Component and over-all performance evaluation of an axial-flow turbojet engine over a range of engine-inlet Reynolds numbers Page: 6 of 44
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standard atmosphere at sea level; 82 is the ratio of compressor-inlet
absolute total temperature to absolute total temperature of RACA stan-
dard atmosphere at sea level; and 02 is the ratio of viscosity at the
compressor-inlet total temperature to viscosity at NACA standard sea-
The inlet conditions were varied to correspond to Reynolds number
indices from 0.2 to 0.95. For each inlet condition the exhaust prese-
t sure was reduced to the minimum of the exhaust system with the engine
operating at rated speed. The inlet temperature and pressure and the
exhaust pressure were then maintained while data were taken over a range
of engine speeds from rated speed to approximately the speed where the
exhaust nozzle was barely choked. A summary of the operating conditions
covered in the investigation is given in the following table:
Reynolds Inlet Inlet Ram-
number total total pressure
index temperature pressure ratio
(oR) (lb/sq ft)
0.2 405 310 1.45
.3 405 465 1.4
.4 405 610 1.4
.4 465 740 1.78
.4 465 740 2.18
.5 465 923 1.78
.5 465 923 2.22
.6 465 1100 1.78
.95 520 2000 2.32
As shown in the table, three ram-pressure ratios P2/P0 were used at a
Reynolds number index of 0.4 and two at 0.5 to verify the generalization
with exhaust-pressure variation. At a Reynolds number index of 0.4, two
sets of inlet conditions were used to determine whether there were any
effects of temperature and pressure other than those of Reynolds number
REJESLS A1D DISCUSSION
The performance data obtained in this investigation were corrected
to standard sea-level conditions in the conventional manner (reference 2)
and are presented in table I. Generalization of data for various engine-
inlet conditions that give the same Reynolds number index requires choked
flow in the exhaust nozzle. The range of engine speeds over which the
exhaust nozzle of the engine was choked is shown in figure 5 for a range
of altitudes and flight Mach numbers. At all altitudes, this minimum
corrected engine speed at which choking occurred decreased linearly
NAGA RM E52B08
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Walker, Curtis L.; Huntley, S. C. & Braithwaite, W. M. Component and over-all performance evaluation of an axial-flow turbojet engine over a range of engine-inlet Reynolds numbers, report, July 10, 1952; (https://digital.library.unt.edu/ark:/67531/metadc59177/m1/6/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.