Turbine Shroud Buffer Air Seals for Differential Thermal Expansion

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Solution Overview

Problem

Sealing between turbine shroud components with different thermal expansion coefficients is challenging due to differential expansion, leading to potential gaps and inefficiencies in gas turbine engines.

Innovation Solution

A turbine shroud assembly with a carrier segment, blade track segment, and a buffer air seal assembly that includes first and second seal members, where buffer air is used to pressurize a buffer chamber between the seal members, urging them into engagement with radial surfaces to maintain a seal, thereby preventing gas leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional sealing methods are used between turbine shroud components with different thermal expansion coefficients, then the structure is simple, but sealing effectiveness deteriorates due to differential expansion causing gaps

Engineering Contradiction:

Improvesealing effectivenessVSAvoidseal assembly complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses a buffer air seal assembly that introduces pressurized air into a buffer chamber to inflate a seal element, creating a pneumatic sealing mechanism. This allows the seal to expand and fill gaps caused by differential thermal expansion between components, maintaining sealing effectiveness without requiring complex mechanical adjustment mechanisms

Inventive Principle:

Principle #29Pneumatics and hydraulics

Solution Approach 2:

The seal element's physical state is changed by varying the air pressure in the buffer chamber. By adjusting the buffer air pressure, the seal element can dynamically adapt its expansion state to compensate for thermal expansion differences, maintaining reliable sealing under varying temperature conditions

Inventive Principle:

Principle #35Parameter changes

2Reliability

If rigid sealing components are used to maintain seal engagement, then sealing is maintained, but wear increases and service life decreases

Engineering Contradiction:

Improveseal engagementVSAvoidseal member life

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent employs a flexible seal element that can deform and conform to the mating surfaces. This flexibility allows the seal to maintain engagement and filling of gaps without requiring high contact pressures that would cause wear, thereby extending seal member life while maintaining reliable sealing

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The buffer air acts as an intermediary that transmits force to the seal element, allowing indirect engagement with the mating surfaces. This reduces direct mechanical contact and wear between rigid components, extending the service life of the seal assembly

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If buffer air pressure is increased to improve seal engagement, then sealing effectiveness improves, but energy consumption increases

Engineering Contradiction:

Improveseal engagementVSAvoidbuffer air energy

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The seal element is designed to achieve effective sealing with partial inflation, not requiring excessive buffer air pressure. The flexible nature of the seal element allows it to engage effectively at moderate pressure levels, reducing energy consumption while maintaining adequate seal engagement

Inventive Principle:

Principle #16Partial or excessive action

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 buffer air seal assembly effectively maintains a seal between the carrier and blade track segments, enhancing the durability and efficiency of the turbine shroud by reducing wear and extending the life of the seal members.

Implementation Method 1

The at least one buffer air passageway may be configured to discharge buffer air radially inward away from carrier segment into the buffer chamber axially between the first seal member and the second seal member to pressurize the buffer chamber to urge the first seal member axially forward and the second seal member axially aft

Methodology Applied

Scientific EffectBuffer air discharge and pressurization: Pressure Gradient

Data Source

PatentUS20260036067A1Turbine shroud assemblies with air activated buffer cavity seals

Publication Date: 2026.02.05 ROLLS ROYCE CORP

AI summary

A turbine shroud assembly adapted for use with a gas turbine engine includes a carrier segment, a blade track segment, and a seal system. The carrier segment arranged circumferentially at least partway around an axis. The blade track segment is coupled to the carrier segment and defines a portion of a gas path of the gas turbine engine. The seal system includes seals arranged radially between the carrier segment and the blade track segment to block gases from flowing between the carrier segment and the blade track segment.