Development and Experimental Validation of Real Fluid Models for CFD Calculation of ORC and Steam Turbine Flows

Abstract

The article describes an interpolation–analytical method of reconstruction of the IAPWS-95 equations of state and the modified Benedict–Webb–Rubin equations of state with 32 terms (mBWR32). The method enables us to provide the thermodynamic closure in 3D computational fluid dynamics (CFD) calculations of turbomachinery flows with real working media, such as steam and Organic Rankine Cycle (ORC) fluids. The described approach allows for the sufficient accuracy of 3D flow calculations and does not require a significant increase in computational cost over perfect gas calculations. The method is validated against experimental data from measurements and compared with computational results from the model using the Tammann equation of state. Three turbine blading systems are considered—a multi-stage configuration from a low-pressure cylinder of a large-power steam turbine and two ORC microturbines working with organic media HFE7100 and R227ea. The calculation results obtained using the described method of approximation of the IAPWS-95 and mBWR32 equations exhibit satisfactory agreement with the experimental data, considering pressures, temperatures and enthalpies in key sections, as well as turbine power and efficiency in a wide range of changing thermodynamic parameters. In contrast, the Tammann equation of state provides acceptable results only for relatively small changes of thermodynamic parameters.

Archives of Thermodynamics

“…The mathematical model of the package is based on the numerical integration of the Reynolds-averaged unsteady Navier-Stokes equations with the use of an implicit quasi-monotonic essentially non-oscillatory scheme ENO-scheme of increased accuracy and Menter's k-ω SST (shear stress transport) two-equation turbulence model [18]. To take into account the thermodynamic properties of steam, the method of interpolation-analytical approximation of the IAPWS-95 equations was used [19,20]. The results obtained with the use of IPMFlow software package have the necessary reliability both by the qualitative structure of the flow and by quantitative assessment of the characteristics of an isolated turbine stage and flow parts of turbomachines as a whole [21].…”