Abstract
The paper describes the development and validation of a novel computational fluid dynamics (CFD)-based throughflow model. It is based on the axisymmetric Euler equations with tangential blockage and body forces and inherits its numerical scheme from a state-of-the-art CFD solver (TRAF code). Secondary and tip leakage flow features are modelled in terms of Lamb–Oseen vortices and a body force field. Source and sink terms in the governing equations are employed to model tip leakage flow effects. A realistic distribution of entropy in the meridional and spanwise directions is proposed in order to compute dissipative forces on the basis of a distributed loss model. The applications are mainly focused on turbine configurations. First, a validation of the secondary flow modelling is carried out by analyzing a linear cascade based on the T106 blade section. Then, the throughflow procedure is used to analyze the transonic CT3 turbine stage studied in the framework of the TATEF2 (Turbine Aero-Thermal External Flows) European program. The performance of the method is evaluated by comparing predicted operating characteristics and spanwise distributions of flow quantities with experimental data.
Highlights
The design process of multistage turbomachinery is based on the efficient use of the currently available tools, such as one-dimensional meanline models, 2D or quasi-3D blade-to-blade, throughflow and 3D viscous, steady, and unsteady analyses
The subject is not new, the proposed methodology attempts to address the issue with simple phenomenological models that naturally fit into the computational fluid dynamics (CFD)-based structure of the throughflow solver
It is intended to provide a framework for the simulation of secondary flows and tip leakage effects, while leaving the task of estimating losses and other required bulk quantities to correlations
Summary
The design process of multistage turbomachinery is based on the efficient use of the currently available tools, such as one-dimensional meanline models, 2D or quasi-3D blade-to-blade, throughflow and 3D viscous, steady, and unsteady analyses. Throughflow methods traditionally represent a key tool for turbomachinery design In preliminary stages, they are able to provide the designer with realistic spanwise distributions of flow parameters. Heavily dependent on empirical correlations for viscous losses and deviations, just like traditional approaches, such methods have no major difficulties in dealing with subsonic, transonic, or supersonic flow regimes. They are able to capture shock waves inside bladed or non-bladed regions of the flow-path, providing a more realistic meridional flow field with respect to classical methodologies. The paper focuses on turbines, but the proposed methodology can be extended to treat compressors cases as well
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