Session: 14-05: Turbine Rim Seal and Rotor-Stator Cavity 2

Paper Number: 153660

Numerical Analysis of Sealing Flows in Gas Turbines Using RANS and LES Approaches 

The flow field developing inside the stator-rotor disc cavity of gas turbines is characterized by highly complex and unsteady behavior, which presents a significant challenge for numerical prediction. The complex nature of the flow, due to strong vortical structures and transient interactions, makes it challenging to be accurately predicted by standard Computational Fluid Dynamics models. The inherent unsteadiness of the involved flow field has a considerable impact on the sealing effectiveness, particularly when predicted by steady Reynolds-Averaged Navier-Stokes (RANS) methods, which tend to overestimate the efficiency of the rim seal by more than an order of magnitude. In this study, a series of numerical simulations were conducted using RANS, unsteady RANS (URANS), and large Eddy Simulation (LES) approaches to gain insight into the rim seal flow. The main objective was to compare the numerical results with experimental data obtained from the test bench at the University of Florence, in order to validate the accuracy of the simulations with real measurements.[AA1]  The RANS, URANS, and LES simulations all demonstrated satisfactory agreement with steady-state measurements of pressure coefficients and velocity fields, offering valuable insight into the time-averaged behavior of the flow. However, the Reynolds-averaged models failed to effectively represent the turbulent fluctuations between the main flow and the secondary flow that drive the ingestion process, which is one of the non-negligible factors for the ingestion of mainstream flow into the cavity. In contrast, LES simulations accurately captured the development of vortices and replicated more realistic flow conditions, resulting in a closer match with experimental data. Therefore, the turbulent fluctuations resolved by LES appeared to be crucial for understanding the unsteady interaction between the mainstream and secondary flows. Although the high computational cost and long transient phases required to reach periodic convergence make LES a resource-intensive approach, it shows great potential to predict this interaction and provide valuable insights into the complex dynamics of the flow.

Presenting Author: Alessio Di Geronimo University of Florence

Presenting Author Biography: Ph.D. student at DIEF of University of Florence. The Ph.D. research is focused on the development of numerical methodologies for the study of secondary air systems and stator/rotor cavities in industrial and aeronautical gas turbines.

Authors:

Alessio Di Geronimo University of Florence
Lorenzo Orsini University of Florence
Antonio Andreini University of Florence
Alessio Bonini Baker Hughes