of the optical fibers are abraded as the blade tip rotates.

First claim

What is claimed is:

1. A blade tip measurement system comprising:
a case and a blade that rotates within the case, the blade having an outer blade tip surface that has a clearance distance from an inner surface of the case as the blade rotates;
a light source that emits light along an optical path and a lens that receives the light and directs the light toward the outer blade tip surface, wherein the outer blade tip surface reflects the light back along the optical path;
an optical interferometer that generates an interference pattern using the reflected light;

a photoreceiver that receives the interference pattern;
a complex logic device configured to determine the clearance distance of the outer blade tip surface from the inner surface of the case based on the interference pattern;
a window, wherein the lens directs the light through the window toward the outer blade tip surface and the outer blade tip surface reflects the light back through the window; and
wherein the optical interferometer comprises multiple optical cavities formed by surfaces of the window and the outer blade tip surface, such that the reflected light creates an interference pattern with the light from the light source.

2. The blade tip measurement system of claim 1 , wherein the multiple optical cavities include a first optical cavity between a blade side inner window surface and an outer window surface opposite from the inner window surface, and a second optical cavity between the inner window surface and the outer blade tip surface.

3. The blade tip measurement system of claim 1 , wherein the complex logic device further is configured to determine time of flight measurements of reflected light that is reflected off the outer blade tip surface and the inner and outer window surfaces to the photoreceiver, and differences in time of flight to the photoreceiver further are used to determine the clearance distance.

4. The blade tip measurement system of claim 1 , wherein the optical path includes an optical coupler and a first optical fiber that transfers the light from the light source to the lens, and a second optical fiber that transfers the interference pattern from the optical coupler to the photoreceiver.

5. The blade tip measurement system of claim 1 , wherein the light source, the photoreceiver, and the complex logic are integrated into an opto-electronics box.

6. The blade tip measurement system of claim 1 , wherein the outer blade tip surface includes a dedicated reflection target onto which the lens directs the light.

7. The blade tip measurement system of claim 1 , wherein the light source is a broadband light source, and the photoreceiver is an array containing numerous photoreceiver cells tuned to different wavelengths within a full bandwidth of the broadband light source.

8. The blade tip measurement system of claim 1 , wherein the light source is a swept or tuned laser and the photoreceiver is a single photoreceiver cell.

9. A blade tip measurement system comprising:
a case and a blade that rotates within the case, the blade having an outer blade tip surface that has a clearance distance from an inner surface of the case as the blade rotates;
a light source that emits light along an optical path and a lens that receives the light and directs the light toward the outer blade tip surface, wherein the outer blade tip surface reflects the light back along the optical path;
an optical interferometer that generates an interference pattern using the reflected light;
a photoreceiver that receives the interference pattern;
a complex logic device configured to determine the clearance distance of the outer blade tip surface from the inner surface of the case based on the interference pattern; and
a reference optical path and a splitter device that splits the light from the light source prior to any reflection by the blade tip surface, to direct a portion of the light along the optical path and a portion of the light along the reference optical path;
wherein the optical interferometer comprises the splitter device that also recombines reflected light that travels along the optical path and reflected light that travels along the reference optical to create the interference pattern.

10. The blade tip measurement system of claim 9 , wherein the reference optical path includes a reference optical fiber that has an end with a reflective element.

11. A blade tip measurement system comprising:
a case and a blade that rotates within the case, the blade having an outer blade tip surface that has a clearance distance from an inner surface of the case as the blade rotates;
a light source that emits light and a photoreceiver that receives reflected light; and
a complex logic device configured to determine the clearance distance of the outer blade tip surface from the inner surface of the case;
wherein the inner surface of the case includes an abradable substrate that is embedded within an abradable layer;
the abradable substrate comprising an optical fiber array including a plurality of individual optical fibers, each of the plurality of individual optical fibers of the optical fiber array having a respective end including a respective reflective element that receives light from the light source and reflects light back to the photoreceiver;
the respective ends of the plurality of individual optical fibers of the optical fiber array being positioned at different depths within the abradable substrate relative to an inner surface of the abradable substrate that is initially aligned with the inner surface of the case, such that as the blade rotates within the case the outer blade tip surface abrades the abradable substrate so as to abrade one or more of the plurality of individual optical fibers of the optical fiber array according to how deep the blade tip surface abrades the abradable substrate, thereby removing respective reflective elements of the one or more of the plurality of individual fibers of the optical fiber array; and
the complex logic device measures an extent of abrasion of the abradable substrate based on optical energy of reflected light received by the photoreceiver from the optical fiber array, and determines the clearance distance based on the extent of abrasion of the abradable substrate.

12. The blade tip measurement system of claim 11 , wherein each of the plurality of individual optical fibers of the optical fiber array extends perpendicular to the inner surface of the abradable substrate.

13. The blade tip measurement system of claim 11 , wherein each of the plurality of individual optical fibers of the optical fiber array is curved such that respective end portions of each of the plurality of individual optical fibers of the optical fiber array extend parallel to the inner surface of the abradable substrate; and
the end portions of each of the plurality of individual optical fibers of the optical fiber array respectively includes an identifying feature that is unique to a respective individual optical fiber, whereby the complex logic determines the one or more of the plurality of individual optical fibers of the optical fiber array that are abraded based on removal of the respective identifying feature.

Assignees

• Parker Hannifin Corp

Inventors

• Boyd Lewis J
• Altieri Russell E

Classifications

• F01D7/00

  Rotors with blades adjustable in operation; Control thereof (for reversing F01D1/30) · CPC title

• F01D25/24

  Casings (modified for heating or cooling F01D25/14); Casing parts, e.g. diaphragms, casing fastenings (casings for rotary machines or engines in general F16M {; special arrangements in stators dealing with breaking-off of part of rotor F01D21/045}) · CPC title

• G01B9/02001

  characterised by controlling or generating intrinsic radiation properties · CPC title

• G01B11/026

  by measuring distance between sensor and object (G01B11/0608 takes precedence) · CPC title

• G01B2290/25

  Fabry-Perot in interferometer, e.g. etalon, cavity · CPC title