Air Duct Attenuator with Tunable Resonant Chambers
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Solution Overview
Problem
Existing solutions for attenuating noise and vibration in air intake ducts of vehicle engines are either too large, impractical for compact engine bays, or require loose materials that can be ingested by the engine, and fail to provide effective broadband attenuation below 2000Hz.
Innovation Solution
A compact attenuator device with primary and secondary chambers, separated by a baffle, which allows for adjustable parameters to tune broadband response without significant size changes, using a coaxial or non-coaxial enclosure around the air duct to achieve effective noise and vibration reduction across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If insulation and muffling are used to attenuate noise and vibration, then noise and vibration attenuation is improved, but the overall duct size increases which is difficult to accommodate in a congested engine bay
Solution Approach 1:
The attenuator is nested within the existing air duct structure, with the enclosure surrounding the duct and chambers arranged concentrically. The primary and secondary chambers are positioned within the duct volume, allowing attenuation functionality to be integrated into the existing space without requiring additional external volume for the attenuator itself.
Solution Approach 2:
The attenuator is divided into multiple chambers (primary and secondary chambers) separated by baffles, with each chamber contributing to broadband attenuation. This segmentation allows the attenuation function to be distributed across multiple smaller volumes rather than requiring a single large attenuator, making it more adaptable to constrained engine bay spaces.
2Object-affected harmful factors
If multiple quarter-wave or Helmholtz resonators are used to provide attenuation over several narrow frequency bands, then noise and vibration attenuation is improved, but the available engine bay space is exceeded since each resonator has significant volume
Solution Approach 1:
The attenuator combines multiple resonant chambers (primary and secondary chambers) into a single integrated unit that provides broadband attenuation. Instead of using separate quarter-wave or Helmholtz resonators distributed throughout the engine bay, the invention merges these functions into one compact structure with multiple chambers that work together to attenuate across a wide frequency range.
Solution Approach 2:
The invention transitions from a distributed arrangement of multiple resonators in three-dimensional space to a compact multi-chamber structure that achieves broadband attenuation through strategic spatial arrangement. The primary and secondary chambers are positioned to create resonant frequencies across different bands within a reduced volume, effectively using spatial dimensionality to achieve multiple attenuation functions simultaneously.
3Object-affected harmful factors
If loose materials are placed within the duct to provide attenuation, then noise and vibration attenuation is improved, but the risk of materials being ingested by the vehicle engine increases
Solution Approach 1:
The attenuator uses a rigid enclosure structure with defined chambers and baffles, eliminating the need for loose insulating materials. The enclosure acts as a barrier that contains the attenuation functionality while preventing any potential ingestion of materials by the engine, thereby maintaining reliability while providing effective attenuation.
4Object-affected harmful factors
If the supply duct is better designed to eliminate noise and vibration, then noise and vibration is reduced, but the complexity of duct design increases
Solution Approach 1:
The invention extracts the noise and vibration attenuation function from the main duct design and separates it into a distinct attenuator unit. This allows the duct to maintain its simple, straightforward geometry for air transport while the attenuator handles the acoustic management function, reducing overall design complexity compared to integrating attenuation features directly into the duct structure.
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 attenuator provides effective broadband attenuation of noise and vibration in the range of 500-2000Hz, suitable for engines with 4-8 cylinders, and can be tuned for various configurations without increasing overall size or position, ensuring an aesthetically acceptable and practical solution for both gasoline and diesel engines.
Implementation Method 1
the primary and secondary chambers act as resonators susceptible of tuning to give broadband attenuation of noise and vibration
Implementation Method 2
tuned quarter-wave and Helmholtz-type resonators have been used to provide attenuation over a narrow frequency band
Data Source
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AI summary
An attenuator for the air inlet tract of an internal combustion engine comprises an unobstructed tube (4) having a surrounding enclosure (9) divided into a primary chamber (11) in fluid communication with the inlet tube, and a secondary chamber (12) in fluid communication with the primary chamber. Two secondary chambers (12, 13) may be provided. The arrangement can be tuned to attenuate a wide range of frequencies.