Aircraft Bleed Air Duct Flush Inlet Scoop Louver Design
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Solution Overview
Problem
Bleed air duct systems in gas turbine engines experience increased noise and vibration due to Helmholtz resonance when the fan bleed flow requirements are zero, leading to inefficiencies and higher operational costs.
Innovation Solution
A flush inlet scoop duct system with a louver configured to create a low pressure region downstream, reducing the formation of Helmholtz resonances by minimizing pressure pulses and acoustic resonance through a flow disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the valve for the fan bleed air duct system is closed when fan bleed flow requirements are zero, then the cooling function is achieved, but Helmholtz resonance is created causing increased noise and vibration
Solution Approach 1:
The louver is extracted as a separate flow disturbance element from the closed valve system. By introducing this localized flow disturbance feature at the inlet scoop, the patent extracts the harmful resonance generation mechanism from the otherwise functional closed duct system, allowing the valve to remain closed for cooling while preventing Helmholtz resonance through the louver's flow disruption.
Solution Approach 2:
The louver acts as an intermediary element between the closed valve system and the potential Helmholtz resonance. This intermediate flow disturbance feature modifies the airflow characteristics in a controlled manner, mediating between the need for system closure (for cooling) and the need to prevent resonance (for noise and vibration control).
2Device complexity
If a traditional duct system is used without flow disturbance features, then the structure is simple, but resonance chamber formation occurs when the valve is closed
Solution Approach 1:
The duct system is segmented by introducing the louver as a distinct flow control element within the inlet scoop. This segmentation divides the otherwise uniform duct interior into regions with different flow characteristics, creating a localized flow disturbance zone that prevents resonance chamber formation while maintaining the overall simplicity of the duct structure.
3Productivity
If the valve is closed to meet zero fan bleed flow requirements, then flow rate control is achieved, but a resonance chamber is formed
Solution Approach 1:
The louver is positioned at the inlet scoop to preemptively create flow disturbance before the air can traverse the entire duct length. This preliminary flow disruption action prevents the formation of coherent pressure waves that would otherwise develop into Helmholtz resonance, allowing the valve to remain closed for flow rate control without generating harmful resonances downstream.
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 solution effectively reduces noise signatures and vibration levels in bleed air ducts, maintaining high volumetric flow rates and operational efficiency without adverse impacts on gas turbine engine performance.
Implementation Method 1
When the valve is in a closed position, a resonance chamber is formed from which a Helmholtz resonance may be created, powered by airflow over the flush scoop
Implementation Method 2
The louver extends into the flow of fluid received from the local flow stream of fluid and is configured to create a low pressure region within the flow passageway, downstream of the louver
Data Source
AI summary
A bleed air duct that preferably includes an inlet section configured to include a flush scoop and a louver. The louver is located and configured such that in the desired operating flow range of the duct, the fluid entering the flush scoop is disturbed and as a result creates a low pressure region downstream of the louver. The low pressure region substantially eliminates the generation of any pressure pulses and acoustic resonance also known as Helmholtz resonance.