Experimental study of a ducted contra-rotating lift fan for vertical/short takeoff and landing unmanned aerial vehicle application

Abstract

This study explores the aerodynamic characteristics of a ducted contra-rotating lift fan for vertical/short takeoff and landing application by means of force, pressure, and flow field measurements. The effect of rotating frequency and contra-locomotion on the force generation was examined using a miniature six-component force sensor. Additionally, for the sake of considering the ground effect, the flow field at the exit was investigated using high-response pressure measurement. Results revealed that the lift shows a quadratic generation trend on increasing the r/min where the inherent unsteady flow contradicts the conventional quasi-steady model of propeller. The contra-rotating mechanism can significantly augment the lift while still being lower than double single rotors. The unsteadiness of the contra-rotating rotors is quite obvious where two high-pressure regions are revealed and rotate. When the lift fan approaches the ground, the lift will be augmented significantly due to the surplus of the wake jet.