Aircraft Exhaust Duct Mounting Assembly with Compliant Isolators
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Solution Overview
Problem
Aircraft airframe panels are weakened and aerodynamic performance is compromised due to oversized openings required for thermally protecting exhaust ducts from hot gas turbine exhausts, which create drag and structural issues.
Innovation Solution
A mounting assembly with compliant isolator rings and mounting plates that form a slot to receive the exhaust duct flange, allowing thermal expansion and contraction while suspending the duct away from the airframe panel, using metallic encapsulated insulation materials and aluminum alloy components for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an over-sized opening is provided in the airframe panel to accommodate thermal protection clearance, then the exhaust duct is thermally protected from the airframe panel, but the airframe panel strength is reduced and drag is increased
Solution Approach 1:
The mounting assembly divides the opening into multiple smaller openings distributed across the airframe panel, rather than using a single large opening. This segmentation maintains thermal protection clearance while preserving panel strength by distributing the structural load across multiple localized mounting points.
Solution Approach 2:
A mounting assembly with compliant isolators acts as an intermediary between the exhaust duct and the airframe panel. This intermediary structure provides the necessary thermal clearance while mechanically coupling the duct to the panel through distributed mounting plates and fasteners, thereby maintaining panel strength.
2Object-affected harmful factors
If an over-sized opening is provided in the airframe panel to accommodate thermal protection clearance, then the exhaust duct is thermally protected from the airframe panel, but aerodynamic performance is degraded due to increased drag
Solution Approach 1:
The mounting assembly segments the thermal protection function across multiple distributed mounting points rather than requiring a single large opening. This reduces the total open area visible to airflow, thereby minimizing drag while maintaining sufficient clearance for thermal protection.
Solution Approach 2:
The mounting assembly serves as an intermediary that provides thermal clearance without creating a large continuous opening in the airframe panel. The distributed mounting plates and fasteners maintain aerodynamic continuity while still allowing the exhaust duct to be thermally protected from the panel surface.
3Stability of the object's composition
If a rigid mounting structure is used to secure the exhaust duct, then structural stability is improved, but thermal expansion and contraction of the exhaust duct cannot be accommodated
Solution Approach 1:
The mounting assembly incorporates compliant isolators that change their physical parameters (stiffness, compliance) based on thermal conditions. These isolators maintain structural stability during normal operation but can deform to accommodate thermal expansion and contraction of the exhaust duct, providing adaptability to thermal variations.
Solution Approach 2:
The mounting assembly transitions from a purely rigid structure to a dynamic system with compliant isolators that can adapt their mechanical properties. The isolators provide rigid support when needed but can deform elastically to accommodate thermal expansion, allowing the system to dynamically adjust to changing thermal conditions.
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 effectively protects the airframe panel from heat damage, reduces drag, and isolates vibrations, improving aerodynamics and structural integrity by accommodating thermal expansion and contraction of the exhaust duct.
Implementation Method 1
accommodates thermal expansion and contraction of the engine exhaust duct relative to the airframe panel
Implementation Method 2
at least one compliant isolator ring connected to the first mounting plate, a second compliant isolator ring connected to the second mounting plate
Implementation Method 3
the first compliant isolator ring and the second compliant isolator ring define a slot therebetween to receive the peripheral flange of the engine exhaust duct in a manner that suspends the engine exhaust duct in the opening away from the airframe panel
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A mounting assembly (220) for mounting a portion of an engine exhaust duct (202) in an opening (206) of an airframe panel aircraft (101), including a peripheral flange (203) disposed on the portion of the exhaust duct (202), and at least one mounting member (221) having an outer peripheral flange portion for connection to the airframe panel (210) and having an inner peripheral flange portion with at least one compliant isolator member (230) to receive the peripheral flange (203) of the exhaust duct (202) in a manner that suspends the exhaust duct (202) in the opening (206) away from the airframe panel (210) and accommodates thermal expansion and contraction of the exhaust duct (202) relative to the airframe panel (210). Embodiments include a method of mounting an engine exhaust duct (202) in an opening (206) of an outer airframe panel (210) of an aircraft (101).