Date

2021-6

Author

KAYA, DERYA

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This study focuses on accurate prediction of total forces and moments acting on a propeller in all flight conditions through Blade Element and Momentum Theory (BEMT) and design optimization of a UAV propeller. Under various flight conditions such as hover, vertical climb, and forward flight, propeller generates different aerodynamic loads in different free-stream velocities, propeller disk angles of attack, and propeller’s angular speeds. For this reason, it is important to have a mathematical model that predicts all forces and moments generated by the propeller under these different flight conditions. Propeller aerodynamic loads at different flight conditions can also be found experimentally (e.g., wind tunnel or real-flight tests) or computationally (i.e., Computational Fluid Mechanics (CFD) methods) but these methods are time-consuming. As well, experimental methods are not affordable for optimization studies. The mathematical model obtained from model-based calculations of propeller aerodynamic loads is more useful compared to CFD and experimental methods. However, some assumptions in classical Blade Element Theory and assuming the induced veloctiy constant cause inaccurate prediction of the propeller’s forces and moments in model-based approaches. On the other hand, the Improved BEMT (IBEMT) model proposed in this study can estimate the propeller performance in wide flight regimes from hover to forward flight for unmanned aircraft applications. It is computationally efficient in fast optimization studies. Induced velocity is calculated iteratively at each annulus of the rotor disc. Euler integration is used in the calculation of the propeller’s aerodynamic loads at each blade section and azimuth angle. The improved model is validated with wind tunnel experiments and it is compared with the results of experimental data of another study and CFD result for which the geometric properties of the propeller used and operating conditions are known in detail. Besides, in this study, design optimization of a propeller is also conducted using MATLAB® Optimization Tool-Box and the IBEMT model.

Subject Keywords

Propeller Aerodynamics, Blade Element and Momentum Theory, Induced Velocity, Wind Tunnel Experiments, Propeller Design Optimization

URI

https://hdl.handle.net/11511/91601

Collections

Graduate School of Natural and Applied Sciences, Thesis