Vented Rear Wall Jet Blast Deflector Noise Reduction
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Solution Overview
Problem
Current ground run-up enclosures with combined jet blast deflection and noise attenuating walls are aerodynamically inefficient, leading to loss of momentum in high velocity engine exhaust airflow, recirculation of exhaust flow, and increased noise levels due to inefficient mixing and reflection of sound.
Innovation Solution
A ground run-up enclosure design featuring a separate jet blast deflector located close to a vented rear noise attenuating wall, which provides a stable mixing air supply to the discharge lip of the deflector, reducing the facility's length while maintaining aerodynamic and acoustic advantages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a separate jet blast deflector is located well ahead of the rear noise wall to provide mixing air source, then the mixing air supply is adequate, but the overall length of the ground run-up enclosure increases
Solution Approach 1:
The invention divides the rear wall into solid portions and vent portions, creating separate functional zones. The vents are strategically positioned to provide mixing air directly to the jet blast deflector discharge lip, eliminating the need for a long enclosed space while ensuring adequate mixing air supply.
Solution Approach 2:
The vented portions of the rear wall act as an intermediary mechanism, channeling ambient air from the rear of the facility directly to the discharge lip of the jet blast deflector. This intermediary structure provides the necessary mixing air without requiring a long distance between the deflector and rear wall.
2Device complexity
If a combined jet blast deflector and rear noise wall is used, then the structure is simpler, but aerodynamic efficiency is reduced causing momentum loss and recirculation
Solution Approach 1:
The invention separates the jet blast deflector from the rear noise wall, creating two distinct components. The deflector focuses on aerodynamic function while the vented wall provides noise attenuation and mixing air supply, achieving both simplicity and aerodynamic efficiency through functional segmentation.
Solution Approach 2:
The rear wall is designed with different local properties: solid portions for noise attenuation and vented portions for aerodynamic function. This local differentiation allows the structure to simultaneously achieve noise reduction and maintain aerodynamic efficiency by providing mixing air where needed.
3Length of stationary object
If the jet blast deflector is located close to the rear noise wall, then the enclosure length is reduced, but mixing air supply becomes insufficient
Solution Approach 1:
The rear wall incorporates vented portions that allow air to pass through from the rear ambient environment to the discharge lip region. This porous approach to the wall structure provides adequate mixing air supply while maintaining a compact enclosure length.
4Object-affected harmful factors
If tall noise attenuating walls are used to surround the test aircraft, then noise attenuation is improved, but the facility becomes larger and more complex
Solution Approach 1:
The rear wall is segmented into solid and vented portions, allowing noise attenuation functionality to be concentrated in the solid sections while the vented sections provide aerodynamic benefits. This segmentation achieves effective noise attenuation without requiring the entire wall structure to be excessively tall or long.
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
This design improves airflow momentum, reduces recirculation, and enhances noise attenuation by providing a stable and efficient mixing air supply, resulting in a more compact and effective noise reduction system for high power aircraft engine testing.
Implementation Method 1
providing a vent in the rear noise attenuating wall to provide a mixing air source for the high velocity air discharged at the discharge lip of the jet blast deflector
Data Source
AI summary
An apparatus and method for reducing noise from aircraft high power ground run-ups. The ground run-up enclosure includes a vented tall rear noise attenuating wall and a separate jet blast deflector to direct the jet blast up and out of a facility. The vented rear wall is positioned behind the jet blast deflector and extends above a discharge lip of the deflecting surface of the jet blast deflector surface. An exit port of the rear vent channel allows airflow moving through the rear vent to exit and combine with the airflow deflected along the jet blast deflecting surface discharge lip. The vent opening in the rear wall is located in the back of the rear noise attenuating wall.