Experimental Investigation of Unsteady Flow in Circumferential Skewed Axial Fans at Off-design Conditions

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.