Exhaust Turbine and Jet Propulsion Systems Page: 3 of 50
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NACA TM 1294
The advantages of gas turbines as main power plants are essentially:
(1) The absence of oscillating masses; very high rpm's, therefore
minimum weight per unit power
(2) Cheap domestic fuels
(3) No alternating stresses, limitation of high tensile stresses
to few, easily exchangeable parts, thus long life; fewer
sources of disturbance, therefore, higher safety of
(4) Lessened fire risk
(5) No cooling, no ignition installation (except for pulse
In addition, there will probably be smaller over-all dimensions,
thus diminution of head drag, less noise, easier starting (due to elimi-
nation of compression), etc.
I. Gas and Blade Temperature
The reason that installations showing the advantages listed above
have not been constructed before now results, above all, from the fact
that the admissible gas temperatures which are limited by the occurring
blade temperatures were so low that the working process was not suffi-
ciently economical to promise ability of competing with the reciprocating
The investigations performed in the DVL concerning the influence of
the gas temperature on the blade temperature of exhaust turbines of
various designs brought the result that the partial loading of the tur-
bine rotor with relative-wind air is a suitable means of guaranteeing a
safe operating of the turbine even for very high gas temperatures.
For gas temperatures up to 10000 C, exhaust turbines of this type
of construction with 50 percent exhaust loading have, partly, completed
an operating time of 250 hours and proved good in every respect in the
altitude chamber up to 10 kilometers altitude as well as in flight tests
up to (for the present) about 8.3 kilometers flight altitude, and in
20-hour-runs at full power. In extensive special investigations of the
dependence of the blade temperatures on the gas temperature one measured,
for instance, in the test chamber (for gas temperatures of tg = 8900 C,
for the selected special profiles), blade temperatures of ts = 3900 C
which, for tg = 10000 C, increased to 4400 to 4600 C.
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Leist, Karl & Knörnschild, Eugen. Exhaust Turbine and Jet Propulsion Systems, report, April 1951; (digital.library.unt.edu/ark:/67531/metadc63008/m1/3/: accessed February 19, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.