Component and over-all performance evaluation of a J47-GE-25 turbojet engine over a range of engine-inlet Reynolds number indices

Walker, Curtis L., Braithwaite, Willis M., Fenn, David B.

An investigation was conducted in an altitude test chamber to evaluate the performance of an axial-flow turbojet engine over a range of engine-inlet Reynolds number indices. The range of Reynolds number indices investigated provided data which were applicable over a range of flight conditions, for example, altitudes from 15,000 to 55,000 feet at a flight Mach number of 0.7. Secondary effects of exhaust-nozzle flow coefficient, air-flow leakage, and inlet temperature which should be considered before analyzing the effect of variations in engine-inlet Reynolds number index are presented. In general, the effect of reducing Reynolds number index was to lower compressor efficiency and air flow with a resultant shift in the compressor map and rematching of compressor with turbine. There was only a slight effect of Reynolds number index variation on the turbine performance. Several minor design modifications proposed by the manufacturer (designated as a block change) did not produce any measurable improvement in engine performance.

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