Optical Tip-Timing Probe Axial Alignment for Turbine Blades

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Solution Overview

Problem

Existing optical spot testing methods for gas turbine engines face inaccuracies due to axial misalignment of the probe, which cannot be accounted for by the Non-Intrusive Stress Measurement System (NSMS) software, leading to potential errors in vibrational characteristic measurements.

Innovation Solution

The Optical Probe Testing System (OPTS) includes a method for accurately positioning an optical tip-timing probe by treating the rotor blade tip with a binary reflective surface treatment, allowing for adjustment of the probe until an on-off transition is achieved in the optical return signal, ensuring proper axial alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the optical probe is bolted on to the support case using conventional mounting methods, then the probe assembly is simple to install, but axial misalignment of the spot on the blade tip occurs (roughly +/−30 mils)

Engineering Contradiction:

Improveease of probe installationVSAvoidaxial alignment precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

A movable probe head with adjustable positioning mechanism serves as an intermediary between the fixed support case and the rotating blade. This intermediary component allows for precise axial alignment adjustment while maintaining a simple bolted mounting structure, resolving the contradiction between ease of installation and alignment precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The probe head is designed to be movable rather than fixed, allowing dynamic adjustment of the probe's axial position. This dynamic capability enables precise alignment with the blade tip spot while keeping the overall mounting system simple and easily installable.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If the probe axial position is not precisely aligned, then the probe assembly is simpler to install, but the measurement accuracy of vibrational characteristics deteriorates

Engineering Contradiction:

Improveease of probe setupVSAvoidvibrational measurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The probe head position is preliminarily adjusted to achieve precise axial alignment with the target spot on the blade tip before conducting vibrational measurements. This preliminary positioning action ensures measurement accuracy while maintaining ease of operation through a simple adjustment mechanism.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system incorporates feedback through the optical return signal that indicates whether the probe is correctly positioned on the target spot. This feedback mechanism allows operators to easily verify and adjust probe positioning, ensuring measurement accuracy without complex setup procedures.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If the NSMS software is used to account for circumferential misplacement, then software compensation is simple, but axial misplacement cannot be accounted for

Engineering Contradiction:

Improvesoftware compensation capabilityVSAvoidaxial position accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

A movable probe head with adjustable axial positioning serves as an intermediary that physically compensates for axial misalignment, complementing the software's circumferential compensation capability. This hardware-software combination provides comprehensive error correction.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

While the NSMS software compensates for errors in the circumferential dimension, the movable probe head provides adjustment capability in the axial dimension. This adds another dimension of correction, addressing the limitation of software-only compensation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution improves the accuracy of optical spot measurements by allowing for precise axial alignment of the probe, reducing errors in vibrational characteristic assessments and ensuring the probe remains focused on the correct location on the blade tip during engine operation.

Implementation Method 1

treating the rotor blade tip with a binary reflective surface treatment, allowing for adjustment of the probe until an on-off transition is achieved in the optical return signal

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS20250076104A1Article and method for accurately positioning optical tip-timing probe

Publication Date: 2025.03.06 RTX CORP

AI summary

A method for accurately positioning an optical tip-timing probe for identifying vibration in a rotor blade tip of a turbine engine, wherein the method includes identifying a target location to be measured on a rotor blade tip of a plurality of rotor blades disposed within a rotor casing of a turbine engine, marking the target location with a reflective material, associating a probe body having probe head cavity with the rotor casing, such that the probe head cavity is aligned with a rotor casing opening which exposes the plurality of rotor blades, disposing the probe head within the probe head cavity to be movably aligned with the rotor casing opening, centering the probe head within the probe head cavity to be located in a nominal starting position and operating the optical tip-timing probe to identify the target location and precisely align the probe head with the target location.