NACA RM SE53F30

APPARATUS
Engine and Installation
The J73 turbojet engine used in this investigation has a thrust of
approximately 9000 pounds, a rated engine speed of 7950 rpm, and
an exhaust-gas temperature of 11850 F (16450 R). The engine is normally
equipped with an hydraulic control system which was inoperative during
this phase of the investigation. For these tests, the fuel system was
so modified that fuel flow was a function of fuel-valve position only.
Other engine components are a 12-stage axial-flow compressor with vari-
able inlet guide vanes, an annular-type combustor with 10 cannular-type
chambers, a two-stage axial-flow turbine, and a fixed-area exhaust
nozzle.
The engine was mounted in a 14-foot diameter altitude chamber. A
group of automatic throttle valves was incorporated at both inlet and
exhaust ends of the test chamber to provide control of simulated altitude
and ram-pressure ratio.
Instrumentation
The transient responses of the engine variables were recorded on
a multiple channel., direct-inking, magnetic motor oscillograph. The
oscillograph chart speed was 5 units per second.
The location of the measuring stations are shown in figure 1. The
sensing devices used for indicating variations in the performance
parameters are given in table I. Inasmuch as the total-pressure profile
at the engine inlet was flat, it was possible to select almost any total-
or static-pressure sensor to record on an oscillograph trace or its
corresponding calibration gage without introducing errors. In the case
of compressor-outlet total pressure, the sensor selected for both the
oscillograph and the calibration gage was approximately the average
total pressure at that station, as indicated from earlier steady-state
data. Appropriate correction factors were employed where necessary for
gage error and sensor location.
PROCEDURE
The oscillograph traces were calibrated by operating the engine at
several widely different engine operating points and recording the
corresponding pen deflections on the oscillograph trace. Fuel changes
were introduced over a range of initial engine speeds at the conditions
shown in the following table:

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