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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
MODELING AND SIMULATION OF TURBULENT FLOW OF SUPERCRITICAL CO2 IN CENTRIFUGAL COMPRESSOR
Submission Author:
Julia Matos , SP , Brazil
Co-Authors:
Julia Matos, Allan Carvalho, Paulo Eduardo Batista de Mello, Fabio Saltara, Daniel Dezan, Leandro Salviano, Jurandir Itizo Yanagihara
Presenter: Julia Matos
doi://10.26678/ABCM.ENCIT2020.CIT20-0120
Abstract
Computational Fluid Dynamics (CFD) has been widely used as a tool for designing, evaluating and improving turbomachinery and in this context supercritical cycles have gained the scientific community’s attention. This study proposes to model, simulate and evaluate the behavior of a centrifugal compressor operating with CO2 in the thermodynamic region above the vapor-liquid critical point. In 2010, Sandia National Laboratories released a report with information regarding its small-scale Brayton cycle operating with supercritical CO2 (S-CO2), which has already been mainly used for validation and analysis of numerical models. To obtain accurate results in of compressor’s performance, fundamental aspects of flows near the critical point were investigated. Thus, a simulation model in commercial software based on a finite volume method was developed from Sandia's experimental project. The flow was numerically modeled and assumed as steady-state, turbulent and three-dimensional and only the impeller was considered. The k-ω-SST turbulence model was adopted and three meshes with different degrees of refinement were generated with later study of the mesh independence carried out by the Grid Convergence Index (GCI) method, in which low numerical uncertainties were observed. The thermodynamic properties definition was made by the generation of specific tables for the working region, used by commercial software with equations of state from Span & Wagner for S-CO2. The results were validated in terms of pressure ratios for different cases by comparing their values with experimental ones, pointing an average mean error of 1.264%, with a maximum value of 3.012% and a minimum of 0.145%. 93.65% of the mesh elements exhibit Y+ values less than 10 and only 1.38% of the mesh elements exhibit Y+ values greater than 15. In 3D simulation, phenomenological and thermodynamic aspects were studied, in order to elucidate a greater degree of relevance of the variables related to the problem.
Keywords
Centrifugal Compressor, Supercritical CO2, CFD, Turbulence, Compressible flow
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