Comparative Cooling of Cylinders of Nonuniform Fin Width With Tight-Fitting Baffles and With Baffles That Provide Constant Flow-Path Areas Page: 7 of 27
[25] p. : ill.View a full description of this report.
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in heat flow from the head to the barrel. In addition, the reduction
in piston temperatures resulting from the improved head cooling further
reduces the heat flow to the barrel (reference 4).
Two factors that affect barrel temperatures are the heat given up
to the lubricating oil and the blow-by past the piston rings. Because
the effect of these factors was not determined for the tests of this
cylinder, no conclusions can be drawn from the barrel temperatures.
An examination of cooling data for the two jackets for this cylinder
did indicate, however, that the decrease in average barrel temperature
due to improved head cooling should be of the order of 60 percent of
the decrease in average head temperature. This examination consisted
in plotting average head temperature against average barrel temperature
for both jackets. The data were obtained from unpublished tests in
which the following items were varied: indicated horsepower, fuel-air
ratio, spark setting, carburetor-air temperature, and cooling-air pres-
sure drop. This plot showed an approximate relationship between aver-
age head and average barrel temperatures; and, for the range of temper-
ature considered in this paper, this relationship indicated that, for a
change in average head temperature, the average barrel temperature
should change by the amount previously mentioned. A further examination
of these cooling data indicated that the value shown in table I for ther-
mocouple 9 for the original jacket is erratic.
Table II gives the differences between the temperatures at 32 points
on the Pratt & Whitney cylinder and the cooling-air temperature ahead of
the cylinder for two comparative series of data, one for the original
jacket and one for the revised Jacket. (See fig. 7 far thermocouple
locations.) The average head temperature Th is the average of temper-
atures of thermocouples 13 and 15 through ; the average barrel
temperature Tb is the average of thermocouples 2 through 11.
Table II shows that the hottest head temperature, indicated by
thermocouple 29 (see fig. 7 for location), was lowered 35 F by the
revision. The next three hottest head temperatures, indicated by
thermocouple 31 (fin space T-16, fig. 3), thermocouple 30 (fin space T-9,
fig. 3), and thermocouple 27 (fin space E-1), fig. 3) were reduced 90 F,
20 F, and 29P F, respectively, by the revision of the jacket. Although
thermocouple 29 was not in an interfin passage, it was located directly
behind an irregularly shaped interfin passage, which explains the
reduction in temperature at this point obtained by revising the jacket.
Several other thermocouples located in irregularly shaped interfin
passages were thermocouples 24, 25, and 32 (fin spaces 1-3, I-3, and
E-4, respectively, fig. 3). The temperatures at thermocouples 24
and 25 were reduced 40 F and 16 F, respectively, but the temperature
at thermocouple 32 was increased 100 F by the revision. The average
had and rear spark-plug-gasket temperatures were reduced 230 F and
4 F, respectively, by the revision,I i I I I I I II
mm
6
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Schey, Oscar W.; Rollin, Vern G. & Buckner, Howard A., Jr. Comparative Cooling of Cylinders of Nonuniform Fin Width With Tight-Fitting Baffles and With Baffles That Provide Constant Flow-Path Areas, report, April 1944; (https://digital.library.unt.edu/ark:/67531/metadc61906/m1/7/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.