Session: 30-14 Turbines 3 and Fluids 2

Submission Number: 177895

Investigation on Cooling Characteristics of Shaft-End Structure in Supercritical CO2 Turbines 

Supercritical carbon dioxide (sCO₂) power cycles have attracted significant attention in advanced energy systems due to their high energy conversion efficiency and compact system layout. Studies indicate that, compared to traditional steam Rankine cycles, sCO₂ cycles offer notable advantages in terms of equipment miniaturization and operational flexibility, making them particularly suitable for small-to-medium power applications in the range of 1–50 MW. However, the high power density and compact design of sCO₂ turbines also introduce severe thermal management challenges. As a result of shorter shaft lengths and higher rotational speeds, bearing positions are closer to high-temperature regions, and the available axial space for cooling is limited. This leads to significant thermal loads on the rotor and shaft ends, inducing high thermal gradients and thermal stresses that may compromise operational safety and service life.

Currently, the design process of cooling structures for sCO₂ turbines predominantly relies on three-dimensional solid model simulations. Although full 3D simulations can provide complete fluid-solid temperature fields with high computational accuracy, they demand substantial computational resources and often encounter convergence difficulties due to the drastic changes in CO₂ properties near the critical point, resulting in prolonged design cycles. To achieve rapid analysis and design, a limited number of studies have adopted zero- or one-dimensional methods, utilizing empirical correlations for heat transfer in rotating flows applicable to conventional fluids to predict cooling performance. However, these approaches suffer from low computational accuracy, cannot resolve fluid-solid temperature fields, and are unsuitable for subsequent strength analysis of rotor-stator components.

To address the aforementioned limitations, this paper proposes a two-dimensional fluid-structure interaction numerical method that integrates the rotor, stator, and coolant flow. The model employs a heat transfer coefficient calculation approach suitable for the rotating flow of sCO₂, enabling fast and accurate simulation of the temperature distribution within the two-dimensional computational domain. Computations were carried out for the temperature fields of both the fluid and solid phases under varying coolant flow rates, thermodynamic states, and turbine operating conditions. The results indicate that cooling efficiency is significantly influenced by factors such as coolant flow rate, rotational speed, and fluid inlet temperature. Based on the observed temperature distribution characteristics, further analysis was conducted to identify the combination of coolant parameters required to ensure thermal safety at the seal installation location. The findings demonstrate that, within typical operational ranges, the fluid inlet temperature has the most substantial impact on cooling efficiency and must be strictly controlled within an upper limit. Coolant flow rate ranks second in influence; although increasing the flow enhances cooling, a diminishing marginal effect is observed. In contrast, variations in inlet pressure exhibit a relatively minor effect. The conclusions provide a theoretical basis for the safe design of sCO₂ turbines.

Presenting Author: Chaohong Guo Institute of Engineering Thermophysics, Chinese Academy of Science

Presenting Author Biography: Dr. Guo earned her Ph.D. from the University of Chinese Academy of Sciences in 2007. She has been a faculty member at the Institute of Engineering Thermophysics, Chinese Academy of Sciences since 2010, advancing from Assistant Researcher to Associate Researcher. In 2015, she was appointed as a Professor at the University of Chinese Academy of Sciences. Her research centers on supercritical carbon dioxide power generation and microscale phase-change heat transfer for advanced energy systems.

Authors:

Jiahao Tian Institute of Engineering Thermophysics, Chinese Academy of Science
Chaohong Guo Institute of Engineering Thermophysics, Chinese Academy of Science
Zhigang Li Institute of Engineering Thermalphysics, Chinese Academy of Science
Haikun Ren Institute of Engineering Thermalphysics
Haisong Zhang Institute of Engineering Thermalphysics
Yong Tian Institute of Engineering Thermalphysics, Chinese Academy of Science
Bo Wang Institute of Engineering Thermalphysics, Chinese Academy of Science
Weiwei Li Institute of Engineering Thermalphysics, Chinese Academy of Science
Xiang Xu Institute of Engineering Thermalphysics, Chinese Academy of Science