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SSRN 2024年

作者： Li, Haoyang Ding, Ming Guo, Zehua Heilongjiang Provincial Key Laboratory of Nuclear Power System & Equipment Harbin Engineering University Harbin150001 China 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

Molten salts have attracted a spate of quantity of interest in energy and chemistry fields due to their large volumetric capacity, and thermodynamic stability at elevated temperatures. However, on account of immature technology and measurement methods, the physical properties of molten salts, such as dynamic viscosity, thermal conductivity, specific heat capacity and density, have large uncertainties, which will be transported with CFD simulation equations and experimental processes. While present investigations normally focus on thermal-hydraulic characteristics, disregarding the impact of uncertainty on reactor safety. Thus, this paper firstly performs a numerical simulation to investigate the thermal-hydraulic performance of FLiNaK (LiF-NaF-KF, 46.5–11.5–42 mol%) in a horizontal tube using a computational fluid dynamic (CFD) tool, STAR-CCM+, and validates the applicability of classic correlations for molten salt. Based on this, an uncertainty analysis methodology, polynomial chaos expansion (PCE) is carried out to analyze the uncertainty that contributes to the heat transfer characteristic. Three primary physical properties of molten salt are considered as the input parameter, tensor product quadrature nodes are employed in this work to calculate the representative sample points to alleviate the computational expense. The contributions of each parameter to heat transfer are also analyzed by the sobol composition method. Finally, deviations in the experimental post-processing (compared with classic correlations) caused by discrepancies in the selected properties from the actual properties due to uncertainty are also taken into account. The result shows the thermal-hydraulic performance can be nicely modeled and simulated results are in good agreement with widely used correlations. Meanwhile, the consequences of uncertainty analysis suggest that the polynomial chaos expansion methodology is robust and neoteric for molten salt analysis. © 2024, The Authors. All righ

关键词： Uncertainty analysis

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Hydrodynamic Pattern in Drying Saline Droplet with Suspended Nanoparticles

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Journal of Bionic engineering 2020年第4期17卷 802-808页

作者： Junheng Ren Xin Zhong Lu Shen Fei Duan School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Evaporation of multicomponent droplets has gained much attention nowadays because of their complex flow fields and various deposition *** we observe strong flows in evaporating sodium chloride saline droplets with suspended alumina oxide *** evolution of flow pattern was studied by tracking the trajectories of particles and the velocity field was investigated with Particle Image Velocimetry *** non-uniform evaporation rate along the droplet surface leads to a concentration gradient which induces the convection *** the evaporation process before crystallization happens,evolution of the flow can be divided into two *** Regime I,a centrosymmetric convection recirculation is formed *** RegimeⅡ,the convection recirculation migrates to the droplet edge and evolves into several small *** the late evaporation stage,crystallization could induce strong convection *** is shown that the flow tends to become more chaotic with a lower salt concentration.

关键词： convection flow concentration gradient saline droplet crystallization

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Theoretical Study on Predicting the Performance of Steam Ejector by Analogy Method

Theoretical Study on Predicting the Performance of Steam Eje...

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IEEE Asia power and Energy engineering Conference (APEEC)

作者： Yiguo Mei Keneng Qian Yuyan Hou Weixiong Chen Huaxin Consulting Design and Research Institute Co. Hangzhou China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

At present, it is difficult to obtain steam with high pressure under conventional laboratory conditions, and there are certain operational risks in the production of high-pressure and high-temperature steam devices. In this paper, a method to predict the critical entrainment ratio of the steam ejector by using the critical entrainment ratio of the air ejector is proposed. According to the one-dimensional calculation model of the ejector, the parameters related to the critical entrainment ratio are derived. The mathematical relationship between the entrainment ratio and each parameter is found through the mathematical tool Matlab. The performance of the ejector with different working mediums is simulated and verified by Fluent. The research results in this paper show that the entrainment ratio of air and steam ejector is linear with the pressure ratio within a certain range of pressure ratio. Under this linear relationship, the experimental entrainment ratio of the air ejector can be used to predict the entrainment ratio of the steam ejector. In a certain linear range, the relative error between the entrainment ratio predicted by the method proposed in this paper and the simulation results is within 10%.

