Electric ducted fans for distributed propulsion of drones
Creators: name:  D. CASTROVIEJO 
name:   P. HENDRICK 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: UAV
FUTURE APPLICATIONS
UAV SERVICES
UAV SPECIFIC TECHNOLOGIES

description: In todays world, the drone industry is quickly expanding. Indeed their role is becoming more vital and an in- creasing number of drones are conceived to effectively conduct military, humanitarian and rescue missions a mong others However, one of their major limitations is their endurance (or range) which limits their applica- tion purp oses Many existing technologies are being upgraded and new ones are being developed in order to further push these limi t s Fundamentally there are two main ways to increase the endurance of a drone without modifying its geometry and this is done either by having a higher power density of the power source more en- ergy for the same weight or hav ing a more e fficient propulsion system. This paper is focused on exploring an existing but rather unpopular technology, known as electric ducted fans (EDFs [ in combination with distrib- uted propulsion which aims to in crease the propulsive efficiency It is cruci al to have a clear definition of what distrib uted propulsion really is It is defined here as the spanwise distribution of the propulsive thrust stream such that overall, the vehicle benefits in terms of structural, aerody- namic, propulsive and/or other efficiencies 2 On the other hand, electric ducte d fans are electric powered pro- pellers equipped with a duct around it (figure 1) To conduct this study rightfully it was essential to have a testbench on which EDF s and propellers could be teste d The testbench (figure 2 3 was built and equipped with throttle, torque, thrust, rpm, current, voltage, temperature, static and dynamic pressure sensors All of the data is then processed by an Arduino Mega board and sent to a Raspberry Pi from which it is transferred to MATLAB and analysed Many factors influencing the EDFs functioning have been treated throughout the study, such as for instance the influence of th e battery charge/discharge and the blade profile on its performance, the electronic speed control- lers impact on the control of the EDF and more. T he effect of the duct on the thrust production and power con- sumption is shown here (figure 4 where EUF means Electric Unducted Fa n for two different EDFs (the QX3300 3 and QX4500 4 From this figure it can clearly be seen that integrating a duct around the propeller allows for a higher thrust production (first approximation leads to an increase of around 35 i n comparison to the same propeller without duct at maximum thrust and a power reduction (for the same produced maximum thrust) of around 50%. These improvements are mainly due to the more uniform flow beneath the propeller and the disappearance of the blade tip vortices allowing for a higher efficiency of the fan It is important to notice that the increase in parasitic drag due to the presence of the duct has not been studied and t his is an important parameter w hich will be integrated in future work of the project. In conclusion, this paper state s that this technology seems to be more efficient if and only if the diameter of the EDFs are big enough as small EDFs diameter s up t o a few centimetres are inefficient Indeed the study was conducted on a Skywalker X8 5 drone which has a 2.12m wingspan with a basic propulsion system composed of a single 30cm diameter retractable propeller. This propeller is more efficient than all of the EDFs studied as their sizes were too small up to 7cm in diameter in comparison to the basic propeller. Henc e a drone on which an EDF of similar size as the propeller can be mounted should have a higher range Furthermore, on a drone of this size distributed propulsion does no t seem to be feasi ble at all and should further be investigated on bigger size d drones wher e more efficient EDFs hence w ith bigger fan diameter in comparison to the basic propulsion system could be installed.