Temperature Adaptability Analysis of Closed Cycle Using CO2-Based Mixed Working Fluid for Underwater Platforms

The supercritical CO2 Brayton cycle system is an important development direction of underwater platform power technology. However, due to the low temperature in the deep sea which is far away from the critical temperature of CO2, the cycle system has temperature adaptability problems. This paper pro...

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Main Authors: Jiaqi FENG, Junpeng WANG, Zhentao CHEN, Zhengyuan LUO, Bofeng BAI
Format: Article
Language:zho
Published: Science Press (China) 2024-12-01
Series:水下无人系统学报
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Online Access:https://sxwrxtxb.xml-journal.net/cn/article/doi/10.11993/j.issn.2096-3920.2024-0051
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author Jiaqi FENG
Junpeng WANG
Zhentao CHEN
Zhengyuan LUO
Bofeng BAI
author_facet Jiaqi FENG
Junpeng WANG
Zhentao CHEN
Zhengyuan LUO
Bofeng BAI
author_sort Jiaqi FENG
collection DOAJ
description The supercritical CO2 Brayton cycle system is an important development direction of underwater platform power technology. However, due to the low temperature in the deep sea which is far away from the critical temperature of CO2, the cycle system has temperature adaptability problems. This paper proposed the plan to use CO2-based mixed working fluid to improve cycle temperature adaptability and further optimize cycle performance. A simple recuperative closed cycle thermodynamic model was established, and the changes in critical parameters of CO2-based mixed working fluid with the type and mass fraction of added gas were analyzed. The influence of the compressor inlet state parameters on the thermodynamic properties of the closed cycle of CO2-based mixed working fluid was clarified. Besides, the influence of the pseudo-critical point position of the mixed working fluid on the pinch point and thermal inertia of the regenerator was discussed. The results show that the mixed working fluid cycle with low critical parameters can further expand the cycle temperature range and pressure ratio to improve the cycle thermodynamic performance. However, only expanding the temperature range and reducing the pressure ratio may have an adverse impact on it. Comprehensive consideration of cycle thermal efficiency, specific power, and pinch point and thermal inertia of regenerator, the maximum thermal efficiency of CO2 + Xe(CO2/Xe: 0.5/0.5)- transcritical Rankine cycle, CO2 + SF6(CO2/SF6: 0.9/0.1)-transcritical liquid Brayton cycle, CO2 + SF6(CO2/SF6: 0.5/0.5)-transcritical Rankine cycle can be increased by 3.79% than that of the supercritical CO2 Breton cycle, and the maximum specific power can be increased by 31.6%. The pinch point of the regenerator is located at the cold end, which does not increase its thermal inertia and does not slow down the system response speed.
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publishDate 2024-12-01
publisher Science Press (China)
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series 水下无人系统学报
spelling doaj-art-0c5ebcf998d7473dac7a3b13906d383b2025-01-07T02:42:15ZzhoScience Press (China)水下无人系统学报2096-39202024-12-013261053106210.11993/j.issn.2096-3920.2024-00512024-0051Temperature Adaptability Analysis of Closed Cycle Using CO2-Based Mixed Working Fluid for Underwater PlatformsJiaqi FENG0Junpeng WANG1Zhentao CHEN2Zhengyuan LUO3Bofeng BAI4State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, ChinaState Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, ChinaState Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, ChinaState Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, ChinaState Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, ChinaThe supercritical CO2 Brayton cycle system is an important development direction of underwater platform power technology. However, due to the low temperature in the deep sea which is far away from the critical temperature of CO2, the cycle system has temperature adaptability problems. This paper proposed the plan to use CO2-based mixed working fluid to improve cycle temperature adaptability and further optimize cycle performance. A simple recuperative closed cycle thermodynamic model was established, and the changes in critical parameters of CO2-based mixed working fluid with the type and mass fraction of added gas were analyzed. The influence of the compressor inlet state parameters on the thermodynamic properties of the closed cycle of CO2-based mixed working fluid was clarified. Besides, the influence of the pseudo-critical point position of the mixed working fluid on the pinch point and thermal inertia of the regenerator was discussed. The results show that the mixed working fluid cycle with low critical parameters can further expand the cycle temperature range and pressure ratio to improve the cycle thermodynamic performance. However, only expanding the temperature range and reducing the pressure ratio may have an adverse impact on it. Comprehensive consideration of cycle thermal efficiency, specific power, and pinch point and thermal inertia of regenerator, the maximum thermal efficiency of CO2 + Xe(CO2/Xe: 0.5/0.5)- transcritical Rankine cycle, CO2 + SF6(CO2/SF6: 0.9/0.1)-transcritical liquid Brayton cycle, CO2 + SF6(CO2/SF6: 0.5/0.5)-transcritical Rankine cycle can be increased by 3.79% than that of the supercritical CO2 Breton cycle, and the maximum specific power can be increased by 31.6%. The pinch point of the regenerator is located at the cold end, which does not increase its thermal inertia and does not slow down the system response speed.https://sxwrxtxb.xml-journal.net/cn/article/doi/10.11993/j.issn.2096-3920.2024-0051underwater platformco2-based mixed working fluidclosed cycletemperature adaptability
spellingShingle Jiaqi FENG
Junpeng WANG
Zhentao CHEN
Zhengyuan LUO
Bofeng BAI
Temperature Adaptability Analysis of Closed Cycle Using CO2-Based Mixed Working Fluid for Underwater Platforms
水下无人系统学报
underwater platform
co2-based mixed working fluid
closed cycle
temperature adaptability
title Temperature Adaptability Analysis of Closed Cycle Using CO2-Based Mixed Working Fluid for Underwater Platforms
title_full Temperature Adaptability Analysis of Closed Cycle Using CO2-Based Mixed Working Fluid for Underwater Platforms
title_fullStr Temperature Adaptability Analysis of Closed Cycle Using CO2-Based Mixed Working Fluid for Underwater Platforms
title_full_unstemmed Temperature Adaptability Analysis of Closed Cycle Using CO2-Based Mixed Working Fluid for Underwater Platforms
title_short Temperature Adaptability Analysis of Closed Cycle Using CO2-Based Mixed Working Fluid for Underwater Platforms
title_sort temperature adaptability analysis of closed cycle using co2 based mixed working fluid for underwater platforms
topic underwater platform
co2-based mixed working fluid
closed cycle
temperature adaptability
url https://sxwrxtxb.xml-journal.net/cn/article/doi/10.11993/j.issn.2096-3920.2024-0051
work_keys_str_mv AT jiaqifeng temperatureadaptabilityanalysisofclosedcycleusingco2basedmixedworkingfluidforunderwaterplatforms
AT junpengwang temperatureadaptabilityanalysisofclosedcycleusingco2basedmixedworkingfluidforunderwaterplatforms
AT zhentaochen temperatureadaptabilityanalysisofclosedcycleusingco2basedmixedworkingfluidforunderwaterplatforms
AT zhengyuanluo temperatureadaptabilityanalysisofclosedcycleusingco2basedmixedworkingfluidforunderwaterplatforms
AT bofengbai temperatureadaptabilityanalysisofclosedcycleusingco2basedmixedworkingfluidforunderwaterplatforms