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Investigation of uncertainty quantification methods for constitutive models and the application to LOFT LBLOCA

ANNALS OF NUCLEAR ENERGY 2019年第Oct.期132卷 119-133页

作者： Xiong, Qingwen Gou, Junli Chen, Wei Dang, Gaojian Shan, Jianqiang Xi An Jiao Tong Univ Sch Nucl Sci & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Nucl Power Inst China Chengdu 810041 Sichuan Peoples R China

Best estimate (BE) codes are developed to carry out realistic safety analysis of the nuclear reactor, and generally hundreds of constitutive models are comprised in a BE code. Nevertheless, uncertainties of these constitutive models are often not properly handled in the best estimate plus uncertainty (BEPU) analysis. It is not sufficient to fully evaluate the uncertainties of different sorts of models with only one method. Thereby a structural method for uncertainty quantification (UQ) of constitutive models is proposed and relevant description is presented. Based on the method, constitutive models will be classified into two categories according to the characteristics, namely the independent model and the dependent model, and different methods will be adopted for different sorts of model. Several statistical methods for UQ of constitutive models such as the non-parametric curve estimation method, the Bayesian calibration method and the coverage calibration method are evaluated and the characteristics of these methods are discussed. In addition, several methods for the construction of surrogate model are utilized to reduce the computational cost, and a model selection technique is adopted to opt the optimal model among all alternative models. The large break loss of coolant accident (LBLOCA) experiment LOFT LP-02-6 is utilized to verify the proposed structural method, and the BEPU analysis of the LP-02-6 experiment is carried out. The results show that uncertainty intervals of the identified models obtained through the structural method are reasonable, uncertainties of the peak cladding temperature (PCT) as well as the accumulator injection time (AIT) are quantified, and the sensitivity analysis is carried out to evaluate the influence of different input parameters on the 1st PCT, 2nd PCT and the AIT. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Uncertainty quantification BEPU Constitutive model LBLOCA

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Experimental Investigation on Ejector Performance Using R134a as Refrigerant

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Journal of Thermal Science 2019年第4期28卷 727-735页

作者： DAI Zhengshu YU Bo LIU Pengpeng CHEN Guangming ZHANG Hua School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China State Key Laboratory of Air-conditioning Equipment and System Energy Conservation Zhuhai 519070China Institute of Refrigeration and Cryogenics Zhejiang UniversityHangzhou 310027China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093China

Ejector refrigeration has the advantage of low capital cost,simple design,reliable operation,long lifespan and almost no *** only weakness is the low efficiency and its intolerance to deviations from design operation condition.R134 a used in ejector refrigeration system gives better performance in comparison with many other environmental friendly refrigerants as the generation temperature is from 75℃to 80℃.The present work experimentally investigated the on-design and off-design performance of the ejector with fixed geometry using R134 a as refrigerant,and cycle performance of the ejector refrigeration *** experimental prototype was constructed and the effects of primary flow inlet pressure,secondary flow inlet pressure and ejector back pressure on ejector performance and cycle performance were investigated *** operation conditions are:primary flow inlet pressure from 2.2 MPa to 3.25 MPa,secondary flow inlet pressure from 0.36 MPa to 0.51 MPa,ejector back pressure from 0.45 MPa to 0.67 *** were drawn from the experimental results,and the experimental data can be used for validation of theoretical model for both critical and subcritical mode.

关键词： ejector performance refrigeration R134a experiment

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Numerical studies of nitrogen spontaneous condensation flow in laval nozzles using varying droplet growth models

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INTERNATIONAL JOURNAL OF multiphase flow 2019年 121卷 103118-000页

