Title: wind tunnel test of props Post by: shadman_alam on July 14, 2011, 03:38:00 AM while searching for aerofoil designs.. i came across this.. its a case study on various props... their efficiency and thrust... at various rpm... and alot more..
http://www.ae.illinois.edu/m-selig/pubs/BrandtSelig-2011-AIAA-2011-1255-LRN-Propellers.pdf Propeller Performance Data at Low Reynolds Numbers Results Although the propellers tested here are limited to non-folding, two-bladed propellers, a wide range of propeller styles were tested nonetheless. The majority of the propellers tested had diameters ranging from 9 in. to 11 in., though a few larger sizes were tested. For this series of tests, all of the propellers were tested without any alterations. Thus, any sharp and some times ragged leading edges that result from manufacturing processes remained. Some of the models tested are intended to be used on aircraft with electric motors, while others are designed to be used with fuel powered engines. With such a wide range of designs tested, a wide range of performance characteristics are observed. Here, the general trends found in the data are highlighted, although trends in the thrust and power coefficient are discussed briefly, the propeller efficiency is the main focus. Looking at the entire set of data, one general trend is observed throughout (and will be illustrated in the figures to follow): as the propeller speed is increased, the performance improves. This result is most evident through increased efficiency. The degree of the improvement varies from propeller-to-propeller, but it is a trend that is consistent. This improvement is also seen in the thrust coefficient curves, as higher thrust coefficients are obtained with increasing propeller speed. The increased thrust is most easily seen looking at the static thrust plots. A. APC Propellers Three types of APC propellers were tested, namely the Slow Flyer, Sport, and Thin Electric propellers. Both the Slow Flyer and Thin Electric propellers are designed to be used solely with electric motors. The Sport propellers are designed to handle the increased torque produced by gas powered engines. The airfoil profiles on the Slow Flyer propellers are quite thin with a sharp leading edge, where the remaining two have thicker airfoil sections with rounded leading edges. All of the APC propellers show some variation in the performance curves that is consistent with the overall trends. The Slow Flyers show the least variation in efficiency and the differences are larger near peakefficiency. The Sport propellers exhibit the largest efficiency variance that is observed over the entire range of advance ratio. Similar to the Slow Flyers, the Thin Electric propellers also show increased performance differences near peak efficiency. One interesting trend is found in the thrust and power coefficients for the Thin Electric propellers; it is seen that variations in these coefficients are dramatically increased over a small range of advance ratio near the peak efficiency. The result is shown for the APC Thin Electric 11×8 propeller in Figs. 11–14. B. Graupner Propellers The four styles of Graupner propellers tested include the CAM, CAM Slim, Slim, and Super Nylon propellers. The former three are all designed specifically for use with electric motors, and the latter are intended to be used with gas powered engines. The CAM and Super Nylon propellers are designed with moderately thick airfoils with conventional round leading edges; where as, the CAM Slim and Slim propellers are designed with much thinner airfoil sections that have sharp leading edges. The CAM propellers all show significant differences in the efficiency curves over the range of propeller speeds. These differences are rooted in significant variations in the thrust characteristics and minor variations in the power characteristics. Both the CAM Slim and Slim propellers show only minor variations in peak efficiency, with the Slim propeller showing some of the smallest variations in performance. The CAM Slim propellers show minor variations in both the thrust and power coefficients over a small range of advance ratio that correspond to the region of peak efficiency (see Figs. 15–18). Finally, the Super Nylons show moderate variations in the efficiency, with increased differences seen near the peaks. D. Master Airscrew Propellers The Master Airscrew propellers tested included propellers limited to electric applications as well as propellers that could be used with either gas powered engines or electric motors. The Electric series propellers are designed to only be used with electric motors. Both the G/F and Scimitar series are designed for use with gas powered engines but can be easily used with electric motors as well. The Master Airscrew propellers are designed with relatively thick airfoils with round leading edges, but they have a sharp leading edge that is a result of the manufacturing process. The Master Airscrew Electric series propellers show performance variations that are moderate in magnitude and consistent with the overall trends. The G/F series show some of the largest variations in both the efficiency and thrust coefficient curves, as the differences are exacerbated for the lower pitched propellers. The Master Airscrew G/F 11×4 shows that the peak efficiency nearly doubles over the range of propeller speeds tested (see Figs. 23–26). The Scimitar series shows moderate changes in performance for varying propeller speeds, where the differences are magnified over certain ranges of advance ratio. Conclusion In the research reported here, 79 propellers were tested and nearly all fit in the 9- to 11-in. diameter range. Thrust and torque were measured over a range of propeller advance ratios for discrete propeller speeds (RPM’s) – typically four different values of RPM to examine low Reynolds number effects. Also static thrust was measured over a range of propeller speeds from nominally 1,500 to 7,500 RPM depending on the propeller diameter. The results showed significant Reynolds number effects with degradation in performance with lower RPM’s. Also, over a range of propellers, the propeller efficiency varied greatly froma peak near 0.65 down to near 0.28 for an exceptionally poor propeller. It is envisioned that the data gathered in these experiments will serve several purposes. The results will give aircraft designers a large database that can be used for selecting appropriate propellers for a wide variety of applications. Further, any beneficial or adverse trends found in the data will be used to improve design capabilities. Finally, prediction tools could be refined using the data gathered here. Title: Re: wind tunnel test of props Post by: aditya on July 14, 2011, 07:25:44 AM was searching for propeller testing articles....
nice post.. {:)} {:)} {:)} Title: Re: wind tunnel test of props Post by: shadman_alam on July 14, 2011, 04:38:14 PM thank you.. where do u fly in delhi?
Title: Re: wind tunnel test of props Post by: aditya on July 15, 2011, 08:20:45 PM in y.m.c.a. ground in faridabad...
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