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Experimental study of compact swirl flames with lean premixed CH₄/H₂/air mixtures at stable and near blow-off conditions

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2021年 122卷 110294-110294页

作者： Zhang, Weijie Wang, Jinhua Mao, Runze Lin, Wenjun Lin, Bingxuan Wu, Yun Zhang, Meng Huang, Zuohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Air Force Engn Univ Sci & Technol Plasma Dynam Lab Xian 710038 Peoples R China

An experimental study on the compact lean premixed flames stabilized on a bluff-body and swirl burner is performed. The flames are featured with a strengthened Inner Recirculation Zone (IRZ). The objective is to identify the critical causes of blow-off near the lean limit. Meanwhile, the effects of hydrogen addition on the flame stabilization are also examined. Premixed CH4/H-2/air mixtures are adopted with varied hydrogen fractions up to 80%. Flames far from and close to the blow-off conditions are both obtained for comparison. Simultaneous PIV/OH-PLIF measurements are performed, and flow-flame dynamics are analyzed. Results show that the flow straining near the flame root is dominant to induce the root extinction and initiate the blow-off. The strain is observed to mainly result from the shear deformation. The weakened root burning intensity is demonstrated with the CH* chemiluminescence. With hydrogen addition, the flame root is strengthened due to the enhanced resistance to the strain. The increased burning velocity and temperature with hydrogen are also beneficial for the flame stabilization. The inner shear layer vortices are anticipated to promote the blow-off by convecting cold unburned mixture into the IRZ.

关键词： Lean premixed combustion Hydrogen-enriched combustion Compact swirl flames Blow-off PIV/OH-PLIF

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Oxidation of Typical Zr-1nb Alloy in High-Temperature Air Under 700–900 °C

SSRN

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SSRN 2022年

作者： Jiang, Guanyu Xu, Donghai Liu, Lu Ding, Xin Kuang, Wenjun Wang, Mingjun Key Laboratory of Thermo-Fluid Science & Engineering Ministry of Education School of Energy and Power Engineering Xi’an Jiaotong University Shaanxi Province Xi’an710049 China School of Materials Science and Engineering Xi’an Jiaotong University Shaanxi Province Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi'an Jiaotong University Xi’an China

m-ZrO2 is always the dominant phase, while oxide shapes, the integrity and roughness of oxide films share evident differences. At 900 °C, M5 alloy exhibits kinetics transition and breakaway oxidation at approximately 80 min. The pre-transition oxidation follows a parabola kinetics with the rate exponent n being 1.65. The presence of ZrO and ZrO0.35 sub-oxides accounts for the high reaction activation energy (149.6 kJ/mol). During the kinetics transition, some intergranular cracks turn transgranular, and pores distribute on the oxide layer and O/M interface. Air ingress through the oxide layer is jointly affected by air transport and ion diffusion. © 2022, The Authors. All rights reserved.

关键词： Oxidation

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Technical and economical analysis of a novel rotary air preheater system

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APPLIED THERMAL engineering 2019年 154卷 102-110页

作者： Bu, Yufan Wang, Limin Deng, Lei Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The injection of ammonia as a reducing agent into the selective catalytic reduction (SCR) system is usually excessive in order to achieve the strict NOx removal efficiency, which results in the formation of ammonium bisulfate on account of the reaction between the escaped ammonia and sulfur oxides in the flue gas. Ammonium bisulfate is viscous and corrosive and can seriously affect the rotary air preheater (RAPH) as well as other exhaust systems. The mitigation strategies require additional operating expenses of cleaning, ash-blowing. To address the problem, a split design of the rotary air preheater is provided in this paper. A traditional RAPH is split into two sub-preheaters, between which the recirculating flue gas extracted from the cold end of the second preheater is mixed with the main flue gas. After the mixing point, a reaction chamber is installed to induce the reaction between ammonia and sulfur trioxide to form as much (NH4)(2)SO4 as possible. Thus, the blockage and corrosion can be avoided both in the two preheaters by a proper split design and continuous adjustment of the recirculation flow rate. To realize the calculation of temperature distribution, a numerical finite difference method is adopted to model the preheaters. The economical analysis of the proposed system including break-even curves is also conducted, which is given as references for the measures to relieve the blockage problem in the RAPH.

