APU Plenum Pleated Screen Foreign Object Damage Prevention
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Solution Overview
Problem
Current aircraft auxiliary power unit (APU) plenums are vulnerable to foreign object debris (FOD) ingestion due to cylindrical or annular screens that create pressure differentials, limit airflow recovery, and complicate inspection and servicing.
Innovation Solution
A plenum duct with a pleated screen supported by screen supports within the duct, positioned proximate to the inlet aperture but distal from the compressor inlet, allowing for better airflow swirl recovery and easy access for inspection and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cylindrical or annular screen is used to prevent FOD ingestion, then protection against foreign object debris is improved, but pressure differential across the screen increases and airflow recovery is limited
Solution Approach 1:
The patent employs a pleated screen configuration where the screen surface is folded into pleats, creating a curved geometry that allows airflow to follow the contour of the pleats. This curved surface design reduces flow separation and pressure differential compared to flat cylindrical screens, while maintaining effective FOD protection through the pleated structure's ability to filter debris while allowing smooth airflow passage.
2Reliability
If a cylindrical or annular screen is positioned close to the compressor inlet to maximize protection, then FOD prevention is improved, but airflow swirl recovery is limited
Solution Approach 1:
The pleated screen extends the filtering surface into the third dimension by creating folds and pleats that project into the flow cavity. This dimensional transformation allows the screen to provide comprehensive FOD protection while maintaining adequate distance from the compressor inlet face, preserving airflow swirl recovery characteristics by not placing a flat barrier directly at the inlet plane.
3Reliability
If a cylindrical or annular screen is installed in the duct, then FOD protection is provided, but access for inspection and servicing is limited requiring duct teardown
Solution Approach 1:
The pleated screen is designed as a modular component that can be independently accessed and removed from the duct assembly. The screen is segmented from the duct structure, allowing it to be extracted through the inlet aperture without requiring disassembly of the entire duct, thereby facilitating easy inspection and maintenance while maintaining continuous FOD protection during operation.
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 pleated screen effectively prevents FOD ingestion while maintaining airflow efficiency and facilitating easy removal and inspection, reducing the risk of damage to the compressor and turbine.
Implementation Method 1
A pleated screen is disposed on the pair of screen supports... effectively prevents FOD ingestion... Lateral edges of the pleated screen are engaged on screen supports coupled to the main body proximate a periphery of the inlet aperture
Data Source
AI summary
A plenum duct for an auxiliary power unit includes a main body having an inlet aperture and a flow cavity. A pair of screen supports are coupled to the main body proximate a periphery of the inlet aperture, said screen supports extending into the flow cavity. A pleated screen is disposed on the pair of screen supports.