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• March 24, 2016 Create Date
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National Advisory Committee for Aeronautics, Technical Notes - Performance at Low Speeds of Compressor Rotors Having Low-Cambered NACA 65-Series Blades with High Inlet Angels and Low Solidities

Three compressor rotors having low—cambered 6—percent-thick NACA
65—series blade sections were tested at low Speeds. The tests were made
at solidities of 0.5, 0.75, and 1.0, without guide vanes or stators,
over ranges of blade-setting angles and quantity-flow rates.

The rotor operated with an overall efficiency greater than 80 per-
cent for all solidities over a moderate range of angles of attack for
all blade—setting angles. The measured blade-element performance is
compared with performance estimated from two-dimensional cascade data
in order to extend the correlation of cascade and compressor—rotor data
over an inlet—angle range from 6&0 to 76°. The comparison indicates
that the measured.rotor turning angles were within £20 of those predicted
from cascade data.

Multistage axial—flow compressors are designed, in general, for
constant axial velocity and, when used as a part of the modern Jet engine,
require a short diffuser and/or a stator blade between the last stage and
the combustion chamber to reduce the velocity to practical limits. If
the absolute velocity leaving the last-stage rotor could be sufficiently
reduced by operating the later stages of the multistage compressor at
higher inlet angles and lower axial velocity, then air might be introduced
more directly into the combustion chamber. In order to determine if this
operation is practical, detailed design data of reference 1 have been
supplemented by low-speed two-dimensional data reported in reference 2 for
thin low-cambered NACA 65-series blade sections at high inlet angles and
low solidities.

Flow through a two-dimensional cascade is somewhat different from
that through rotating blade rows; therefore, a correlation is needed
between the simpler two-dimensional cascade flows and the flow through a
rotating compressor. Performance data of three rotors were obtained for
three blade—setting angles and for solidities of 0.5, 0.75, and 1.0 for
a range of inlet angles from 6&0 to 760 by using NACA 65-(c10A10)06 blade
sections (where etc is the design lift coefficient of an isolated air-
foil, as in ref. 2), and a comparison is made with two-dimensional data
of reference 2.