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National Advisory Committee for Aeronautics, Technical Notes - Method of Experimentally Determining Radial Distributions of Velocity Through Axial Flow Compressor

A method is presented by which the energy and continuity rela-
tions are simultaneously solved to express the velocity distributions
downstream of any compressor blade row in terms of outlet total
temperature, total pressure, and relative flow angle. The method
is intended for use in units in which only a limited amount of
experimental data can be obtained. The determination of the veloci-
ties downstream of a stationary blade row assumes that the con-
dition of simple radial equilibrium is satisfied and that the
entropy is constant along the radius. The method for the rotor
requires no such assumption, however, and the effect of the radial
displacement of flow passing through the rotor is considered.

The experimental determination and analysis of the performance
of a multistage axial-flow compressor requires a knowledge of the
radial distribution of flow in the individual components of each
stage. Several methods of determining radial distributions of
flow downstream of a blade row have previously been devised pri-
marily for design andtheoretical studies (references 1 to 3).

These methods are not readily applicable to the problem
of experimental evaluation of flow distributions in an existing
compressor. One of these methods of computing the velocity distri-
bution has been presented in reference 1 and simplified in refer-
ence 2. This method, which is based on simple radial equilibrium
and incompressible flow, defines the axial-velocitydistribution
in terms of the absolute tangential-velocity distribution. Refer-
ence 5 presents a. general method of determining the radial distri-
bution of flow for the compressible case, which considers the
radial displacement of flow in passing through a blade row. This
general method is also expressed in terms of absolute velocity
distributions and absolute flow angles.