Abstract
The development of multi-rotor helicopter concepts, driven by the active introduction of brushless electric motors, leads to the necessity of assessing the multi-rotor scheme main advantages implementing possibility and determining the rational areas of its application. The article analyzes the concept of a multi-rotor platform with a distributed power plant. Parametric study of characteristics depending on the number of rotors for a line of multi-propeller aircraft with take-off weight from 0.5 to 120 tons was carried out. Evaluation of weight and dimensional characteristics of blades, main rotor heads, gear boxes, as well as power wires of electric motors and structure beams connecting the elements of the distributed power plant is obtained. Evaluation of drag and thrust losses on blowing, as well as power requirements for typical flight modes was carried out. Estimation of the required number of rotors for the implementation of the gearless condition and flight safety with one engine failed are obtained. Rational areas of multi-rotor scheme application are defined.
Highlights
In order to increase the weight of the cargo, economically lifted by vertical take-off and landing helicopters, it is necessary to increase the rotor disk area
When the number of rotors increases, the mass of the construction components connecting the modules of the distributed power plant grows
The drag power for the continued take-off mode decreases and its dependence on the number of propellers takes a flat form when the number of propellers nprop is over 14–16. As it can be seen, when the number of propellers is more than 4, the drag power is determined by the hovering mode and has the drag power continued takeoff margin, which admits the failure of more than one engine under the condition of a fully electric distributed power plant or distributed power plant with modules consisting of the main rotor and gas turbine engines, which is more typical for super-heavy multi-propeller helicopter projects
Summary
In order to increase the weight of the cargo, economically lifted by vertical take-off and landing helicopters, it is necessary to increase the rotor disk area. Because of the difficulties connected with the construction of propellers with a very big diameter, the increase of rotor disk area can be reached by constructing multi-rotor bearing systems. This possibility was pointed out by N.E. Zhukovsky in his work "About the payload lifted by helicopters" in 1904 [1]. Unmanned aircraft with electric or hybrid power plant as well as brushless electric engines with specific capacity up to 0.5 MW are in mass production, which allows us to create aircraft for general aviation and aircraft for individual use [2]. The advantages of brushless electric engines are realized through reducing the amount of noise and harmful emissions as well as through increasing the reliability and simplification of the design by means of eliminating gearboxes, transmissions, as well as swash plates, due to the separate rotation control of brushless electric engine frequency and main rotor speed
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