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Effects of Combustor Wall Temperature on the Outer Recirculation Zone Combustion Modes Transition in Lean Premixed Dme/Air Swirl Flames

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SSRN 2024年

作者： Lin, Wenjun Zhang, Weijie An, Zhenhua Wang, Jinhua Huang, Zuohua Zhang, Huangwei State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Mechanical Engineering National University of Singapore 9 Engineering Drive 1 Singapore117576 Singapore Department of Mechanical Engineering and Science Kyoto University Kyoto daigakuKatsura Nishikyo-ku Kyoto615-8540 Japan

In this study, the effects of wall thermal conditions on the ORZ combustion modes transition in the DME/air swirl flames are investigated using the Large Eddy Simulation (LES) and Flamelet Generated Manifold (FGM) method. The results show that the ORZ chemistry and temperature are highly sensitive to the wall thermal condition. Based on the correlation between the temperature and species observed in the time-averaged numerical results, the relation between the combustion mode and temperature in the ORZ is discovered. Through temporal analysis of species and heat release rate in the ORZ, the stable Mode II and Mode IV as well as the unstable Mode III are identified. The chemical reaction pathway analysis for typical probe in the ORZ reveals that different combustion modes undergo distinct (lowtemperature or high-temperature) chemical reaction pathways. Afterwards, the definition of combustion modes used in experiments is refined by utilizing the chemical reaction data from the simulations. And it is applied to identify the combustion mode across the entire computational domain. The results confirm the consistency between the combustion modes determined in experiments based on OH and CH2O and those determined in simulations using chemical reaction rates. Finally, this explains the mechanism of the flickering flame in Mode III is the competition between the low-temperature and high-temperature reaction in the ORZ. Whereas the unstable Mode III can be stabilized by changing the wall temperature to reach the Mode II or Mode IV. © 2024, The Authors. All rights reserved.

关键词： Temperature

Thermal-Hydraulic Characteristics of Helical Cruciform Single Rod Based on Cfd Investigation

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SSRN 2024年

作者： Chen, Yiwen Zhang, Dalin Jiang, Dianqiang Deng, Jian Zhang, Xisi Wang, Xinan Tian, Wenxi Qiu, Suizheng Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China Nuclear Power Institute of China 328 Changshun Avenue Chengdu610213 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China China Institute of Atomic Energy Beijing611731 China

To increase power density in nuclear reactors, the helical cruciform fuel (HCF) is designed as a fundamental element. HCF takes advantages of strong mixing effects, self-supporting features, and strengthened heat transfer, potential to increase the fuel performance in nuclear reactors. In this paper, friction factor and heat transfer coefficient empirical correlations of HCF single rod cooled by water were proposed using a geometric dimensionless number based on numerical simulation. The velocity field, and temperature distribution were obtained to discuss influences of geometric sizes on the fuel performance. Finally, correlations with a geometric dimensionless number were validated with various cases, whose application conditions were also proposed and discussed. This paper provides a guide for study of heat transfer and fluid flow in helical structures, and a reference for establishment of reactor system model using helical cruciform fuels. © 2024, The Authors. All rights reserved.

关键词： Heat transfer coefficients

Thermal Modulation of Radiation Fields Enhancing the Adaptability of Cpv-Hydrogen Systems to Hot Outdoor Conditions

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SSRN 2023年

作者： Zhu, Yizhou Zhang, Ting’an Geng, Jiafeng Jing, Dengwei Xi'an University of Science and Technology China Department of Chemical Engineering School of Water and Environment Chang'an University Shaanxi Xi’an710064 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

The efficiency of photovoltaic (PV) modules operating outdoors often subject to significant decrease due to high PV surface temperature under hot outdoor conditions despite of the high irradiation in this period. Meanwhile, the commercial electrolytic water splitting unit requires additional heat sources to preheat the electrolyte, which is neither economical nor energy efficient. This study introduces a proton exchange membrane (PEM) water electrolyzer system coupled with concentrated photovoltaic (CPV) and a pipe-based liquid spectral beam splitting filter acting also as an electrolyte preheater. The results of continuous experiments during local summer daytime show that the average PV surface temperature of the proposed system can be reduced by 23.5 K compared to that without spectral beam splitting filter. Moreover, the average efficiencies of photovoltaic, electrolysis and solar-to-hydrogen can be increased by 7.5%, 8.1% and 5.2%, respectively. Both simulation and experimental results confirm that our design can reduce the sensitivity of system efficiency toward weather factors, especially high-intensity summer irradiation. This work provides a promising option for application of large-scale solar hydrogen production in regions with sufficient sunlight while high outdoor temperature. © 2023, The Authors. All rights reserved.

