On the basis of the baseline nozzle with annular mixer

the far field noise spectra performance and the noise reduction of the nozzle with lobed mixer were investigated under cold jet condition through scaled model experiments of high bybass ratio turbofan engine mixing exhaust system. The experiments were carried out on the jet noise experiment rig in the anechoic chamber. The experimental results show that

compared with the baseline nozzle with annular mixer

the nozzle with lobed mixer has better jet noise reduction at low frequencies

but the sound pressure level increases at high frequencies

while overall sound pressure level reduces at downstream(θ=150°)but increases at middlestream and upstream. With increased velocity differences between core exit flow and fan exit flow of lobed mixer

the nozzle with lobed mixer has better noise reduction at low frequencies

but the sound pressure level increases at high frequencies

while overall sound pressure level reduces at downstream(θ=150°)but increases at middlestream and upstream.