Segmented Blade Outer Air Seal for Stable Tip Clearance

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The existing blade outer air seal (BOAS) configurations in gas turbine engines are sensitive to temperature changes, leading to inconsistent tip clearance and reduced efficiency due to the full ring arrangement, which does not allow for flexible control of tip clearance during different power settings and results in a conical shape that increases weight and complexity.

Innovation Solution

A segmented BOAS configuration using circumferential segments with hooks that connect to the inside diameter of the power turbine case, allowing each segment to expand freely with temperature changes and be controlled by the case, reducing sensitivity to temperature and enabling consistent tip clearance across varying power settings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a full ring BOAS configuration is used, then tip clearance control is provided, but the system becomes sensitive to temperature changes causing inconsistent clearance and reduced efficiency

Engineering Contradiction:

Improvetip clearance controlVSAvoidtemperature adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The BOAS is divided into multiple circumferential segments rather than using a full continuous ring. Each segment is independently supported by the case structure, allowing differential thermal expansion. The segments are positioned at different circumferential locations and can expand independently based on local temperature conditions, maintaining consistent tip clearance across varying thermal states.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a full ring BOAS is used, then sealing function is achieved, but the case must be conical increasing weight and complexity

Engineering Contradiction:

Improvesealing functionVSAvoidcase weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The BOAS is segmented into discrete circumferential elements rather than requiring a continuous ring structure. This segmentation allows the case to maintain a cylindrical geometry without the conical shape imposed by full ring configurations. Each segment is independently supported, eliminating the need for a conical case structure and reducing overall weight.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The segmented BOAS configuration serves multiple functions: it provides sealing, allows thermal expansion accommodation, maintains cylindrical case geometry, and reduces weight. The universal segmented approach replaces the need for complex conical case structures while achieving the same sealing objective with reduced complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Loss of energy

If a full ring BOAS is used, then air leakage is controlled, but freedom to control tip clearance during different power settings is limited

Engineering Contradiction:

Improveair leakage controlVSAvoidpower setting adaptability

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The BOAS is divided into multiple circumferential segments that can independently respond to thermal changes. This segmentation provides the freedom to control tip clearance across different power settings by allowing each segment to expand or contract based on local temperature conditions, maintaining optimal clearance whether the engine is at low or high power.

Inventive Principle:

Principle #1Segmentation

4Strength

If continuous unitary ring BOAS is used, then structural integrity is maintained, but thermal expansion sensitivity increases

Engineering Contradiction:

Improvestructural integrityVSAvoidthermal expansion sensitivity

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The BOAS structure is segmented into discrete circumferential elements rather than using a continuous unitary ring. Each segment maintains sufficient structural integrity for its local function while being thermally isolated from adjacent segments. This allows each segment to expand independently with local temperature changes without transmitting thermal stress throughout the entire structure, reducing overall thermal sensitivity.

Inventive Principle:

Principle #1Segmentation

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 segmented design provides more consistent tip clearance and reduced weight by allowing the BOAS to be driven by the flow path rather than assembly constraints, resulting in improved efficiency and a cylindrical shape that minimizes weight and diameter growth with increasing stages.

Implementation Method 1

A piston seal is received in the groove and extends radially inward to engage the forward seal and bias the end radially inward into engagement with the forward hook

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

A spring is arranged axially between and in engagement with the second case and the base portion of the first stage blade outer air seal

Methodology Applied

Scientific EffectSpring force: Spring

Data Source

PatentEP3453839B1Gas turbine engine blade outer air seal

Publication Date: 2021.03.31 RTX CORP

Figure 1~2
Figure 3~4
Figure 5~6C

AI summary

A gas turbine engine sealing system includes a case (50) including forward and aft hooks (62, 64). The aft hook (64) is arranged radially outward of the forward hook (62). A blade outer air seal (65) has a J-hook (68) that receives the aft hook (64) and includes an end (72) received by the forward hook (62).