作者： Sun, Wan Chen, Shuangtao Hou, Yu Bu, Shanshan Ma, Zaiyong Zhang, Luteng Chongqing Univ Minist Educ Key Lab Low Grade Energy Utilizat Technol & Syst Chongqing 400044 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Spontaneous condensation of gas at transonic or supersonic flow is a great concerned phenomenon in many cryogenic engineering fields. An accurate model is of great significance to better understand the mechanism of such condensation and arising issues. In this paper, numerical studies for the effect of droplet growth model modification on the nitrogen condensation flow through Laval nozzles were performed in ANSYS CFX via user defined language. The used four profiles of Laval nozzle were designed with different expansion rate (3000, 5000, 7000 and 10000 s(-1)) in Ji's experiment (Ji 1990). The throat size is 6.5 (height) x 3.2 (width) mm. Firstly, the classical nucleation model with non-isothermal correction was successful to accurately predict the location of condensation onset in experiment by the down calibration for nucleation rate. The supercooled degree is about 9K and nucleation rate is at the order of 10(20) m(-3).s(-1). Secondly, the simulations of condensation flow using different droplet growth models including Gyarmathy and Young models were accomplished. Based on the analysis of interphase heat and mass transfer, the influence mechanism caused by modification for droplet growth rate on two-phase flow fields was revealed. The results indicate that this modification has a considerable effect on the development of droplet size and relaxation time of gas back to equilibrium, but little influence on location prediction of condensation onset. Finally, the effect of inlet total pressure on two-phase flow parameters was also analyzed. At low pressure, a larger supercooled degree (similar to 11 K) is required to trigger the occurrence of spontaneous condensation. Correspondingly, the influence intensity resulting from the change of droplet growth model on the interphase mass transfer and thermal fields will obtain some enhancement, but still inappreciable compare to the expansion effect. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Droplet growth Laval nozzles Nitrogen condensation Nucleation Two-phase flow

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Feasibility analysis and simulation of argon recovery in low oxygen-purity cryogenic air separation process with low energy consumption

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CRYOGENICS 2019年 97卷 109-121页

作者： Ye, Hengyang Zheng, Jieyu Li, Yanzhong Xi An Jiao Tong Univ Sch Energy & Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

This paper has discussed and simulated different low oxygen-purity air separation processes with or without argon recovery to find out efficient air separation process using HYSYS platform, and proposed a novel mixing-column process that provides high argon recovery rate based on energy saving effect. For comparison, all the proposed cases are simulated under the same process conditions of 50,000 Nm(3)/h feed air, 95% gaseous oxygen purity, 0.03 MPa gauge pressure, and 300 Nm(3)/h liquid oxygen output. Three main performance parameters including oxygen recovery rate, energy consumption and argon recovery rate are compared, and the simulation results show that among five types of processes without argon recovery, the triple-column process, whose energy requirement decreases by 14.9% compared with conventional dual-column process, achieves the lowest energy consumption. Argon production is required in many aspects during air separation process. The feasibility of argon recovery in low oxygen-purity air separation process is studied. The process with argon recovery named mixing-column process is proposed, whose argon recovery rate can reach up to 60.88%, which further increases up to 62.23% with the optimized raw argon flow rate and mixing-ingredient. The energy consumption of the proposed mixing-column process is decreased by 3.5% compared with conventional dual-column process, while the argon recovery rate of the triple-column process can only reach to 4.55% in despite of energy saving by 12%. In addition, more stable argon recovery performance as well as higher argon recovery rate is realized by this novel process when using varied oxygen purity in low oxygen-purity (<= 99%) process.

关键词： Cryogenic Air separation Argon recovery Feasibility analysis Simulation

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Simultaneous removal of NOx and SO2 from coal-fired flue gas based on the catalytic decomposition of H2O2 over Fe2(MoO4)3

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CHEMICAL engineering JOURNAL 2019年 371卷 486-499页

作者： Liu, Xuan Wang, Changan Zhu, Tao Lv, Qiang Li, Yang Che, Defu Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Sch Energy & Power Engn Xian 710049 Shaanxi Peoples R China Xian Thermal Power Res Inst Co Ltd Xian 710032 Shaanxi Peoples R China

