Time-Space Evolution of Secondary Flow Structures in a Two-Stage Low-Speed Turbine

Abstract

The aim of this work is to highlight the unsteady effects related to wake-blade and blade rows interactions, but also the time-space evolution of secondary flow structures in a two-stage low-speed turbine model designed and constructed to perform unsteady measurements with different techniques [1]. In this case attention has been addressed to the analysis of the flow field in the first stage of the turbine model. Measurements are performed with aerodynamic probes downstream of the first stator and using a single slanted hot-wire anemometer downstream of the first rotor. Time-dependent relative flow field downstream of the first rotor (obtained from phase-locked averaging technique) have been reconstructed for different relative positions between stator and rotor blades. From these results the time-dependent secondary flow vectors have been obtained as well. The mean reference flow used to determine the secondary flow structure has been evaluated for each frame by mass-averaged technique. The evolution of the secondary flow structure due to the influence of the upstream and downstream stators on the first rotor has been investigated. The main unsteady effects put in evidence the variation of the intensity and spatial extension of the vortex flow structure.