Mechanical Design • CNC Machining • Systems
A turbine-generator assembly supporting high-speed rotor-shaft rotation from high temperature and pressure supercritical CO2 Rankine cycle to generate electricity.
The turbine converts thermal energy from supercritical CO₂ into mechanical and electrical power. A sealed enclosure with endcaps, O-rings, and shaft seals maintains the high-pressure flow, while a Pelton-style rotor spins up to 30,000 RPM on ball bearings. A nozzle accelerates the CO₂ into a high-velocity jet that drives the rotor and shaft. The system follows a Rankine cycle: CO₂ flows from a tank to an evaporator, expands through the turbine, and is then condensed.
All turbine components were defined using GD&T to ensure proper fit, sealing, and alignment at high speeds. Parts were designed in SolidWorks with clear dimensioning for accurate machining and assembly.
Section views highlighted O-ring sealing and the keyed rotor-shaft connection, guiding CNC manufacturing and ensuring consistency.
Mechanical Design
The aluminum enclosure was machined in the CNC Mill and serves as the static housing for the spinning rotor.
Circular aluminum stock was faced, bored, and drilled to create the end caps on the CNC Mill with Fusion360 Cam.
The steel rotor was first cut with precision in the wire EDM to optimize concentricity and cut square key hole. The rotor was then faced in the CNC mill.
The steel shaft was turned in the CNC lathe to create grooves for retaining rings. A key slot was CNC milled for rotor coupling.
Cylinder steel stock was turned in the CNC lathe for the main inner and outer geometry profiles. The bell curve was milled with a 1/16th inch ball end mill.
The end disks responsible for sealing end caps with o-rings and the spacers used for the rotor stack were both CNC milled from aluminum scrap.
Build Process
3-axis CNC milling was used to machine the enclosure, end caps, and flat components, including facing, pocketing, and drilling operations.
The CNC lathe was used to machine cylindrical features such as the shaft and nozzle, ensuring concentricity and precise fits for rotating components.
Wire EDM was used to cut the rotor profile and keyway with high precision, maintaining tight tolerances and sharp internal features.
System Integration
The full rotor stack was assembled with ball bearings, spacers, and the rotor on the shaft, retained by retaining rings. This assembly required precise concentric and axial alignment within the enclosure.
The final turbine assembly was tested with compressed air and a 1:10 gear reducer connected to a power generator to evaluate rotational speed and energy transfer. The max voltage came out to be 8V at 10,000 RPM reduced to 1,000.
The turbine/nozzle's inlet and outlet were connected within the Rankine cycle included the evaporator, condensor, CO2 tank, generator, pressure and temperature sensors, and all conections.
This project improved my ability to design for manufacturability and strengthened my CNC machining skills. I worked through the full process from CAD to assembly, seeing how design decisions impact fabrication and fit. Moving forward, I would focus more on tolerances during machining to reduce post-processing and improve efficiency.