关键词： Electrical engineering Simulation Fitting Production Media Numerical simulation Market research

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Effect of Tungsten Size on Thermal Analysis and Mechanism of Lithium Perchlorate-Based Electrically Controlled Solid Propellant

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SSRN 2023年

作者： Yang, Meng Yoh, Jack J. Tang, Chenglong Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Aerospace Engineering Seoul National University Seoul08826 Korea Republic of

Electrically controlled solid propellant (ECSP) is a novel and potential of propellant with excellent properties, which can achieve multiple ignitions and extinguishments through supplying and cutting electric power. At present, thermochemistry coupled with electrochemical reaction processes are complex and not understood clearly, especially its based thermal decomposition mechanism without electric power. In this work, the baseline ECSP was prepared using lithium perchlorate (LiClO4, LP) as oxidant, and tungsten as metal additive to obtain high energy ECSP samples. The scanning electron microscope (SEM), differential scanning calorimeter (DSC) and thermogravimetry (TGA) were used to investigate thermal analysis characteristics of ECSP and the effect of metal tungsten sizes on reaction process and mechanism. The heat release and effective activation energy (Eα) of baseline ECSP were lower than those of metalized ECSP. In addition, with W size increasing, heat release and Eα of ECSP increase. Based on thermal analysis and kinetic results, the decomposition mechanisms of ECSP main components and samples were proposed. The absorbed and crystal water evaporated, then main components molten for all cases at low temperature ( © 2023, The Authors. All rights reserved.

关键词： Thermogravimetric analysis

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Data Mining-Assisted Multi-Objective Optimization of Blade Angle Distributions for Efficiency and Stability Enhancement of a Free-Form Centrifugal Impeller

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SSRN 2024年

作者： Chen, Zhikai Chen, Ziying Sun, Jieshuai Guo, Yi Spence, Stephen Peng, Xueyuan Feng, Jianmei School of Energy and Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Manufacturing and Biomedical Engineering Trinity College Dublin Dublin 2 Ireland State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China

The design optimization process for a centrifugal compressors faces significant trade-offs between efficiency, pressure ratio, and stable operating range. To address this challenge, a data mining assisted-optimization combining machine learning modelling method and non-dominated sorting genetic algorithm III (NSGA-III) has been proposed to enhance efficiency and pressure ratio while considering expansion of operational stability. A validated CFD numerical model was established for data generation. A Light-GBM model with Bayesian hyperparameter tuning and a deep feedforward neural network (DNN) model were constructed, and the better one was selected for performance prediction. Data mining techniques, including Sobol sensitivity analysis and SHAP, were employed to identify the key sensitive parameters and their interactions. Finally, a NSGA-III-based multi-objective optimization was conducted to determine the optimal geometry of the free-form surface impeller. Results showed that the blade angle distributions at the leading edge of mid-span and shroud profile were the most sensitive parameters affecting isentropic efficiency at the design point, with their recommended ranges identified. The optimized impeller has an increase in total pressure ratio of 2.98% and isentropic efficiency of 0.67% at the design point, especially exhibiting excellent aerodynamic performance at higher mass flow rate conditions. The maximum improvements of total pressure ratio and isentropic efficiency were 12.91% and 9.53%, respectively, corresponding to the near choke mass flow rate at the design speed. Additionally, operating stability was expanded with a 1.22% increase in total pressure ratio at near surge mass flow rate at the design speed, which contributed to a delay in the onset of surge. © 2024, The Authors. All rights reserved.

