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.pdfPropeller 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.
ConclusionIn 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.
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