Effects of Inlet-Flow-Air Distortion on Steady-State Altitude Performance of an Axial-Flow Turbojet Engine Page: 4 of 49
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NACA RM E55A04
The effects of distortion.were assessed with respect to ccpressor
surge limits, aerodynamic conditions within the engine, component per-
formance, over-all engine performance, and compressor blade vibration.
The first two items are discussed in reference 6, and the last three are
covered herein with sufficient aerodynamic information to aid in ex-
plaining the observed results.
The variable inlet guide vanes of the engine used for this study
.ere scheduled to move from a closed to an open position at an inter-
mediate engine speed. For this study, however, data were obtained over
a complete range of corrected engine speeds with both open and closed
juide vanes. With the guide vanes open, data were also obtained with
the exhaust nozzle open as well as at the rated area. The investigation
covered a range of altitudes from 15,000 to 50,000 feet at a flight Mach
number of 0.8.
ENGINE AND INSTALLATION
The engine used in this investigation is shown in figure 1 in-
stalled in the altitude test chamber. The engine is in the 9000-pound-
thrust class with a rated speed of 7950 rpm and a rated turbine-outlet
temperature of 11850 F. It was comprised of a 12-stage axial-flow can-
pressor, a cannular combustor with 10 can-type liners, a two-stage tur-
bine, and an exhaust nozzle. A variable-area exhaust nozzle was used
during the study reported herein. The important compressor parameters
are:
Inlet hub-tip ratio ... . .................... O.455
Pressure ratio at rated conditions ............... 7.0
Air flow at rated speed, lb/sec ............ ..... 142
Rated engine speed, rpm . ...... .... .......... 7950
In order to provide ample surge margin at reduced engine speeds,
the engine was equipped with variable-position inlet guide vanes which
rotated 300 fran the closed to open position. The guide vanes were
scheduled to begin opening at 6000 to 6300 rpm and to reach the open
position at 7000 to 7300 rpm; the opposite was true as the speed de-
creased. For this investigation, however, manual operation of the vanes
was substituted.
Because an instrumentation failure extensively damaged one engine
part way through the investigation, a second engine of the same produc-
tion configuration was used to complete the program. Slight differences
in performance and distortion effects were found, and the engines are
therefore designated when specific results are given.3
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Conrad, E. William; Hanson, Morgan P. & McAulay, John E. Effects of Inlet-Flow-Air Distortion on Steady-State Altitude Performance of an Axial-Flow Turbojet Engine, report, September 27, 1955; (https://digital.library.unt.edu/ark:/67531/metadc61089/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.