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Microscopic characteristics study of liquid ammonia spray under different flash boiling conditions

Fuel 2025年 401卷

作者： Liu, Xiao Zeng, Gangwei Yao, Xiaoxin Tang, Chenglong Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Liquid ammonia, as a zero-carbon fuel, has received widespread attention in the field of internal combustion engines. The development of ammonia spray and evaporation models urgently requires accurate particle size distribution data. In this study, microscopic characteristics of liquid ammonia spray were firstly experimentally investigated under conditions of high injection pressure (up to 80 MPa) and ambient pressure (up to 4 MPa) with a single-hole injector (0.3 mm). Statistical results of microscopic parameters, including Sauter Mean Diameter (SMD), characteristic droplet diameter, and droplet number density were obtained over a wide range. The results indicate that ambient pressure or RP significantly affects the microscopic characteristics of ammonia spray. In flare flash boiling region (pressure ratio RP ≤ 0.3), ammonia spray produces more droplets with smaller diameter and the statistical SMD is around 15 μm. The droplet size increases and number density decreases with the increasement of ambient pressure or RP. In the transition flash (0.3 P ≤ 1) and non-flash boiling region (RP > 1), the SMD statistical results are approximately 20 and 24 μm, respectively. Increasing the injection pressure can promote atomization and generate more smaller droplets, with a more uniform distribution. Ambient temperature slightly affects the microscopic characteristics of liquid ammonia spray within the temperature range selected for this study, but evaporation becomes more pronounced as the ambient temperature increases. The wide range droplet size distribution and SMD are believed to provide important data for ammonia spray modeling and simulation. © 2025

关键词： Internal combustion engines

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flow and residence time distribution characteristics in continuous hydrothermal reactor under different heating schemes

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Chemical engineering Science 2025年 316卷

作者： Li, Yi Wang, Junying Li, Xiaoyu Jin, Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi710049 China

Residence time distribution (RTD) is of significance for reflecting materials or intermediate products dispersion and actual reaction time inside continuous hydrothermal reactors of supercritical water gasification technology. Generally, RTD is strictly related to flow field, which can be affected by wall heating schemes. In order to propose methods to regulating RTD, effects of different heating schemes on flow and RTD characteristics are investigated and compared by numerical simulation. The results indicate that increasing heat flux, interrupting boundary flow by interlace heating, and setting cooling walls can significantly regulate RTD. By analyzing the correspondence of flow and RTD, the mechanisms of increasing materials and intermediate products dispersion can be attribute to the increase of flow instability and the generation of additional vortices. For example, in the cases of present work, the narrow-strip double-vortex generated by mixing between thermal boundary flow and branch flow may significantly increase average residence time and materials distribution range from 10.93 s and 1.00 to 22.83 s and 1.51. In the region above branch inlet without time-averaged vortex structure, the increasing of flow instability caused by wall heating is observed to widen materials distribution range from 0.75 to 0.99. Heating scheme customized according to these mechanisms can regulating RTD as expected, proving the feasibility and significance of regulating RTD by heating schemes. © 2025

关键词： Reaction intermediates

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Identification of flow cut-off pattern and prediction of cut-off time of gas-liquid two-phase flow in pipeline-riser system

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Physics of Fluids 2025年第5期37卷

作者： Liu, Tianyu Wang, Hanxuan Zou, Suifeng Du, Yaohua Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

For offshore pipeline-riser systems, cyclic flow cut-off in slugging flow pattern should be identified and necessarily mitigated to satisfy the requirement of normal operation of gas-liquid separator. Since conventional studies on flow pattern identification were not directly related to the harmfulness of slugging and the decision of flow control, this study develops a risk assessment method for offshore riser systems based on the characteristic parameters of riser outlet signals, achieving an identification accuracy exceeding 90% at different valve openings. Notably, the method maintains exceptional performance under high-pressure conditions, with identification accuracy reaching 96.74% at 10 MPa. On the other hand, this study focuses on the prediction of cut-off duration time in a cycle instead of the cycle period. We establish a predictive model for flow cut-off duration time under different choking conditions. Validation across diverse pipeline systems demonstrates strong reliability of the model, exhibiting maximum prediction errors of 30%. The model's coefficients can be fitted by a small dataset without significant loss of accuracy, and the coefficients are conservative, indicating strong applicability in the field operation. These findings offer significant theoretical insights and practical solutions for enhancing the operational safety of offshore oil and gas transportation systems. © 2025 Author(s).

关键词： Marine risers

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Numerical Simulation Study on Two-Phase flow of Thermal Runaway Evolution and Jet Fire of 18650 Lithium-Ion Battery Under Thermal Abuse

SSRN

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SSRN 2023年

作者： Wang, Jia-Hao Mei, Mei Jiang, Ziqi Qiu, Huihe Wang, Ying Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Clear Water Bay Hong Kong

This study investigates the impact of particles on the external jet flame of 18650 lithium-ion batteries using a two-dimensional transient numerical simulation. The mixing characteristics of jet flames and particles generated by battery combustion are analyzed using a multi-component Navier-Stokes equation and Lagrangian method. The model is validated by comparing it with experimental measurements of flame height. The results show that particles have a significant impact on the jet flame's characteristics and dynamic behavior during the battery's thermal runaway process. The study includes an analysis of the velocity field, temperature field, flow field, component concentration distribution, and lift-off height. Two stages of the jet flame are identified: unstable and stable. The presence of particles causes the unstable flame height to be 1-2 times higher than the stable flame height. This research provides reference for the safety assessment of actual batteries. © 2023, The Authors. All rights reserved.

