Validation of the gas generator method of calculating jet-engine thrust and evaluation of XB-70-1 airplane engine performance at ground static conditons
Henry H. Arnaiz, William G. Schweikhard, NASA Dryden Flight Research Center, United States. National Aeronautics and Space Administration
National Aeronautics and Space Administration, 1970 - Technology & Engineering - 43 pages
Deficiencies in established techniques of measuring aircraft thrust in flight led to the application of the gas generator method of calculating engine thrust to the XB-70-1 airplane. A series of tests on a ground static-thrust stand [were]performed on the airplane to establish at ground static conditions the accuracy of this method, to measure the installed thrust of the YJ93-GE-3 engine, and to determine the effect of instrumentation errors and nonuniform flows at the engine compressor face on the thrust calculation. Tests with an aerodynamically choked inlet, an opened inlet-bypass system, and varying combinations of operating engines were also conducted. Results showed that the accuracy of the gas generator method was ±2 percent for the normal operation of the XB-70-1 airplane at ground static conditions and for the upper 70 percent of the engine's throttle range. They also showed that the effect of individual instrument errors on the thrust calculation was reduced because of the large number of measurements and that abnormally high inlet flow distortion affects the thrust calculation. When corrected for inlet losses, the installed thrust of the YJ93-GE-3 engine agreed favorably with the engine manufacturer's uninstalled estimated thrust for all power settings except those at the low end.--P. [i].
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100-percent rpm 4100 Differential 60 80 Power-control-lever 80 Power-control-lever angle accuracy aircraft airplane calculated thrust characteristics Closed Closed Closed control room Differential 20 chamber engine airflow engine fuel flow engine net thrust engine performance Engine power settings Engine speed engines operating figure 17 flight testing flowmeter foreign object damage free-stream gas generator method gross thrust ground runs ground static-thrust tests inlet bypass test inlet duct inlet losses inlet throat choking instrumentation errors left-hand boundary-layer-control bleed left-hand inlet load cell loading platforms Mach number Maximum afterburner measured thrust method of calculating NASA November 20 obtained operating engines Percent change pit structure plot primary nozzle range ratio secondary nozzle sensors six-engine operation standard-day static pressure Zone static-thrust calibration facility terminal shock test conditions thermocouple throat choking test thrust calculation thrust error thrust loads thrust measuring thrust values thrust-calculating procedure total pressure total temperature transducers turbojet velocity XB-70-1 ground static-thrust