3D CFD simulation of a turbocharger compressor used as a turbo expander for Organic Rankine cycle

Generating electricity from low grade waste heat resources can contribute to the energy mix required to reduce carbon emissions and dependence on fossil fuels. The conversion of low grade waste heat can be achieved efficiently using Organic Rankine cycles (ORC). Radial-inflow turbine is one suitable technology for the expander in these cycles. The design of such turbines operating with non-ideal gas is challenging and requires advanced modeling techniques to be developed and validated. This paper proposes a novel and cost-effective solution to develop a design approach that combines numerical modeling and experiments. An ORC loop is developed at Dyn-fluid laboratory for teaching and research purposes. The experimental setup allows experiments of high speed turbines up to 60,000 rpm and 9 kW in a modular way. The first expander to be experimentally and numerically tested will be an adapted compressor from a standard turbocharger. The considered com- pressor wheel has 6 main blades and 6 splitters blades with an outer diameter of 44 mm and a backswept angle of 45°. The expected performance of the compressor used as a turbo expander are then estimated using 3D CFD real gas simulations and will be ultimately validated against the experimental results. The synergy between numerical modeling and experiments is expected to support the reduction in cost of the manufacturing of turbines prototypes, estimated to represent more than 50% of the total cost of the ORC system.