Geared Turbofan Diffuser Case Flange Positioning

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Solution Overview

Problem

Gas turbine engine manufacturers seek further improvements in thermal, transfer, and propulsive efficiencies beyond what is achieved with geared architectures.

Innovation Solution

A gas turbine engine design featuring a compressor section with a compressor case and a diffuser case attached at an attachment interface, where the diffuser case surrounds multiple stages of the high-pressure compressor and includes bleeds for cabin pressurization, particularly at high altitude and low engine power conditions, with a geared architecture driven by the turbine section to optimize fan and turbine speeds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the diffuser case is attached to the compressor case at a forward location, then the structural support for the outer flowpath is improved, but the cabin pressurization system complexity increases due to longer bleed air pathways

Engineering Contradiction:

Improvestructural supportVSAvoidbleed air system complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The diffuser case is segmented into multiple sections with the attachment interface positioned to divide the compressor into forward and aft portions. This segmentation allows the outer flowpath static structure to be supported at an optimal location while the bleed air pathways are minimized by attaching the diffuser case at or behind the third-to-aftmost disk center plane, balancing structural support with system simplicity

Inventive Principle:

Principle #1Segmentation

2Strength

If the attachment interface is positioned forward of the compressor, then the outer flowpath static structure support is enhanced, but the bleed air pathway length increases reducing pressurization efficiency

Engineering Contradiction:

Improveouter flowpath supportVSAvoidpressurization efficiency

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The attachment interface position is optimized by changing the parameter of diffuser case positioning to be at or behind the third-to-aftmost disk center plane. This parameter change simultaneously achieves adequate outer flowpath support while minimizing bleed air pathway length, thereby maintaining pressurization efficiency without compromising structural support

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the diffuser case surrounds more compressor stages, then the engine performance is improved, but the thermal stresses on the compressor case increase

Engineering Contradiction:

Improveengine performanceVSAvoidthermal stresses

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The diffuser case is designed to surround a specific number of compressor stages (at least one stage of the second compressor) rather than the entire compressor. This segmentation allows the diffuser case to provide performance benefits while the attachment interface position (at or behind the third-to-aftmost disk) helps manage thermal stress distribution by creating a natural thermal boundary

Inventive Principle:

Principle #1Segmentation

Data Source

PatentEP2906806B1Geared turbofan engine with optimized diffuser case flange location

Publication Date: 2021.06.16 RTX CORP

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AI summary

A gas turbine engine has a compressor section, a compressor case substantially surrounding the compressor section, and a diffuser case attached at an attachment interface to the compressor case. The attachment interface is between a forward and an aft end of the compressor. A geared turbofan is also disclosed.