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Investigation on the Influence of Entrained Air to Internal Flow of Centrifugal Pumps under Cavitation Condition

International Journal of Fluid Machinery and systems 2022年第1期15卷 56-63页

作者： Fanjie, Deng Jianping, Yuan Song, Yang Biaobiao, Wang Qiaorui, Si Research Center of Fluid Machinery Engineering and Technology Jiangsu University Jiangsu Zhenjiang212013 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Sichuan Chengdu610000 China

The introduction of air is often used in engineering to delay the occurrence of cavitation. A steady simulation on a single-stage and single-suction centrifugal pump was used to study the influence of the air on the internal flow under cavitation condition at 1% inlet void fraction. Steady simulation based on SST k-ω turbulence model and Rayleigh-Plesset cavitation model included in Ansys CFX 17.0 were processed to obtain vapor volume fraction, gas volume fraction and the turbulent energy of the impeller under the condition of natural cavitation and cavitation with entrained air. A homogeneous two-phase flow model was adopted to describe the air-water mixed flow. The experimental cavitation performance curve provides boundary condition support for the numerical simulation. In conclusion, it shows that the head of the pump keeps steady after 1% air entrained like natural cavitation. Then it goes worse when the cavitation number decreases but with lower NPSHr which means cavitation performance is improved by 1% air entrained. It indicated that the entrained air changes the distribution of the vapor in the passage of the impeller. However, the descent of the pressure over a certain value will also do harm to the internal flow of the model pump whether it is ventilati ng or not. The internal flow of the pump will be seriously damaged and even be blocked completely due to more and more vapor generated causing a dramatic decline of the head. © 2022, Turbomachinery Society of Japan. All rights reserved.

关键词： Cavitation

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Multi-Agent Reinforcement Learning with Region Division and Leader-Follower Communication

Multi-Agent Reinforcement Learning with Region Division and ...

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2024 China Automation Congress, CAC 2024

作者： Wang, Chao Xu, Xiang Shenzhen Key Laboratory of Control Theory and Intelligent Systems School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen China

ISBN: (纸本)9798350368604

The integration of multi-agent reinforcement learning (MARL) into complex systems has paved new ways for collaborative problem-solving. However, traditional approaches to MARL frequently encounter the challenge of achieving efficient communication among agents, essential for coordinated action. This paper introduces a region division and leader-follower(RDLF) communication algrithm with the MARL framework. RDLF divides the environment into several regions, each managed by a leader agent that coordinates the actions of follower agents and handling inter-region communication. This hierarchical structure reduces unnecessary communication, enhancing learning efficiency. Experimental results in multi-particle environments demonstrate RDLF’s superiority over existing MARL algorithms, especially with increasing agent numbers. RDLF effectively addresses scalability and communication challenges in large-scale multi-agent systems, providing a robust foundation for its application in complex and dynamic environment. © 2024 IEEE.

关键词： Adversarial machine learning

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A novel approach for radionuclide diffusion in the enclosed environment of a marine nuclear reactor during a severe accident

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Nuclear science and Techniques 2022年第2期33卷 53-65页

作者： Fang Zhao Shu-Liang Zou Shou-Long Xu Xuan Wang Jun-Long Wang De-Wen Tang School of Resource Environment and Safety Engineering University of South ChinaHengyang 421001China Hunan Provincial Key Laboratory of Emergency Safety Technology and Equipment for Nuclear Facilities Hengyang 421001China Shanghai Nuclear Engineering Research and Design Institute Co.LTD Shanghai 200000China Science and Technology On Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610213China

