Trades in the aerodynamic design of proprotors that could be used to power convertible-rotor aircraft have been examined. The key design challenge is to maximize overall aerodynamic efficiency of the proprotor in both hover and forward flight, while preserving adequate stall margins for maneuvering flight and compressibility margins for high speed flight. To better assess proprotor performance, a new formulation of the blade element momentum theory for high-speed propellers and proprotors was developed. This approach uses an efficient and robust numerical method to solve simultaneously for the axial and swirl induced velocity components in the wake of the proprotor. The efficacy of the approach was validated against measurements of the performance of two NACA high-speed propellers at advance ratios up to 2.5 and tip Mach numbers up to supersonic conditions. The importance of calculating accurately the swirl component of the induced velocity is emphasized. Parametric studies and design optimization studies were performed for different convertible-rotor aircraft platforms with the goal of developing a better understanding of the tradeoffs that would be needed for the development of advanced proprotors to power such convertible-rotor aircraft. The effects that solidity, diameter, rotational speed, blade twist and taper, number of blades, tip sweep, and airfoil characteristics have on proprotor performance were all explored. Particular importance was given to proprotors that may have variable tip speed, and assessing the relative advantages of variable diameter versus variable rotational shaft speed concepts. Proprotors with variable blade twist were also considered. It was found that significant improvements in proprotor performance may only be practically realized by varying one or more of diameter, shaft speed, or blade twist during flight.
|Advisor:||Leishman, J. Gordon|
|Commitee:||Baeder, James, Yu, Kenneth|
|School:||University of Maryland, College Park|
|School Location:||United States -- Maryland|
|Source:||MAI 51/03M(E), Masters Abstracts International|
|Keywords:||BEMT, Optimization, Propeller, Proprotor, Tiltrotor|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be