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National Advisory Committee for Aeronautics, Technical Notes - Experimental Investigation of an Impulse Type Supersonic Compressor Rotor Having a Turning of 73° at the Mean Radius

The potentiality of the impulse supersonic compressor to produce
very high pressure ratio per stage has created considerable interest in
its use for turbojet engines. In this type of compressor, the flow is
turned through a very large angle with_little or no pressure rise. The
flow leaving the rotor is supersonic and must be diffused in the stator
where the kinetic energy imparted by the rotor is converted to static
pressure. The demand for high-performance compressors in aircraft pro—
pulsion has initiated several theoretical and experimental studies of
the supersonic impulse rotor. (For example, see refs. 1 to 9.) None

of the existing methods of design has resulted in an accurate prediction
of the operation of a supersonic impulse rotor.
The performance values of the impulse rotors alone given in refer-
ences 8 and 9 were good; however, attempts to recover the kinetic energy
by placing stators behind the rotor have generalLy resulted in poor
stage performance. Even though the successful design of stators seems
to be the major problem in supersonic impulse compressors, the design
of efficient rotor sections remains important since poor flow condi—
tions leaving a rotor would increase the difficulty of obtaining good
pressure recoveries in the stator. _

The present paper is part of an investigation performed at the
Langley Laboratory of the NACA in an effort to develop a supersonic
impulse rotor with uniform exit flow and a design method which accu-
rately predicts the operation of a supersonic impulse rotor. In the ,
present study, an impulse rotor was designed by using a simplified quasi-
three-dimensional.design. The method used was to design sections which
were effectively based on the two-dimensional vortex-flow theory (ref. 5)
but modified to account partially for the compressions due to the three-
dimensional flow.