WP2 – Novel radial turbomachinery for sCO2 applications (Leader POLIMI)

WP2 aimed at studying the configuration of optimal radial turbomachinery for sCO2 power and storage systems in the medium power range (1–10 MWe), targeting maximum efficiency and reliability, while addressing the novel application with particular reference to turbomachinery used in the storage cycle, achieving TRL 3.

The full set of computational models and tools developed by POLIMI for turbomachinery design and analysis was applied, ranging from mean-line codes for preliminary sizing to advanced two-phase CFD models for turbomachinery flows under near-critical conditions. Continuous interaction with UNIGE was ensured regarding the feasibility of cycle operating points, as optimised in WP1.

T2.1
In T2.1, mean-line codes were systematically applied to obtain surrogate models and sizing of all turbomachinery involved in the processes [Romei 2020], based on the optimised operating points from WP1. Feasibility boundary conditions for the cycle layout (e.g., minimum pressure distance from the critical point) were identified.

These surrogate models (developed by POLIMI) were employed in WP1 for preliminary turbomachinery sizing and estimation of related capital costs (UNIGE), as well as for eco-design quantitative assessments (UNIFI).

T2.2
T2.2 focused on the aerodynamic design of high-temperature machines (e.g., 350–550°C), including a novel hot compressor (charging phase) and expander (discharging phase). Special attention was given to associated technological challenges.

Structural integrity aspects were considered during shape optimisation [Persico 2019], through the introduction of geometric constraints and dedicated FEM analyses, as well as by evaluating the performance impact of leakage and secondary flows.

The resulting high-temperature machines were analysed to generate high-fidelity maps of performance and operational rangeability.

T2.3
T2.3 addressed the design of near-critical machines, including both a compressor (discharging phase) and a novel cold sCO2 turbine. Emphasis was placed on the interaction between aerodynamics and thermodynamics, as proximity to saturation conditions made these machines prone to phase change phenomena.

The optimisation was based on CFD models developed by POLIMI, incorporating advanced thermodynamic models for simulating two-phase flows capable of capturing both cavitation and condensation, depending on the thermodynamic state at the intake resulting from cycle optimisation.

The resulting near-critical machines were analysed to obtain high-fidelity maps of performance and operational rangeability.