# US 12,223,640 B2 · Turbine blade creep monitoring

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- Number: US 12,223,640 B2
- Document ID: US12223640B2
- Status: Granted
- Kind: B2
- Application number: 17/712,676
- Filed: 2022-04-04
- Published: 2022-11-03
- Granted: 2025-02-11
- Earliest claimed: 2021-04-29
- Assignees: ROLLS-ROYCE plc
- Applicants: ROLLS-ROYCE plc
- Inventors: Adriano Pulisciano; Bilal M Nasser
- Web page: https://patentgrep.com/patent/US12223640B2

## CPC

- F01D 5/005: {Repairing methods or devices}
- G06T 7/001: {using an image reference approach}
- F01D 5/14: Form or construction (selecting particular materials, measures against erosion or corrosion F01D5/28)
- F01D 21/003: {Arrangements for testing or measuring (for measuring vibrations G01H)}
- F01D 25/00: Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D 25/285: {Temporary support structures, e.g. for testing, assembling, installing, repairing; Assembly methods using such structures}
- G01B 11/16: for measuring the deformation in a solid, e.g. optical strain gauge
- G01N 21/954: Inspecting the inner surface of hollow bodies, e.g. bores
- G02B 23/24: Instruments {or systems} for viewing the inside of hollow bodies, e.g. fibrescopes
- G06T 7/593: from stereo images
- G06T 7/85: {Stereo camera calibration}
- F05D 2220/323: for aircraft propulsion, e.g. jet engines
- F05D 2230/80: Repairing, retrofitting or upgrading methods
- F05D 2240/30: Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
- F05D 2260/80: Diagnostics
- F05D 2260/83: Testing, e.g. methods, components or tools therefor
- F05D 2270/30: Control parameters, e.g. input parameters
- G01B 11/24: for measuring contours or curvatures
- G06T 2207/10021: Stereoscopic video; Stereoscopic image sequence
- F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D)
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS

## Abstract

A method of monitoring turbine blade creep in a gas turbine engine is provided. The method includes: receiving stereo images of a turbine blade of a row of turbine blades, the images having been obtained using a stereo borescope located in the engine adjacent the row of turbine blades; identifying same features of the blade in each of the stereo images; mapping each of the identified features by triangulation onto a 3D space to produce a 3D depth map of at least part of the blade; providing a 3D reference model of the blade; and comparing the 3D reference model with the 3D depth map to measure one or more deviations in shape of the blade to determine an amount of creep-induced distortion of the blade.

## Claims

### Claim 1

A method of monitoring turbine blade creep in a gas turbine engine, the method including:
receiving stereo images of a turbine blade of a row of turbine blades, the stereo images being over a whole radial length of the turbine blade, and having been obtained using a stereo borescope located in the engine adjacent the row of turbine blades;
identifying a trailing edge, a platform edge, and a shroud edge of the blade in each of the stereo images;
mapping each of the trailing edge, the platform edge and the shroud edge by triangulation onto a 3D space;
measuring in the 3D space a distance between a radially inner landmark at a corner platform edge closest to the trailing edge, and a radially outer landmark at a corner of the shroud edge closest to the trailing edge on the blade; and
comparing the measured distance with the distance between the radially inner landmark and the radially outer landmark for a turbine blade that has not experienced creep to determine an amount of creep-induced distortion of the blade.

### Claim 2 (depends on 1)

The method according to claim 1, further including:
calibrating the stereo borescope to determine imaging distortions produced thereby; and
using the calibration to adjust the images to remove or reduce imaging distortions before the mapping onto the 3D space.

### Claim 3 (depends on 1)

The method according to claim 1, further including, preliminary to receiving the image of a turbine blade:
locating the stereo borescope in the engine adjacent the row of turbine blades; and
using the borescope to obtain the image of the turbine blade of the row of turbine blades.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the stereo borescope is used to obtain a stereo video of the turbine blade as the row of turbine blades rotates, the stereo images being stills extracted from the stereo video.

### Claim 5

A method of monitoring turbine blade creep in a gas turbine engine, the method including:
receiving stereo images of a turbine blade of a row of turbine blades, the stereo images having been obtained using a stereo borescope located in the engine adjacent a row of turbine blades, and the stereo images including a seal segment located radially outwardly of the blades, in use the blades moving past the seal segment as the row of turbine blades rotates;
identifying same features of the blade in each of the stereo images;
identifying the seal segment in each of the stereo images;
mapping each of the identified features by triangulation onto a 3D space to produce a 3D depth map of at least part of the blade, the 3D depth map including a shroud of the blade;
mapping the seal segment by triangulation onto the 3D space such that the produced 3D depth map also includes the seal segment;
providing a 3D reference model of the blade and the seal segment; and
comparing the 3D reference model with the 3D depth map to measure one or more deviations in shape of the blade to determine an amount of creep-induced distortion of the blade, wherein the creep-induced distortion is determined by measuring relative twisting between the shroud and the seal segment.

