Rear Fuselage Propulsion Cooling via Ambient Air Heat Exchange

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Solution Overview

Problem

The existing aircraft propulsion systems with contra-rotating fan rotors and gas generators face challenges in cooling auxiliary equipment, particularly due to their rear placement within the fuselage, which increases the demand for effective thermal energy discharge and requires innovative cooling solutions.

Innovation Solution

The implementation of a cooling circuit with heat exchangers located in the connection means and nacelle, which exchange heat with ambient air, effectively addressing the thermal management needs by utilizing surfaces exposed to icing conditions and optimizing heat discharge through the tail unit and nacelle fairing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If gas generators are housed in the fuselage with auxiliary equipment, then the propulsion system can be integrated, but the auxiliary equipment requires effective cooling due to heat generation

Engineering Contradiction:

Improveintegration of propulsion systemVSAvoidheat generation from auxiliary equipment

Core Design Contradiction:

Stability of the object's compositionVSTemperature

Solution Approach 1:

A cooling circuit acts as an intermediary system between the heat-generating auxiliary equipment and the ambient air. The cooling circuit includes heat exchangers that transfer heat from the auxiliary equipment to the ambient air, enabling thermal management without direct exposure of equipment to external conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The cooling function is extracted as a separate system from the propulsion system. The cooling circuit is implemented as an independent subsystem with dedicated heat exchangers, allowing thermal management to be handled separately from the gas generator and auxiliary equipment integration.

Inventive Principle:

Principle #2Taking out (Extraction)

2Device complexity

If auxiliary equipment is disposed in the vicinity of the engine, then the propulsion system is compact, but the equipment is difficult to cool due to distance from fuselage wall

Engineering Contradiction:

Improvepropulsion system configurationVSAvoidcooling circuit implementation

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The cooling circuit utilizes the longitudinal dimension of the fuselage by extending heat exchangers along the fuselage length. This allows heat exchange surfaces to be positioned at locations with adequate access to ambient air flow, solving the cooling problem while maintaining the compact auxiliary equipment arrangement near the gas generator.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Use of energy by moving object

If electrical machines are used for starters, then electrical energy demand is met, but cooling requirements increase

Engineering Contradiction:

Improveelectrical energy supplyVSAvoidcooling demand of electrical machines

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The cooling circuit serves multiple functions simultaneously: it cools the auxiliary equipment near the gas generator, cools the electrical machines for starter systems, and manages thermal energy from various propulsion components. This multi-functional approach addresses the increased cooling demand from electrical machines without requiring separate cooling systems.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution enables efficient thermal energy discharge and meets the high cooling demands of modern aircraft systems, maintaining aerodynamic performance while ensuring effective heat transfer and de-icing of heat exchange surfaces.

Implementation Method 1

said cooling circuit comprises at least one heat exchanger exchanging heat with the ambient air

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

heat exchanger exchanging heat with the ambient air housed in the tail unit of the aircraft

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS10773813B2Aircraft with a propulsion unit comprising a fan at the rear of the fuselage

Publication Date: 2020.09.15 SAFRAN AIRCRAFT ENGINES SAS

AI summary

The present invention relates to an aircraft comprising a fuselage (1) and a propulsion unit at the rear of the fuselage, the propulsion unit comprising at least one fan rotor (7, 8), a nacelle (14) fairing the fan and at least one connection means (15) connecting the nacelle to the fuselage, the fan being rotated by the energy supplied by at least one gas-turbine gas generator (2a, 2b) housed in the fuselage, said gas generator comprising auxiliary equipment cooled by a cooling circuit.The aircraft is characterised in that said cooling circuit comprises at least one heat exchanger exchanging heat with the ambient air housed in one of said connection means (15) and/or in said nacelle (14). The cooling circuit optionally comprises also a heat exchanger exchanging heat with the ambient air, housed in the tail unit.