Ram Air System Boundary Layer Cooling for Aircraft Skin
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Solution Overview
Problem
Aircraft ram air systems generate high-temperature exhaust that increases the temperature of components and fuel tanks, leading to unscheduled maintenance and increased weight due to the need for insulation and heat shields, which also raise manufacturing costs.
Innovation Solution
A ram air system that forms a boundary layer of cooling air between the aircraft skin and the hot exhaust flow, reducing the need for heat shields and insulation by using a passive or actively controlled system with openings and apertures to channel cool air from the free stream airflow, thereby protecting the skin from high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If heat shields and insulation are added to protect skin panels from hot exhaust flow, then the skin panels are protected from high temperatures, but the weight of the aircraft increases
Solution Approach 1:
The patent introduces cool air as an intermediary substance between the hot exhaust flow and the skin panels. This cool air forms a protective boundary layer that acts as a thermal mediator, absorbing heat from the exhaust flow before it reaches the skin, thereby eliminating the need for heavy heat shields and insulation while still providing temperature protection.
Solution Approach 2:
The invention uses pneumatic principles by introducing and circulating cool air through the exhaust flow path. The system utilizes air pressure and flow dynamics to create a protective cooling environment around the skin panels, replacing solid thermal protection structures with a fluid-based thermal management approach.
2Object-affected harmful factors
If heat shields and insulation are added to protect skin panels, then the skin panels are protected from high temperatures, but the manufacturing costs increase
Solution Approach 1:
The cool air serves as a cost-effective intermediary that provides thermal protection without requiring expensive heat shield materials and insulation components. This approach simplifies the manufacturing process and reduces material costs while achieving the same protective function.
Solution Approach 2:
The invention extracts the essential protective function from heavy physical heat shields and insulation materials, achieving temperature protection through a lighter, more manufacturable air-based system. This removes the need for complex thermal protection assemblies and their associated manufacturing costs.
3Temperature
If insulation is added between pack bay and fuel tanks, then fuel temperature increase is reduced, but the weight of the aircraft increases
Solution Approach 1:
The patent uses cool air as a thermal intermediary between the hot pack bay and the fuel tanks. This air layer absorbs and carries away heat that would otherwise transfer to the fuel, providing temperature control without requiring physical insulation barriers between the components.
4Object-affected harmful factors
If thicker skin panels or heat shields are used, then protection from hot exhaust is improved, but the device complexity increases
Solution Approach 1:
The cool air boundary layer provides a simple, elegant intermediary solution that protects skin panels without requiring complex heat shield structures or multi-layer insulation systems. The approach uses natural fluid dynamics to create thermal protection, reducing structural complexity.
Solution Approach 2:
The system utilizes the aircraft's own operational air supply to provide cooling protection. The cool air is drawn from the aircraft's existing environmental control system, allowing the system to self-regulate and provide thermal protection without additional complex control mechanisms or external systems.
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
This solution reduces the weight and manufacturing costs of the aircraft by eliminating or reducing the size of heat shields and insulation, while maintaining component temperatures within a desired range through continuous cooling air recirculation and boundary layer formation.
Implementation Method 1
forming a boundary layer of cooling air between an exterior skin of an aircraft and a relatively hot ram air exhaust flow
Implementation Method 2
Such film cooling produced by the boundary layer insulates the skin from the hot exhaust flow
Implementation Method 3
facilitates forming a boundary layer of cooling air between an exterior skin of an aircraft and a relatively hot ram air exhaust flow
Data Source
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AI summary
A ram air system (214) includes a bay (212) comprising an exterior wall (228) defining an interior volume (230) that at least partially encloses a ram air duct (234). The ram air duct (234) includes an outlet (218) configured to discharge an exhaust airflow (250) at a first temperature. At least one of the exterior wall (228) and the ram air duct (234) defines an aperture (256) therein providing for flow communication between the interior volume (230) and the exhaust airflow (250) such that cooling air flows from the interior volume (230) to form a boundary layer (258) between the exhaust airflow and the exterior wall downstream of the outlet. The boundary layer (258) is at a second temperature that is lower than the first temperature.