A severe accident in a marine nuclear reactor leads to radionuclide leakage,which causes hidden dangers to workers and has adverse effects of environmental *** is necessary to propose a novel approach to radionuclide diffusion in a confined environment after a severe accident in a marine nuclear ***,this study proposes a new method for the severe accident analysis program MELCOR coupled with computational fluid dynamics scSTREAM to study radioactive diffusion in severe *** radionuclide release fraction and temperature calculated by MELCOR were combined with the scSTREAM calculations to study the radionuclide diffusion behavior and the phenomenon of radionuclide diffusion in different space environments of the reactor under the conditions of varying wind velocities of the ventilation system and diffusion *** results show that the wind velocity of the ventilation system is very small or zero,and the turbulent diffusion of radionuclides is not obvious and diffuses slowly in the form of condensation sedimentation and gravity *** the wind speed of the ventilation system increases,the flow of radionuclides meets the wall and forms eddy currents,affecting the time variation of radionuclides diffusing into chamber *** wind velocity of the ventilation system and the diffusion speed has opposite effects on the time variation trend of radionuclide diffusion into the four chambers.

关键词： Radionuclide diffusion MELCOR coupled with scSTREAM Severe accident Marine nuclear reactor

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PREDICTION OF CRITICAL HEAT FLUX BASED ON RANDOM FOREST ALGORITHM 29

PREDICTION OF CRITICAL HEAT FLUX BASED ON RANDOM FOREST ALGO...

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2022 29th International Conference on Nuclear Engineering, ICONE 2022

作者： Sun, Zhuo Han, Mingyang Yuan, Peng Gong, Lei Chen, Di Yuan, Guanghui Zhang, Shuang Nuclear Power Institute of China Chengdu China Science and Technology on Reactor System Design Technology Laboratory Chengdu China

ISBN: (纸本)9780791886410

The accurate prediction of critical heat flux(CHF) is of great significance to the safe operation of the reactor. At present, most of the traditional methods for predicting CHF are based on relational fitting in mathematical form, which are not accurate enough and may can not taking full advantage of experimental data. Therefore, a prediction model based on random forest algorithm (RF) is proposed, the model is based on CHF 2006 look-up table, and the accuracy and smoothness of the model have been verified when predicting CHF. In this paper, the variation trend of CHF predicted value and actual value with pressure, mass flow rate and thermodynamic quality is given. It has been verified that the error of this method is acceptable, the predicted value is in good agreement with the experimental value, and conforms to the corresponding physical laws, which can provide a reference for the development of high-precision CHF prediction models or CHF-related experiments. Copyright © 2022 by ASME.

关键词： Heat flux

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CFD simulation of thermal hydraulic characteristics in a typical upper plenum of RPV

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Frontiers in Energy 2021年第4期15卷 930-945页

作者： Mingjun WANG Lianfa WANG Yingjie WANG Wenxi TIAN Jian DENG Guanghui SU Suizheng QI State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and TechnologyXi’an Jiaotong UniversityXi’an 710049China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610213China

A comparative computational fluid dynamics(CFD)study was conducted on the three different types of pressurized water reactor(PWR)upper plenum,named TYPE 1(support columns(SCs)and control rod guide tubes(CRGTs)with two large windows),TYPE 2(SCs and CRGTs without windows),and TYPE 3(two parallel perforated barrel shells and CRGTs).First,three types of upper plenum geometry information were collected,simplified,and adopted into the BORA facility,which is a 1/5 scale system of the four-loop PWR ***,the geometry,including the upper half core,upper plenum region,and hot legs,was built using the Salome *** that,an unsteady calculation to simulate the reactor balance operation at hot full power scenario was ***,the differences of flowrate distribution at the core outlet and temperature distribution and transverse velocity inside the hot legs with different upper plenum internals were *** results suggest that TYPE 1 upper plenum internals cause the largest flowrate difference at the core outlet while TYPE 3 leads to the most even distributed *** distribution and evolution pattern of the tangential velocity inside hot legs is highly dependent on the upper plenum *** counter-rotating swirls exist inside the TYPE 1 hot leg and only one swirl revolving around the hog leg axis exist inside the TYPE 2 hot *** TYPE 3,two swirls like that of TYPE 1 rotating around the hot leg axis significantly increase the temperature homogenization *** research provides meaningful guidelines for the future optimization and design of advanced PWR upper plenum internal structures.

