APU Inlet Spray Nozzle Layout for Direct Compressor Cleaning
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Solution Overview
Problem
Auxiliary power units (APUs) in aircraft are difficult to clean due to their location and exposure to harsh environments, which can lead to damage from sand, salt, pollution, and corrosive chemicals, reducing their lifespan.
Innovation Solution
A system with a spray nozzle positioned within the air inlet housing of the APU to directly spray cleaning fluid onto the compressor, utilizing a ring with nozzles extending from it to target the impeller, and a butterfly valve for controlled fluid flow, with a reservoir to collect used fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the APU is mounted in difficult-to-reach areas to save space, then the aircraft layout efficiency is improved, but the ease of cleaning the APU deteriorates
Solution Approach 1:
The APU cleaning system uses self-service by incorporating a spray nozzle that directs cleaning fluid through the air inlet housing directly onto the compressor impeller. The system cleans itself without requiring external access to the compressor, allowing the APU to be mounted in space-constrained locations while maintaining cleanability.
2Productivity
If the spray nozzle is positioned to directly spray the compressor, then the cleaning effectiveness is improved, but the device complexity increases
Solution Approach 1:
The air inlet housing serves multiple functions: it directs airflow to the compressor and simultaneously houses the spray nozzle for cleaning operations. This multi-functionality allows direct spraying of the compressor without adding separate access mechanisms, maintaining simplicity while achieving effective cleaning.
3Duration of action of stationary object
If cleaning fluid is sprayed directly at the compressor to remove debris, then the compressor lifespan is improved, but the risk of fluid ingestion into the compressor increases
Solution Approach 1:
The system uses a controllable spray mechanism that can be activated only when the compressor is not operating. The spray nozzle is positioned to clean the impeller surface, and the timing control ensures cleaning occurs during shutdown periods, eliminating the risk of fluid ingestion while maintaining compressor lifespan through regular cleaning.
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
Effectively cleans the APU compressor, improving its performance and durability by directly targeting and removing debris and corrosive substances, while being easily accessible and maintainable.
Implementation Method 1
a spray nozzle positioned within the air inlet housing oriented to spray a cleaning fluid directly at the compressor
Data Source
AI summary
An auxiliary power unit includes an air inlet housing; a compressor arranged to receive air from the air inlet housing; and a spray nozzle positioned within the air inlet housing oriented to spray a cleaning fluid directly at the compressor, the spray nozzle having a connection for connecting to a source of cleaning fluid.