关键词： Ammonium bisulfate Split design Economical analysis The rotary air preheater Blockage and corrosion

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Experimental study on ash deposition of Zhundong coal in oxy-fuel combustion

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JOURNAL OF THE ENERGY INSTITUTE 2019年第6期92卷 1697-1709页

作者： Han, Tao Wang, Chang'an Sun, Ruijin Zhu, Chenzhao Liu, Yinhe Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

To facilitate the large-scale utilization of high-alkali and-alkaline earth metals (AAEMs) coals in power generation, the ash deposition behaviors of a typical Zhundong coal in oxy-fuel combustion were experimentally investigated using a drop tube furnace. A wall-temperature-controlled ash deposition probe by which the bulk gas temperature could be measured simultaneously was designed and employed in the experiments. The deposition tendencies, ash morphologies, chemical compositions of deposited ash particles were studied respectively under various oxygen concentrations, bulk gas temperatures, probe surface temperatures and probe exposure times. The experimental results revealed that the oxygen concentration had a significant influence on the deposition behavior during oxy-fuel combustion of high-alkali coal. Compared with air case, more fine ash particles were generated during the combustion of Zhundong coal in 21% 02/79% CO2 atmosphere but the deposition tendency was weaker. However, a higher oxygen concentration could aggravate the tendency of ash deposition. The high contents of iron (Fe), calcium (Ca), sulfur (S), and sodium (Na) in Zhundong coal could result in the generations of low-melting point compounds. Calcium in flue gas existed as CaO and was captured prior to SO3 by the probe surface during the ash deposition process. At the initial 30 min of the ash deposition process, the dark spherical fine ash particles rich in Fe, Na, oxygen (O), and S were largely produced, while in the range of 60-90 min the light spherical fine ash particles with high contents of Ca, barium (Ba), O, and S were generated on the other hand. The deposition mechanisms at different stages were different and the melted CaO (BaO)/CaSO4 (BaSO4) would give rise to a fast growth rate of ash deposit. (C) 2019 Energy Institute. Published by Elsevier Ltd. All rights reserved.

关键词： Zhundong coal Deposition Oxy-fuel combustion Low-melting point compounds

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Experimental Study on Morphology and Chemical Composition of Ash Deposition during Oxy-fuel Combustion of High-Alkali Coal

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ENERGY & FUELS 2019年第4期33卷 3403-3420页

作者： Wang, Chang'an Sun, Ruijin Liu, Chengchang Han, Tao Zhu, Chenzhao Liu, Yinhe Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The Zhundong coalfield has attracted ever-increasing attention as a result of its super-large reserve of coal resources. However, the power plants encounter great challenges in the utilization of Zhundong coal as a result of its high-alkali feature, which deteriorates the phenomenon of ash deposition and slagging. Oxy-fuel combustion of Zhundong coal benefits the near-zero emission of pollutants in coal-fired power plants, while previous studies mainly focused on the behaviors of alkali and alkaline earth metals and ash deposition during air combustion. The present study focused on the characteristics of ash deposition during oxy-fuel combustion of high-alkali coal, especially the differences in morphologies and chemical compositions of ash deposits using a drop-tube furnace, with the ash deposition mechanisms being further elucidated. Experimental results showed that the contents of sulfur (S), chlorine (Cl), and calcium (Ca) in ash deposits from oxy-fuel combustion were lower at the identical O-2 content but the contents of aluminum (Al) and silicon (Si) were increased in comparison to air conditions. The average particle size of ash deposits under oxy-fuel conditions was smaller with less calcium sulfate and mullite than the case in air combustion of Zhundong coal. The adhesion phenomenon between ash particles was aggravated in the ash deposits of high-alkali coal, with the oxygen content elevated. The proportion and diameters of spherical particles declined with an increasing oxygen concentration in the ash deposits of Zhundong coal. The contents of iron (Fe) and calcium in ash deposits of high-alkali coal were closely bound with the decrease of the melting point of ash and the formation of spherical ash particles. The caking phenomenon became more serious as the flue gas temperature was increased in the ash deposits of Zhundong coal. The deposition propensity of Zhundong coal was inclined to the minimum when the probe surface temperature was 550 degrees C, whil

关键词： Redox reactions Atmospheric chemistry Reaction products Coal Deposition

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Experimental investigation of solar hydrogen production via photo-thermal driven steam methane reforming

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APPLIED ENERGY 2024年 368卷

作者： Dong, Hao Fang, Juan Yan, Xiangyu Lu, Buchu Liu, Qibin Liu, Xunliang Univ Sci & Technol Beijing Sch Energy & Environm Engn Beijing 100083 Peoples R China Chinese Acad Sci Inst Engn Thermophys Beijing 100190 Peoples R China Chinese Acad Sci Key Lab Long Durat & Large Scale Energy Storage Beijing 100190 Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

