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Comparative Analysis on Energy Losses in Hydrogen and Helium Turbo-Expanders for Hydrogen Liquefiers

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SSRN 2022年

作者： Zhou, Kaimiao Chen, Liang Li, Shanfeng Zhao, Kang Zhang, Ze Chen, Shuangtao Hou, Yu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Beijing institute of Aerospace Testing Technology Beijing100074 China

The helium Brayton cycle and the hydrogen Claude cycle are the baseline processes for large-scale hydrogen liquefaction. Helium and hydrogen turbo-expanders are the crucial components, respectively, determining the system efficiency and reliability. In this paper, a comparative analysis is performed on the energy losses in helium and hydrogen turbo-expanders for hydrogen liquefaction systems. Similarity analysis is carried out to set the baseline design of helium and hydrogen turbo-expanders. Mean-line method is employed in the design, and losses in nozzle and impeller are determined. CFD simulations are performed to illustrate the internal flow field and loss mechanisms in helium and hydrogen turbo-expanders. The CFD predictions of isotropic efficiency agree well with that by the loss models. The results show that the passage loss in the impeller is the dominant loss for cryogenic hydrogen and helium turbo-expanders. Due to the higher sound speed and lower viscosity, the hydrogen turbo-expander has smaller nozzle loss and incidence loss compared with the helium turbo-expander, but the tip clearance loss and residual velocity loss in the hydrogen expander are larger. © 2022, The Authors. All rights reserved.

关键词： Helium

Propagation and Burning Velocity of Iron-Methane-Oxygen-Nitrogen Turbulent Expanding Flames

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SSRN 2023年

作者： Cai, Xiao Su, Limin Su, Shouguo Wang, Jinhua Alden, Marcus Li, Zhongshan Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Division of Combustion Physics Lund University P.O. Box 118 LundS221 00 Sweden

The propagation and burning velocity of iron-methane-oxygen-nitrogen turbulent expanding flames were experimentally studied by employing a newly optimized spark-ignition, fan-stirred combustion chamber, in which micron-sized iron particles can be dispersed homogeneously. Fine iron particles with averaged diameter of 1.9 μm was used in the present study. The flame trajectory of iron-methane mixture at different turbulence intensities and iron concentrations was recorded using a high-speed camera. It was found that the flame propagation speed increases as iron-methane turbulent flame expands. The acceleration process is mainly caused by the extension of flame surface dissipation spectrum by increasing the largest flame scales (flame radius). The turbulent burning velocity, ST increases significantly with the turbulence intensity, which is well known feature in gaseous flames. However, the iron concentration does not have an obvious effect on the ST, which is unique to iron flame in turbulence environment. Because the turbulent flame propagation is dominated by turbulent heat transfer, which is characterized by turbulence intensity. In addition, the formation of iron flame front is controlled by the couple effects of iron concentration and turbulence intensity in turbulent environment. Furthermore, the laminar burning velocity, SL was accurately determined using a nonlinear extraction method. A correlation of turbulent burning velocity was obtained based on the experimental iron-methane data. The measured ST and its correlation would be used to develop practical iron burners and to validate turbulent combustion models of iron flames. © 2023, The Authors. All rights reserved.

关键词： Iron

Study on the Flame Structure and flow Field of Hydrogen-Enriched Combustion in Array Micro-Tube

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SSRN 2024年

作者： Tian, Liang Feng, Wenbin Han, Xiao Liu, Yuzhi Liu, Hongfang Cai, Xiao School of Energy and Environmental Engineering Hebei University of Technology Tianjin300401 China National Key Laboratory of Science and Technology on Aero-Engine Aero thermodynamics Research Institute of Aero-Engine Collaborative Innovation Center for Advanced Aero-Engine Beihang University Beijing100191 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China

Addressing climate change and reducing greenhouse gas emissions are critical priorities. Utilizing hydrogen-rich methane or pure hydrogen as fuels within gas turbines, facilitated by array micro-tube premixed combustion technology, is anticipated to markedly accelerate the decarbonization process of the energy sector. In this study, the flame structure of the array micro-tube premixed burner under various fuel compositions was examined using OH-Planar Laser-Induced Fluorescence (OH-PLIF) and Particle Image Velocimetry (PIV) measurement techniques. The effects of the equivalence ratio (φ) and the hydrogen power ratio (HPR) on the characteristics of the flame front, including its curvature, density, volume, and the associated flow field properties, were discussed. As φ and HPR increase, the wrinkled structure of the flame front is significantly enhanced, with a more pronounced effect on smaller scales. This enhancement leads to the separation of the unburned pockets from the main flame. Concurrently, both the flame length and flame area decrease with the augmentation of φ and HPR, indicating a more concentrated combustion process and increased combustion intensity under hydrogen-enriched and pure hydrogen conditions. The study also observed a slight increase in both the negative and positive curvatures of the flame front, with a more notable increase in negative curvature. The increased negative curvature results in an elevated degree of wrinkling and a higher value of Σ (flame surface density), reaching a maximum of 0.876 mm-1 under the conditions where φ is 0.8 and (mean progress variable) is 0.5, resulting in the smallest observed flame volume of 100.6 mm3. Upon coupling the flame with the flow field, it was discovered that the exit flow field of the array micro-tube exhibits symmetry and a characteristic conical flame shape. The burning velocity of the side flame brushes increases, and the velocity peak shifts upstream. The above findings confirms that the additio

