Acoustic and Aerodynamic Performances of One Phononic Crystal Duct with Periodic Mufflers

The acoustic muffler is one of the practical solutions to reduce the noise in ducts. The acoustic and aerodynamic performances are two critical indices of one muffler for the air intake system of a hydrogen fuel cell electric vehicle (FCEV). In this study, the concept of phononic crystal is applied to design the muffler to obtain superior acoustic performance. One duct with periodic and compact resonator-type mufflers is designed for broadband noise attenuation. The two-dimensional (2D) transfer matrix method and bandgap theory are employed to calculate the transmission loss (TL) and acoustic bandgap. It is numerically and theoretically demonstrated that broadband noise attenuation could be acquired from 500Hz to 3500Hz. Afterwards, the three-dimensional (3D) computational fluid dynamics (CFD) approach is applied to predict the pressure distribution. The results indicate that the proposed hybrid muffler and the phononic crystal duct possess low pressure loss values. Furthermore, the influence of inlet flow velocity and air temperature on the transmission loss and pressure drop are investigated through a systematic study. The two factors primarily work on sound attenuation in the high-frequency range. The increase of the inlet flow velocity might cause the TL amplitude to decrease around the peaks, while the enhancement of the inlet air temperature might make the TL curve move towards the high-frequency domain. It shows that acoustic resonator-type mufflers are conducive to broad noise attenuation with the low-pressure loss and a compact structure. It provides one avenue to control the noise in the duct.