The Design of Airplane-Engine Superchargers Page: 2 of 22
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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
TECHNICAL MEMORANDUM NO. 39
THE DESIGN OF AIRPLANE--ENGIINE SUPERCHARGERS*
By Werner von der Null
Suitable superchargers for airplane engines are a
requisite for successful high-altitude flying. The under-
lying principles for the computation and design of air-
plane-oenine superchargers must be given further study.
The results obtained through tests on the various forms of
rotor va ns and counter vanes and on the design of the
ca sing should prove useful for improvement of design.
Well-known computation methods have shown themselves, with
slight modifications, to be suitable. The use of single-
stage centrifugal superchargers for supercharging to one
atmosphere at 8 to 9 '-ilometers (25,000 to 29,000 feet)
altitude appears, with suitable regulation, entirely pos-
sible without supercharger air cooling.
I. UINDERL ING POSSIBILITIES OF SUPERCHARGING
In its present form the airplane engine is unsuited
for self-charging at the higher altitudes since the air
pumping occurs too slowly, Modern high-altitude engines
are therefore provided with devices for charging the en-
gine at high altitudes, namely, superchargers. Any arrange-
mont that lowers the specific volume of the combustion
air before entrance to the engine cylinder is essentially
suitable as an airplane-engine supercharger. The most suit-
able arrangement will be that which combines the highest
efficiency with the minimum bulk and weight - that is, which
pumps in the required air at the fastest rate. Installa-
tions of this type that meet the conditions required are the
compressors and the "dynamic pressure superchargers;" i.e.,
those utilizing the forward velocity of the airplane.
From the point of view of economy in the utilization
of energy, three types of superchargers are distinguished:
1) those whose driving power is derived from the gross out-
*"Dio Gestaltung von Flugmotorenladern." Luftfahrtforschung,
vol. 14, nos. 4/5, April 20, 1937, pp. 244-253.
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von der Nüll, W. The Design of Airplane-Engine Superchargers, report, October 1937; (digital.library.unt.edu/ark:/67531/metadc52953/m1/2/: accessed September 24, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.