Session: 32-04 Low Pressure Turbines 1

Paper Number: 128711

128711 - Sealing Flow Rate Effects on Unsteady Loss Production in a Low Pressure Turbine Stage 

The interest in increasing efficiency in aircraft and power generation turbines has led to an increase in turbine inlet temperature (TIT). The increase of this parameter results in the need to create efficient cooling technologies able to keep the temperature of materials below the limit necessary to ensure mechanical properties. In addition, it is necessary to avoid hot gases ingestion into components not designed to withstand high temperatures, such as stator/rotor cavity disks. Nowadays, one way to improve the performance of gas turbines is to reduce the leakage flow rate and to optimize the sealing systems. This is because the losses due to the interaction process between the main flow and the flows entering/exiting the cavities are very significant in the case of stator/rotor cavity systems. In the present work, URANS simulations are carried out to describe the unsteady interaction process between the main flow and the ingested/ejected flow from a stator/rotor cavity system of a low-pressure turbine. Numerical simulations, performed on the cavity rig at the University of Genova, are compared and validated with experimental results acquired in previous work by the authors. The effect related to the stator/rotor interaction, and the related ingestion into the cavity of the wake generated by the upstream rotor rods, as well as the blocking effect related to the presence of the downstream rotor rods on the sealing properties of the cavity are studied in details. In this paper, several calculations are performed and analyzed, varying the flow rate of cooling air injected into the cavity. The value of the cooling flow rate ranges from zero to a value that can seal the cavity, avoiding ingestion of the flow from the main channel. For these cooling flow rates, the total pressure drop distribution is calculated. In this way, the effect that the cooling flow rate has on the stage efficiency and the leakage flow rate through the cavity can be understood. The analysis focused on the unsteady loss generation mechanisms acting outside the stator row and in the rear part of the axial slot separating the cavity flow ejection slot from the plane of the leading edge of the downstream rotor row. The results of the work provide a better understanding of the mechanisms responsible for producing additional losses and how this mechanism is affected by the cooling flow rate. This can help the designer to improve the efficiency of the LPT stage.

Presenting Author: Daniele Biassoni University of Genova

Presenting Author Biography: I am a PhD Student at University of Genova. I obtained the Master's Degree in Mechanical Engineering - Energy and Aeronautics. My research interests include design optimization of axial flow turbines and post-processing of big data from high fidelity CFD simulations.

Authors:

Dario Barsi University of Genova
Daniele Biassoni University of Genova
Davide Lengani University of Genova
Daniele Simoni University of Genova
Marina Ubaldi University of Genova