Ram Air Thermal Management System for Aircraft

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Solution Overview

Problem

Current thermal management systems for aircraft face challenges in efficiently cooling components using ram air, as existing heat sinks like fuel and engine air streams are often too hot, leading to increased engine specific fuel consumption, weight, and space requirements, and introducing blockages or thermal distortions when placing heat exchangers at the engine inlet.

Innovation Solution

A thermal management system that integrates a cooling circuit, heat exchanger, and pumping device to circulate a fluid through the heat load, utilizing ram air as a heat sink by transferring heat from the fluid to a cooling air stream and then reintegrating it into the engine air stream downstream of the engine fan, reducing the need for large ducts and minimizing ram drag.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If heat exchangers are placed at the inlet of the engine to cool components, then cooling effectiveness is improved, but blockage at the front of the engine occurs and thermal and pressure distortions affect engine fan performance

Engineering Contradiction:

Improvecooling effectivenessVSAvoidblockage and thermal distortions

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the heat exchanger from the engine inlet location and relocates it to the engine exhaust stream. This removes the harmful blockage and distortion effects at the inlet while maintaining cooling functionality through the exhaust gas heat exchange path.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces the engine exhaust stream as an intermediary heat transfer medium. Instead of directly cooling at the inlet, the system uses the exhaust gases as a heat sink to absorb heat from the cooling circuit, indirectly achieving component cooling without inlet interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If large, long ducts are used to transport ram air through heat exchangers, then heat transfer capacity is improved, but weight and space requirements increase

Engineering Contradiction:

Improveheat transfer capacityVSAvoidduct weight

Core Design Contradiction:

Loss of energyVSWeight of stationary object

Solution Approach 1:

The patent merges the cooling air stream path with the existing engine air stream path. The cooling circuit integrates with the engine's natural airflow paths, eliminating the need for separate large ducts and reducing overall system weight and space.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The engine air stream serves multiple functions: it provides cooling for the engine components and also acts as the heat sink for the external heat exchangers. This multi-functionality eliminates dedicated cooling ducts and reduces system weight.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Temperature

If ram air is discarded overboard after heat exchange, then heat load removal is improved, but ram drag increases and engine specific fuel consumption increases

Engineering Contradiction:

Improveheat load removalVSAvoidram drag and fuel consumption

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

Instead of discarding the cooled ram air overboard, the patent recovers it by reintegrating it into the engine air stream downstream of the fan. This recovers the kinetic energy and reduces ram drag while maintaining heat load removal effectiveness.

Inventive Principle:

Principle #34Discarding and recovering

Solution Approach 2:

The patent converts the potentially harmful discarded air into a beneficial resource by injecting it downstream into the engine stream. The cooled air that would have been waste now contributes to engine cooling and reduces overall system temperature, improving efficiency without increasing fuel consumption.

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

This approach enhances refrigeration efficiency, reduces engine power extraction, allows for smaller ducts, and maintains engine performance by using ram air as a heat sink, thereby cooling components effectively without increasing weight or space requirements.

Implementation Method 1

a heat exchanger configured to enable heat transfer between the fluid and a cooling air stream

Methodology Applied

Scientific EffectHeat transfer: Heat Exchanger

Implementation Method 2

an engine fan configured to draw in an inlet air stream

Methodology Applied

Scientific EffectAerodynamic heating: Aerodynamic Heating

Data Source

PatentUS9840967B2Ram air thermal management system

Publication Date: 2017.12.12 ROLLS ROYCE NORTH AMERICAN TECHNOLOGIES INC

AI summary

An aircraft may have a heat generating component and an engine, at least one of which generates a heat load, and a thermal management system to cool the heat load. The engine may have a duct and an engine fan configured to draw an inlet air stream into an inlet portion of the duct, where at least a portion of the inlet air stream may be used as an engine air stream. The thermal management system may include a cooling circuit configured to circulate a fluid through the heat load such that at least a portion of it may be transferred to the fluid, a heat exchanger configured to enable heat transfer between the fluid and a cooling air stream, and a pumping device. The pumping device may be configured to draw the cooling air stream through the heat exchanger and into a portion of the engine air stream.