Abstract: The unsteady characteristic of the inner flow in lower pressure axial fans with circumferential forward-skewed blades, backward-skewed blades is investigated experimentally at off-design conditions. The unsteady three-dimensional flow in circumferential skewed rotors upstream and downstream according to flow rates is successfully measured with a NI data collection platform and a hot-wire CTA unit (with a X probe). Based on the measurement results, axial, circumferential and radial components of the averaged velocity and turbulent velocity are analyzed to obtain the aerodynamic performance of circumferential skewed rotors; and the turbulent intensity, Reynold tensor and velocity spectrum are discussed to investigate the intrinsic unsteady flow in these rotors. The results show that the three-dimensional flow is captured by this measure system, which can be used for multi-physics measurement; the circumferential skewed blades are found to control the unsteady flow in the shroud and hub region at off-design conditions to expand stable operation; the inlet disturbed flow under off-design conditions was observed in the shroud and hub region, with low frequency and wide band characteristic.

Key words: Axial flow fan, Hot-wire, Unsteady flow