Design optimization and similarity analysis of non-azeotropic organic radial inflow turbine for OTEC power and water cogeneration

• Optimized RIT with R1224yd(Z)/R1243zf, achieving 94.13% circumferential efficiency via PSO. • CFD simulations confirmed design accuracy, with errors within 5% at the design point. • Air-model turbine similarity method validated RIT design on- and off- OTEC design conditions. This paper builds upon a previously proposed novel OTEC power and water cogeneration system, focusing on optimizing and verifying the performance of a radial inflow turbine (RIT) using the non-azeotropic R1224yd(Z)/R1243zf mixture as the working fluid. The study primarily aims to enhance the circumferential efficiency of the RIT while avoiding local optima in the optimization process. Three optimization algorithms—Particle Swarm Optimization (PSO), Genetic Algorithm (GA), and Grey Wolf Optimization (GWO)—were employed to identify key design parameters, with PSO yielding a maximum circumferential efficiency of 94.13%. CFD simulations of the preliminary design showed a strong correlation with the optimization results, with parameter errors within 5% at the design point. The off-design performance of the RIT was also evaluated under varying operational conditions, demonstrating excellent adaptability and minimal performance degradation. To validate the design and simulation, a similarity method for constructing an air-model turbine was proposed. This method successfully addressed challenges related to the OTEC RIT’s unique operating conditions, confirming the similarity between the ORC RIT and the model turbine. The optimization algorithms and similarity approach provide valuable insights into the design and performance evaluation of organic working fluid turbines for OTEC systems, providing a basis for the experimental study of the similar air turbine.