### Claim 6 (depends on 5)

The method according to claim 5, wherein the 3D depth map includes a platform and a shroud of the blade, and the creep-induced distortion includes creep-induced twisting and/or creep-induced elongation of the blade between the platform and the shroud.

### Claim 7 (depends on 5)

The method according to claim 5, further including:
calibrating the stereo borescope to determine imaging distortions produced thereby; and
using the calibration to adjust the images to remove or reduce imaging distortions before the mapping onto the 3D space.

### Claim 8 (depends on 5)

The method according to claim 5, further including, preliminary to receiving the image of a turbine blade:
locating the stereo borescope in the engine adjacent the row of turbine blades; and
using the borescope to obtain the image of the turbine blade of the row of turbine blades.

### Claim 9 (depends on 5)

The method according to claim 5, wherein the stereo borescope is used to obtain a stereo video of the turbine blade as the row of turbine blades rotates, the stereo images being stills extracted from the stereo video.

### Claim 10

A system for monitoring turbine blade creep in a gas turbine engine, the system including:
a computer readable medium for storing stereo images of a turbine blade of a row of turbine blades, the stereo images being over a whole radial length of the turbine blade, and having been obtained using a stereo borescope located in the engine adjacent the row of turbine blades; and
a processor-based sub-system operationally connected to the computer readable medium and adapted to:
identify a trailing edge, a platform edge and a shroud edge of the blade in each of the stereo images;
map each of the trailing edge, the platform edge and the shroud edge by triangulation onto a 3D space;
measure in the 3D space a distance between a radially inner landmark at a corner of the platform edge closes to the trailing edge on the blade, and a radially outer land mark at a corner of the shroud edge closest to the trailing edge on the blade; and
compare the measured distance with the distance between the radially inner landmark and the radially outer landmark for a turbine blade that has not experienced creep to determine an amount of creep-induced distortion of the blade.

### Claim 11 (depends on 10)

The system according to claim 10, further including a stereo borescope adapted to be located in the engine adjacent the row of turbine blades for obtaining the stereo images of the turbine blade of the row of turbine blades, the computer readable medium being operatively connectable to the stereo borescope to receive therefrom the images of the turbine blade.

### Claim 12 (depends on 10)

The system according to claim 10, wherein the stereo borescope is adapted to obtain a stereo video of the turbine blade as the row of turbine blades rotates, the stereo images being stills extracted from the video.

### Claim 13

A system for monitoring turbine blade creep in a gas turbine engine, the system including:
a computer readable medium for storing stereo images of a turbine blade of a row of turbine blades, the images having been obtained using a stereo borescope located in the engine adjacent the row of turbine blades, and the stereo images including a seal segment located radially outwardly of the blades, in use the blades moving past the seal segment as the row of turbine blades rotates; and
a processor-based sub-system operationally connected to the computer readable medium and adapted to:
identify same features of the blade in each of the stereo images;
identify the seal segment in each of the stereo images;
map each of the identified features by triangulation onto a 3D space to produce a 3D depth map of at least part of the blade, the 3D depth map including a shroud of the blade;
map the seal segment by triangulation onto the 3D space such that the produced 3D depth map also includes the seal segment;
provide a 3D reference model of the blade and the seal segment; and
compare the 3D reference model with the 3D depth map to measure one or more deviations in shape of the blade to determine an amount of creep-induced distortion of the blade, wherein the creep-induced distortion is determined by measuring relative twisting between the shroud and the seal segment.

### Claim 14 (depends on 13)

The system according to claim 13, further including a stereo borescope adapted to be located in the engine adjacent the row of turbine blades for obtaining the stereo images of the turbine blade of the row of turbine blades, the computer readable medium being operatively connectable to the stereo borescope to receive therefrom the images of the turbine blade.

### Claim 15 (depends on 13)

The system according to claim 13, wherein the stereo borescope is adapted to obtain a stereo video of the turbine blade as the row of turbine blades rotates, the stereo images being stills extracted from the video.