Acoustics Laboratory, Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, United Kingdom.
J Acoust Soc Am. 2011 Mar;129(3):1184-92. doi: 10.1121/1.3533724.
Perforated liners with a narrow frequency range are widely used as acoustic dampers to stabilize combustion systems. When the frequency of unstable modes present in the combustion system is within the effective frequency range, the liners can efficiently dissipate acoustic waves. The fraction of the incident waves being absorbed (known as power absorption coefficient) is generally used to characterize the liners damping. To estimate it, plane waves either side of the liners need to be decomposed and characterized. For this, a real-time algorithm is developed. Emphasis is being placed on its ability to online decompose plane waves at multiple mode frequencies. The performance of the algorithm is evaluated first in a numerical model with two unstable modes. It is then experimentally implemented in an acoustically driven pipe system with a lined section attached. The acoustic damping of perforated liners is continuously characterized in real-time. Comparison is then made between the results from the algorithm and those from the short-time fast Fourier transform (FFT)-based techniques, which are typically used in industry. It was found that the real-time algorithm allows faster tracking of the liners damping, even when the forcing frequency was suddenly changed.
具有窄频带的穿孔衬垫被广泛用作声学阻尼器来稳定燃烧系统。当燃烧系统中存在的不稳定模式的频率处于有效频率范围内时，衬垫可以有效地耗散声波。被吸收的入射波的分数（称为功率吸收系数）通常用于表征衬垫的阻尼。为了估计它，需要分解和表征衬垫两侧的平面波。为此，开发了一种实时算法。重点是其在多个模式频率下在线分解平面波的能力。首先在具有两个不稳定模式的数值模型中评估算法的性能，然后在带有衬垫段的声驱动管道系统中进行实验实现。实时连续表征穿孔衬垫的吸声性能。然后将算法的结果与工业中常用的基于短时快速傅里叶变换（FFT）的技术的结果进行比较。结果发现，即使激励频率突然改变，实时算法也可以更快地跟踪衬垫的阻尼。
