Aerodynamic Design and Performance Analysis of a Multi-Stage Low Pressure Section for Geothermal Steam Turbine

Geothermal power generation utilizes steam and brine extracted from deep underground reservoirs, harnessing geothermal heat to produce electricity. This process eliminates the need for fossil fuels, significantly reducing emissions of CO₂, NOₓ, and SOₓ, thereby contributing to climate change mitigation. As a clean and renewable energy source, geothermal power is poised for expanded adoption in the global effort to combat global warming. This work presents the aerodynamic design and performance evaluation of a three-stage low pressure section intended for geothermal applications. A comparative analysis is conducted to assess the performances with two different working fluids: pure steam and a binary mixture of water and carbon dioxide. To capture real gas effects using a single fluid model, thermodynamic property look-up tables (LUT) are generated using the NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP), enabling accurate yet numerically robust simulations across a wide range of operating conditions. A detailed discussion of the results, reported in terms of stage performance characteristics, span-wise flow quantities distributions along the turbine, and blade loading, is provided in order to highlight the impact of different fluid compositions on the aerodynamic behavior of the machine. Finally, some design insights are provided for the future development of steam turbines for geothermal applications.