Ceramic Seal Runner Mounting for Thermal Expansion and Edge Loading

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Solution Overview

Problem

Existing runner mount designs for ceramic seal runners in gas turbine engines experience excessive stresses and wear due to edge loading, and they compromise the sealing surface by dedicating part of the radially outer surface for mounting, leading to reduced effectiveness and lifespan.

Innovation Solution

A mounting assembly comprising a retaining member, a middle member, and a forward member, which axially and radially aligns the ceramic seal runner, converting radial thermal expansion to axial compression and maintaining the runner in place without loading the radially outward facing seal surface, using materials with matched thermal expansion coefficients to ensure sealing engagement over a range of temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the runner mount contacts both radially inner and radially outer surfaces of the runner, then the runner is securely held in place, but excessive stresses occur in the runner and runner mount due to edge loading

Engineering Contradiction:

Improverunner and runner mount stress resistanceVSAvoidrunner mount secure holding

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention extracts the mounting function from the radially outer surface of the runner, using only the radially inner surface for mounting purposes. The mounting assembly includes a mounting member that contacts only the radially inner surface, while the radially outer surface remains dedicated to sealing engagement with the seal ring, eliminating edge loading stresses.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention segments the runner surface functions by dedicating the radially inner surface to mounting and the radially outer surface to sealing. This functional segmentation allows each surface to perform its specific role without compromising the other, preventing stress concentration at the outer surface.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a portion of the radially outer surface is dedicated to mounting, then the runner can be held in place, but the sealing surface area is reduced compromising seal effectiveness

Engineering Contradiction:

Improverunner positioningVSAvoidsealing surface area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The mounting function is extracted from the radially outer surface and relocated to the radially inner surface. This extraction preserves the entire radially outer surface for sealing engagement, maximizing the sealing surface area while still providing secure mounting through the inner surface.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the mounting assembly applies radial loads to the runner, then the runner is retained axially, but thermal expansion causes excessive stress in the ceramic runner

Engineering Contradiction:

Improveaxial retentionVSAvoidradial thermal stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The invention changes the mounting approach from radial loading to axial loading. The mounting member contacts the radially inner surface and applies axial forces for retention, while accommodating radial thermal expansion through compliance features that allow the runner to expand freely without generating excessive stress.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The mounting assembly is designed to accommodate radial thermal expansion of the ceramic runner by using compliant mounting members that can deflect radially outward as the runner expands with temperature, preventing stress buildup while maintaining axial retention.

Inventive Principle:

Principle #37Thermal expansion

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 reduces stress and wear on the runner and mount, maintains effective sealing, and frees the radially outer surface for sealing, enhancing the assembly's durability and reducing leakage risks.

Implementation Method 1

The mounting assembly converts radial thermal expansion to axial compression applied to the step portion of the ceramic runner

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

said ceramic runner is axially retained by frictional engagement of said step portion with each of said foot portion of said middle member and said wall of said retaining member

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS10927960B2Mounting assembly for a ceramic seal runner

Publication Date: 2021.02.23 ROLLS ROYCE CORP

AI summary

A seal assembly is disclosed for sealing a higher pressure fluid cavity from a lower pressure fluid cavity. The seal assembly comprises a mounting assembly, a circumferential ceramic runner carried by the mount assembly, and a carbon seal ring sealingly engaged to the runner. The runner comprises an axially-extending sealing portion and a radially-inward-extending step portion. The mounting assembly comprises a retaining member, a forward member, and a middle member. The step portion of the runner is axially retained between the retaining member and the middle member.