Ram Door Fairing for Auxiliary Power Unit Intake
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Solution Overview
Problem
Conventional ram door assemblies for aircraft auxiliary power units face inefficiencies due to turbulence and airflow distortions, which can impact the performance of the auxiliary power unit and increase aerodynamic resistance, leading to suboptimal performance and increased drag.
Innovation Solution
A ram door assembly with a hingeable ram door and a fairing on its interior surface, designed to direct airflow efficiently into the intake duct, reducing drag and improving airflow quality by minimizing distortions and turning losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ram door assemblies are used, then the auxiliary power unit can be installed, but turbulence and airflow distortions form at the intake opening, reducing intake airflow efficiency
Solution Approach 1:
The patent introduces a three-dimensional fairing structure with curved surfaces that extends into the airflow path, creating a streamlined contour that guides air smoothly around the ram door assembly. This dimensional addition transforms the two-dimensional flat door into a three-dimensional aerodynamic shape, eliminating turbulence and improving airflow efficiency
2Productivity
If adjustments are made to address airflow inefficiencies, then intake efficiency may improve, but the size and weight of the auxiliary power unit and/or ram door assemblies increase
Solution Approach 1:
The fairing incorporates curved and rounded surfaces instead of flat or angular geometries, creating a streamlined shape that reduces airflow separation and turbulence. The curved contour allows air to flow smoothly around the assembly, improving intake efficiency without requiring additional structural support or increasing overall size
3Device complexity
If conventional ram door assemblies are used, then the structure is simple, but aerodynamic resistance and total coefficient of drag increase
Solution Approach 1:
The fairing adds a third dimension to the ram door assembly by extending a streamlined structure into the airflow path. This dimensional enhancement creates a smooth transition surface that reduces pressure drag and minimizes wake formation, thereby reducing overall aerodynamic resistance while maintaining structural simplicity
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 ram door assembly with a fairing enhances airflow efficiency, reduces drag by up to 14.9%, and improves the performance of the auxiliary power unit, allowing for a more compact and lightweight design, thereby decreasing fuel burn and operating costs.
Implementation Method 1
turbulence, vortices, or other distortions may form as air enters the intake opening
Implementation Method 2
increase in the overall aerodynamic resistance, e.g. the total coefficient of drag, of the aircraft
Data Source
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AI summary
A ram door assembly is provided for an intake opening of an intake duct of an auxiliary power unit of an aircraft. The ram door assembly includes a ram door hingeably mounted adjacent to the intake opening and moveable between an open position to a closed position. The ram door has an interior surface and an exterior surface. The ram door assembly further includes a fairing (170) positioned on the interior surface (158) of the ram door (152).