Steady-state and surge characteristics of a compressor equipped with variable inlet guide vanes operating in a turbojet engine Page: 3 of 56
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The present paper is an analysis of the following experimental in-
vestigations of a current production engine with a compressor having
variable-position inlet guide vanes:
(1) Internal aerodynamic phenomena in the low-speed region where
steady-state stall often exists and the high-speed region of
stall-free compressor operation
(2) Engine accelerations to determine compressor surge character-
istics, amplitudes, frequencies, and reproducibility
(3) Effects of variations in inlet-guide-vane position on compressor
surge pressure ratio and engine surge fuel flow, and effects of
flight condition on engine surge limits
This report presents a comprehensive examination of the internal per-
formance of the compressor. Compressor surge limits are presented in
terms of compressor pressure ratio, engine fuel flow, and engine speed.
The steady-state stall operation is shown in terms of stage pressure
ratios, temperature ratios, and pressure coefficients. Effects of inlet-
guide-vane position and stall on over-all compressor performance are
demonstrated by plots of pressure ratio as functions of speed and air
flow.
The investigation was made at the NACA Lewis laboratory at simulated
altitudes from 15,000 to 45,000 feet, flight Mach numbers from 0.3 to 1.2,
and inlet-air temperatures from ambient to 1600 F. Engine speed was
varied from about 60 to 100 percent of rated speed.
APPARATUS
The subject turbojet engine, which is in the 9000-pound-thrust class,
is shown installed in the altitude test chamber in.figure 1. The 12-
stage axial-flow-compressor rotor is shown in figure 2. Thelrotor tip
diameter, which is constant for all compressor stages, is 32- inches.
The hub-tip radius ratio varies from 0.46 at the first stage to 0.88 at
the twelfth stage. At rated engine operating conditions (7950 rpm), the
sea-level performance of-the compressor is as follows:
Air flow, W, lb/sec .... . .................... 141
Adiabatic efficiency, r . . .. ..... ... ..... . . . .0.81
Pressure ratio, P3/P2 . ...................... . . . .6.9
The compressor is equipped with variable-position inlet guide vanes
to improve the off-design performance. The guide-vane assembly consists
of 21 blades whose angle setting can be varied from 130 to 43. In the,... 'C.L
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Wallner, Lewis E. & Lubick, Robert J. Steady-state and surge characteristics of a compressor equipped with variable inlet guide vanes operating in a turbojet engine, report, June 20, 1955; (https://digital.library.unt.edu/ark:/67531/metadc60969/m1/3/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.