关键词： Sensitivity analysis

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Effects of Inherent Aaems on Catalytic Gasification of Biomass with Large Particle Size Under Oxygen-Steam Atmosphere

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SSRN 2023年

作者： Ren, Jiyun Li, Yuhang Li, Yang Huang, Xiaole Jin, Xiaoling Yang, Chenglong Zhao, Hanchen Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Xi’an Thermal Power Research Institue Co. Ltd. Xi’an710032 China

Oxygen-steam gasification of biomass is a promising technology because of its ability to improve syngas quality and reduce energy consumption. In this study, a fixed-bed reactor is employed to assess the effects of inherent alkali and alkaline earth metals (AAEMs) on the catalytic gasification of candlenut wood with large particle size under oxygen-stream atmosphere. The results show that the acid-washing would remarkably remove the inherent AAEMs in biomass, which is affected by the grain direction. In terms of the gasified chars derived from acid-washed biomass, AAEMs content gradually decreases along the end surface and radial direction, which could also be observed from the 3D reconstruction of X-ray CT images. A large number of mesopores (20-30 μm) align along the grain direction in the biomass sample. Numerous micropores (10-20 μm), mesopores (20-30 μm), and macropores (30-50 μm) are present in the gasified char derived from the biomass sample. Micropores (10-20 μm) prevail in the gasified char from the acid-washed biomass sample. Inherent AAEMs facilitate an augmentation in char yield as well as BET and total pore volume of gasified char. AAEMs and grain direction have a slight effect on functional groups of gasified char. The tar component is remarkably affected by the grain direction. Acid-washing pretreatment augments the content and organic species of M2-M4 compounds (containing 2-4 benzene rings) in the tar. It also leads to a decrement in concentrations of H2, CH4, and CO2 by 14.49% and 13.35%, 0.51% and 0.89%, 2.32% and 1.37% in syngas for two-grain direction, respectively. But it raises the CO concentration by 17.1% and 15.18%, resulting in a reduction of 4.09% and 1.53% in syngas calorific value. A decrement in the volume fraction of CnHx induced from AAEMs is significantly affected by the grain direction. © 2023, The Authors. All rights reserved.

关键词： Biomass

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Numerical and Experimental Investigation of Proton Exchange Membrane Fuel Cell with Perpendicular Gas Supply Through the Ridge

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SSRN 2023年

作者： Zhang, Yan Lu, Xinyu Su, Jinzhan School of International Trade and Economics China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi’an Jiaotong University Xi’an710049 China

The structural design of the cathode flow field in proton exchange membrane fuel cell (PEMFC) is essential for efficient gas supply and effective water removal. For investigating the mechanism behind the effect of gas flow direction on improving the performance of PEMFC, a novel modified serpentine flow channel with vertical inlets through the ridge for PEMFC was proposed and investigated by numerical and experimental methods. Under the operating voltage of 0.4 V, the vertical air supply mode exhibits a 7% higher current density compared to the parallel air supply mode. Compared with conventional air supply mode through the serpentine flow channel, vertical air supply mode modified serpentine through a tunnel inside the ridge exhibited higher oxygen uniformity and higher current density. Furthermore, we conducted research on the impact of physical parameters, including the porosity and thickness of the GDL, as well as the vertical gas supply pore density, on the performance of the PEMFC within the vertical gas supply mode. At an operating voltage of 0.4 V, the current density of PEMFC with a GDL thickness of 0.28 mm is 1.0009 A/cm2, which is 3.02% and 6.13% higher than that of PEMFC with vertical inlets with GDL thickness of 0.38 and 0.48 mm, respectively. With a porosity of 0.6, the current density of PEMFC reaches 1.0395 A/cm2, surpassing that of PEMFCs with porosities of 0.2 and 0.4 by approximately 24.8% and 6.6%, respectively. Moreover, higher vertical inlet densities lead to improved PEMFC performance. Simulation and experimental results demonstrate that this modified flow field effectively addresses uneven current density distribution and enhances power output at low voltage. © 2023, The Authors. All rights reserved.

关键词： Porosity

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Effects of Inherent Aaems on Catalytic Gasification of Biomass with Large Particle Size Under Oxygen-Steam Atmosphere

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SSRN 2023年

作者： Ren, Jiyun Li, Yuhang Jin, Xiaoling Huang, Xiaole Li, Yang Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Xi’an Thermal Power Research Institue Co. Ltd. Xi’an710032 China

