Off-Design Analysis of a Supercritical CO₂ Brayton Cycle with Ambient Air as the Cold Source Driven by Waste Heat from Gas Turbine

Abstract

Utilizing energy efficiently could greatly relieve current energy crisis. Therefore, in this article, a simple supercritical CO₂ Brayton cycle for waste heat recovery from gas turbine is presented. The system uses ambient air as its cold source, which is more convenient and economic. Considering temperature difference between heat source and turbine inlet, it is of great significance to research the effects of turbine inlet temperature on the system performance due to the high temperature range of the exhaust gas from gas turbine. For this purpose, a control strategy is proposed and a mathematical model is established on off-design conditions to predict system performance when turbine inlet temperature increases from 673.15 K to 773.15 K. Results indicate that both turbine power output and system net power output increase with the rise of turbine inlet temperature, as well as total heat transfer in heater and cooler. Furthermore, the system thermal efficiency also increases until it becomes maximum on design point. In addition, the efficiency of turbomachinery varies slightly.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors gratefully acknowledge the financial support by the National Key Research and Development Program of China (Grant No. 2016YFB0600104), and the National Natural Science Foundation of China (Grant No. 51976145).

Notes on contributors

Jianming Han

Jianming Han is a master student of Institute of Turbomachinery, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, China. He received his Bachelor of Engineering degree in 2017 from Northwest University, Xi'an, China. His research direction is new power cycle and waste heat utilization.

Qingya Ma

Qingya Ma is a master student of Institute of Turbomachinery, School of Energy and Power Engineering, Xi'an Jiaotong University, China. He obtained his Bachelor of Engineering degree in 2018 at Xi'an Jiaotong University, China. His research includes low temperature Kalina cycle and ammonia turbine design.

Zihua Wang

Zihua Wang is a master student of Institute of Turbomachinery, School of Energy and Power Engineering, Xi'an Jiaotong University, China. He received his Bachelor of Engineering degree in 2018 at Xi'an Jiaotong University, China. His research focuses on organic Rankine cycle and turbine design.

Mengjuan Xu

Mengjuan Xu is a Ph.D. candidate of Institute of Turbomachinery, School of Energy and Power Engineering, Xi'an Jiaotong University, China. She received her Master of Engineering degree in 2009 at Wuhan University of Technology, China. She is currently engaged in research on carbon dioxide energy storage system.

Yunfei Song

Yunfei Song is a master student of Institute of Turbomachinery, School of Energy and Power Engineering, Xi'an Jiaotong University, China. He obtained his Bachelor of Engineering degree in 2017 at Xi'an Jiaotong University, China. His research interest is PCHE performance simulation in supercritical carbon dioxide Brayton cycle.

Jiangfeng Wang

Jiangfeng Wang is a professor and Ph.D. of Institute of Turbomachinery, School of Energy and Power Engineering, Xi'an Jiaotong University, China. His research includes low temperature heat source recycling (solar energy, geothermal, and industrial waste heat), thermal system integration and dynamic characteristics, distributed energy system and building energy saving.

Yiping Dai

Yiping Dai is a professor and Ph.D. of Institute of Turbomachinery, School of Energy and Power Engineering, Xi'an Jiaotong University, China. He has more than 20 years of experience in system design, optimization, and industrial application for low-temperature waste heat recovery. Meanwhile, he researches primary frequency regulation of power systems, involving turbine generation unit modeling for power system dynamic analysis and the effect of control system on the stability of the power grid in China. He is also experienced in wind power prediction and its influence on the stability of the power grid.