Investigation of Turbojet Engine Performance at Speeds and Gas Temperatures Above Rated Using Turbine-Blade External Water-Spray Cooling from Stationary Injection Orifices Page: 2 of 33
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NACA RM E54G30
NATIONAL ADVISORY COlTTEE FOR AERONAUTICS
INVESTIGATION OF TURBOJET ENGINE PERFORMANCE AT SPEEDS AND GAS TE~AERA-
TURES ABOVE RATED USING TURBINE-BLADE EXTERNAL WATER-SPRAY
COOLING FROM STATIONARY INJECTION ORIFICES
By John C. Freche and Roy A. McKinnon
As another phase of an investigation of external water-spray cool-
ing of turbine rotor blades, a turbojet engine with a centrifugal-nrow
compressor which permitted overspeed, overtemperature operation was mod-
ified for spray cooling. A stationary water-injection configuration
which consisted of two large (0.200-in. diam.) and two small (0.052-in.
diam. ) stationary orifices located in the inner ring of the stator dia-
phragm near the stator blade trailing edges was used. The effective-
ness of spray cooling as a method which permits operation at overspeed,
overtemperature conditions with this engine was investigated and the
overspeed, overtemperature performance was obtained.
Operation with spray cooling was conducted over a range of speeds
from rated (11,750 rpm) to approximately 107 percent rated and turbine
inlet-gas temperatures up to 20000 F. At approximately 107 percent rated
speed 19400 F inlet-gas temperature, and a coolant-to-gas flow ratio of
0.029 (9070 lb of coolant/hr), both the blade root and midspan were ap-
parently cooled satisfactorily. The average blade root temperature was
about 2000 F with a maximum temperature- difference of 1000 F existing
between the blade leading and trailing edges. The average midspan tem-
perature was approximately 6000 F, and the maximum temperature difference
between the leading and trailing edges was about 4000 F. Substantial
chordwise temperature differences, approximately 10000 F, occurred at
the blade tip, between the midchord and the trailing edge. Several rotor
blade failures occurred near the tip which could be attributed to thermal
stresses induced by these temperature differences. The failures indi-
cated the need for more uniform cooling at the blade tip, although the
injection configuration employed may be satisfactory for limited appli-
cation and appears promising for blades of shorter span.
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Freche, John & McKinnon, Roy A. Investigation of Turbojet Engine Performance at Speeds and Gas Temperatures Above Rated Using Turbine-Blade External Water-Spray Cooling from Stationary Injection Orifices, report, October 11, 1954; (digital.library.unt.edu/ark:/67531/metadc62727/m1/2/: accessed February 19, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.