Offset-Core Nacelle Heat Exchangers for Steam-Recovery Propulsion

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Solution Overview

Problem

Existing aircraft propulsion systems lose significant heat energy in exhaust gas flows, and existing heat exchangers are too large compared to engine size, limiting their efficiency and space for additional heat recovery systems.

Innovation Solution

An aircraft propulsion system with an offset gas generating core engine and nacelle-mounted heat exchangers, including a condenser and evaporator assembly, where steam is generated from recovered water to enhance engine efficiency and power output without increasing compressor work, and a bypass airflow cools the gas flow in the condenser.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If large heat exchangers are used to capture heat energy and generate steam, then engine efficiency is improved, but the heat exchangers become large compared to the overall engine size

Engineering Contradiction:

Improveengine efficiencyVSAvoidheat exchanger size

Core Design Contradiction:

Use of energy by moving objectVSVolume of moving object

Solution Approach 1:

The condenser and evaporator heat exchangers are nested within the nacelle structure, utilizing the available internal volume of the nacelle to house these components. This allows the heat exchangers to be integrated into the existing engine architecture without significantly increasing the overall engine volume, while still providing sufficient heat capture surface area to improve engine efficiency through steam generation.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Quantity of substance

If heat exchangers are added to recover heat energy, then more steam is generated, but the available space within the nacelle is reduced

Engineering Contradiction:

Improvesteam flowVSAvoidnacelle space

Core Design Contradiction:

Quantity of substanceVSVolume of stationary object

Solution Approach 1:

The heat exchangers are arranged in a three-dimensional configuration within the nacelle, utilizing vertical and radial spaces that would otherwise be unused. The condenser and evaporator are positioned to maximize thermal communication with the exhaust gas flow paths, effectively using the available nacelle volume in multiple dimensions to accommodate the heat recovery system without compromising other engine components.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Use of energy by moving object

If steam flow is increased to improve engine efficiency, then more heat recovery is required, but the compressor work increases

Engineering Contradiction:

Improveengine efficiencyVSAvoidcompressor work

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The system converts the harmful waste heat in the exhaust gas flow into a beneficial resource by using it to generate steam through the condenser and evaporator assembly. This recovered steam is then injected into the core flow to increase engine efficiency without requiring additional compressor work, as the steam generation utilizes otherwise wasted thermal energy from the exhaust.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 system increases engine efficiency and power output by recovering heat energy and generating steam, while providing larger heat exchanger areas within the nacelle, maintaining compact engine size and reducing compressor work requirements.

Implementation Method 1

a condenser where water in the gas flow is condensed into a liquid form

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 2

an evaporator assembly that is in thermal communication with the exhaust duct where water recovered by the condenser is heated to generate a steam flow

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

an ejector duct where a portion of a bypass airflow is thermally communicated with the condenser to cool the gas flow

Methodology Applied

Scientific EffectHeat transfer: Heat Exchanger

Data Source

PatentUS12577904B2Offset core with side ejector nacelle nozzles

Publication Date: 2026.03.17 RTX CORP

AI summary

A propulsion system for an aircraft includes a fan that is rotatable about a fan axis, a core engine that is configured for generating a gas flow utilized to generate shaft power for driving the fan, a nacelle that surrounds the core engine and the fan, a condenser where water in the gas flow is condensed into a liquid form, an exhaust duct assembly where the gas flow exhausted from the core engine is directed to the condenser, an ejector duct where a portion of a bypass airflow is thermally communicated with the condenser to cool the gas flow, and an evaporator assembly that is in thermal communication with the exhaust duct where water recovered by the condenser is heated to generate a steam flow that is subsequently communicated to the core engine.