Design and investigation of a partial admission radial 2.5-kW organic Rankine cycle micro-turbine

In recent years, organic Rankine cycle (ORC) micro-turbine distributed energy systems have become increasingly popular. Design methods for this type of fluid-flow machinery are still being developed. In this paper, a 2.5-kW radial-flow four-stage ORC micro-turbine with HFE7100 is experimentally and numerically analysed. CFX ANSYS was used for the numerical analysis as well as a computational fluid dynamics (CFD) in-house code based on finite volume discretisation with Godunov-type upwind differencing, a high-resolution essentially non-oscillatory (ENO) scheme and a turbulence model with two-equation shear stress transport (SST). The experimental stand and measurements are described. The numerical results are compared with experimental ones and prove to be satisfactory. The developed micro-turbine does not require the use of any traditional lubricant (oil-free technology) because the bearings are lubricated with the vapour of the low-boiling HFE7100. The developed micro-turbine is an innovative solution providing maintenance-free operation and high durability with low friction losses. The experimental studies have also confirmed a considerable reduction in noise and vibration levels.