Multi-objective efficiency optimization of a 30 kWe ORC turbine

Due to the demand of the district heating network and electric power grid ORC turbines can operate in the condensation and cogeneration modes. This approach requires the design of an expander which is characterized by high efficiency in each modes of operation. Multi-objective efficiency optimization of a one stage axial ORC turbine working on MM (Hexamethyldisiloxane) was carried out. An Implicit Filtering algorithm (IF) is used to find a flowpath with maximum efficiency. During the optimization the rotor profiles (hub and shroud) and the shape of endwall contours of the rotor domain were changed. Five optimization tasks were carried out with different weights of the efficiency of both modes of operation. Pareto frontiers were obtained and a decision-making method was used to select an optimum solution. The optimization of rotor row allows for significant efficiency improvements in two regimes of operation, with respect to a baseline geometric configuration designed with the help of classical methods. The turbine efficiency was increased by 3.1 pp. in the condensation mode and by 4.8 pp. in the cogeneration mode.

Pareto front of best solutions

Total pressure losses in the rotor before (left) and after (right) optimization – condensation work (top), cogeneration work (bottom)