Computation of the Aerodynamic Characteristics of Propellers Using the BEMT-method Including the Condition of Stalled Flow
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
The flow around a propeller is complex in nature and has to date still not been completely understood. However, since predicting the aerodynamic characteristics of propellers is an important aspect of the design of aircraft, a number of methods have been devised that by using simplifying assumptions is able to predict the aerodynamic coefficients of interest. One such is the blade element momentum theory method (BEMT-method) which have been found to give accurate results at high advance ratios. At lower advance numbers, where the flow over at least part of the propeller blade is stalled, the theory has traditionally not been found to be as accurate. This report presents a program written in Matlab that, by using the BEMT-method, is capable of predicting the aerodynamic characteristics for a given propeller in the whole operating region, i.e. including low advance ratios. The report include a derivation of the BEMT-equations, as well as a more general discussion of the aerodynamic of propellers, especially focusing on the issues that are important at low advance ratios. The report presents the results from the calculations for a two bladed propeller used on a racing plane, and discuss the issues surrounding the accuracy of the results.
The BEMT-method have also been used for the calculation of other types of rotors and as an example of this, this report also shows how the BEMT-method can be used for predicting the aerodynamic characteristics of a wind turbine and gives an example of a computation. The result from both of the performed computations shows that the results from the BEMT-method where the blades operate with attached flow has good agreement, while when the flow is stalled the accuracy is less good. Although not numerically in agreement, the results show somewhat of a qualitative agreement.
Place, publisher, year, edition, pages
2014. , 63 p.
TRITA-AVE, ISSN 1651-7660 ; 2014:64
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-163923OAI: oai:DiVA.org:kth-163923DiVA: diva2:802778