EGV Pre-Diffuser W-Seal Thermal Expansion Management

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Solution Overview

Problem

The differential thermal expansion rates between the high compressor exit guide vane (EGV) assembly and the pre-diffuser in gas turbine engines lead to disproportionate stresses on the EGV assembly, requiring frequent maintenance and replacement due to varying heat absorption and expansion rates.

Innovation Solution

An annular sealing system with w-seals and interlocking tabs is implemented between the EGV assembly and the pre-diffuser, allowing for differential axial and radial thermal expansion while preventing relative rotation, thus accommodating thermal expansion differences and reducing stress on the EGV assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the EGV assembly and pre-diffuser are rigidly connected, then structural stability is improved, but differential thermal expansion causes disproportionate stresses on the EGV assembly

Engineering Contradiction:

Improvestructural stabilityVSAvoidthermal stress

Core Design Contradiction:

Stability of the object's compositionVSStress or pressure

Solution Approach 1:

The connection between the EGV assembly and pre-diffuser is changed from rigid to dynamic through the implementation of flexible seals (w-seals) that allow relative movement. The seals are designed to accommodate differential thermal expansion while maintaining the sealing function, enabling the lighter EGV assembly to expand freely without generating excessive stresses.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The sealing system parameters are specifically designed to accommodate thermal expansion differences. The w-seals have specific geometric parameters (wave depth, wavelength, thickness) that allow them to deform elastically within a defined range, absorbing the dimensional changes caused by thermal expansion while maintaining connection integrity.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If the EGV assembly is made lighter with thin elements, then heat absorption is reduced, but thermal expansion rates increase causing disproportionate stresses

Engineering Contradiction:

Improveheat absorptionVSAvoidthermal stress

Core Design Contradiction:

TemperatureVSStress or pressure

Solution Approach 1:

The sealing system is segmented into multiple w-seals positioned at different locations (inner and outer seals) to independently manage thermal expansion at different radii. This segmentation allows each seal to accommodate local expansion patterns without transmitting stresses to the entire EGV assembly structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The flexible w-seals act as intermediary elements between the EGV assembly and pre-diffuser. These seals absorb the thermal expansion differences through their own elastic deformation, preventing the transmission of expansion-induced stresses to the lighter EGV assembly while maintaining the functional connection.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Stress or pressure

If seals are added to accommodate thermal expansion, then thermal stress is reduced, but device complexity increases

Engineering Contradiction:

Improvethermal stressVSAvoidsealing system complexity

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The patent employs flexible w-seals (thin film elements) instead of complex mechanical adjustment mechanisms. The w-seal geometry (wave pattern with specific amplitude and wavelength) provides the necessary compliance to accommodate thermal expansion while maintaining a relatively simple overall structure. The flexibility is inherent in the seal design rather than requiring additional actuating mechanisms.

Inventive Principle:

Principle #30Flexible shells and thin films

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 reduces thermal stress and wear on the EGV assembly by allowing independent thermal expansion while maintaining the EGV assembly's positional stability relative to the pre-diffuser, thereby minimizing maintenance costs and extending the lifespan of the EGV assembly.

Implementation Method 1

the various engine components absorb different amounts of heat energy, which may in turn cause different rates of thermal expansion in the components

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the first set of tabs and the second set of tabs interlock to prevent rotation of the EGV assembly relative to the pre-diffuser

Methodology Applied

Scientific EffectMechanical constraint: Mechanical Fastener

Data Source

PatentUS10161414B2High compressor exit guide vane assembly to pre-diffuser junction

Publication Date: 2018.12.25 RTX CORP

AI summary

A pre-diffuser and exit guide vane (EGV) system for a gas turbine engine includes an annular EGV assembly containing a number of guide vanes and having an annular opening bounded by a radially inner annular sealing surface at a first radius and a radially outer annular sealing surface at a second radius. First and second seals substantially matching the first and second radii respectively join the EGV assembly to an annular pre-diffuser having an annular opening bounded by radially inner and outer annular sealing surfaces at substantially the first and second radii. The seals seal the inner sealing surface of the EGV assembly to the inner sealing surface of the pre-diffuser and the second seal seals the outer sealing surface of the EGV assembly to the outer sealing surface of the pre-diffuser, such that the EGV assembly annular opening is in fluid communication with the annular opening of the pre-diffuser.