The purification of flue gas has drawn the increasing attention in recent years. In the present study, a novel oxidation-absorption process was proposed for simultaneous removal of NOx and SO2 from coal-fired flue gas based on the catalytic decomposition of H2O2 over Fe-2(MoO4)(3), in which gaseous pollutants were first oxidized by center dot OH radicals and then absorbed with ammonia solution. The effects of H2O2 dosage, temperature, gas hourly space velocity (GHSV) and flue gas component on simultaneous removal efficiency were systematically investigated. The results indicated that the removal efficiencies of 91.4% for NOx and 100% for SO2 could be achieved under the optimal conditions. The signal of center dot OH radical was verified by fluorescence test. The center dot OH radicals were essential for NO oxidation and the subsequent NOx removal, while SO2 was primarily removed in absorption process. Moreover, the presence of SO2 was favorable for NOx removal, mainly because the existence of SO2 promoted NO oxidation. X-ray photoelectron spectroscopy (XPS) analysis further confirmed that SO2 could reduce part of Fe3+ to Fe2+ on catalyst surface, thereby reducing the consumption of H2O2 by Fe3+ and promoting the majority of H2O2 to generate center dot OH. The continuity test revealed that the synthesized Fe-2(MoO4)(3) showed satisfactory stability. The surface morphology and crystal structure of the catalyst exhibit negligible change after 15 h of reaction. Products analysis indicated that NH4NO3 and (NH4)(2)SO4 were the primary products after removal of NOx and SO2. A three-step mechanism was preliminarily developed to interpret the simultaneous removal process in H2O2/Fe-2(MoO4)(3) system.

关键词： Simultaneous removal of NOx and SO2 Fe-2(MoO4)(3) center dot OH radicals Catalyst stability Removal mechanism

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fEffect of alkali and alkaline metals on gas formation behavior and kinetics during pyrolysis of pine wood

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Fuel 2021年 290卷

作者： Li, Jinhu Burra, Kiran G. Wang, Zhiwei Liu, Xuan Gupta, Ashwani K. The Combustion Laboratory Department of Mechanical Engineering University of Maryland College ParkMD20742 United States Faculty of Engineering China University of Geosciences WuhanHubei430074 China College of Environmental Engineering Henan University of Technology Zhengzhou450001 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China

This study examines the acid and alkaline treatment of pine wood to help understand the effect of alkali and alkaline earth metals (AAEMs) content on the pyrolysis behavior at different temperatures. Acid and alkali pretreatment of pine wood were conducted to modify AAEMs content by ion-exchanging method. Thermal kinetic behavior of the pretreated samples was first conducted by a thermogravimetric analyzer (TGA) at different heating rates that provided activation energies of pyrolysis. Gas formation behavior of the samples for different extents of conversion was carried out in a fixed-bed reactor at two different temperatures of 823 K and 1073 K. Evolutionary behavior of the gas components during pyrolysis, including flow rate, and yield and their energy content were measured and compared. Results showed that the values of activation energies increased with the extent of conversion for all the pretreated samples examined. The effect of AAEMs on pyrolysis behavior of biomass varied with the extent of conversion. The presence of AAEMs in biomass decreased the decomposition energy at low conversion while it greatly improved under high conversion. Besides, alkali treated sample with higher AAEM content enhanced the gas and char yield while it reduced the bio-oil production at low temperature with low conversion. However, at high temperature the opposite trend was observed. Presence of AAEMs was favorable for the generation of H2, CO, CO2 and CnHm at low temperature, while it showed an inhibition effect on CO and CnHm yield and syngas energy at high temperature. The catalytic mechanism of AAEMs on the pyrolysis behavior at different temperatures was discussed based on activation energy and gaseous formation. Results revealed decomposition of carboxylate at low temperature and formation of stable biomass-Na (BM-Na) structure at high temperature that led to the variation of activation energy and changed gaseous products yield and syngas energy. Acid washing pretreatment wa

关键词： Activation energy

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Yolk-shell-like mesoporous CoCrOx with superior activity and chlorine resistance in dichloromethane destruction