Oxygen-steam gasification of biomass is a promising technology because of its ability to improve syngas quality and reduce energy consumption. In this study, a fixed-bed reactor is employed to assess the effects of inherent alkali and alkaline earth metals (AAEMs) on the catalytic gasification of candlenut wood with large particle size under oxygen-stream atmosphere. The results show that the acid-washing would remarkably remove the inherent AAEMs in biomass, which is affected by the grain direction. In terms of the gasified chars derived from acid-washed biomass, AAEMs content gradually decreases along the end surface and radial direction, which could also be observed from the 3D reconstruction of X-ray CT images. In all biomass samples and gasified chars, micropores (0-10 μm) dominate and are distributed along the grain direction. In general, pores of 20-30 μm and above 30 μm comprise a minor proportion. Inherent AAEMs facilitate an augmentation in char yield as well as BET and total pore volume of gasified char. AAEMs and grain direction have a slight effect on functional groups of gasified chars. The tar component is remarkably affected by the grain direction. Acid-washing pretreatment augments the content and organic species of M2-M4 compounds (containing 2-4 benzene rings) in the tar. It also leads to a decrement in concentrations of H2, CH4, and CO2 by 14.49% and 13.35%, 0.51% and 0.89%, 2.32% and 1.37% in syngas for two-grain direction, respectively. But it raises the CO concentration by 17.1% and 15.18%, resulting in a reduction of 4.09% and 1.53% in syngas calorific value. A decrement in the volume fraction of CnHx induced from AAEMs is significantly affected by the grain direction. © 2023, The Authors. All rights reserved.

关键词： Biomass

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Experimental investigation on heat transfer characteristics of high temperature air in round tube

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International Journal of Advanced Nuclear Reactor Design and Technology 2021年 3卷 200-205页

作者： Qin, Hao Wang, Chenglong Tian, Wenxi Qiu, Suizheng Su, Guanghui Department of Nuclear Science and Technology Xi'an Jiaotong University Shaanxi Xi'an710049 China Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology Xi'an Jiaotong University China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

Air is widely utilized as working fluid in heat exchangers with high heat flux and high temperature, and the empirical correlations for predicting local and total heat transfer coefficients are indispensable for thermal design and optimization of the heat exchange applications. Experimental investigation on heat transfer characteristics of high temperature air in round tube is conducted. The experimental system is designed and constructed. The data processing method for obtaining wall temperature and heat transfer coefficient is introduced. The measured local and total heat transfer coefficients are compared with the widely adopted correlations, including Taylor's correlation and Gnielinski's correlation. The suggested empirical correlations obtained from the experimental data are presented, which may contribute to the design of heat exchangers concerning with high temperature air. © 2021 Xi'an Jiaotong University

关键词： Heat transfer coefficients

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Editor, Applied Energy Paper Entitled: "Industrialized Bimetallic Nano Oxygen Carrier for Dual-Stage Hydrogen Production from Mid-Temperature Chemical Looping Reforming"

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SSRN 2024年

作者： Tang, Sanli Gai, Zhongrui Li, Yang Liu, Yunlian Liu, Mingkai Pan, Ying Jin, Hongguang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China University of Chinese Academy of Sciences Beijing100049 China

Chemical looping methane reforming has emerged as a promising avenue to produce blue hydrogen. Among the various oxygen carriers investigated for this process, Fe2O3 and NiO have garnered significant attention due to their affordability and favorable thermodynamic properties. Usually, such oxygen carriers had satisfactory H2 yields only in the oxidation stage with temperatures over 800 °C. This limitation poses challenges for industrial reactor design and product gas separation. In this study, we present a nanoscale Fe/Ni bimetallic oxygen carrier for dual-stage hydrogen generation from mid-temperature chemical looping methane reforming. The lab-scale oxygen carrier can produce H2 in both the reduction and the oxidation steps, reaching 75% overall H2 purity while reducing the temperature to 500-600 °C. Moreover, the 10-kg scale oxygen carrier achieved >90% CH4 conversion, >78% H2 purity and 2.8-3.5 H2 molecules produced per CH4 molecule. Made into beads, the 10-kg scale oxygen carrier still maintained an outlet H2 purity of >70% with redox stability over 150 cycles. These findings contribute to the advancement of chemical looping methane reforming for blue hydrogen production and supply. © 2024, The Authors. All rights reserved.

关键词： Hydrogen production

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