THE INVESTIGATION OF TIP CLEARANCE EFFECTS IN DUCTED ROTOR AERODYNAMIC CHARACTERISTICS USED IN UNMANNED AERIAL VEHICLES

摘要

The paper investigated the influence of tip clearance on ducted fan aerodynamic characteristics based on theoretical analysis and numerical simulation. From the theoretical analysis, it proved that the rotor was being off-loaded which could avoid flow separation. From the numerical simulation, with the increase of tip clearance, thrust coefficient was dropped greatly, especially when tip clearance was over 2%D which was less than the open rotor’s. As to power coefficient, it was totally different, C_P of open rotor was higher than ducted rotor’s. Although the power needed by tip clearance 3%D and 5%D was a little lower than the other two, C_T/ C_P value was also lower. For the tip clearance 5%D, C_T/ C_P was almost the same as open rotor.