Version 1
: Received: 19 October 2024 / Approved: 21 October 2024 / Online: 22 October 2024 (08:28:54 CEST)
How to cite:
Da Valle, L.; Torre, A. F. M.; Merli, F.; Cernat, B. C.; Lavagnoli, S. Cavity Instabilities in a High-Speed Low-Pressure Turbine Stage. Preprints2024, 2024101675. https://doi.org/10.20944/preprints202410.1675.v1
Da Valle, L.; Torre, A. F. M.; Merli, F.; Cernat, B. C.; Lavagnoli, S. Cavity Instabilities in a High-Speed Low-Pressure Turbine Stage. Preprints 2024, 2024101675. https://doi.org/10.20944/preprints202410.1675.v1
Da Valle, L.; Torre, A. F. M.; Merli, F.; Cernat, B. C.; Lavagnoli, S. Cavity Instabilities in a High-Speed Low-Pressure Turbine Stage. Preprints2024, 2024101675. https://doi.org/10.20944/preprints202410.1675.v1
APA Style
Da Valle, L., Torre, A. F. M., Merli, F., Cernat, B. C., & Lavagnoli, S. (2024). Cavity Instabilities in a High-Speed Low-Pressure Turbine Stage. Preprints. https://doi.org/10.20944/preprints202410.1675.v1
Chicago/Turabian Style
Da Valle, L., Bogdan Cezar Cernat and Sergio Lavagnoli. 2024 "Cavity Instabilities in a High-Speed Low-Pressure Turbine Stage" Preprints. https://doi.org/10.20944/preprints202410.1675.v1
Abstract
This study investigates the time-resolved aerodynamics in the cavity regions of a full-scale, high-speed low-pressure turbine stage representative of geared turbofan engines. The turbine stage is tested in the von Karman Institute’s short-duration rotating facility at different purge rates (PR) injected through the upstream hub cavity. Spectra from the shroud and downstream hub cavity show perturbations linked to blade passing frequency and rotor speed. Asynchronous flow structures associated with ingress/egress mechanisms are observed in the rim seal of the purged cavity. At 0% PR, the ingress region extends to the entire rim seal, and pressure fluctuations are maximized. At 1% PR, the instability is suppressed and the cavity sealed. At 0.5%, the rim-seal instability exhibits multiple peaks in the spectra, each corresponding to a state of the instability. Kelvin-Helmholtz instabilities are identified as trigger mechanisms. A novel technique, based on the properties of the cross-power spectral density, is developed to determine speed and wavelength of the rotating structures, achieving higher precision than the commonly used cross-correlation method. Moreover, unlike the standard methodology, this approach allows to calculate the structure characteristics for all the instability states. Spectral analysis at the turbine outlet shows that rim-seal-induced instabilities propagate into regions occupied by secondary flows. A methodology is proposed to quantify the magnitude of the induced fluctuations, showing that the interaction with secondary flows amplifies the instability at the stage outlet.
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
,
