Fluid dynamic design optimization of high-expansion ratio ORC turbines









  • SenterNovem Unieke Kansen Regeling (UKR01003)








    Organic Rankine Cycle (ORC) turbogenerators are an efficient and reliable option for the generation of electricity from low- to medium temperature heat (starting from approximately 90°C) in the small to medium power range (from few kWe up to 1-2 MWe). They are especially suitable for renewable energy sources like solar radiation, biomass thermal conversion, geothermal heat exploitation, and industrial heat recovery. A more detailed introduction about ORC technology is given in the section Knowledge Center for Organic Rankine Cycles (KCORC).


    Involved People:

    Facilities used:

    Typically for ORC turbogenerators, the expansion in the turbine occurs partly in the thermodynamic dense-gas region, relatively close to the critical point of the working fluid. At these conditions, the thermodynamic behavior of the working fluid differs from that predicted by the simple thermodynamic ideal gas law. This in turn leads to unconventional fluid dynamic behavior, known as real-gas effects. State-of-the-art thermodynamic models are therefore required for accurate fluid dynamic simulations of the flow through the turbine blades.

    The ORC turbogenerator developed and manufactured by Tri-O-Gen B.V. has an electrical output of 120-160 kWe and can be used to recover waste heat produced by medium-scale internal combustion engines. Current existing units recover waste heat from engines running on landfill gas, biogas, natural gas or bio-oil. Many other applications are possible.

    In addition to the aforementioned real-gas effects, the expansion in the Tri-O-Gen turbine is characterized a very high pressure ratio, leading to hypersonic flow and shock waves, which could induce flow losses. Secondly, as concluded by a recent study, the specialized thermodynamic model that was used for the original turbine design turned out to give inaccurate predictions for certain operating conditions [1]. Hence, there appears to be a potential for performance improvement of this turbine, which would have a significant positive impact on the conversion efficiency of the ORC turbogenerator.

    Fig. 1. The Tri-O-Gen unit and turbogenerator.


    This project aims at evaluating and improving the fluid dynamic performance of this type of high expansion ratio ORC turbine using, amongst others, a state-of-the-art flow solver (zFlow) and thermodynamic model (FluidProp).

    Work Program:

    The fluid dynamic performance of the current design will be evaluated based on accurate simulations. Advanced flow solvers, including the zFlow solver, are adopted, which are coupled to a state-of-the-art thermodynamic model for the working fluid that is more accurate than the one used for the original design. Based on the evaluation, the stator will be redesigned using the more accurate models and possibly new insights. If necessary, advanced optimization methods including Genetic Algorithms may be used.

    Fig. 2. Mach flow field of the expansion in the turbine stator ring.









  • Harinck, J., Turunen-Saaresti, T., Colonna, P., Rebay, S., Buijtenen, J.P. van, Computational Study of a High-Expansion Ratio Radial ORC Turbine Stator, ASME Journal of Engineering for Gas Turbines and Power, 2009. (in print)













  • Harinck, J., Turunen-Saaresti, T. and Colonna, P., Performance and CFD analyses of a high-expansion ratio radial ORC turbine, Delft University of Technology, Process and Energy Department, Energy Technology Section, Leeghwaterstraat 44, 2628 CA Delft, The Netherlands, Scientific Report ET-2262, October 2007, (confidential).













  • Harinck, J., Van Buijtenen, J.P., Van den Braembussche, R.A., Alshalihi, Z., Optimisation of a 3D Radial Turbine by means of an Improved Genetic Algorithm, Proceedings of the 6th European Conference on Turbomachinery, Fluid Dynamics and Thermodynamics, pp. 1033 - 1042, Lille, France, March, 2005.













  • Buijtenen, J.P. van; Larjola, J.; Turunen-Saaresti, T.; Honkatukia, J.; Esa, H.; Backman, J. & Reunanen, A. Design and Validation of a New High Expansion Ratio Radial Turbine for ORC Applications, Proceedings of the 5th European Conference on Turbomachinery, 2003, 1-14.







    Project partners:








  • Tri-O-Gen B.V.