naca-tn-235

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National Advisory Committee for Aeronautics, Technical Notes - Propeller Design - Practical Application of the Blade Element Theory - I
This report is the first of a series of four on propeller
design and contains a description of the blade element or mod—
ified Drzewiecke theory as used in the Bureau of Aeronautics,
U. 3. Navy Department. Blade interference corrections are used
which were taken from R-& M. No. 659 of the British Advisory
Committee for Aeronautics. The airfoil characteristics used
were Obtained from tests of model prOpellers, not from tests
of model wings.
he U. S~ Navy nethod of aircraft prepellcr design is
based on data Obtained from a cembination of the blade element
theory, model propeller tests in a wind tunnel, and tests of
full scale propellers in flight. The data are plotted as curves
for propellers of standard Havy form, making the actual oper—
ations in designing_a propeller very short and simple. For the
analysis or design of special propellers not conforming to the
standard, the modified blade element theory is used, with air—
foil section characteristics which give resultant powers and
efficiencies checking the standard model data.
Although the blade element theory is well known to aeronauer.
tical engineers, the accuracy of the results obtained through
its use depends upon corrections which can'be Obtained only
through experienceT It is the intention to present in this
report a modified form of the theory with data which makes its
application sufficiently accurate for practical use.
In the simple blade element or Drzewieche theory the pro—
peller blade is considered as made up of a nuMber of small ele—
ments and the forces acting on each are found. From the summa~--u_
tion of the forces on the elements the resultant forces on the
Whole blade are determined.
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