关键词： pressurized water reactor(PWR) upper plenum internal structures temperature distribution computational fluid dynamics(CFD)

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An end-to-end instance segmentation method based on improved ConvNeXt V2

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International Journal of Wireless and Mobile Computing 2024年第4期26卷 384-392页

作者： Wang, Wenlu Sun, Ying Xu, Manman Bai, Dongxu Huang, Li Zou, Chunlong Chen, Baojia Tang, Dalai Key Laboratory of Metallurgical Equipment and Control Technology of Ministry of Education Wuhan University of Science and Technology Hubei Wuhan China Research Centre for Biomimetic Robot and Intelligent Measurement and Control Wuhan University of Science and Technology Hubei Wuhan China Hubei Key Laboratory of Mechanical Transmission and Manufacturing Engineering Wuhan University of Science and Technology Hubei Wuhan China College of Computer Science and Technology Wuhan University of Science and Technology Hubei Wuhan China Hubei Province Key Laboratory of Intelligent Information Processing and Real-time Industrial System Wuhan University of Science and Technology Hubei Wuhan China College of Mechanical Engineering Hubei University of Automotive Technology Hubei Shiyan China Hubei Key Laboratory of Hydroelectric Machinery Design and Maintenance China Three Gorges University Hubei Yichang China School of Computer Information Management Inner Mongolia University of Finance and Economics Hohhot China

In order to improve the efficiency of indoor mobile robots in locating and segmenting environmental instances, an instance segmentation method based on RTMDet is proposed. Firstly, the more powerful ConvNeXt V2 is used as the backbone network of the model, which improves the performance of the existing RTMDet model. Subsequently, NAS-FPN is used as a converged network to detect the network at any given time. Finally, AdamW is used as the model optimiser, which effectively solves the problem of excessive memory occupation when updating parameters and improves the performance of the model. The proposed method obtains the highest evaluation index in all cases. After training and testing on the Cityscapes data set, the recognition accuracy reaches 65.0%. © 2024 Inderscience Enterprises Ltd.

关键词： Statistical tests

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Research on the application of Cobalt-Based Alloy Laser Additive Manufacturing in reactor Internals 29

Research on the application of Cobalt-Based Alloy Laser Addi...

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2022 29th International Conference on Nuclear Engineering, ICONE 2022

作者： Wang, Qingtian Cao, Rui Zhang, Xianjun Science and Technology on Reactor System Design Technology Laboratory Chengdu China Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9780791886458

In view of the quality problems of manual TIG coating of cobalt-based alloy, the Laser Additive Manufacturing process was studied, especially the optimization of process parameters. Then a series of experiments were carried out on the cobalt-based alloy Additive Manufacturing layer and compared with the traditional manual TIG coating layer. The results show that the microstructure, the hardness, the wear resistance and corrosion resistance are better than. Copyright © 2022 by ASME.

关键词： Microstructure

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One-DOF Rigid and Flat-Foldable Origami Polyhedrons with Slits

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Acta Mechanica Solida Sinica 2023年第4期36卷 479-490页

作者： Yuehao Zhang Yuanqing Gu Yan Chen Ming Li Xiao Zhang School of Mechanical Engineering Tianjin UniversityTianjin 300350China Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education Tianjin UniversityTianjin 300350China Space Structure and Mechanism Technology Laboratory of China Aerospace Science and Technology Group Co.Ltd Aerospace System Engineering ShanghaiShanghai 201109China

Rigid origami has great potential in aerospace applications,especially deployable polyhedrons with one degree of freedom(DOF)and flat-foldability,whose types are few to *** this paper,we create a novel foldable cube and a rhombic dodecahedron by introducing slits and diagonal creases to the surfaces,whose one-DOF rigid and flat-foldable properties are verified by kinematic ***,based on the isohedral quadrilateral transform,we project the creases and slits of the rhombic dodecahedron onto a tetrahedron to obtain a novel foldable tetrahedron that has two flat-foldable motion paths due to the existence of collinear *** the second path,unnecessary creases are removed,and an origami tetrahedron with simplified creases is *** origami tetrahedrons possess a small folded *** analysis reveals that these newly discovered origami polyhedrons are flat-foldable with one DOF,demonstrating favorable application prospects for space architectures and extraterrestrial habitats.

