Effect of inlet temperature and humidity on thrust augmentation of turbojet engine by compressor-inlet injection Page: 3 of 48
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NACA RM E50D19
results of experimental investigations of this method of thrust aug-
mentation for centrifugal-flow engines, which included the injection
of water and water-alcohol mixtures, are reported in references 1
and 2. These investigations, however, were conducted without con-
trol of inlet temperature or humidity. An investigation, therefore,
has been conducted to determine the effect of compressor-inlet tem-
perature and humidity on engine performance with injection at the
compressor inlet, and the results are reported herein.
For this investigation, which was conducted at conditions of
zero ram and sea-level pressure, the inlet temperature was controlled
by mixing atmospheric air with exhaust gases recovered from the
exhaust jet of the engine used for the tests. By this method of
heating, the compressor-inlet temperature was varied over a range
from 600 F to 2300 F. The performance of the engine was determined
for no injection and over a range of injection rates from I to
4 pounds per second for various mixtures of water and alcohol. Both
fixed-area and variable-area tail-pipe exhaust nozzles were used.
Rated engine speed and tail-pipe temperature were maintained for all
operating conditions while using the variable-area nozzle, and,
depending on operating conditions, either rated speed or rated tail-
pipe temperature was maintained while using the fixed-area nozzle.
The effect of specific humidity of the inlet air on both unaugmented
engine performance and engine performance at two injection rates was
investigated over a range from 50 to 280 grains per pound at two
compressor-inlet temperatures. For these tests, the inlet humidity
was varied by evaporating water in the hot exhaust gases used for
heating the inlet air.
Egine. - The engine used in this investigation was a J33
centrifugal-flow turbojet engine with a sea-level, static-thrust
rating of 4000 pounds when operated at a speed of 11,500 rpm and
tail-pipe temperature of 12000 F. Both a 19-inch conical fixed-area
and a clamshell-type variable-area exhaust nozzle were used.
Engine installation and bleedback system. - As shown in fig-
ure 1, the test equipment was enclosed in two adjacent chambers:
a closed cell containing the engine proper, and a muffler into which
the exhaust jet was discharged. The engine and inlet cowl were
mounted on a frame suspended from the ceiling of the test cell by
rods with ball-bearing ends, and the engine tail pipe moved freely
through a sliding seal in the wall separating the cell and muffler.
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Shillito, Thomas B. & Harp, James L., Jr. Effect of inlet temperature and humidity on thrust augmentation of turbojet engine by compressor-inlet injection, report, July 3, 1950; (https://digital.library.unt.edu/ark:/67531/metadc58542/m1/3/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.