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APPLIED CATALYSIS B-ENVIRONMENTAL 2020年第0期264卷 118493-000页

作者： Feng, Xiangbo Tian, Mingjiao He, Chi Li, Lu Shi, Jian-Wen Yu, Yanke Cheng, Jie Xijing Univ Shaanxi Key Lab Safety & Durabil Concrete Xian 710123 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Sch Energy & Power Engn Xian 710049 Shaanxi Peoples R China Univ Chinese Acad Sci Natl Engn Lab VOCs Pollut Control Mat & Technol Beijing 101408 Peoples R China Xi An Jiao Tong Univ State Key Lab Elect Insulat & Power Equipment Ctr Nanomat Renewable Energy Sch Elect Engn Xian 710049 Shaanxi Peoples R China Columbia Univ Dept Chem Engn New York NY 10027 USA Chongqing Univ Sci & Technol Inst Hlth & Environm Chongqing 401331 Peoples R China

Promoting chlorine resistance and inhibiting by-product generation are critical issues in catalytic destruction of chlorinated volatile organic compounds (CVOCs). Herein, a yolk-shell-like mesoporous CoCrOx as a robust catalyst was synthesized for deep destruction of dichloromethane (DCM) considering its superior mass transfer and molecule enrichment ability. The strong interaction between Co and Cr elements in CoCrOx results in efficient generation of active Cr6+ and oxygen species, which greatly enhances the activity of CoCrOx in DCM oxidation, much higher than that of Co3O4, Co3O4+Cr2O3 and Cr2O3. Chloromethane (CH3Cl), trichloromethane (CHCl3) and tetrachloromethane (CCl4) can be detected as the cleavage of C-H bond and generation of C-Cl bond during DCM destruction. We found that the acid sites can effectively inhibit the formation of by-products over CoCrOx material, which is a promising material for CVOC elimination. The results from this work provide some new insights into the design of catalysts for CVOC destruction.

关键词： Catalytic destruction Dichloromethane CoCrOx composite Stability By-products

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Thermo-economic analysis of a combined cooling, heating and power system based on carbon dioxide power cycle and absorption chiller for waste heat recovery of gas turbine

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ENERGY CONVERSION AND MANAGEMENT 2020年 224卷 113372-113372页

作者： Li, Bo Wang, Shun-sen Wang, Kai Song, Liming Xi An Jiao Tong Univ Sch Energy & Power Engn Inst Turbomachinery State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Peoples R China

A novel combined cooling, heating and power system which consists of carbon dioxide power cycle, absorption chiller and heaters is proposed in this paper for waste heat recovery of gas turbine. In the proposed cogeneration system, the absorption chiller and heaters are driven by the residual energy of carbon dioxide power cycle and flue gas simultaneously. Detailed mathematic models are established to simulate and evaluate the system from the perspective of thermodynamics and economics. The results of parametric analysis indicate that there is an optimal value for the turbine inlet temperature, at which the exergy efficiency is maximized and the levelized cost of exergy is minimized. As the split ratio increases, the exergy efficiency and levelized cost of exergy of the proposed system first increase then decrease simultaneously. Single-objective optimization is carried out to maximize the exergy efficiency of the proposed system. The optimal results show that the exergy efficiency and levelized cost of exergy of the cogeneration system are 4.62% higher and 0.90 cent lower than that of standalone power cycle, respectively. Compared with the alternative cogeneration system in which only low-temperature flue gas or the waste heat of power cycle is used to drive the refrigeration subsystem and heating subsystem, the exergy efficiency of proposed system is enhanced by 2.89% and 1.3%, respectively. Finally, multi-objective optimization is carried out with exergy efficiency and levelized cost of exergy as objective functions. Pareto frontier is calculated and recommended point is given for the engineering practice.