Solar-driven steam methane reforming (SMR) is a sustainable technology for hydrogen production. For solar energy utilization, photo-thermochemistry combines the advantages of solar photochemistry and thermochemistry, which can utilize the solar energy in the long-wavelength spectrum and the strong activation ability of photons in the short-wavelength spectrum. In this work, the photo-enhanced reaction of solar hydrogen production from SMR using a Co/Al2O3 catalyst is experimentally investigated. The performance of the reaction in different light conditions is compared with those under dark conditions. Results show that the H2 yield by photothermochemical reaction (149.9 mmol & sdot;h- 1 & sdot;g- 1) can be increased by 30.8% at 600 degrees C compared with the thermochemical reaction (114.6 mmol & sdot;h- 1 & sdot;g- 1), indicating photo energy can promote the reaction. To achieve hydrogen production rate equivalent to that under light irradiation, a temperature rise of 30-40 degrees C is needed under thermochemical conditions. In-situ infrared studies demonstrate that light can encourage the formation of methyl (CH3*) and hydroxyl (OH*) groups, and the enhancement of these key intermediates in SMR reactions promotes hydrogen generation under photo-thermochemical conditions. The photoactivation effect reduces the apparent activation energy by 28.6% and is the main reason for the increase in photo-thermochemical activity. These findings provide valuable guidance on the use of solar energy for steam methane conversion to hydrogen.

关键词： Hydrogen production Solar fuel Photo-thermochemical reaction Steam methane reforming Photoactivation

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Two-Phase flow study in the 3D fine-mesh flow field and gas diffusion layer of proton exchange membrane fuel cells

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2025年 244卷

作者： Lv, Xuecheng Li, Yang Huang, Heng Zhou, Zhifu Wu, Wei-Tao Wei, Lei Lyu, Jizu Gao, Linsong Li, Yubai Song, Yongchen Dalian Univ Technol Key Lab Ocean Energy Utilizat & Energy Conservat Minist Educ Dalian 116024 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Nanjing Univ Sci & Technol Sch Mech Engn Nanjing 210094 Peoples R China Southern Univ Sci & Technol Dept Mech & Energy Engn Shenzhen 518055 Peoples R China Guangdong Ocean Univ Sch Mech Engn Zhanjiang 524088 Peoples R China Xiangtan Univ Sch Mech Engn & Mech Xiangtan 411105 Peoples R China

The two-phase flow transport mechanisms in the 3D flow field and gas diffusion layer (GDL) of proton exchange membrane fuel cells are not fully understood. In this study, the GDL structure was reconstructed using micro-CT technology, and the two-phase flow behavior in the 3D fine-mesh flow field (FMFF) and GDL was simulated and analyzed using the phase-field lattice Boltzmann method. The results show that the FMFF significantly enhances gas convection in both the flow field and GDL, reduces liquid water saturation, increases the pore area for gas transport at the interface between the two, and makes the distribution of gas and liquid in the GDL more uniform. Liquid water tends to accumulate above the air stagnation zone and below the concave baffle. Additionally, increasing the gas flow rate reduces the liquid water volume transported to the upper side of the flow field plate. Hydrophilic flow field plates facilitate liquid water transport above the plate but tend to accumulate liquid water in the flow field;conversely, hydrophobic flow field plates exhibit the opposite behavior. Comprehensive analysis reveals that flow field plates with a contact angle between 90 degrees and 110 degrees offer the most balanced performance.

关键词： Proton exchange membrane fuel cell 3D flow field Gas diffusion layer Two-Phase flow Water management

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A study on corrosion behavior of 15CrMo in saturated saline steam with sodium sulfate

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CORROSION SCIENCE 2021年 181卷 109240-109240页

作者： Bai, Bing Xiao, Gang Deng, Lei Zhang, Naifeng Chen, Chao Bu, Yufan Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Sinopec Shengli Oilfield Co Steam Inject Serv Dongying 257001 Peoples R China

To obtain the corrosion behavior of 15CrMo exposed in saturated saline steam with Na2SO4 at the initial stage, the experiments are implemented in a novel setup. The results show corrosion products are mainly composed of FeOOH, Fe2O3 and Fe3O4. Compared with deionized steam, saline steam promotes the generation of FeOOH and Fe2O3. The generation of Fe3O4 is inhibited by salinity. The contents of FeOOH and Fe2O3 increase with temperature while that of Fe3O4 decreases. The contents of FeOOH and Fe2O3 decrease with time and that of Fe3O4 shows the reverse trend. The content of FeSO4 keeps low all the time.

