Simulation Tool for Turbomachinery Operating with Trans-Critical Real Fluids

The SCO2 Brayton cycle is gaining interest across a variety of power generation applications due to its potential for providing higher efficiencies. The range of industrial applications include: industrial waste and heat recovery, coal and nuclear power plants, and renewable energy sources such as solar thermal and fuel cells. All of these cycle loops require compressors that operate near the critical point of CO2, with transients that pass through sub-critical to super-critical regimes. However compressor design at these conditions presents many challenges due to the lack of design and simulation tools that account for the correct fluid property variations in this regime. Our proposed work here addresses this deficiency. Statement of How this Problem or Situation is Being Addressed: The design of compressors for SCO2 power cycles presents many challenges since they operate with fluid inlet conditions very close to the critical point. Accurate performance prediction at these conditions require the formulation to handle the rapid variation of thermodynamic properties near the critical point. Furthermore phase change models within a real fluid framework are necessary to model condensation. The issue is further complicated by the fact that the properties of CO2 mixtures with contaminants such as water are not as well understood and equations of state are very poorly characterized. All these issues will be addressed within the context of a high fidelity numerical framework in our effort here. Commercial Applications and Other Benefits: The SCO2 Brayton cycle is gaining interest across a variety of power generation applications including nuclear, fossil fuel, waste heat as well as solar thermal and fuel cells due to its potential for providing efficiencies up to 5% points higher than a steam Rankine cycle. However the design of compressors for these systems is complex. Our proposed work here would provide a high-fidelity design tool that would permit accurate performance predictions in this thermodynamic regime and enable the commercialization of optimal compressor designs for these more efficient power generation systems. Key Words: Compressors, Supercritical CO2, Brayton Cycle, Critical Point Thermodynamics, Equation of State