关键词： CCHP Waste heat recovery Carbon dioxide power cycle Absorption refrigeration cycle Thermo-economic analysis Optimization

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Effects of shear inhomogeneities on the structure of turbulent premixed flames

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COMBUSTION AND FLAME 2019年 208卷 63-78页

作者： Jin, Wu Steinmetz, Scott A. Juddoo, Mrinal Dunn, Matthew J. Huang, Zuohua Masri, Assaad R. Univ Sydney Sch Aerosp Mech & Mechatron Engn Sydney NSW 2006 Australia Xian Jiatong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

This paper studies the effects of shear inhomogeneities on the structure and stability characteristics of turbulent piloted premixed flames. The shear is introduced by splitting the fuel-air mixture in two stream and feeding each stream at different velocities through two annular concentric tubes residing within the pilot annulus. The shear is varied by varying the proportion of fluid injected through the streams and also by changing the recess distance of the inner tube with respect to the jet exit plane. It is noted that with increasing rates of shear, the Bunsen-like flames become shorter with the flame tip opening downstream of the pilot stream. Measurements of flow fields reveal useful information about the level and location of the shear layers. Joint imaging of Laser-Induced Fluorescence (LIF) of OH and CH show that, with increasing rates of shear, the degree of flame front fragmentation increases implying the occurrence of local extinction even in regions extremely close to the pilot. The flame surface area, marked by LIF-CH is taken as an indicator of consumption rates of reactants. For all flames examined here, the peak flame surface area increases with increasing shear and subsequently decreases as the flame shortens and approaches blow-off. The peak flame surface density decreases with increasing shear. Regime diagrams show that the flames investigated here bridge the regions of broadened preheat thin reactions as well as the distributed reaction zone. While the thickness of the CH layer remain somewhat uniform, the number of flame fragments, as indicated by breaks in the CH profiles, increases with increasing shear before stabilizing at some peak value. The observed mechanism of local extinction in highly sheared Bunsen-like, turbulent piloted premixed flames complements existing results for bluff-body stabilised flames. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

关键词： Premixed flames Shear inhomogeneity Local extinction

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Defect engineering on sea-urchin-like transition-metal oxides for high-performance supercapacitors

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JOURNAL OF power SOURCES 2022年 533卷 231409-231409页

作者： Yin, Baoyi Hao, Liang Wei, Tao Wang, Chen Zhu, Bao Li, Xiaogan Yang, Qiguo Dalian Univ Technol Sch Microelect Dalian 116024 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Univ Jinan Sch Mat Sci & Engn 336 Nanxinzhuang West Rd Jinan 250022 Shandong Peoples R China Fudan Univ Sch Microelect State Key Lab ASIC & Syst Shanghai 200433 Peoples R China Natl Integrated Circuit Innovat Ctr Shanghai 201203 Peoples R China

Reasonable design of nanostructures and application of Defect engineering have been proved to be essential for the construction of high-performance electrochemical energy storage devices. Herein, a defect engineering strategy is developed to fabricate a 3D multi-layered sea urchin-like structure assembled by 1D nanowire, which shows a high specific surface area for electrochemical active sites. More significantly, the phosphate-doping treatment introduces N/P elements in P-NiCo2O4, thus generates Co/Ni-P and Co/Ni-N bonds to create more oxygen vacancies. Vacancy defects manipulate the electronic structure of the electrode materials to obtain good physical and electrochemical properties. The prepared sea urchin-like P-NiCo2O4 electrode in this work exhibits exceptionally excellent charge storage capability in aqueous solutions with high specific capacitance (467 C g 1 at 1 A g 1), good rate capability, and ultra-high cycling stability at 20 A g 1 (87.2% capacitance retention over 10,000 cycles). Furthermore, the assembled asymmetric supercapacitor using P-NiCo2O4 cathode and AC anode shows a high energy density of 31.25 Wh kg 1 at a much large power density of 7500 W kg 1, and an outstanding cycling performance at 10 A g 1 (83.4% capacitance retention over 10,000 cycles). The prepared P-NiCo2O4 electrode materials are expected to be used in high-performance supercapacitors.

关键词： Defect engineering Oxygen vacancy High-power density Band generation

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