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Evolution and design of propulsion systems for unmanned aerial vehicles: the compromise between payload mass and operational range based on the constructal law of design and evolution


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Abstract

Unmanned aerial vehicles (UAVs) are widely applied. However, for a fuller fulfillment of UAVs’ potential, it is important to understand the promising directions of their evolution. This was carried out based on of the modern thermodynamics and the constructal law of design and evolution (1995) developed by the famous American physicist A. Bejan. The evolution of conventional airplanes obeys this law and is in line with the evolution of animal locomotion. However, UAV design and parameters are different from the design and parameters of conventional airplanes. The performed analysis shows that UAV evolution also obeys the constructal law. This allows determining the rational ratios between the masses of UAV subsystems and other parameters, such as operational range or speed. As with other moving objects, those ratios may be achieved during the process of evolution or design as a compromise between required large payload mass and long operational range. At unchanged vehicle’s maximum takeoff and a required large payload masses the maximal operational range is the criterion that describes UAVs’ movements’ in space efficiency. In order to increase this range it is necessary to increase the UAV’s energy supply (the fuel / battery mass) by reducing the mass of other components and the propulsion systems’ (PS) efficiency. However reserves for reducing payload or body masses have already been exhausted. Therefore, the required compromise may only be established by perfection of PSs. Electric PSs may have a significant potential and benefits. These PSs may have five cardinal architectures: all electric; hybrid electric; heat engines-electric generators (full or partial). The analysis showed that the maximal of operational range and correspondingly the maximal efficiency of UAVs’ movement may be achieved by using PSs based on the high power density microturbines (MTG) or simple plug-in series hybrid PSs also based on the MTGs.

Keywords

evolution, constructal law, unmanned aerial vehicles, propulsion system, microturbine generator

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