Modeling and characterization of non-ideal compressible flows in unconventional turbines

The vast majority of energy conversion systems currently makes use of fossil fuels, whose combustion generates harmful greenhouse gases. Transitioning to renewable energy sources is thus paramount to limiting the environmental impact of human activities on the climate. In this regard, the harvesting of wasted thermal energy constitutes a promising strategy to increase the efficiency of industrial processes and mobile engines. For instance, technologies such as organic Rankine cycle (ORC) systems enable the energy discarded during the conversion processes to the atmosphere to be repurposed and generate CO2-neutral electricity or additional mechanical work. The efficiency of such systems is subordinate to that of each of the components, among which, is the turbine. Designing more efficient ORC turbines inherently leads to a higher thermodynamic cycle efficiency. However, these turbines operate with complex organic compounds, and part of the expansion process often occurs in the dense vapor state, where the thermodynamic properties exhibit significant deviations from the variations predicted by the ideal gas law. As a consequence, available guidelines for the design of turbomachinery operating with air or steam cannot be used, as they would lead to incorrect sizing and wrong performance estimations. The development of generalized guidelines for turbine design is possible only through a thorough investigation of the internal non-ideal compressible flow inside the vane passage, and by accurately discerning all the possible loss sources. The research outlined in this thesis aims at characterizing non-ideal compressible internal flows of dense vapors and developing new guidelines for the design of unconventional turbines operating with organic fluids, such as those operating in organic Rankine cycle power systems. The influence of both the complexity of the fluid molecules and the thermodynamic state on the flow field is evaluated for some paradi
Flight Performance and Propulsion