Experimental investigation of unsteady flow in axial skewed fans according to flow rates

Unsteady flow in axial fans with circumferential skewed blades were measured at off-design conditions using a hot-wire test, to investigate the effect of sweep on aerodynamic limit and aeroacoustic sound source. Two circumferential skewed fans, with the blade skew angles at 8.3° forward and backward, respectively, were investigated in this study. The instantaneous flow field in the upstream and downstream of these fans was measured at off-design operations, using a two-dimensional (2D) probe based on a Constant Temperature Anemometry (CTA) system, and a NI PXI data collecting system. From the measured results, the characteristics of time domain and frequency domain were presented. The three-dimensional (3D) structure and turbulent characteristics of inlet and outlet flow in circumferential skewed fans were analyzed according to flow rate. Unsteady flow instability and its relation with circumferential skewed blades, to expand stall-free operation range and suppress noise of axial fans, were discussed. The sweep blade is found to be effective in controlling unsteady flow to improve aerodynamic limit and reduce noise source in these rotors at off-design operations.

We experimentally investigated unsteady upstream and downstream flow in axial fans with circumferential skewed blades at off-design operations using a CTA and NI PXI system.Figure optionsDownload as PowerPoint slideHighlights
► The instantaneous velocity components of axial skewed fans upstream and downstream were measured.
► The 3D structure and turbulence characteristics in these skewed rotors according to flow rate were present.
► Effect of unsteady flow of sweep blades at off-design operations on aerodynamic limit and aeroacoustic source was revealed.