关键词： Rigid origami Flat-foldability Cube Rhombic dodecahedron Tetrahedron

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INVESTIGATION ON THE SIMULATION OF TURBULENT HEAT TRANSFER OF LIQUID METAL FLOW IN A NARROW RECTANGULAR CHANNEL 29

INVESTIGATION ON THE SIMULATION OF TURBULENT HEAT TRANSFER O...

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2022 29th International Conference on Nuclear Engineering, ICONE 2022

作者： Zhang, Xue Yu, Hongxing Deng, Jian Du, Sijia Zhang, Xilin Zou, Ziqiang Feng, Wenpei Zhang, Yaoxiang Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China Hefei China

ISBN: (纸本)9780791886434

Liquid metal has the advantages of high boiling point and strong thermal conductivity and is selected as the coolant for a new generation nuclear system. In addition, the narrow rectangular channel is used in the small reactors or research reactors due to its compact structure and high heat transfer capacity. In order to accurately simulate the turbulent heat transfer of liquid metals in narrow rectangular channels, based on the relevant experimental data, this paper explored suitable numerical simulation methods. First of all, according to the research object, the appropriate experimental data was selected, and the geometric modeling, mesh division, and the mesh independence verification were carried out. It was ensured that the y+ meets the requirements of each turbulence model and wall treatment model. Several typical turbulence models and the wall treatment models were evaluated. For the low Prandtl number fluid such as liquid metal, it is necessary to select a suitable turbulent Prandtl number model in the RANS simulation. The sensitivity of the calculation results to the turbulent Prandtl number was analyzed. Finally, the existing turbulent Prandtl number models were evaluated. The suitable at different Pe was given based on experimental value, so that the turbulent heat transfer of liquid metal in a narrow rectangular channel can be accurately simulated. Copyright © 2022 by ASME.

关键词： Liquid metals

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THE DEVELOPMENT OF FISSION PRODUCT DIFFUSION/RELEASE MODEL FOR FAILED TRISO PARTICLES 30

THE DEVELOPMENT OF FISSION PRODUCT DIFFUSION/RELEASE MODEL F...

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30th International Conference on Nuclear Engineering, ICONE 2023

作者： Zheng, Junqiang He, Yanan Wu, Junmei Wu, Yingwei Li, Yuanming Tian, Wenxi Su, Guanghui Qiu, Suizheng School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an China State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace Xi'an Jiaotong University Xi'an China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institution of China Chengdu China

ISBN: (纸本)9784888982566

TRISO coated fuel particle has been adopted in the design of various reactors and Accident Tolerant Fuel (ATF) due to its excellent accident tolerant performance under high temperatures and other severe conditions. Accurately estimating fission product release from TRISO-coated fuel particles is indispensable to calculate the mechanistic source term. In most models, a bare kernel is substituted conservatively for failed particle. Thus, a theoretical method was proposed to describe the transport of fission products in intact and failed fuel particles. In this paper, to analyze the diffusion and release characteristics of intact TRISO-coated fuel particles' fission products, the fission products diffusion model of TRISO-coated fuel particles with thermal-mechanical coupling was established based on the COMSOL Multiphysics software and verified by the IAEA CRP-6 benchmark. The results indicate that the predictions by the developed fission product transport model is reasonable. Moreover, to analyze fission product release for failed partials, a conceptual theoretical method was proposed. The adsorption and desorption constraint model for fission products at the gas-solid interface and the gas phase diffusion model were added to the original model to analyze. Subsequently, predictions comparison for fission products' fractional release in failed particles between the proposed method and the Settings adopted in BISON were completed. The result suggests that the gas-phase diffusion model is feasible and seems favorable to simulate the diffusion of fission products in the failed coating layers. © 2023 by JSME.

关键词： Fission products

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