Axial fan tip clearance noise: Experiments, Lattice–Boltzmann simulation, and mitigation measures. Issue 1 (March 2018)

• Record Type: Journal Article
• Authors: Zhu, Tao; Carolus, Thomas H
• Other Names: McLaughlin Dennis K. guest-editor.
• Is Part Of: International journal of aeroacoustics. Volume 17:Issue 1/2(2018)
• Page Start: 159
• Page End: 183
• Publication Date: 2018-03
• Subjects: Axial flow fan -- tip clearance noise -- Lattice-Boltzmann method; Aerodynamic noise -- Periodicals; Acoustical engineering -- Periodicals; Sound -- Periodicals; 629.1323
• DOI: 10.1177/1475472X17743627
• Languages: English
• ISSNs: 2048-4003

Abstract

The effect of tip clearance in an axial fan on its aerodynamic and aeroacoustic performance is investigated experimentally as well as via a Lattice–Boltzmann flow simulation method. An increase in tip clearance degrades fan pressure rise and efficiency, but also increases significantly the overall sound power emitted by the fan. A large tip clearance causes a clear structure of well distinguishable unsteady vortices which interact with neighboring blades and hence produce an increase in broadband sound. Moreover, if, compared to the design flow rate, there is a moderate flow rate reduction, the local tip vortex systems of all individual blade tips form a circumferentially coherent flow structure, resulting in distinct humps of sound pressure in the acoustic far field. By means of a rigid ring-type protrusion fixed to the inner casing wall, the generation of the tip clearance vortices and slowly rotating coherent flow structures could be suppressed. As a consequence, the sound emitted by the fan is substantially reduced.