Bayesian Optimization Design of Inlet Volute for Supercritical Carbon Dioxide Radial-Flow Turbine

Chao Bian,Xiaofang Wang,Shaojie Zhang,Haitao Liu,Jinguang Yang,Feng Zhao

doi:10.3390/machines9100218

Abstract

The radial-flow turbine, a key component of the supercritical CO2 (S-CO2) Brayton cycle, has a significant impact on the cycle efficiency. The inlet volute is an important flow component that introduces working fluid into the centripetal turbine. In-depth research on it will help improve the performance of the turbine and the entire cycle. This article aims to improve the volute flow capacity by optimizing the cross-sectional geometry of the volute, thereby improving the volute performance, both at design and non-design points. The Gaussian process surrogate model based parameter sensitivity analysis is first conducted, and then the optimization process is implemented by Bayesian optimization (BO) wherein the acquisition function is used to query optimal design. The results show that the optimized volute has better and more uniform flow characteristics at design and non-design points. It has a smoother off-design conditions performance curve. The total pressure loss coefficient at the design point of the optimized volute is reduced by 33.26%, and the flow deformation is reduced by 54.55%.

Highlights

With the increasing demand for clean and efficient use of energy, it has become difficult to further enhance the thermal system with water vapor as the work substance to meet people’s needs, as the components of this thermal system are extensively investigated and used to a high design level
For the Guassian process, it can be seen that the coefficient of determination R2 is greater than 0.95 for both optimization objectives Ks and Fd, and the other error indicators root mean square error (RMSE), maximum absolute error (MAE), and maximum relative error (MRE) are very small
To reduce the flow losses and flow distortions in the supercritical CO2 centripetal turbine inlet volute, this paper employs the Bayesian optimization algorithm based on numerical simulation to optimize the inlet volute

Summary

Introduction

With the increasing demand for clean and efficient use of energy, it has become difficult to further enhance the thermal system with water vapor as the work substance to meet people’s needs, as the components of this thermal system are extensively investigated and used to a high design level. The supercritical CO2 (S-CO2) Brayton cycle has gained widespread attention due to its high cycle thermal efficiency, compact structure, and environmental friendliness [1,2,3]. The radial-inflow turbine is a key component of the S-CO2 Brayton cycle, which affects the efficiency of the entire cycle, and is suitable for operating conditions where the mechanical power of the turbine is less than 30 MW [4]. The inlet volute, as the infusion and acceleration component of the radial-flow turbine, affects its internal flow and loss and has an important impact on the performance of the whole machine.

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Results

Conclusion