Numerical Investigation of the Flow Behavior Inside a Supercritical CO2 Centrifugal Compressor

Centrifugal compressors are one of the best choices among compressors in supercritical Brayton cycles. A supercritical CO2 centrifugal compressor increases the pressure of the fluid which state is initially very close to the critical point. When the supercritical fluid is compressed near the critical point, wide variations of fluid properties occur. The density of carbon dioxide at its critical point is close to the liquid density which leads to reduction in the compression work. This paper explains a method to overcome the simulation instabilities and challenges near the critical point in which the thermophysical properties change sharply. The investigated compressor is a centrifugal compressor tested in the Sandia supercritical CO2 test loop. In order to get results with the high accuracy and take into account the nonlinear variation of the properties near the critical point, the computational fluid dynamics (CFD) flow solver is coupled with a look-up table of properties of fluid. Behavior of real gas close to its critical point and the effect of the accuracy of the real gas model on the compressor performance are studied in this paper, and the results are compared with the experimental data from the Sandia compression facility.

[1]  Robert Fuller,et al.  Performance Characteristics of an Operating Supercritical CO2 Brayton Cycle , 2012 .

[2]  Eric M. Clementoni,et al.  Supercritical Carbon Dioxide Brayton Power Cycle Development Overview , 2012 .

[3]  G. Angelino.  Carbon Dioxide Condensation Cycles For Power Production , 1968 .

[4]  F. Menter.  Two-equation eddy-viscosity turbulence models for engineering applications , 1994 .

[5]  Stefano Rebay,et al.  Influence of Thermodynamic Models in Two-Dimensional Flow Simulations of Turboexpanders , 2010 .

[6]  Benjamín Monge Brenes.  Design of supercritical carbon dioxide centrifugal compressors , 2014 .

[7]  W. Wagner,et al.  A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple‐Point Temperature to 1100 K at Pressures up to 800 MPa , 1996 .

[8]  M. McLinden,et al.  NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 8.0 , 2007 .

[9]  Z. Spakovszky,et al.  An Investigation of Real Gas Effects in Supercritical CO2 Centrifugal Compressors , 2015 .

[10]  Enrico Rinaldi,et al.  Computational Fluid Dynamic Simulation of a Supercritical CO2 Compressor Performance Map , 2015 .

[11]  Nikola D. Baltadjiev.  An investigation of real gas effects in supercritical CO₂ compressors , 2012 .

[12]  Hiroshige Kikura,et al.  Research on Flow Characteristics of Supercritical CO2 Axial Compressor Blades by CFD Analysis , 2010 .

[13]  Gary E Rochau,et al.  Operation and analysis of a supercritical CO2 Brayton cycle. , 2010 .

[14]  Gary E Rochau,et al.  Summary of the Sandia Supercritical CO2 Development Program (Presentation). , 2011 .

[15]  Enrico Rinaldi,et al.  Computational Fluid Dynamics of a Radial Compressor Operating With Supercritical CO2 , 2012 .

[16]  Stefano Rebay,et al.  Real-gas effects in Organic Rankine Cycle turbine nozzles , 2008 .

[17]  Vaclav Dostal,et al.  A supercritical carbon dioxide cycle for next generation nuclear reactors , 2004 .