Reverse-Core Turbofan Engine Architecture for Shaft Dynamics

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current axial turbine engines face challenges in shaft dynamics and rotor critical speeds due to increased length and reduced diameter of compressor, combustor, and turbine sections, which affect fuel efficiency and torque carrying capabilities.

Innovation Solution

A reverse-core turbofan engine architecture is introduced, featuring a propulsor section with counter-rotating fan-tip turbines, a heat exchanger on the core duct, and fluid coupling between the propulsor section and compressor section, utilizing hollow struts and a lobe mixer to manage airflow and reduce temperature, thereby alleviating shaft stress and enabling efficient fuel usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the number of compression stages and mechanical speeds are increased to improve fuel efficiency, then fuel efficiency is improved, but shaft critical speed and torque carrying capabilities deteriorate due to increased length and reduced diameter of shaft

Engineering Contradiction:

Improvefuel efficiencyVSAvoidshaft critical speed and torque carrying capabilities

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent inverts the conventional axial flow direction by using a reverse-core configuration where air flows axially backward from the propulsor section, then forward through the gas generator. This reversal allows the shaft to be positioned more favorably, improving its critical speed and torque carrying capabilities while maintaining the increased compression stages needed for fuel efficiency.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent transitions from a conventional axial arrangement to a three-dimensional reverse-core configuration, utilizing radial and axial flow directions in combination. The core duct system guides air through multiple directional changes (axial backward, then axial forward, then radially outward), creating a compact layout that preserves shaft performance while enabling increased compression stages.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Use of energy by moving object

If the compressor, combustor, and turbine sections are increased in length to improve fuel efficiency, then fuel efficiency is improved, but shaft critical speed deteriorates

Engineering Contradiction:

Improvefuel efficiencyVSAvoidshaft length

Core Design Contradiction:

Use of energy by moving objectVSLength of moving object

Solution Approach 1:

The patent uses a reverse-core configuration that exploits three-dimensional space more effectively. By guiding air through a path that moves axially backward, then forward, then radially outward through the core duct, the design achieves increased compression stages without proportionally increasing shaft length, thus maintaining shaft critical speed.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The reverse-core gas generator is nested within the propulsor section, with the core duct system integrated into the overall engine architecture. This nesting allows the compressor, combustor, and turbine to be arranged in a compact configuration that reduces the effective shaft length while maintaining the necessary compression stages for fuel efficiency.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Use of energy by moving object

If the compressor, combustor, and turbine sections are reduced in diameter to improve fuel efficiency, then fuel efficiency is improved, but torque carrying capabilities deteriorate

Engineering Contradiction:

Improvefuel efficiencyVSAvoidtorque carrying capabilities

Core Design Contradiction:

Use of energy by moving objectVSForce

Solution Approach 1:

The inverted axial flow configuration allows the shaft to be positioned and oriented more favorably within the engine, improving its torque carrying capabilities. The reverse-core arrangement enables the shaft to better support the increased compression stages without requiring a larger diameter, thus maintaining fuel efficiency improvements.

Inventive Principle:

Principle #13The other way round (Inversion)

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

This architecture enhances fuel efficiency while minimizing adverse design and dynamic effects on the engine shaft, allowing for the use of lightweight materials and reducing structural temperature, thus improving overall engine performance and reducing material stress.

Implementation Method 1

A heat exchanger is disposed on the core duct

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

A lobe mixer may be operably coupled to the exit of the core duct

Methodology Applied

Scientific EffectMixing:

Implementation Method 3

At least one hollow strut may be laterally disposed in the core duct operably coupling the high pressure turbine to the fan-tip turbine

Methodology Applied

Scientific EffectTorque transmission:

Data Source

PatentEP3080424B1Architecture for an axially compact, high performance propulsion system

Publication Date: 2022.05.04 RTX CORP

Figure 1
Figure 2
Figure 3

AI summary

A reverse-core turbofan engine including a propulsor section including a fan and a fan-tip turbine configured to deliver air to a core duct, including a first portion, disposed aft of the propulsor section, and direct air aft, toward an inlet of a reverse-core gas generator, and a second portion, configured to receive air from an exit of the gas generator and direct the air forward and radially outward of the propulsor, toward the fan-tip turbine in the propulsor, thereby driving the propulsor.