关键词： Steam-injection boiler Corrosion Saline steam 15CrMo

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Ni-based core-shell structured catalysts for efficient conversion of CH4 to H2 : A review

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CARBON CAPTURE SCIENCE & TECHNOLOGY 2024年 11卷

作者： Guan, Yu Song, Guoqiang Li, Claudia Lim, Kang Hui Wang, Bo Xia, Lianghui Song, Huchao Liu, Yinhe Wu, Chunfei Kawi, Sibudjing Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Natl Univ Singapore Dept Chem & Biomol Engn Singapore 119260 Singapore Queens Univ Belfast Sch Chem & Chem Engn Belfast BT7 1NN Antrim North Ireland

Methane (CH4) serves as a primary constituent of natural gas and a potent greenhouse gas. Catalytic conversion of CH4 into H2 presents a promising avenue for mitigating CO2 emissions from direct CH4 combustion, while also facilitating the transition towards cleaner energy sources. Substantial efforts have been dedicated to enhancing the efficiency of methane conversion and the selectivity for hydrogen in catalyst design. Among these endeavors, core-shell structured Ni -based catalysts have emerged as highly advantageous catalysts for CH4 conversion, with a multitude of benefits including high catalytic activity, coking resistance, and longtime stability. In this review, we provide an overview of Ni -based core-shell catalysts. Furthermore, the synthesis methods of core-shell Ni -based catalysts are explored. We then delve into the myriad advantages these core-shell structured catalysts confer upon methane conversion, specifically emphasizing their remarkable stability and resistance to sintering, and CO2 activation capacity in dry reforming of methane. Moreover, this review comprehensively outlines the versatile applications of Ni -based core-shell structured catalysts in processes such as steam reforming of methane (SRM), dry reforming of methane (DRM), partial oxidation of methane (POM), and catalytic methane decomposition (CMD) for H2 production. Additionally, we delve into the recent advancements in the field of computational chemistry, with a particular focus on density functional theory (DFT) and machine learning (ML). These techniques play pivotal roles in screening Ni -based catalysts and offer insights into the intricate reaction mechanisms underlying methane conversion. Finally, we summarize the key findings of this review and provide forward-looking perspectives. This comprehensive review serves as a valuable reference in the realm of hydrogen production from methane on core-shell structured catalysts, fostering a deeper understanding of this promising ar

关键词： Methane Core-shell nanocatalyst H2 production Stability Anti-sintering

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Ash deposition behaviors during combustion of raw and water washed biomass fuels

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JOURNAL OF THE ENERGY INSTITUTE 2019年第4期92卷 959-970页

作者： Deng, Lei Jin, Xi Long, Jimiao Che, Defu Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Sch Energy & Power Engn Xian 710049 Shaanxi Peoples R China

Biomass-fired boilers have the tendency to suffer from severe problems of fouling and slagging due to the high potassium content of biomass fuel. The troublesome potassium, however, can be removed efficiently by water washing pretreatment. In this study, the ash deposition behaviors during combustion of raw and water washed biomass fuels were investigated by a one-dimensional furnace and a deposition probe. Two biomass fuels (corn stalk and wheat straw) were used, and deposition mass, deposition efficiency, composition and morphology of the deposit were studied. The ash deposition while firing raw biomass exhibits a "fast-slow-fast-slow" trend with the sampling time. After water washing, the deposition mass decreases dramatically, and the deposition efficiency reduces gradually as the sampling time increases. The analyses of elemental composition, morphology and chemical composition on the deposit from raw biomass imply that the condensation/thermophoresis is quite significant in the earlier deposition stage, whereas the chemical reaction is remarkable in the later stage. After water washing, the potassium content of the deposit decreases significantly. Morphology and chemical composition analyses indicate that the deposit from water washed biomass ascribes to the physical accumulation of non-viscous fly ash particles. The deposition mass can easily approach a maximum value. The ash fusion temperatures of deposits increase remarkably after water washing. In addition, ash deposition mechanisms during biomass combustion are discussed. (C) 2018 Energy Institute. Published by Elsevier Ltd. All rights reserved.

关键词： Ash deposition Biomass combustion Fouling Water washing Grate-fired boiler

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