Thermomechanical coupling mechanisms of a rotary variable nozzle for supercritical CO 2 turbines under extreme operating conditions

Abstract

Addressing the operational stability challenges of supercritical carbon dioxide turbines under off-design conditions, this paper presents a novel inlet regulation mechanism featuring a rotary variable nozzle. Using a fully coupled fluid-thermal-structural multiphysics analysis, the reliability of this structure is investigated under extreme conditions of 500°C and 14 MPa. The results reveal that the nozzle opening governs the thermo-mechanical state of the mechanism. As the opening increases from 0° to 60°, the internal flow transitions from a localized gap jet to a fully developed diffused flow, reducing the maximum von Mises stress by 45% (from 485 MPa to 328 MPa) and increasing turbine isentropic efficiency by 4.8 percentage points. At the 120° opening, however, the maximum stress reaches 612 MPa, exceeding the material allowable by 33%, and the radial deformation (0.07 mm) exceeds the design clearance (0.04 mm) by 75%, posing significant seizure and low-cycle fatigue risks. The 60° opening maintains a clearance utilization below 30% and achieves the optimal balance between thermal uniformity and structural integrity. This research elucidates the complex coupling phenomena within the novel SCO₂ variable inlet structure, providing a critical theoretical foundation for its future reliability design and optimization.

Keywords

variable inlet turbine (VIT)rotating variable nozzle VICS thermo-mechanical coupling stress concentration

Get full access to this article

View all access options for this article.

References

Van

Infante

Kiss

. Low-grade waste heat recovery using heat pumps and power cycles. Energy 2015; 89: 864–873. https://doi.org/10.1016/j.energy.2015.06.030

Zhou

, et al. Research on aerodynamic optimization design of variable geometry turbine with large flow adjustment range. J Aero Power 2024; 40(X): 20240258. https://doi.org/10.13224/j.cnki.jasp.20240258

Wang

Jiang

, et al. Research of variable cycle engine modeling technologies. In: Jia

Zhang

, et al. (eds) Proceedings of 2016 Chinese intelligent systems conference. CISC 2016. Lecture notes in electrical engineering. Singapore: Springer, 2016, vol 404, pp. 267–273. https://doi.org/10.1007/978-981-10-2338-5_26

Yao

Zhi

Zhou

, et al. Aerodynamic performance measurement of a novel variable geometry turbine adjustable guide vane scheme by experimental study. Aero Sci Technol 2023; 140: 1270–9638. https://doi.org/10.1016/j.ast.2023.108413

Zhou

Zheng

. A novel design to-wards reducing leakage loss for variable geometry turbines. Processes 2023; 11(1): 21. https://doi.org/10.3390/pr11010021

Yan

Song

Yao

, et al. Experimental study on endwall film cooling performance of an adjustable guide vane. Int J Therm Sci 2025; 208: 109440. https://doi.org/10.1016/j.ijthermalsci.2024.109440

Morrison

Stuart

Starke

, et al. Investigation of a novel turbine housing to produce a non-uniform spanwise flow field at the intake to a mixed flow turbine and provide variable geometry capabilities. ASME J Turbomachinery 2023; 145(6): 061013. https://doi.org/10.1115/GT2021-59382

Wang

Yuan

Zhang

, et al. Design and aerodynamic performance analysis of a variable geometry axisymmetric intake for TBCC. Int J Turbo Jet Engines 2021; 40: 379–385. https://doi.org/10.1515/tjj-2020-0030

Yang

Liu

, et al. Shock wave control of a variable geometry turbine nozzle based on global profile and local bulge coupling optimization. Energy 2025; 318: 134807. https://doi.org/10.1016/j.energy.2025.134807

10.

Jiang

Ming

Chen

, et al. Aerodynamic performance comparisons of two kinds of variable nozzle vanes for a variable geometry turbine. Int J Aerosp Eng 2024; 2024(25): 9032152. https://doi.org/10.1155/2024/9032152

11.

Zhong

Chen

Zhao

, et al. Analysis of influence factors of guide vanes torque in variable geometry turbine adjusting mechanism. IEEE Access 2023; 11: 131726–131748. https://doi.org/10.1109/ACCESS.2023.3335814

12.

Zou

Song

Wang

, et al. An efficient multi-fidelity simulation approach for performance prediction of adaptive cycle engines. J Glob Power Propuls Soc 2024; 8: 310–322. https://doi.org/10.33737/jgpps/191167

13.

Wang

. Simulation and analysis of variable geometry turbine guide vane regulation mechanism. Harbin: Harbin Institute of Technology, 2020.

14.

Bai

. Research on the adjustment law of the driving part of the variable geometry VIT guide vane adjustment mechanism. Boston, MA: Northeastern University, 2021.

15.

Xia

Yang

, et al. Experimental and numerical analysis of thermal protection performance for composite conductive structures of aircraft leading edges. J Therm Sci Technol 2023; 22(5): 498–505.

16.

Wang

, et al. Flow and heat transfer of aeroengine turbine guide vanes based on fluid-thermal-solid coupling. J Aero Power 2025; 40(X): 20240464. https://doi.org/10.13224/j.cnki.jasp.20240464

17.

Wang

Zhang

, et al. Prediction of stress-fatigue life on the impeller of the reactor coolant pump based on fluid-thermal-structure interaction method. Ann Nucl Energy 2023; 193: 110029. https://doi.org/10.1016/j.anucene.2023.110029

18.

Chen

Lin

, et al. Fluid-heat-solid coupling numerical study on influence of gas-solid two-phase flow on elbow tube of gas-steam ejection power system. J Aero Power 2023; 37(11): 2668–2679. https://doi.org/10.13224/j.cnki.jasp.20220510

19.

Zhang

Zhou

Wang

, et al. Thermal-structure coupling analysis of neutron target system of beryllium palladium copper composite based on fluent. Mech Eng Power Eng 2023; 49(3): 60–66.

20.

Fang

Cheng

, et al. Review on mechanics of ultra-high-temperature materials. Acta Mech Sin 2021; 37: 1347–1370. https://doi.org/10.1007/s10409-021-01146-3

21.

Riccardo

Giuseppe

, et al. Thermoelastic stress analysis for composite laminates: a numerical investigation. Compos Sci Technol 2023; 241: 110103.

22.

Yang

, et al. Load-tracking performance optimization for a supercritical CO2 recompression cycle under bypass control utilizing variable turbine inlet guide vanes. Ann Nucl Energy 2025; 214: 111230. https://doi.org/10.1016/j.anucene.2025.111230

23.

Zhong

Chen

Wang

, et al. Angle-regulating rule of guide vanes of variable geometry turbine adjusting mechanism. Appl Sci 2023; 13: 6357. https://doi.org/10.3390/app13116357

24.

Racca

Verstraete

Casalino

. Radial turbine thermo-mechanical stress optimization by multidisciplinary discrete adjoint method. Int J Turbomach Propuls Power 2020; 5(4): 30. https://doi.org/10.3390/ijtpp5040030

25.

Abdelrazik

Osama

Ahmed

, et al. ANSYS-fluent numerical modeling of the solar thermal and hybrid photovoltaic-based solar harvesting systems. J Therm Anal Calorim 2023; 148(21): 11373–11424. https://doi.org/10.1007/S10973-023-12509-2

26.

Abdelrazik

Sharafeldin

Elwardany

, et al. Computational modeling of high-concentration solar systems using ANSYS-Fluent: verified models, implemented methods, & existing challenges. Renew Sustain Energy Rev 2026; 226: 116305. https://doi.org/10.1016/J.RSER.2025.116305

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.55 MB