Theoretical Performance Analysis of Fixed Pitch Propeller Operating at Low Reynolds Number Condition

Abstract

The propeller performance data at its design point and off design points are the basis for the selection of suitable propeller for an unmanned air vehicles (UAVs) system. Various research have been conducted for the development of a tool for theoretical prediction of the propeller performance but are not readily available in the public domain. In addition, the commercially available propellers only have performances at design point. Thus, the current work focuses on developing an analytical tool for the prediction of the propeller performance which is based on the Blade Element Momentum Theory (BEMT). An arbitrary base line propeller has been designed for developing the current tool. The airfoil properties at various radial sections have been calculated from the XFOIL and the tool has been developed in Matrix Laboratory (MATLAB). The output from the developed tool was compared with existing experimental data for Harrington rotor 1 and thin electric APC 11x8 propeller. The preliminary calculations were carried out at the rotating speed and free stream velocity of 7500 RPM and 80 < B respectively. The capability of the prediction tool were then explored at various operating conditions. The rotating speed and forward speed were changed from 6500 RPM to 8500 RPM and from 65 < B to 90 < B respectively. The performance analysis was done for the base line propeller to study the effects of rotational speed, free-stream velocity and advanced ratio. For the base line propeller at its design point, the thrust coefficient, torque coefficient and propulsive efficiency were calculated to be 0.0724, 0.0347 and 83.5% respectively. One way fluid structure interaction analysis was performed in ANSYS to study blade stress due to pressure and centrifugal loading. The comparison of BEMT prediction with CFD result was performed for baseline propeller at design point.