关键词： Lithium-ion batteries

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Investigation on turbulent characterization of arrayed micro-tube premixed hydrogen flames using an enhanced flamelet library

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Applied Thermal engineering 2025年 275卷

作者： Han, Xiao Yin, Yanxu Wang, Bosen Chang, Yunxin Cai, Xiao Research Institute of Aero-Engine Beihang University Beijing100191 China National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics Beihang University Beijing100191 China Collaborative Innovation Center for Advanced Aero-Engine Beihang University Beijing100191 China Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an710049 China

Lean turbulent premixed hydrogen/air flames exhibit increased flame wrinkling and significantly enhanced flame speeds, posing challenges for stable combustion. In the novel arrayed multi-flame burner, flame instabilities are intensified by flame-flame interactions. This study develops a distributed and efficient numerical framework for the Large Eddy Simulation-Flamelet Generated Manifold (LES-FGM) method, incorporating an improved 1D flamelet library. The framework is applied to investigate flame dynamics in both bluff-body and conical flame systems under varying equivalence ratios (= 0.4–0.7) and Karlovitz numbers (Ka = 1–100). By accounting for preferential diffusion, thermal-diffusive instability, and heat loss in stretched flames, the framework improves the accuracy of the flamelet library and captures key physical effects. 1D simulations are performed to validate and analyze the influence of differential diffusion on flame characteristics. The impact of transient flame stretching is analyzed in detail, revealing its critical role in stability transitions across varying turbulence intensities. Additionally, this study examines turbulence effects and micromix multi-flame interactions. The flame stretch factor varies from 1.1 to 2.4 in these three cases. At lower equivalence ratios, higher Ka suppresses tip-opening but intensifies small-scale flame wrinkling. Flame pocket detachment becomes more frequent. Vortex interactions play a key role in flame instability. The strain rate of conical flames is 40 % lower than that of bluff-body flames. These findings provide novel insights into flame dynamics in multi-flame burner arrays, which are critical for optimizing combustion performance in gas turbine combustors. © 2025 Elsevier Ltd

关键词： Large eddy simulation

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Heavy Oil Upgrading Using Naoh/Cuso4 Composite Catalyst in Aquathermolysis

SSRN

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SSRN 2022年

作者： Zhou, Yantao Zhao, Qiuyang Miao, Yan Wang, Xuetao Zhang, Yanlong Wang, Yechun Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xinjin Weihua Institute of Clean Energy Research Foshan528216 China

To obtain an inexpensive and efficient catalyst in the in-situ upgrading of heavy oil, the NaOH/CuSO4 composite catalyst was proposed in this work. Firstly, the experiments found the viscosity of heavy oil increased with addition of CuSO4 under 300°C in aquathermolysis. Then, the addition of NaOH was found to improve the catalyst capacity of CuSO4 significantly. The NaOH/CuSO4 decreased the viscosity by 81.43% under 300°C. The further analysis revealed the Cu atoms of CuSO4 enter into the heavy oil molecules to increase viscosity, and the NaOH inhabits the viscosity increasing reaction. Besides, the Cu and CuOx with a higher catalytic capacity produced with the addition of NaOH. These conclusions are helpful to understand the aquathermolysis upgrading mechanism and develop a type of inexpensive and efficient composite catalyst. © 2022, The Authors. All rights reserved.

关键词： Sulfur compounds

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Experimental Study on Leakage of High-Energy Fluids Through Narrow Elliptical Slits

SSRN

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SSRN 2024年

作者： Bi, Qincheng Zhang, Tao Zhao, Jinle Wang, Teng Yang, Zhendong Gui, Miao State Key Lab Multiphase Flow Power Engn Xi'an Jiaotong University Shaanxi Xian710049 China Department of Power Engineering North China Electric Power University Baoding071003 China State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China Xi'an University of Technology Shaanxi Xian710048 China School of Nuclear Science and Technology Xi'an Jiaotong University Shaanxi Xian710049 China

This study is focused on the leakage flow rate of high-energy fluid passing through narrow elliptical slits with large aspect ratios, which is an issue in the application of the leak-before-break concept. Experiments were conducted using a high-temperature and high-pressure experimental platform at Xi’an Jiaotong University, where the temperature reached up to 320 ℃ and the pressure reached up to 10 MPa. These temperatures and pressures encompass a wide range of operating conditions (single-phase cold water, liquid-vapor (two-phase) mixture, and superheated steam). A series of narrow elliptical slits with different aspect ratios (528-2083) and hydraulic diameters (226-412 um) were used in the experiments. The experimental results were compared with previous model. Based on the experimental data and the the effects of the aspect ratio, the mathematical model was corrected, and the results obtained from the modified model conform well with the experimental results. © 2024, The Authors. All rights reserved.

