Validation of a radial-inflow turbine model for super-critical CO2 applications

A one-dimensional model for a radial inflow turbine for super-critical carbon dioxide (S-CO2) Brayton cycle applications is described. The model accounts for the main phenomena present in the volute, nozzle, and impeller of a single-stage turbine. These phenomena include internal losses due to friction, blade loading, and angle of incidence and parasitic losses due to windage and blade-housing leakage. The model was developed to support the analysis of S-CO2 cycles in conjunction with small-scale loop experiments. Such loops operate at less than one MWt thermal input. Their size permits components to be reconfigured in new arrangements relatively easily and economically. However, the small thermal input combined with the properties of carbon dioxide lead to turbo-machines with impeller diameters of only one to two inches. At these sizes the dominant phenomena differ from those in larger more typical machines. There is almost no treatment in the literature of turbo-machines at these sizes. Model predictions are compared against data from an experiment performed for Sandia National Laboratories in the small-scale split-flow Brayton cycle loop currently located at Barber-Nichols Inc. (authors)