Design and performance analysis of radial-inflow turboexpander for OTEC application

Ocean thermal energy conversion (OTEC) is a potential source of renewable energy. In order to design a turbine for maximizing the output power for very low working temperature application like OTEC, careful one-dimensional design followed by detailed three dimensional simulation is required. In this work a radial-inflow turbine with R-22 as working fluid is designed for a closed-cycle ocean thermal energy conversion plant of 2kWe capacity. Design speed of the turbine is 34000rpm. Inlet and outlet temperatures of designed turbine are 24.5°C and 14°C respectively. Three-dimensional fluid flow analysis inside the turbine at design and off-design conditions were carried out. Important dimensions of the turbine are: rotor tip and shroud radii of 24mm and 19mm respectively; blade widths at rotor inlet and outlet of 6mm and 11mm respectively; axial length of 17.5mm; diffuser of 62mm long. Volute casing designed has a circular cross section. The importance of the number of blades, blade filleting and stagger angle from the point of view of turbine performance are reported.