Aircraft Outflow Valve Obstacle Control for Cabin Noise Reduction
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Solution Overview
Problem
Existing thrust recovery valves in aircraft generate bothersome noise due to fixed obstruction elements that remain inserted during various flight regimes, leading to increased noise pollution at higher altitudes despite reduced tonal noise propagation.
Innovation Solution
A thrust recovery valve system with an obstruction system that extends or retracts an obstacle based on differential pressure to manage noise generation, using a pivotable gate and control circuitry to adjust the obstacle's position, minimizing noise by extending at lower pressures and retracting at higher pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a fixed obstruction element is inserted in the flow passage, then tonal noise generation is reduced, but broadband noise increases at higher altitudes
Solution Approach 1:
The patent applies the dynamics principle by making the obstruction element movable rather than fixed. The obstacle can extend into the flow passage at lower altitudes to reduce tonal noise, and retract at higher altitudes to minimize broadband noise generation. This dynamic adjustment allows the system to adapt to different flight conditions and eliminate both types of noise effectively.
2Object-affected harmful factors
If an obstacle is extended into the airflow, then tonal noise is reduced, but the device complexity increases
Solution Approach 1:
The patent applies the self-service principle by designing the obstruction system to be automatically actuated by the airflow itself. The differential pressure across the obstacle serves as the actuation mechanism, eliminating the need for external motors or complex control systems. The obstacle automatically extends when differential pressure is low and retracts when differential pressure is high, reducing device complexity while maintaining noise reduction effectiveness.
3Object-affected harmful factors
If the obstacle is made movable to adjust noise reduction, then noise control effectiveness is improved, but the use of energy increases
Solution Approach 1:
The patent applies the self-service principle by utilizing the existing differential pressure across the valve as the actuation force for the obstacle. This eliminates the need for additional energy-consuming actuators or control systems. The obstacle moves automatically based on the flow conditions, achieving noise control without additional energy consumption.
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 effectively reduces and eliminates noise propagation into the cabin by dynamically adjusting the obstacle's position, minimizing both tonal and broadband noise across different flight conditions, enhancing passenger comfort and operational efficiency.
Implementation Method 1
The acceleration of the airflow may be dependent on a differential pressure across the outflow valve as the airflow flows through the outflow valve. For example, at lower differential pressures, the thrust recovery valve system may position the obstacle in the extended position to reduce and/or eliminate generation of tonal noise
Implementation Method 2
The outflow valve may be configured to accelerate the airflow as the airflow flows through the flow passage. The thrust recovery valve system may be configured to transfer a thrust to the aircraft produced by the acceleration of the airflow.
Data Source
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AI summary
A thrust recovery valve system is configured to use an outflow valve (106) to discharge a fluid flow (F) from a cabin of an aircraft to an external environment surrounding the aircraft. The outflow valve (106) includes a frame (138) supported by a body of the aircraft and a gate (136) configured to displace from the frame (138) to define a flow passage for the discharge of the fluid flow. The thrust recovery valve system includes an obstacle (130) configured to extend into the fluid flow in an extended position and retract from the fluid flow in a retracted position. In examples, the obstacle is configured to extend from and/or retract into a wall surface (139) defined by the frame.