Rub Button Tip Clearance Measurement

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Solution Overview

Problem

Current methods for determining tip clearance in gas turbine engines are inefficient and costly, as they require disassembly to measure rotor blade tip gaps and contact with the shroud, leading to inefficiencies and potential material loss or heat generation.

Innovation Solution

A system using a rub button with a head portion that extends into the flow path, featuring a profile varying according to a defined function of its height, allowing tip clearance measurement through image analysis without disassembly, using a borescope to capture and correlate image dimensions with known dimensions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional disassembly methods are used to measure tip clearance, then measurement accuracy is improved, but productivity is reduced and loss of time increases

Engineering Contradiction:

Improvetip clearance measurement accuracyVSAvoidmeasurement efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces mechanical disassembly and physical measurement methods with an optical imaging system. A borescope captures images of the rub button head portion, and image processing algorithms automatically determine tip clearance dimensions, eliminating the need for manual disassembly and measurement while maintaining accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates a visual copy (image) of the rub button head portion and its profile. By capturing and analyzing the image of the head portion with its defined function profile, the system derives tip clearance measurements without physical contact or disassembly, thus improving productivity while preserving measurement precision.

Inventive Principle:

Principle #26Copying

2Loss of energy

If rotor blade tip gaps are reduced to improve efficiency, then energy loss is reduced, but reliability deteriorates due to increased risk of contact with shroud

Engineering Contradiction:

Improveair leakage lossVSAvoidblade tip contact risk

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent introduces a rub button as an intermediary element between the rotor blade tip and the shroud. The rub button with its head portion extending into the flow path acts as a sacrificial component that contacts first, protecting the actual rotor blade from damage while enabling precise measurement of the clearance gap.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the potentially harmful contact between rotor blade and shroud into a beneficial measurement opportunity. By placing the rub button in the flow path, any contact or near-contact events are transformed into measurable profile changes that provide precise tip clearance data, turning a reliability risk into a diagnostic advantage.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Manufacturing precision

If rotor blade contacts shroud during operation, then material is removed or heat is generated, but this leads to loss of substance and reduced reliability

Engineering Contradiction:

Improvetip clearance controlVSAvoidblade tip material loss

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent implements beforehand cushioning by positioning the rub button's head portion into the flow path ahead of the rotor blade tip. This creates a protective buffer zone where the rub button absorbs any potential contact with the shroud, preventing material loss from the actual rotor blade while maintaining precise tip clearance control.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS9957834B2Rotor blade tip clearance

Publication Date: 2018.05.01 RTX CORP

AI summary

A system includes, in one example, a shroud configured to circumscribe a plurality of rotor blades of a gas rotor engine, and at least one rub button including a head portion having a height configured to extend into a flow path region of the shroud along a central axis of the rub button that extends radially into the flow path region. The head portion includes a profile, orthogonal to the central axis, that varies according to a defined function of the height of the head portion.