APU Bracket Mounting via Heat Shield and Support Strap
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Solution Overview
Problem
Auxiliary power units (APUs) face challenges in withstanding extreme temperatures and harsh operating conditions, particularly in retrofitted systems where maintaining component integrity and attachment during thermal events is difficult.
Innovation Solution
A steel 'U'-shaped bracket with gearbox and compartment mounting faces is designed to securely attach to an APU gearbox below the sump level line and a compartment above, using aluminum mounting pads positioned below the sump level line to prevent damage from extreme temperatures and ensure structural integrity, with a support strap limiting downward movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bracket is used to attach the APU gearbox to the compartment, then the APU can be securely mounted, but the bracket may be damaged by extreme temperatures during operation
Solution Approach 1:
A heat shield is positioned between the exhaust system and the bracket to block direct exposure to extreme temperatures. The heat shield acts as an intermediary element that protects the bracket from thermal damage while allowing the bracket to maintain its structural integrity and attachment function during high-temperature operation
Solution Approach 2:
The heat shield is designed as a sacrificial protective element that can be easily replaced. Instead of designing the bracket to withstand extreme temperatures, a simpler, less expensive heat shield is used to protect it, allowing the bracket to remain a standard, replaceable component rather than requiring specialized high-temperature materials
2Power
If taller APUs are installed in existing environments, then more power is available, but the packaging space and integration become more difficult
Solution Approach 1:
The bracket utilizes vertical space by extending upward from the gearbox mounting face to reach the compartment ceiling or upper structure. This vertical dimension allows the APU to be positioned lower in the available space, accommodating taller APUs without increasing the horizontal footprint or compromising integration in existing packaging environments
3Ease of operation
If mounting pads are positioned above the sump level line, then easier access is provided, but the mounting pads may be damaged by extreme temperatures
Solution Approach 1:
The heat shield is positioned to protect the mounting pads located in the temperature-prone zone. This allows mounting pads to be positioned at optimal locations for both accessibility and thermal protection, with the heat shield serving as a protective barrier that enables mounting pads to be placed closer to high-temperature areas without direct exposure
Data Source
AI summary
An example auxiliary power unit bracket includes, among other things, a gearbox mounting face and a compartment mounting face, the gearbox mounting face configured to attach to an auxiliary power unit gearbox below a sump level line, the compartment mounting face configured to attach to a portion of an auxiliary power unit compartment above the sump level line.