Labyrinth-Coiling Quarter Wavelength Tubes Embedded in Honeycomb Cells for Advanced Acoustic Liner Designs

What is it about?

The study focuses on the design of an acoustic liner to tackle noise from modern turbofan engines, particularly addressing broadband components. Introducing innovative locally-reacting liner designs based on coiled quarter wavelength tubes, the research compares three proposed models (B, C, D) with a conventional liner (A) available in literature. Sound absorption results in impedance tube reveal that model B, featuring a six-branch labyrinth resonator, outperforms the reference model in sound absorption, notably at lower frequencies, but with an excessive reduction of the perforation ratio. Model C helps reaching the best compromise since it has almost the same perforation ratio with respect to the reference and high sound absorption at lower frequencies with respect to model A. Significantly, model D achieves superior performance with only one-third the thickness of the traditional liner. Grazing impedance tube simulations compare the sound transmission loss of the proposed models, showing that model C can reach comparable performance but at lower frequencies respect to model A, and that model D can replace model A but with 1/3 of the thickness.

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Photo by Ramon Kagie on Unsplash

Photo by Ramon Kagie on Unsplash

Why is it important?

The study emphasizes the potential of coiled quarter wavelength tubes in mitigating tonal noise, offering a transformative solution for quieter and more sustainable aviation. This solution can be an interesting alternative for lower frequencies and thinner liner designs.

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