关键词： flow fields

Applying multi-scale simulations to materials research of nuclear fuels:A review

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Materials Reports(Energy) 2021年第3期1卷 64-80页

作者： Chunyang Wen Di Yun Xinfu He Yong Xin Wenjie Li Zhipeng Sun School of Nuclear Science and Technology Xi'an Jiaotong UniversityXi'an710049China State Key Laboratory of Multiphase Flow Xi'an Jiaotong UniversityXi'an710049China China Institute of Atomic Energy Beijing102413China Key Laboratory of Nuclear Reactor System Design Technology Nuclear Power Institute of ChinaChengdu610213China

Computational simulation is an important technical means in research of nuclear fuel *** nuclear fuel issues are inherently multi-scopic,it is imperative to study them with multi-scale simulation *** present,the development of multi-scale simulation for nuclear fuel materials calls for a more systematic approach,in which lies the main purpose of this *** most important thing in multi-scale simulation is to accurately formulate the goals to be achieved and the types of methods to be *** this regard,we first summarize the basic principles and applicability of the simulation methods which are commonly used in nuclear fuel research and are based on different scales ranging from micro to macro,***-Principles(FP),Molecular Dynamics(MD),Kinetic Monte Carlo(KMC),Phase Field(PF),Rate Theory(RT),and Finite Element Method(FEM).And then we discuss the major material issues in this field,also ranging from micro-scale to macro-scale and covering both pellets and claddings,with emphasis on what simulation method would be most suitable for solving each of the ***,we give our prospective analysis and understanding about the feasible ways of multi-scale integration and relevant handicaps and challenges.

关键词： Computational simulation Nuclear fuel Multi-scale modeling Irradiation behavior

Parametric Investigation of Multi-Pulsed Cryogen Spray Cooling for Skin Protection During Hyperthermal Laser Lipolysis Through in Vitro Experiment and Numerical Simulation

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SSRN 2022年

作者： Xin, Hui Yu, Fangbo Deng, Chenggang Chen, Ming Li, Dong Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi'An710049 China School of Mechanical Engineering Ningxia University Ningxia Yinchuan750021 China

Laser lipolysis is now a commonly accepted modality to remove fat. Transcutaneous hyperthermal laser lipolysis has attracted researchers’ interest because of its advantages of non-invasive nature and high efficiency. Owing to the competitional absorption of laser energy between skin and adipose tissue, it is necessary to develop efficient skin cooling technology to protect epidermis and dermis from thermal damage. In vitro laser experiment was carried out using streaky pork which has similar optical and thermal properties with human adipose tissue. Temperature changes of pigskin epidermis under 1210nm laser irradiation with different power (6W~12W) and irradiation duration (3s~13s) were obtained by infrared thermal imager. The experimental results showed that the epidermis temperature will exceed the safety threshold of 47°C when laser power is equal to 6W and irradiation duration longer than 5s, or laser power is equal or larger than 9W and irradiation duration equal or longer than 3s. To protect skin from thermal injury, multi-pulsed cryogen spraying cooling (MP-CSC) by using R134a was introduced. Numerical simulation was conducted to match cooling and laser parameters by simplifying skin tissue to a multi-layered model. It is suggested that hyperthermal laser lipolysis with power of 6W/9W and irradiation duration of 7s can be realized, accompanied by MP-CSC with pulse duration of 10ms, pulse delay of 2000ms and pulse number of 5. © 2022, The Authors. All rights reserved.

关键词： Cooling

Numerical Simulations on Hybrid Thermal Management of Mini-Channel Cold Plate and Pcm for Lithium-Ion Batteries

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SSRN 2024年

作者： Liu, Yang Zhou, Zhifu Wu, Wei-Tao Wei, Lei Li, Yang Liu, Xinyu Huang, Heng Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China

In this study, a novel battery thermal management system (BTMS), combining phase change material (PCM) and mini-channel cold plates (MCPs), was modeled and analyzed. First, the effects on single cell cooling using MCPs and PCM alone are investigated at different coolant rates, temperatures, and PCM thicknesses. Then, the hybrid thermal management system (HTMS) is developed with the aim of reducing the cooling load of the PCM through hybridization with MCPs and the optimal combination of them is investigated. At the end of this work, the thermal performance of a battery pack with a hybrid thermal management structure has been analyzed, where the cold plate can take away the heat from the PCM to restore its thermal storage capacity. The results show that the combination of 3 channel and 10 mm PCM with 0.1 m/s coolant velocity and 20°C coolant temperature is the quit suitable regarding the cooling performance. Under 2C discharging rate, this design reduces the maximum battery temperature to 40°C, which is 32.5% lower, and the average temperature to 35℃, which is 41% lower than it without cooling. The study's findings offer potential new strategies and predictions for hybrid thermal management that utilize MCPs and PCM. © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

