The Effects of Piston-Head Shape, Cylinder-Head Shape, and Exhaust Restriction, on the Performance of a Piston-Ported Two-Stroke Cylinder Page: 2 of 42
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NASA Technical i-.
3 1176 01433 74561U-HUtJt!-
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
TECHNICAL NOTE NO. 756
THE EFFECT OF PISTON-HEAD SHAPE, CYLINDER-HEAD SHAPE,
AND EXHAUST RESTRICTION, ON THE PERFORMANCE OF
A PISTON-PORTED TWO-STROKE CYLINDER
By A. R. Rogowski, C. L. Bouchard, and C. Fayette Taylor
SUMMARY
A full-scale, three-dimensional, steady-flow model
of the two-stroke engine described in WI.A.C.A. Technical
Note No. 674 (reference 1), was constructed for the pur-
pose of observing the scavenging-air flow obtained with
the various inlet--port arrangements tested in the actual
engine. Based on experience gained from correlation of
the flow tests with engine tests, several piston-head
shapes were developed, and the most promising wore tested
in the engine. Several modifications of the successful
round-edge piston previously used, were also tested. Three
types of cylinder head: spherical, cylindrical, and flat
in cross section were tried, first in the flow model and
then in the engine. The flat head was modified by milling
a portion of the surface away to form steps. ~The cylin-
drical and modified flat heads were run at various angles
to the plane of symmetry.
Piston-and cylinder-head shapes were developed at
compression ratio of 7, purely from the.standpoint of
scavenging, and would not be suited to compression-igni-
tion use without considerable modification.
A flat-top piston, with edge rounded to a 3/4-inch
radius was found best. The best cylinder-head shape tried
was spherical, with radius nearly the same as that of the
cylinder bore.
An investigation was also made of the possibility of
producing a supercharging effect by restricting the ex-
haust ports while using normal piston and cylinder head.
A limited amount of supercharging was found possible by
this means, but the not gain was small owing to inc eas6d
pumping loss.
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Rogowski, A. R.; Bouchard, C. L. & Taylor, C. Fayette. The Effects of Piston-Head Shape, Cylinder-Head Shape, and Exhaust Restriction, on the Performance of a Piston-Ported Two-Stroke Cylinder, report, March 1940; (https://digital.library.unt.edu/ark:/67531/metadc54614/m1/2/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.