Experimental and theoretical analysis of nonlinear acoustic characteristics of perforated acoustic liners

Perforated acoustic liner is one of the key components commonly used to suppress combustion oscillation in afterburners of military aircraft engines. The acoustic pressure generated by combustion oscillation is relatively high, and the nonlinear characteristics of these liners are significant. This paper employs both experimental and theoretical methods to study the nonlinear absorption coefficient and acoustic impedance of perforated acoustic liners in the range of 0 to 200 Pa. The results indicate that nonlinear effects increase the primary absorption frequency up to 70 Hz as the acoustic pressure amplitude rises from 2 Pa to 200 Pa. For small acoustic pressure amplitudes, it is recommended to use acoustic liners with smaller perforations, whereas for larger amplitudes, the perforation diameter should be increased (d > 4 mm). For liners with a perforation diameter of 1.1 mm, the inclination angle has little effect on the absorption coefficient. When the acoustic pressure amplitude is small, the acoustic liner has an optimal backing cavity height. However, at larger acoustic pressure amplitudes (200 Pa), increasing the backing cavity height is beneficial for the absorption coefficient. When the backing cavity height increased from 20 mm to 130mm, the absorption coefficient more than doubled. The nonlinear acoustic characteristics of perforated acoustic liners can provide valuable insights for the design of anti-vibration screens in afterburners.