Ceramic Gas Turbine Seal Segment Thermal Mismatch

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Solution Overview

Problem

Ceramic shroud segments in gas turbine engines face challenges due to differential thermal mismatches with metallic parts, requiring innovative mounting solutions that accommodate thermal expansion and are compatible with ceramic matrix composite forming techniques.

Innovation Solution

A seal segment design featuring circumferentially spaced passageways for support bars that allow radial fixation and circumferential movement, enabling accommodation of thermal mismatches and simplifying production with a plate-like shape compatible with ceramic matrix composite materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If ceramic shroud segments are used to withstand high temperatures, then temperature resistance is improved, but differential thermal mismatch with metallic parts worsens

Engineering Contradiction:

Improvetemperature resistanceVSAvoidthermal mismatch

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The shroud ring is divided into multiple discrete seal segments that can be independently mounted and accommodated. Each segment can move relative to its support bar within the passageway, allowing differential thermal expansion without compromising the entire structure. This segmentation enables the ceramic segments to handle high temperatures while individually accommodating thermal mismatch stresses.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The passageway cross-sectional shape is changed from circular to non-circular (rectangular, square, or oval). This geometric parameter change allows the seal segment to move freely in the circumferential direction while maintaining radial fixation. The altered parameter enables thermal expansion accommodation without requiring complex adjustment mechanisms.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If complex mounting arrangements are used to accommodate thermal mismatch, then thermal compatibility is improved, but device complexity worsens

Engineering Contradiction:

Improvethermal compatibilityVSAvoidmounting complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The mounting function and thermal accommodation function are merged into a single integrated structure. The passageway simultaneously provides mechanical support for the seal segment and allows for thermal expansion through its non-circular geometry. This eliminates the need for separate adjustment mechanisms or complex mounting arrangements, reducing overall device complexity while maintaining thermal compatibility.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Instead of using complex active mechanisms to accommodate thermal expansion, the invention uses a passive geometric constraint system. The non-circular passageway shape inherently permits circumferential movement while maintaining radial position, inverting the approach from active adjustment to passive geometric accommodation, thereby simplifying the mounting arrangement.

Inventive Principle:

Principle #13The other way round (Inversion)

3Temperature

If ceramic matrix composite materials are used, then high temperature capability is improved, but manufacturing compatibility worsens

Engineering Contradiction:

Improvehigh temperature capabilityVSAvoidforming compatibility

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The plate-like seal segment design serves multiple functions: it provides the necessary high-temperature ceramic matrix composite structure, enables simple manufacturing through conventional forming techniques, and facilitates straightforward mounting in the shroud ring. This universal design approach makes the component compatible with various ceramic matrix composite forming methods while maintaining high temperature capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The solution effectively addresses thermal mismatch issues and simplifies production, ensuring reliable attachment and thermal integrity of ceramic shroud segments while maintaining structural integrity at high temperatures.

Implementation Method 1

differential thermal mismatches can make fixing of the segments to the engine problematic and can lead to unacceptable loadings on the segments

Methodology Applied

Scientific EffectDifferential thermal expansion: Thermal Expansion

Data Source

PatentEP2690260B1Seal segment

Publication Date: 2019.10.23 ROLLS ROYCE PLC

Figure 1~2
Figure 3~5

AI summary

A seal segment is provided for a shroud ring of a rotor of a gas turbine engine. The seal segment is positioned, in use, radially adjacent the rotor. The seal segment has first and second circumferentially spaced passageways each of which extends in the fore and aft direction. In use, a first support bar is contained within the first passageway, and a second support bar is contained within the second passageway. The first and second support bars being mountable to complementary formations provided by the casing of the engine. The first passageway is configured such that the seal segment is fixed relative to the first support bar in the radial and circumferential directions. The second passageway is configured such that the seal segment is fixed relative to the second support bar in the radial direction but allows relative movement of the seal segment and the second support bar in the circumferential direction to accommodate differential thermal expansion of the seal segment and the casing.