Curvature Adaptive Voxel-Based Monte Carlo Method with Application for Customized Retinal Laser Surgery

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SSRN 2024年

作者： Zhang, Hao Li, Dong Chen, Bin Zhang, Hanfeng Liang, Yao Zheng, Yuping Wang, Guoxiang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Ophthalmology 2nd affiliated hospital Medical School Xi’an Jiaotong University Xi’an710049 China Department of Mechanical Engineering The University of Akron AkronOH44325 United States

Accurate prediction of light propagation and energy deposition in biological tissues is crucial for the success of laser-based medical treatments. We propose a novel Curvature Adaptive Voxel-based Monte Carlo method (CAVMC) to correct for light reflection and refraction at curved interfaces by introducing coordinate transformation with an artificial surface parallel to the curved interface. This approach achieves an optimal balance between simulation accuracy and efficiency. Our study demonstrates that for small optical mismatches, the relative error can be reduced significantly, with the energy deposition error dropping from 34.7% to 6.6%. For large optical mismatches, CAVMC substantially improves accuracy, reducing computational errors by more than 50%. We validated CAVMC in a customized retinal laser therapy scenario for diabetic retinopathy, demonstrating its ability to accurately predict laser energy deposition and thermal effects, which is crucial for avoiding tissue damage during treatments. The efficiency and accuracy of the CAVMC method make it valuable for personalized retinal laser surgery and potentially other medical applications. Overall, CAVMC offers a robust tool for simulating light propagation in heterogeneous biological tissues, enhancing the precision and safety of medical treatments. © 2024, The Authors. All rights reserved.

关键词： Laser surgery

Numerical Simulations for Comparison of Cold Plate Cooling and Hfe-7000 Immersion Cooling in Lithium-Ion Battery Thermal Management

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SSRN 2024年

作者： Liu, Xinyu Zhou, Zhifu Wu, Wei-Tao Wei, Lei Hu, Chengzhi Li, Yang Huang, Heng Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China

In this work, fluorinated liquids can be used as a new immersion coolant for effective battery thermal management (BTM) because of their insulating and non-flammable inert characteristics. In this research, the liquid chosen for immersion cooling is HFE-7000, characterized by a boiling point of 34°C. The analysis of bubble kinetics is employed to investigate the heat transfer mechanism in two-phase immersion cooling by examining the behavior of bubbles during the boiling process. The square ternary Li-ion batteries are subjected under loads of 2C and 3C cooled by immersion cooling and a mini-channel cold plate as a comparison. It turns out that immersion liquid cooling modules offer superior thermal performance. Under constant current (CC), the peak temperature is reduced by 4.89°C and 9.31°C compared with the mini-channel cold plate cooling (CPC). Under dynamic load conditions, the maximum temperature rise of the battery is reduced by 29.89% and 43.89% compared to CPC. As a passive heat dissipation method, two-phase immersion cooling reduces the design requirements for active control. Also, it delivers an efficient battery thermal management system (BTMS) designed for upcoming electric vehicles (EVs). © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

Research on Bionic Airfoil Design Method Based on Re-Evolution Optimization and Multi Objective Application on Horizontal Axis Wind Turbines

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SSRN 2023年

作者： Huang, Shengxian Yan, Hua Qiu, Huihe Wang, Ying Shanghai Key Laboratory of Multiphase Flow and Heat Transfer of Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Clear Water Bay Hong Kong

The design of specific airfoil for wind turbine is a crucial factor in the research of wind turbine performance and stability. Based on biomimetic methods and numerical optimization methods, a brand new airfoil design method is proposed without relying on any traditional airfoil and airfoil design experience. A new airfoil is successful designed that gives consideration to both aerodynamic performance and roughness sensitivity. Based on the actual engineering environment of a horizontal axis wind turbine, the multi-island genetic algorithm is used to adjust the profile of the biomimetic airfoil (Dol-Rot24°). The optimized airfoil is named as Dol-Opt. In the performance verification of the Dol-Opt airfoil, it is found that compared with the Dol-Rot24°, the lift coefficient of the Dol-Opt airfoil is increased by 171.06%, and the lift-to-drag ratio is increased by 52.41% at most. Moreover, the roughness sensitivity of the Dol-Opt is also the optimum among the three airfoils (S809, Dol-Rot 24°, Dol-Opt). By conducting numerical simulations, it is found that the newly optimized wind turbine blades exhibit greatly improved energy efficiency. The purpose of this study is to provide effective references for the design, bionic methods, and practical engineering applications of wind turbine specific airfoils. © 2023, The Authors. All rights reserved.

关键词： Airfoils