High thermal efficiency in airplane service Page: 2 of 8
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NATIONAL ADVISORY CO ITT E FOR AERONAUTICS.
TECHNICAL NOTE NO. 39.
HIGH THERMAL EFFICIENCY IN AIRPLANE SERVICE.
S. W. Spa:rrov,
Automotive Power Plant Section,
Bureau of Standards.
To make higher engine efficiencies possible without
making every effort to insure the attainment of this higher
efficiency in actual service can seldom be justified. In
most cases the wide difference between the average per-
formance of an engine and that in the laboratory may be
attributed to the difficulty of the problem rather than to
failure to appreciate its importance. Instances where this
difficulty appears to have been surmounted are thus deserv-
ing of careful study.
In this regard, the details of design of certain for-
eign engines, whose high average efficiency has received
much publicity are of particular interest. In an examina-
tion of these engines at the Bureau of Standards, the un-
usual type of air-fuel ratio control suggested itself as
a possible source of the high efficiency. Fig. 2 shows
this type diagrammatically, while Fig. 1 is typical of a
construction common on American engines. In the latter
type, the rate of fuel flow is altered to produce the mix-
ture ratio changes. This may be accomplished by restrict-
ing the fuel passage or, as shown in the figure, by chang-
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Sparrow, S. W. High thermal efficiency in airplane service, report, December 1920; (digital.library.unt.edu/ark:/67531/metadc53714/m1/2/: accessed September 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.