Abstract
Improving the comprehension of turbomachinery fluid-dynamics is vital to increase their performance and calls for the improvement of advanced instrumentation. In this context, novel data acquisition and data reduction techniques have been recently developed at Politecnico di Milano for turbulence measurements performed with FRAPP. These improvements address a gap in the capabilities of such probes, as turbulence data were among the few information they could provide only on a quality level. First, the technique is validated against hotwire measurements on a low-speed wind tunnel, where a combustor simulator is inserted. Second, the probe is applied in relevant sections of a single-stage axial turbine, thanks to its robustness and reliability also in a harsh flow environment, where the use of hot wires is critical. In this paper, the measured turbulence intensity using FRAPP is compared among three different operating conditions obtained by changing the rotor rotational speed. Furthermore, the paper explores the impact of nonuniform stage inlet conditions resembling the combustor outlet disturbances. The regions with the highest turbulence levels are observed in areas characterized by secondary flows, wakes and residual swirl profile. The stator-rotor interaction contributes to the turbulence generation both downstream of the stator and the rotor. Additionally, an increase in blade loading corresponds to higher intensity in secondary flows, leading to elevated turbulence levels at rotor exit. The injection of combustor non-uniformities has a diminished impact as the rotor load increases, given that the flow field becomes predominantly influenced by strong secondary flows.
