APU Inlet Spray Nozzle for Compressor Cleaning Access
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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 at the compressor, utilizing a ring with nozzles extending from it to clean the impeller and compressor components, and a control unit to manage the cleaning process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the APU operates in harsh environments (salty, sandy, polluted), then the APU provides power in difficult settings, but the compressor components accumulate debris and corrosive substances that reduce lifespan
Solution Approach 1:
The spray nozzle system performs preliminary cleaning action by injecting cleaning fluid into the compressor housing before debris can cause significant damage. The system proactively removes accumulations of sand, salt, and pollution from the impeller and compressor components, preventing degradation before it occurs
Solution Approach 2:
The APU cleaning system is self-service in that it uses the APU's own operational characteristics to facilitate cleaning. The compressor motor is activated to rotate the impeller during cleaning, using the existing mechanical system to enable access and effectiveness of the cleaning process without requiring external disassembly or complex positioning equipment
2Object-affected harmful factors
If anti-ice spray is applied to the aircraft during icing conditions, then the aircraft is protected from ice accumulation, but the corrosive liquid is ingested into the compressor which reduces compressor life
Solution Approach 1:
The cleaning system converts the harmful effect of corrosive anti-ice spray ingestion into a beneficial cleaning opportunity. By detecting when anti-ice spray has been ingested and subsequently cleaning the compressor with appropriate cleaning fluids, the system transforms the harmful exposure into a controlled cleaning event that removes the corrosive substances and prevents long-term damage
Solution Approach 2:
The spray nozzle system acts as an intermediary between the harmful external environment (anti-ice spray, sand, salt) and the vulnerable compressor components. It introduces cleaning fluid as a mediating substance that contacts and removes harmful deposits from the impeller and compressor surfaces, protecting the components from direct prolonged exposure to corrosive elements
3Adaptability or versatility
If the APU is located in difficult-to-reach areas of the aircraft, then the APU provides power where needed, but the APU becomes difficult to access for cleaning
Solution Approach 1:
The cleaning system extracts the need for physical access to the impeller by introducing cleaning fluid directly into the compressor housing through the spray nozzle. The fluid delivery system is positioned to inject cleaning agent at the air inlet housing, allowing cleaning to occur without requiring disassembly or direct access to the impeller, thus solving the accessibility problem while maintaining the APU's flexible mounting locations
4Reliability
If cleaning fluid is sprayed at the compressor, then debris and corrosive substances are removed, but the cleaning system becomes complex
Solution Approach 1:
The spray nozzle system is designed with multi-functionality to reduce overall complexity. The same spray nozzle infrastructure can deliver different cleaning fluids for different cleaning needs, and the system can service both the impeller and compressor components through a single integrated fluid delivery mechanism, eliminating the need for multiple separate cleaning systems
Solution Approach 2:
The cleaning system uses pneumatic and hydraulic principles to achieve effective cleaning with simple components. High-pressure cleaning fluid is delivered through the spray nozzle to create sufficient cleaning force without requiring complex mechanical contact or elaborate positioning mechanisms. The fluid dynamics themselves provide the cleaning action, simplifying the mechanical complexity of the system
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
Enhances the durability and performance of APUs by effectively removing debris and corrosive substances, thereby extending their operational life and maintaining compressor efficiency.
Implementation Method 1
a spray nozzle positioned within the air inlet housing oriented to spray a cleaning fluid directly at the compressor
Data Source
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AI summary
An auxiliary power unit (10) includes an air inlet housing (26); a compressor (12; 56) arranged to receive air from the air inlet housing (26); and a spray nozzle positioned within the air inlet housing (26) oriented to spray a cleaning fluid directly at the compressor (12; 56), the spray nozzle having a connection for connecting to a source of cleaning fluid.