THE IMPACT OF MEAN SWIRLING FLOWS ON SOUND PROP-AGATION IN THE ABSENCE OF LINERS: A PARAMETRIC STUDY

摘要

The current trends for next generation turbofan engines are towards shorter nacelles and increased distances between the fan and the outlet guide vanes. This leads to an overall reduction in lined surface areas as well as an increase in the relative importance of the interstage liner. This paper seeks clarification on the effect of swirling flows per se on sound propagation in an annular duct in the absence of acoustic treatment to create a baseline for a future study in which both swirling flow and acoustic treatments are included. Geometric and mean flow parameters and frequency range were carefully chosen to correspond to realistic values. Axial wavenumbers are calculated using a Finite Difference code.