Aircraft APU Inlet Diverter Fairing Aerodynamic Drag Reduction
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Solution Overview
Problem
Conventional diverter structures for aircraft APU air inlets generate additional aerodynamic drag, which increases fuel consumption and weight, and are complex and costly due to mechanical actuators required for movable doors, posing reliability issues.
Innovation Solution
The implementation of aerodynamically improved diverter structures with a smooth ramp design and fairing to reduce airflow detachment and drag, while maintaining functionality to prevent undesired fluid ingestion, using a diverter assembly with an S-shaped cross-sectional configuration and a fairing bracket for enhanced airflow distribution and pressure recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional diverter structures are used for aircraft APU air inlets, then the air inlet functionality is maintained, but aerodynamic drag increases and fuel consumption rises
Solution Approach 1:
The diverter structure employs a curved, aerodynamic profile instead of sharp edges or flat surfaces. The curved leading edge and streamlined body shape guide airflow smoothly around the APU inlet, reducing flow separation and wake formation, thereby minimizing pressure drag and skin friction drag while maintaining effective fluid diversion.
Solution Approach 2:
The diverter geometry is optimized by varying key parameters such as curvature radius, thickness distribution, and angle of attack to achieve optimal aerodynamic performance. These parameter adjustments allow the structure to minimize drag coefficients while preserving its fluid diversion function across different flight conditions.
2Adaptability or versatility
If movable doors with mechanical actuators are used in diverter structures, then airflow control flexibility is improved, but device complexity and cost increase
Solution Approach 1:
The invention removes the complex mechanical actuator system and movable door mechanisms from the diverter structure. Instead, it employs a fixed, stationary diverter geometry that achieves airflow control through its aerodynamic shape alone, eliminating moving parts while maintaining functional effectiveness.
Solution Approach 2:
The fixed diverter structure utilizes the aircraft's own airflow and pressure fields to achieve the desired fluid diversion and control functions without requiring external mechanical actuation systems. The aerodynamic forces themselves perform the control function that would otherwise require complex machinery.
3Device complexity
If fixed diverter structures are used, then device complexity is reduced, but aerodynamic drag and flow detachment increase
Solution Approach 1:
The fixed diverter employs carefully designed curved surfaces with optimized radius of curvature to guide airflow smoothly around the APU inlet. These curved geometries prevent flow separation and detachment by maintaining attached flow conditions, achieving effective fluid diversion without the complexity of movable parts.
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 improved diverter structures decrease excrescence drag, reduce fuel burn, and enhance APU efficiency by optimizing air flow and pressure recovery while adhering to design constraints and maintaining operational functionality.
Implementation Method 1
The fairing defines a relatively smooth ramp which slopes aftward toward the air inlet to thereby avoid airflow detachment forwardly of the air inlet
Implementation Method 2
a diverter structure at least substantially surrounding the air inlet... to thereby avoid airflow detachment forwardly of the air inlet
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Diverter assemblies 12 for aircraft air inlets 10 include a diverter structure at least substantially surrounding the air inlet, and a fairing 20 mounted to an upper edge of the diverter structure forwardly of the air inlet.