APU Air Inlet Ice Prevention via Warmer Fluid Flow

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Solution Overview

Problem

Ice buildup in auxiliary power unit air inlet assemblies, particularly near noise attenuating components, obstructs airflow and can damage the engine, due to cold air causing ice formation and potential breakage.

Innovation Solution

A second flow of warmer fluid is directed near the noise attenuating component within the inlet air assembly conduit to inhibit ice formation, using sources like bleed air or heated air from the auxiliary power unit or aircraft compartment, which is distinct from the primary airflow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If a noise attenuating component is installed in the inlet air assembly, then noise propagation is reduced, but ice formation occurs on the component due to cold air flow

Engineering Contradiction:

Improvenoise propagationVSAvoidice formation

Core Design Contradiction:

Object-generated harmful factorsVSObject-affected harmful factors

Solution Approach 1:

A second flow of warmer fluid is introduced as an intermediary substance to interact with the cold first flow near the noise attenuating component. This warmer fluid acts as a mediator that transfers thermal energy to prevent ice formation, allowing the noise attenuating component to remain in place without suffering from ice accumulation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The temperature parameter of the fluid flow is changed by introducing a second flow with different (warmer) temperature characteristics. This parameter change prevents the temperature from dropping to ice-forming levels, thereby eliminating the ice formation problem while preserving the noise attenuation function

Inventive Principle:

Principle #35Parameter changes

2Productivity

If cold air is delivered to the APU through the inlet air assembly, then the APU receives required air supply, but ice blocks the airflow and can foul the engine

Engineering Contradiction:

Improveair supply to APUVSAvoidice blockage

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The second flow of warmer fluid serves as a protective intermediary that prevents ice formation in the airflow path. This intermediary flow ensures that the primary cold air supply to the APU remains free from ice blockages, maintaining both productivity and reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The warmer second flow is applied in advance to prevent ice formation before it can block the airflow. By taking preliminary anti-action against the ice formation process, the system ensures continuous unfettered airflow to the APU without interruptions caused by ice blockages

Inventive Principle:

Principle #9Preliminary anti-action

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

Prevents ice accumulation and potential compressor surges, ensuring uninterrupted airflow and protecting the engine from ice-related damage by maintaining the noise attenuating components at a warmer temperature.

Implementation Method 1

A second flow of fluid is communicated to the noise attenuating component. The second flow of fluid limits formation of ice in the conduit.

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentUS8733694B2Arrangement for maintaining flow to an air inlet of an auxiliary power unit assembly

Publication Date: 2014.05.27 HAMILTON SUNDSTRAND CORP

AI summary

An example auxiliary power unit air inlet assembly includes a noise attenuating component disposed within a conduit. The conduit is configured to communicate a first flow of fluid to an auxiliary power unit. A second flow of fluid is communicated to the noise attenuating component. The second flow of fluid limits formation of ice in the conduit. The first flow of fluid is different than the second flow of fluid.