关键词： Hydrogen production

A New Reduced Reaction Mechanism of the Surrogate Fuel for RP-3 Kerosene

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SSRN 2022年

作者： Liu, Jing Hu, Erjiang Zheng, Weilin Zeng, Wen Chang, Yachao State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shangxi Xi’an710049 China Liaoning Key Lab of Advanced Test Technology for Aerospace Propulsion System Shenyang Aerospace University Liaoning Shenyang110136 China Key Laboratory of Ocean Energy Utilization and Energy Conservation Ministry of Education Dalian University of Technology Dalian116024 China

By combining the reaction class-based global sensitivity analysis (RC-GSA) methodology, species sensitivity analysis (SSA) methodology, decoupling method and genetic algorithm (GA), a reduced reaction mechanism of the surrogate fuel (10% n-dodecane/14% n-decane/30% iso-hexadecane/36% methylcyclohexane/10% toluene, in mole fraction) for RP-3 kerosene was constructed. As an example, the detailed construction process of skeleton mechanism of methylcyclohexane (MCH) was presented, and the skeleton mechanism constructions of other components in the surrogate fuel were similar to that of MCH. First, the dominant reaction classes in the fuel-relevant mechanism of MCH were recognized by the RC-GSA, the representative species in each retained reaction classes were selected by the SSA, and the skeleton fuel-relevant mechanism of MCH was developed. Second, through combining the skeleton fuel-relevant mechanism of MCH with the reduced reaction mechanism of C 0 -C 3 by the decoupling method, the initial skeleton mechanism of MCH was obtained. Third, based on the GA, the rate constants of fuel-relevant reactions in the initial skeleton mechanism of MCH were optimized to enhance the prediction performance. Finally, by coupling the skeleton reaction mechanisms of n-dodecane, n-decane, toluene, iso-hexadecane, MCH, and the reduced reaction mechanism of C 0 -C 3 , a reduced mechanism (containing 121 species and 469 reactions) of the surrogate fuel for RP-3 kerosene was formed. The predicted main species concentrations during the oxidation process in the jet-stirred reactor, the ignition delay times in the shock tube and laminar flame speeds in the constant volume bomb by this reduced mechanism are in good agreement with the corresponding experimental data of RP-3 kerosene. © 2022, The Authors. All rights reserved.

关键词： Sensitivity analysis

Core/Shell Structured Hematite Nanorod Arrays as Photoanodes for Efficient Solar Water Oxidation

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Core/Shell Structured Hematite Nanorod Arrays as Photoanodes...

IUPAC 9th International Conference on Novel Materials and their Synthesis(NMS-IX) & 23rd International Symposium on Fine Chemistry and Functional Polymers(FCFP-XXIII)(IUPAC第九届新型材料和合成国际会议暨第23届国际精细化工和功能聚合物研讨会)

作者： S.Shen Samuel S.Mao Department of Mechanical Engineering University of California at BerkeleyBerkeley CA 94720 United States Department of Mechanical Engineering University of California at BerkeleyBerkeley CA 94720 United States International Research Center for Renewable State Key Laboratory of Multiphase Flow in Power Engineering Xi''an Jiaotong University Shaanxi 710049 China

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

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

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

Turbulent heat transfer in a horizontal helically coiled tube

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Heat Transfer 2000年第5期28卷

作者： Bofeng Bai Liejin Guo Ziping Feng Xuejun Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

An experiment has been conducted in detail to study the turbulent heat transfer in horizontal helically coiled tubes over a wide range of experimental parameters. We found that the enhancement of heat transfer in the coils results from the effects of turbulent and secondary flows. With Reynolds number increasing to a high level, the contribution of the secondary flow becomes less to enhance heat transfer, and the average heat transfer coefficient of the coil is closer to that in straight tubes under the same conditions. The local heat transfer coefficients are not evenly distributed along both the tube axis and the periphery on the cross section. The local heat transfer coefficients on the outside are three or four times those on the inside, which is half of the average heat transfer. A correlation is proposed to describe the distribution of the heat transfer coefficients at a cross section. The average cross-section heat transfer coefficients are distributed along the tube axis. The average value at the outlet section should not be taken as the average heat transfer coefficient. © 1999 Scripta Technica, Heat Trans Asian Res, 28(5): 395–403, 1999

关键词： turbulent heat transfer horizontal helically coiled tube secondary flow local heat transfer