Impact of distorted inlet flow on axial fan psychoacoustics

Paper in proceeding, 2025

Axial cooling fans operating downstream of obstructions are often exposed to distorted inlet flow conditions, consequently impacting acoustic performance. Herein, the impact of upstream obstructions with simple geometries on the psychoacoustics of an axial fan with a rotating ring is investigated. Different loading conditions and inlet shroud lengths are considered, while a reference non-obstructed installation is also recorded. Results show a significant increase in loudness for obstructed installations at intermediate and free discharge loading conditions, regardless of inlet shroud lengths tested. Sharpness, fluctuation strength and roughness demonstrate no sensitivity to loading conditions for obstructed installations, while tonality levels depend on inlet shroud length.