Ram Air Fan Surge Margin Prediction for Heat Exchanger Blockage

Solution Overview

Problem

Aircraft heat exchangers often become blocked with Foreign Object Debris (FOD) in high-particulate environments, leading to unstable Ram Air Fan (RAF) operation and potential hardware failure, with current sensor suites lacking reliable prognostic capabilities for detecting blockages, necessitating costly and conservative cleaning schedules.

Innovation Solution

A method and system using a reduced order model (ROM) to predict RAF surge margin, correlating it with heat exchanger blockage parameters, allowing for timely detection and reporting of blockages through sensor signals, thereby enabling scheduled cleaning and preventing RAF damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If heat exchangers are cleaned on a conservative scheduled basis, then RAF hardware failure is prevented, but service hours are reduced and costs increase

Engineering Contradiction:

ImproveRAF hardware reliabilityVSAvoidservice hours

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system performs preliminary detection of heat exchanger blockage conditions using sensor data and ROM predictions before actual RAF failure occurs. This allows maintenance to be scheduled at the optimal moment - just before blockage becomes critical - rather than following conservative fixed schedules, thus preventing failure while maximizing service hours.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors sensor signals (surge margin, fan speed, temperature differential) and uses the ROM to predict blockage progression. This feedback loop provides real-time information about actual heat exchanger condition, enabling dynamic adjustment of maintenance schedules based on actual wear and blockage rates rather than fixed conservative intervals.

Inventive Principle:

Principle #23Feedback

2Reliability

If heat exchangers are cleaned on a conservative scheduled basis, then RAF hardware failure is prevented, but maintenance costs increase

Engineering Contradiction:

ImproveRAF hardware reliabilityVSAvoidmaintenance cost

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system performs preliminary detection of heat exchanger blockage conditions using sensor data and ROM predictions before actual RAF failure occurs. This allows maintenance to be scheduled at the optimal moment - just before blockage becomes critical - rather than following conservative fixed schedules, thus preventing failure while maximizing service hours.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors sensor signals (surge margin, fan speed, temperature differential) and uses the ROM to predict blockage progression. This feedback loop provides real-time information about actual heat exchanger condition, enabling dynamic adjustment of maintenance schedules based on actual wear and blockage rates rather than fixed conservative intervals.

Inventive Principle:

Principle #23Feedback

3Device complexity

If typical aircraft sensor suite is used, then system complexity is maintained, but reliable prognostic of heat exchanger blockage is not achieved

Engineering Contradiction:

Improvesensor suite complexityVSAvoidblockage detection precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The ROM acts as an intermediary computational model that processes existing sensor signals (surge margin, fan speed, temperature differential) to extract meaningful blockage information. Rather than adding complex specialized sensors, the ROM mediates between standard sensor data and blockage prognosis, achieving precise detection without increasing hardware complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces the need for complex specialized blockage detection sensors with a computational approach using the ROM. The model substitutes physical measurement complexity with algorithmic processing of existing sensor data, achieving accurate blockage prognosis through software rather than hardware complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10346585B2Method of predicting heat exchanger blockage via ram air fan surge margin

Publication Date: 2019.07.09 HAMILTON SUNDSTRAND CORP

AI summary

A method and system for predicting heat exchanger blockage in an aircraft is provided. The method includes generating a reduced order model (ROM) that predicts a ram air fan (RAF) surge margin that correlates to a heat exchanger blockage parameter, calculating, using the ROM, a predicted RAF surge margin value using a sensor signal received from a sensor connected to a ram air fan (RAF), calculating the heat exchanger blockage parameter using at least the predicted RAF surge margin value, and reporting, to a user, the heat exchanger blockage parameter that indicates when a heat exchanger blockage condition is present.