WP3 – Bladeless expander for small-scale sCO2 applications (lead UNIFI)
WP3 aimed to investigate an innovative bladeless turbomachinery solution for small-scale sCO2 cycle applications (0.1–1 MWe), leveraging existing know-how on Tesla turbines designed for two-phase and ORC applications, developed by UNIFI and UNIGE.
T3.1
In T3.1, to fully understand the potential of the Tesla turbine for sCO2 applications, the fluid dynamic assessment of the expander was carried out based on operating points defined in WP1. High-fidelity models ranging from 1D to 3D (e.g., using EES, Matlab-Python, Fluent, CFX) were developed or improved from existing ones, incorporating knowledge and methodologies transferred from WP2 (POLIMI).
The component models were developed to define the optimal geometry of the Tesla expander, its on-design performance, and off-design performance maps. Based on the results of T3.3, the performance models were validated for future design applications.
T3.2
In T3.2, the adaptation of an existing sCO2 test bench located at UNIFI premises was carried out by UNIFI. In parallel, a modification of an sCO2 Tesla turbine prototype provided by UNIGE was performed to ensure proper integration of the turbomachinery within the test bench.
The integrated test rig enabled operation at turbine inlet conditions of approximately 100 bar and 100°C, with outlet conditions around 40 bar. Key parameters such as flow rate, temperature, and pressure of sCO2 were measured at various significant sections. Preliminary start-up tests of the test bench coupled with the Tesla turbine prototype were conducted to ensure system stability.
T3.3
In T3.3, the Tesla bladeless expander prototype (developed by UNIGE) for sCO2 was successfully operated within the UNIFI CO2 test rig, providing a unique reference in the Italian and broader EU landscape for this type of expander.
The main outcome of this task was the proof of concept of the bladeless expander technology in the kW power range, achieving TRL 4. Experimental results were also used to validate the performance models developed in T3.1, as well as the plant thermo-economic models from T1.1.