![]() ![]() 'Assistant Professor, Senior Member AIAA. and the American Society of Mechanical Engineering. ![]() The preliminary 3-D stall-delay model consists of two key parameters (the ratio of local chord to local radius c/r the ratio of rotation speed to freestream velocity A) and three empirical correction factors Copyright © 1998 by the American Institute of Aeronautics and Astronautics, Inc. The following steps were taken in the development of the model: 1) analysis of the 3-D integral boundarylayer equations for a reference system rotating with the blade, 2) description of the effects of rotor rotation on the separation point and its causes, and 3) determination of a simple correction formula to obtain rotating rotor lift coefficient Ci(a) and drag coefficient Cd(a) data from measured 2-D airfoil data. The main aim of the present paper is to describe and analyze the fundamental flow phenomena that characterize the boundary layer on rotating blades, and to develop a preliminary stall-delay model that modifies the 2-D airfoil data so as to simulate the 3-D stall-delay effects. ![]() The continued development of viable and well-established stall-regulated wind-turbine technology makes this research topic timely and particularly relevant to reducing the cost of wind energy. Although the deficiencies of the methods have been known for some time, this area has been neglected. Thus, these results indicate that proper propeller selection for UAVs can have a dramatic effect on aircraft performance.read more read lessĪbstract: Most design and analysis methods widely used for horizontal axis wind turbine performance prediction, such as the PROP code, are based on the traditional 2-D blade element/momentum theory (BEMT) methods, which are inadequate and underpredict the wind turbine rotor power output in the high-wind/peak-power condition, owing to effects of rotation on the wind turbine blade boundary layer. Propeller efficiencies varied greatly from a peak near 0.65 (for an efficient pr opeller) to near 0.28 (for an exceptionally poor propeller). To examine Reynolds number effects, typically four RPM’s were tested in the range 1,500 to 7,500 RPM depending on the propeller diameter. During the tests, the propeller speed (RPM) was fixed while changing the wind-tunnel speed to sweep over a range of advance ratios until reaching the windmill state (zero thrust). In total, 79 propellers were tested and the majority fit in the 9- to 11-in diameter range. Tests were performed at the University of Illinois at Urbana-Champaign (UIUC) to quantify the propeller efficiency at these conditions. Many of these UAVs use propellers that must operate in the low Reynolds number range of 50,000 to 100,000 based on the propeller chord at the 75% propeller-blade station. Abstract: While much research has been carried out on propellers for full-scale aircraft, not much data exists on propellers applicable to the ever growing number of UAVs. ![]()
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