<DOC>
<DOCNO>
695
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<TITLE>
some experiments relating to the problem of simulation of hot jet
engines in studies of jet effects on adjacent surfaces at a free-stream
mach number of 1.80 .
</TITLE>
<AUTHOR>
bressette, w.e.
</AUTHOR>
<BIBLIO>
naca rm l56e07. 1956 .
</BIBLIO>
<TEXT>
an investigation at a free-stream mach number of 1.80 in a blowdown type
 tunnel was made to study the effect on the pressure distribution of a
zero angle of attack wing surface when certain exhaust parameters of a
hot turbojet engine are varied . static-pressure surveys were made on a
wing surface that was located in the vicinity of a small-scale propulsive
jet . this propulsive jet was operated with four types of jet
exhausts . these jet exhausts were a hot jet /hydrogen burned in air/, a
 cold air jet, a cold helium jet, and a jet composed of a mixture of two
 cold gases /hydrogen and carbon dioxide/ . the hot jet, because of its
high exhaust temperature /3,300degreer/ and because combustion was
performed in air, was believed reasonably able to simulate the exhaust
parameters of an actual afterburning turbojet engine . the cold jets
used were selected in order that the effects of a variation in the exhaust
parameters of jet-exit static-pressure ratio, ratio of specific
heats, density, and velocity, could be obtained by comparing each cold
jet with the hot jet or with another cold jet . the tests were made over
 a range of jet-exit staticpressure ratios from 1 to 9 with values of
the ratio of specific heats of 1.27, 1.40, and 1.66 and at variations in
 density and velocity of the order of approximately 8 and 3 times,
respectively .
within the scope of this investigation, it was found that jet-exit
static-pressure ratio and the ratio of specific heats affected the
pressure distribution on the wing associated with jet interference while
 a variation in exit velocity and density did not . the jet-exit
staticpressure ratio affected the wing pressure distribution in a major
way while the ratio of specific heats had only a minor effect . the
addition of temperature in the propulsive jet exhaust at a jet-exit
staticpressure ratio of 4 had little or no effect on the pressure distribution
associated with jet interference on the wing .
</TEXT>
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