Publication

Abstract : The aim of this paper is to theoretically design and computationally model a micro propeller in order to maximize the propulsive efficiency of the MAV and to design an MAV wing planform considering the propeller-wing interaction. The dimension of the micro propeller was set as 4.7” x 2.7” (12cm x 7cm) and the design advance ratio was set to 0.54. The theoretical design for micro propeller was done based on combined blade element and momentum theory. A maximum efficiency of 96% was achieved with thrust of 1N. CFD analysis was carried out to simulate the flow over the propeller, and to estimate the losses and the efficiency degradation due to viscous effects, compressibility effects, and wake interactions. Two micro propellers, with NACA 4412 airfoil as cross section, were modeled in Unigraphics NX; one without a hub and one with a hub of diameter 15 mm. An unstructured 3D mesh was generated around the propeller using GAMBIT 2.4 and analyzed in FLUENT 6.3.26 using a single rotating reference frame. A two equation k-epsilon model was used for analysis. The loss in the efficiency of the propeller was studied. An estimate is also presented to account for the hub interaction. Zimmerman planform with an aspect ratio of 1.14 was selected for the MAV wing and the dimension of the planform was determined based on the propeller diameter. A study of the effect of slipstream behind the propeller on the drag of the wing planform was carried out. The flow downstream of the propeller comprises of two mixing airflows: free stream and propeller-induced slipstream. The propeller-induced slipstream was pulsating in nature. For level-flight condition, continuous decrease in the drag of the wing planform, due to the decrease in the propeller induced pulsating slipstream was observed.