Preliminary Transient Performance Data on the J73 Turbojet Engine, 3: Altitude, 45,000 Feet Page: 4 of 96
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NACA 1R SE55F30
Altitude, Flight Mach Inlet guide Type of Engine-inlet
ft number vane position fuel temperature,
45,000 0 Open Step 60
.8 Open Step 35, 75
.8 Open Ramp 35 75
.8 Closed Step 55
The variable inlet guide vanes, which normally move from closed to open
position at an engine speed of 6800 rpm as speed was increased, were
maintained in a fixed closed or open position during all transients of
this phase of the investigation.
The size of the fuel step or ramp changes was increased until
limited by either compressor surge or combustor blow-out or until it was
felt that large steps in fuel flow would expose the engine to exces-
sively high temperature. Only the traces which were considered pertinent
in determining an operating limit are presented. Thus, in general, at
any given initial engine speed two traces are shown. One gives the
maximum step or ramp change in fuel flow obtained without encountering
compressor surge or stall. The other gives the minimum step or ramp
change in fuel flow which produced compressor surge or stall.
During the period of transient engine operation, both the engine-
inlet total pressure and the exhaust pressure varied from the initial
value. However, the engine operating limit usually occurred before the
engine-inlet total pressure or the exhaust pressure changed appreciably.
The time history of the behavior of the engine-inlet total pressure
during transient engine operation is shown on the oscillograph traces,
but the variation of exhaust pressure is not shown. In general, the
maximum increase in exhaust pressure was 7 percent of the initial value.
The conditions for each oscillograph trace (figs. 2 to 73) pre-
sented herein are given in table II. On each set of oscillograph traces
the figure legend specifies the engine conditions at the beginning of
the change in fuel flow. Each trace is identified by a label below
which is given the calibration factor for the trace. As indicated by
the calibration factor, all traces are considered linear except the
fuel-flow trace which follows the square-law relation. On each trace
is shown the initial value of the engine variable. In the case of
fuel flow, one or more additional values are given. The arrows on each
figure indicate the direction in which the variable is increasing.
Caution should be used in applying the calibration factors to the
traces. Although the horizontal or time scale is linear, the vertical
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McAulay, John E. & Wallner, Lewis E. Preliminary Transient Performance Data on the J73 Turbojet Engine, 3: Altitude, 45,000 Feet, report, July 16, 1953; (digital.library.unt.edu/ark:/67531/metadc65444/m1/4/: accessed February 19, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.