关键词： Aspect ratio

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Development and technical progress in large-scale circulating fluidized bed boiler in China

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Frontiers in Energy 2020年第4期14卷 699-714页

作者： Zhong HUANG Lei DENG Defu CHE State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an 710049China

Circulating fluidized bed(CFB)boilers has realized the clean and efficient utilization of inferior coal like gangue and coal slime,high sulfur coal,anthracite,petroleum coke,oil shale and other *** a country with the largest amount of CFB boilers and the largest installed capacity in the world,China has 440100-600 MWe CFB boilers with a total capacity of 82.29 GWe,including 227 units of 135 MWe,95 units of300 MWe,and 24 supercritical *** statistics of typical 100-300 MWe CFB boilers showed that the average number of unplanned shut-down was only 0.37 times per year,among which the 135 MWe was 0.26 times per year and 300 MWe was 0.46 times per ycai*.The auxiliary power ratio of some 300 MWe CFB boilers based on flow-pattern reconstruction can be reduced to about 4%,which is closed to the same level of pulverized coal(PC)*** paper summarizes the development process and application status of China's large-scale CFB boilers,analyzes the characteristics and technical performance of the iconic units,and introduces solutions to the problems such as water wall wear and bottom ash cooling.

关键词： CFB boiler installed capacity reliability economics ultra-low emission China

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An Investigation on the Formation and flow Characteristics of Nature Gas Hydrates at Different Loop Inclination Angles

SSRN

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SSRN 2022年

作者： Liu, Ni Wang, Cheng Meng, Fei Yang, Liang Liu, Daoping School of Energy and Power Engineering The University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

One of the major issues in flow assurance includes pipeline plugging due to gas hydrate formation and deposition,which makes it imperative to look for appropriate hydrate control strategies. In this study, a high-pressure visual flow loop was used to analyze the influence of different inclination angles (0°–4°) on the formation, flow, morphology evolution, deposition process, and mechanism of hydrates. The macro-parametric data, including pressure, temperature, velocity, hydrate induction time and hydrate volume fraction, were compared and analyzed. Results showed that the hydration reaction rate of downslope section is slightly faster than that of upslope section in inclined section. Although the amount of hydrate finally formed is the same, the hydrate in the downslope section is more dense. While the loop inclination angle had little effect on the amount of hydrate formation, with the increase of inclination angle, the induction time tends to decrease and the hydration reaction time will be longer overall. At 1° inclination angle, the induction time was the shortest and the hydration reaction time was the longest. The deposition process of the horizontal pipe is divided into four stages, in which large hydrate particles in the liquid phase are evenly distributed throughout the pipeline, forming a hydrate moving bed. The hydrate deposition process of the inclined pipe is also divided into four stages. Among them, the large hydrate particles in the liquid phase are concentrated on the upper wall of the pipeline, which causes the density of the upper part of the pipeline to be much higher than that of the lower part, forming a hydrate-fixed *** results of this study can deliver theoretical support to ensure the safe transportation of gas hydrate slurries. © 2022, The Authors. All rights reserved.

关键词： Gas hydrates

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EXPERIMENTAL INVESTIGATION ON THE REFLOODING IN A 5×5 ROD BUNDLE 29

EXPERIMENTAL INVESTIGATION ON THE REFLOODING IN A 5×5 ROD B...

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2022 29th International Conference on Nuclear engineering, ICONE 2022

作者： Liu, Weihua Yuan, Hongsheng Wu, Pan Wang, Ting Shan, Jianqiang School of Nuclear Science and Technology Xi'an Jiaotong University No. 28 Xianning West Road Shaanxi Xi'an China China Nuclear Power Technology Research Institute Co. Ltd No.1001 Shangbu Middle Road Futian District Guangdong Shenzhen518026 China The State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an China

ISBN: (纸本)9780791886410

In the current study, a series of reflood tests with uniformly power input have been carried out at the 5×5 rod bundle film boiling test facility of the Nuclear Safety and Operation laboratory(NUSOL) of Xi'an Jiaotong University and the experimental results have been analyzed in detail. The effect of several parameters, including subcooling of coolant (10K to 75K), coolant flow rate (2.5m/s to 10.0m/s) and input wall linear power density (7 W/cm to 13 W/cm) on quench front of reflooding patterns have been studied. It is observed that the quench front during reflood stage of the rod bundle channel is sensitive to above parameters. Increase in input wall linear power density, and decrease in flow rate and subcooling of coolant results in delayed reflooding. The temperature, heat flux and heat transfer coefficient on the rod surface have been got via the self-development Reflooding Experimental Data Analysis (REDA) code. The data is not only useful for the development of theoretical models for film boiling heat transfer, two-phase void fraction, pressure drop, and rod bundle reflooding prediction, but also can be used as a benchmark data base for evaluating the analysis code of Loss of Coolant Accident (LOCA) in reactor and the design of the residual heat removal system. Copyright © 2022 by ASME.

关键词： Coolants

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