Variable Porosity Aircraft Surface for Drag Reduction
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Solution Overview
Problem
Existing passive porosity systems on aircraft surfaces improve aerodynamics at high Mach numbers but increase drag at lower Mach numbers and incur cruise drag penalties, limiting their application across various flight conditions.
Innovation Solution
A variable porosity system with sliding layers and an actuator mechanism that modulates porosity based on flight conditions, allowing pores to open at design conditions and close at off-design conditions to regulate fluid communication and improve aerodynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If passive porosity is applied to an aerodynamic surface, then aerodynamic efficiency is improved at high Mach numbers, but drag increases at low Mach numbers
Solution Approach 1:
The patent applies the dynamics principle by transitioning from fixed passive porosity to an active variable porosity system. The porous surface's porosity is dynamically adjusted based on flight conditions through an actuator mechanism that opens or closes pores as needed. This allows the system to provide aerodynamic benefits at high Mach numbers while minimizing drag penalties at low Mach numbers, resolving the contradiction between improved aerodynamic efficiency and increased drag.
2Object-affected harmful factors
If passive porosity is applied to reduce acoustic signature, then noise is reduced during certain flight conditions, but cruise drag penalties are incurred
Solution Approach 1:
The patent applies the dynamics principle by making the porous surface actively controllable. The actuator mechanism dynamically opens or closes pores based on real-time flight conditions, allowing the system to reduce noise during specific operations (such as landing) while closing the pores during cruise to eliminate drag penalties. This dynamic control resolves the contradiction between noise reduction and cruise drag.
3Reliability
If fixed porosity openings are applied to condition airflow, then boundary layer is conditioned at engine inlet, but porosity cannot be optimized for multiple flight regimes
Solution Approach 1:
The patent applies the dynamics principle by replacing fixed porosity openings with an actively controlled variable porosity system. The actuator mechanism adjusts pore openness dynamically to optimize airflow conditioning for different flight regimes, including subsonic, transonic, and supersonic conditions. This dynamic adjustment capability enables the system to maintain reliable airflow conditioning across diverse flight conditions, resolving the contradiction between airflow conditioning reliability and flight condition adaptability.
Solution Approach 2:
The patent applies the parameter changes principle by varying the effective porosity parameter of the surface based on flight conditions. The actuator mechanism changes the open area ratio of the porous surface, adjusting parameters such as pore openness and effective porosity to optimize performance for different Mach numbers and flight regimes. This parameter variation enables the system to adapt to multiple flight conditions while maintaining reliable airflow conditioning.
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 system mitigates transonic shock, reduces landing noise, and enhances aerodynamic efficiency by re-energizing boundary layers, delaying stall, and reducing drag across a wide range of flight regimes.
Implementation Method 1
The plenum chamber allows the air stream to transition from a high pressure region of the aerodynamic surface to a lower pressure region
Implementation Method 2
passive porosity comprises the application of a set of fixed openings or pores to one or more surfaces of the aircraft
Implementation Method 3
The pores and the plenum chamber allows for a conditioning of the air stream boundary layer as it passes over the porous aerodynamic surface
Data Source
AI summary
A variable porosity system for an aircraft includes a first layer, a second layer and an actuator mechanism. Each of the first and second layers has at least one pore and are slidable relative to one another. The actuator mechanism is operative to move the first and second layers relative to one another such that the pores are movable into and out of at least partial alignment with one another to allow for fluid communication therebetween. At least one of the first and second layers is substantially continuous with an outer mold line surface of an aerodynamic member such as an aircraft wing. The actuator mechanism is configured to modulate the frequency of the opening and closing of the pores with respect to flight conditions of an aircraft.