Abstract
The commercially available unmanned aerial vehicles are not good enough for search and rescue flight at high altitudes. This is because as the altitude increases, the density of air decreases which affects the thrust generation of the UAV. The objective of this research work is to design thrust optimized blade for an altitude range of 3,000–5,000 m with a density of air 0.7364 kg/m3, respectively, and perform thrust analysis. The property of aluminum alloy 1,060 being lightweight is chosen for designing and testing of blade. The blade element theory-based design and analysis code was developed, and user-friendly aerodynamic inputs were used to obtain the desired outputs. The geometry designed for an altitude range of 3,000-5,000 m faced the total stress of 6.0 MPa which was at 70% of the blade span. This stress is within the limit of yield strength of the aluminum alloy, 28 MPa. The modal analysis shows the first natural frequency occurs at around 12,000 RPM which is safe for operating the blade at 0-5,000 RPM. Experimental analysis of the blade gave a thrust of 0.92 N at 2,697 RPM at 1,400 m. The analytical solution for thrust with the same conditions was 1.7 N with 85.6% efficiency. The validation of experimental results has been done by the CFD analysis. The CFD analysis was performed in ANSYS CFX which gave a thrust value of 2.27 N for the same boundary conditions. Thus, the blade designed for high altitude SAR UAV is structurally safe to operate in 0-5,000 RPM range, and its use in search missions could save many lives in the Himalayas.
Highlights
Unmanned aerial vehicles (UAVs) have experienced rapid development in recent years
The experimental results and analytical value gave 45% test results. This could be due to various factors involved in the experiment. Such as for safety purposes, an experiment was conducted inside a closed room so the free stream air velocity was ignored; aerodynamics profile of the fabricated propeller may not be accurately the same to the designed propeller
The blade was designed for an altitude range of 3,0005,000 m which is suitable for search and rescue operations in Nepal
Summary
Unmanned aerial vehicles (UAVs) have experienced rapid development in recent years. There are many institutes which have been actively involved in exploring the more potential applications of UAV. These UAVs range from large (weight > 300 kg) [1, 2] to mini (takeoff weight < 300 kg, altitude 300 m) [3, 4] and even microUAVs (takeoff weight 5 kg, altitude 250 m) [5]. High altitude long endurance (HALE) UAV (17-25 km) [6] has been growing interest in recent years. Helios (wingspan 73 m) developed by NASA and UAS ascended to an altitude of over 29 km [6]. Zephyr (wingspan 25 m, weight 75 kg) designed and built by British Company QinetiQ holds the official endurance world record of 14 days, 22 min, 8 sec without refueling [9]
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