Analysis and study of the influence of the geometrical parameters of mini unmanned quad-rotor helicopters to optimise energy saving

Abstract

 The article discusses lift force generated by mini UAVs (Unmanned Aerial Vehicles). CFD (Computational Fluid Dynamics) simulations were made on the base of a 3D scanned propeller model. Influence of some geometrical parameters of propeller (like velocity or pitch) and quadcopter (like gap) on lifting force was considered. Different propeller pitches were used and pitch influence on propeller lift force was analysed. Normally, lifting force will increase with the increasing of propeller pitch but for different rotation velocities, this increasing is different and in all cases, it can be approximated by a linear relationship. To obtain dependency functions, an equation for calculation of lift force given took into account the correction coefficients. This equation gave reliable results at pitch values equal to 0.3 – 0.7 of the propeller diameter and at rotation velocities of 2000 min^-1 – 8000 min^-1.
 Lift force dependency from distance between rotors was also considered. Simulations and experiments showed that the lifting force of a quadcopter increased about 15% on gap distances from 5 mm to 35 mm. From a distance of 70 mm, the lifting force will decrease about 2% and then will stabilise. At increasing of distance between propellers from 5 mm until 25 mm, the power consumption decreased 8% - 10% and after the gap distance equal to 40 mm, it will be stable and minimal. It can be asserted that quadcopters have different optimal distances between the propellers at different rotation speeds to generate the same force. Equations for calculation of optimal gap distances for different multicopters were derived and calculation results are presented in graphs and tables.