Design and manufacturing a small-scale radial-inflow turbine for clean organic Rankine power system

With growing on the energy demand and availability of the low-grade temperature heat source, the organic Rankine cycle as a power system can be efficiently utilized to generate electricity. The turbine design and its performance have the main impact on determining the system power and overall system efficiency. Therefore, design a small-scale organic Rankine system requires the development of an appropriate turbine. To achieve this aim, this work offers an innovative complete design method to develop a radial-inflow turbine for small-scale organic Rankine cycle power applications, which includes a preliminary design (i.e. one-dimensional design calculation phase) and a three-dimensional flow analysis using the computational fluid dynamic technique. A thermodynamic analysis of the organic Rankine cycle was integrated with the design methodology. Where the three-dimensional geometry model was built based on the thermodynamic and aerodynamic design, and then was imported into the ANSYS-CFX software to conduct viscous numerical simulations. The optimum design of the radial-inflow turbine was manufactured using a three-dimensional printing (pioneering) technique, and the experimental testing was conducted at off-design points to validate the turbine design.

The evaluation of the turbine’s performance (efficiency and power) was presented under design and off-design points in terms of rotational speeds, expansion ratios, and inlet temperatures with five different organic fluids. The turbine numerical results showed that R600 as a working fluid has a higher predicted turbine efficiency of 78.32% and power of 4.8 kW with cycle thermal efficiency of 9.15% compared with 8.045% for R245fa. Depending on the experimental results at off-design points, the highest cycle thermal efficiency of 4.25% with a turbine efficiency of 45.22% was achieved. These results assured the precision of the proposed PD methodology at off-design points in making performance maps of the turbine.