This two-part paper presents detailed laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective of this study was to provide additional insight into unsteady blade-row interactions within high speed compressors which affect stage efficiency, energy transfer, and other design considerations. Part I of this paper describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the “rotor-wake-generated” and “unresolved” unsteadiness, respectively. The term “rotor-wake-generated” unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term “unresolved” unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctuations, etc. A procedure for calculating auto and cross correlations of the rotor-wake-generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.

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