Steady and Unsteady Three-Dimensional Flow Field Downstream of an Embedded Stator in a Multistage Axial Flow Compressor: Part 1 — Unsteady Velocity Field

Abstract

A comprehensive investigation of the three-dimensional unsteady flow and thermal field downstream of an embedded stator in a multistage compressor, acquired with a high-response hot-film probe and aspirating probe, is presented and analyzed. Some of the earlier data (five-hole probe and high-response Kulite probe) from the same compressor is used with the present data to provide an integrated and comprehensive interpretation of the flow and thermal fields. The emphasis is on the unsteady flow, unsteady thermal, and integrated flow fields. Part 1 covers the description of the facility and the development of the hot-film technique for multistage flow field measurement. In addition, the unsteady velocity field is presented and interpreted. Part 2 provides an integrated assessment of the stagnation pressure, temperature and velocity fields to derive a comprehensive understanding of the time-averaged flow features. The final part covers velocity-velocity and velocity-temperature correlations and the assessment of their magnitudes in the average-passage equations. The results from an area traverse of the unsteady velocity field derived from a 45 degree slanted film probe downstream of the second stator of a three-stage axial flow compressor are presented and discussed in this paper. The measurements were conducted at the peak efficiency operating point using a four-rotation method. The ensemble-averaged unsteady three-dimensional velocity data is resolved into the time-averaged component, revolution and blade periodic, and aperiodic components. Some of the features of the rotor 2 flow, measured at the exit of stator 2, reveal the extent of the spread of the upstream rotor wakes and the unsteadiness due to rotor hub and leakage flow regions and levels of periodic and aperiodic unsteadiness. Both the revolution and blade periodic velocity fluctuations are seen to be significantly greater than the aperiodic fluctuations.