Geared Gas Turbine Core Split Power Ratio

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Solution Overview

Problem

The challenge in gas turbine engine design is to improve efficiency while managing high fan blade tip speeds, which decrease efficiency due to compressibility effects, and to optimize power distribution between compressor sections without imposing thermal and mechanical stresses on the fan drive turbine.

Innovation Solution

A gas turbine engine design featuring a two-spool or three-spool architecture with a gear arrangement between the low pressure spool and the fan, including multiple compressor stages and turbine stages, optimizing power ratios and pressure ratios to enhance overall efficiency and reduce fan tip speeds, while maintaining compactness and lightweight structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If fan diameter is increased to improve fuel consumption efficiency, then fuel efficiency is improved, but fan blade tip speeds increase causing compressibility effects that decrease efficiency

Engineering Contradiction:

Improvefuel efficiencyVSAvoidfan blade tip speed

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The low pressure turbine section is segmented into two separate turbine sections: a first low pressure turbine section that drives the low pressure compressor section, and a second low pressure turbine section that drives the fan. This segmentation allows independent optimization of each turbine section's operating conditions, enabling the fan to operate at lower tip speeds while maintaining the benefits of larger fan diameter for fuel efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A gear arrangement is introduced as an intermediary between the second low pressure turbine section and the fan. The gear arrangement provides a speed reduction mechanism that allows the fan to be driven at a lower speed than the turbine section rotates, thereby reducing fan blade tip speeds and compressibility effects while maintaining the power output needed for fuel-efficient operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If gear reduction is introduced between low pressure spool and fan to reduce fan tip speeds, then fan blade tip speed is reduced, but device complexity increases

Engineering Contradiction:

Improvefan blade tip speedVSAvoiddevice complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The gear arrangement is merged with the existing low pressure spool structure, integrating the speed reduction mechanism into the conventional architecture rather than adding a completely separate system. The first and second low pressure turbine sections are integrated into the low pressure spool, allowing the gear arrangement to work within the existing structural framework and minimize additional complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If power ratio between compressor sections is optimized to improve overall efficiency, then overall efficiency is improved, but thermal and mechanical stresses on fan drive turbine increase

Engineering Contradiction:

Improveoverall efficiencyVSAvoidthermal and mechanical stress

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The power distribution system is segmented by separating the fan drive function from the main low pressure spool. The second low pressure turbine section is dedicated solely to driving the fan through the gear arrangement, isolating it from the thermal and mechanical stresses that affect the first low pressure turbine section and the low pressure compressor section. This segmentation allows optimization of power ratios for overall efficiency without imposing excessive stresses on any single component.

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 design achieves a significant improvement in overall efficiency, propulsive efficiency, and thrust-specific fuel consumption, resulting in a more fuel-efficient and compact engine with improved power distribution and reduced mechanical stresses.

Implementation Method 1

The fan section is configured to deliver a portion of air into the compressor section, and a portion of air into a bypass duct

Methodology Applied

Scientific EffectFluid flow:

Implementation Method 2

The air is compressed in the low pressure compressor section, and passed into a high pressure compressor section

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 3

Products of this combustion pass downstream over a high pressure turbine section, and then a low pressure turbine section

Methodology Applied

Scientific EffectThermal energy conversion:

Implementation Method 4

a fan drive turbine to drive at least a gear arrangement to drive the fan section

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentUS11598286B2Geared gas turbine engine arrangement with core split power ratio

Publication Date: 2023.03.07 RTX CORP

AI summary

A gas turbine engine according to an example of the present disclosure includes, among other things, a propulsor section, a compressor section including a low pressure compressor and a second compressor section, and a turbine section including a low pressure turbine and a high pressure turbine. The low pressure turbine drives the low pressure compressor and the gear arrangement to drive the propulsor. A core split power ratio is provided by power input to the high pressure compressor divided by a power input to the low pressure compressor measured in horsepower.