Small-scale radial turbine pre-design model for ORCs

Here are gathered the different polynomial functions that estimate the performance of a small scale radial inflow turbine function of specific speeds (ns), specific diameters (ds) and pressure ratio (PR). Four sets of functions performed with varying shroud to tip radius ratio (epsilon=r6s/r4=[0.5 0.6 0.7 0.8]) are presented.
These polynoms were built with R134a, but as minor differences were found with the use of another organic fluid (R245fa, R600a, R152a), these maps are valid for different working fluids. An additional model built with a shroud to tip radius ratio epsilon equal to 0.5 and a blade height ratio b4/r4 equal to 0.05, instead of 0.11 for the other models. It can be useful first to check if the Ns and Ds solutions lie into the convexhull domain of the original dataset, which is given for each epsilon ratio (ConvexHullNsDsEps**.mat), in order to avoid any extrapolation errors. These extrapolation errors are usually mitigated but could arise if unusual turbine design locations are targeted.

For more information about the methodology of the model generation, its boundaries, and other features, please refer to the following paper : "SMALL SCALE RADIAL INFLOW TURBINE PERFORMANCE AND PRE-DESIGN MAPS FOR ORGANIC RANKINE CYCLES, V.Mounier, L.E. Olmedo, J. Schiffmann, Energy, 2017" and the thesis "POTENTIAL AND CHALLENGES OF ORC DRIVEN HEAT PUMPS BASED ON GAS BEARING SUPPORTED TURBOMACHINERY, V.Mounier, Ecole Polytechnique Fédérale de Lausanne, 2018"