Experimental Investigation of the Impact of 3D-Metal-Printed Perforated Leading Edges on Airfoil and Axial Fan Noise
Christof Ocker, Thomas Geyer, Felix Czwielong, Florian Krömer, Stefan Becker, Markus Merkel, Wolfram Pannert
Abstract
An experimental investigation of the aerodynamic performance and noise emission of airfoils and fan blades with perforated leading edges is presented. In a first step, a detailed wind tunnel study was carried out. Therefore, measurements on sixteen airfoils with different leading edge designs were performed for various flow speeds and geometric angles of attack. The airfoils with perforated leading edges were made of an aluminum alloy using a powder bed fusion based additive manufacturing process. For the measurements, two turbulence grids were used to generate different inflow turbulence conditions. The aerodynamic performance was captured with a wind tunnel balance and the acoustic measurements were performed using a planar microphone array. Based on the results from that study, unskewed fan blades with four different perforated leading edge designs were manufactured in a second step. With the aim of reducing turbulence ingestion noise of axial fans, the axial fans were examined with regard to their aerodynamics, total-to-static efficiency and sound emissions under free inflow and grid-generated turbulent inflow conditions. The investigations on airfoils and fan blades with perforated leading edge show a notable frequency-dependent noise reduction, but also a loss of aerodynamic performance.