Fan Casing Mounting Assembly for Thermal Expansion
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Solution Overview
Problem
Aircraft engine heat exchangers face space constraints, thermal expansion issues, and high cycle fatigue due to limited space and weight of current cooler designs, necessitating a mounting system that allows for thermal growth while maintaining stability and ease of installation.
Innovation Solution
A mounting assembly comprising self-contained components such as washers, bushings, and floating bodies with pre-load fasteners and wear attenuators, providing a flexible connection for thermal loading and a fixed connection for dynamic loading, allowing for axial and circumferential movement to accommodate thermal growth and tolerance mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fixed rigid mounting system is used to maintain structural stability, then dynamic loading resistance is improved, but thermal expansion accommodation deteriorates
Solution Approach 1:
The mounting system is divided into separate functional components: rigid mounting elements (bolts, nuts, washers) that provide structural stability, and flexible elements (bellows, expansion joints) that accommodate thermal growth. This segmentation allows each component to perform its specific function without compromising the other.
Solution Approach 2:
Flexible intermediate elements such as bellows and expansion joints are introduced between the rigid mounting structure and the heat exchanger components. These intermediaries absorb thermal expansion and contraction while maintaining the structural integrity of the overall mounting system.
2Reliability
If a heavy-duty rigid mounting system is used to ensure stability, then reliability under dynamic loading is improved, but device complexity and weight increase
Solution Approach 1:
The mounting system transitions from a purely static rigid structure to a dynamic system that can adapt to thermal conditions. Flexible elements like bellows and expansion joints allow the structure to move and adjust dynamically in response to thermal expansion and contraction, reducing the need for overly robust rigid components.
3Manufacturing precision
If precise tolerance control is enforced during manufacturing, then assembly fit is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The mounting system incorporates elements with inherent compliance that can accommodate variations in dimensional parameters. The flexible bellows and expansion joints are designed with parameters (such as expansion capacity and flexibility) that allow them to absorb tolerance mismatches between mating components, reducing the need for tight manufacturing tolerances.
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 solution enables efficient heat dissipation, reduces the risk of high cycle fatigue, and simplifies installation by allowing for thermal expansion while maintaining structural integrity, thus addressing the constraints of current heat exchanger designs.
Implementation Method 1
a fastener having a threaded section, the threaded section configured to pass through the at least one fastener opening, the fastener opening, and be retained in the internally threaded section of the at least one bushing and having a length that passed through the at least one bushing and provides for a pre-load force
Implementation Method 2
The mounting assembly is configured to provide a fixed connection for dynamic loading, a flexible connection for thermal loading, and shifting during installation to allow for tolerance mismatch
Data Source
AI summary
A fan casing assembly for a turbine engine including a fan casing having a peripheral wall, a surface cooler having a first surface confronting the peripheral wall and a mounting assembly having a lower portion generally retained between the first surface of the annular surface cooler and the peripheral wall and having a floating body extending through the set of fan casing fastener openings and an upper portion located radially exterior of the annular fan casing and operably coupled to the lower portion.