Partial Admission Effect on the Flow Field of an ORC Tesla Turbine

orc2019 Tracking Number 30

Over recent years, Tesla turbine gained a renewed interest from the international scientific community, as it combines reliability, efficiency and low cost. These are key aspects for the success of an expander suitable for small-distributed energy systems, thus Tesla turbine could represent an attracting solution for the market. The test case is a turbine with efficiency 29% for a 0.57 kW expander utilizing R1233zd(E) as working fluid. The three-dimensional fluid dynamics inside the stator, the stator-rotor gap and the rotor is determined by means of CFD analyses. The comprehensive evaluation of the set of the three regions is of paramount importance to determine the machine flow field, as it is significantly affected by the interactions amongst each component. In particular, the effects of discrete admission to the rotor are relevant in terms of flow field distortion, while the effects on the performance parameters (power and efficiency) are slighter. The performance results of the 3-D computational fluid dynamics are close to the ones of the 2-D in-house developed code, which assumes continuous admission to the rotor. The results inside the rotor are shown in terms of velocity, pressure and temperature fields. Particular interest is focused on the distinctive shape of the temperature distribution inside the rotor, arising from the spiral trajectories of the fluid determined by the four admission nozzles.