Tunable Acoustic Liners Using Shape Memory Polymers
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Solution Overview
Problem
Current acoustic noise absorbing devices, particularly broadband acoustic liners, are limited by their passive design, which restricts their ability to adapt to varying operating conditions, leading to suboptimal noise attenuation across multiple octaves, and existing adaptive designs face challenges in efficiently controlling resonator dimensions and air flow impedance.
Innovation Solution
The development of a tunable resonant acoustic noise absorbing device using shape memory polymers (SMP) and composites that dynamically change the depth of resonance chambers and orifice parameters, allowing for in-situ modification of acoustic impedance to adapt to changing environmental conditions, thereby enhancing noise absorption across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive acoustic liner designs are used, then manufacturing simplicity is maintained, but adaptability to varying operating conditions deteriorates
Solution Approach 1:
The acoustic liner incorporates movable internal partitions that can dynamically adjust the resonator volume in response to varying operating conditions. This dynamic adjustment capability allows the liner to adapt its acoustic impedance to different frequency ranges while maintaining a relatively simple overall structure, resolving the contradiction between manufacturing simplicity and adaptability.
Solution Approach 2:
The system changes the effective resonator volume parameter by moving internal partitions, thereby adjusting the resonant frequency and acoustic impedance. This parameter change mechanism enables the liner to adapt to different operating conditions without requiring complete redesign, balancing manufacturing simplicity with operational versatility.
2Volume of stationary object
If resonator volume is increased to broaden attenuation bandwidth, then noise attenuation performance improves, but device complexity increases
Solution Approach 1:
The resonator is divided into multiple chambers with movable internal partitions. By segmenting the resonator volume and selectively adjusting the volume of individual chambers, the system can broaden the attenuation bandwidth without requiring a single large complex structure. Each chamber can be independently controlled to target specific frequency ranges.
Solution Approach 2:
Movable internal partitions enable dynamic reconfiguration of the resonator volume distribution. This dynamic capability allows the system to achieve broad bandwidth attenuation by adjusting which chambers are active and their respective volumes, avoiding the need for a permanently complex multi-chamber structure.
3Object-affected harmful factors
If multiple degree of freedom liner designs are used to achieve broadband attenuation, then noise attenuation performance improves, but manufacturing complexity increases
Solution Approach 1:
The MDOF liner is segmented into multiple chambers separated by movable partitions. This segmentation allows each chamber to be manufactured and tuned relatively simply, while the collective system achieves broadband attenuation. The modular chamber design simplifies manufacturing compared to monolithic complex structures.
Solution Approach 2:
The movable internal partitions can be actuated by the acoustic pressure field itself or simple actuators, allowing the system to self-adjust its configuration for optimal broadband performance without requiring complex external control systems, thereby reducing manufacturing and operational complexity.
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 solution enables a significant 1500 Hertz shift in primary frequency through controlled air pressure and SMP diaphragm movement, achieving a 500-600 Hertz tuning range, which is more effective than previous designs, and can be further optimized for broader applications like jet engine noise reduction.
Implementation Method 1
tunable resonant acoustic noise absorbing device using shape memory polymers (SMP) and composites that dynamically change the depth of resonance chambers
Implementation Method 2
Broadband acoustic liners are based on the mechanism of multiple cavity resonance
Implementation Method 3
A 1500 Hertz shift in the primary frequency of a liner was demonstrated through a change in depth of the acoustic lining
Data Source
AI summary
Tunable perforate acoustic liners are disclosed using shape memory materials, which allow the acoustic liners to tune for multiple frequencies across a wide range, unlike current designs which are limited to specific frequencies or small ranges. The liner will be initiated through a sensor and feedback loop to monitor the current acoustic environment and initiate geometry change needed to more effectively attenuate engine noise.