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7th International Conference on power engineering, ICOPE 2019

作者： Yao, Yashu Xu, Heng Tan, Jingkao Hu, Zhengtao Zhou, Qulan Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The rice husk ash (RHA) contains a large amount of amorphous silica having a large specific surface area and high activity, but after combustion of the rice husk the SiO2 is easily crystallized, which deteriorate the performance. Therefore, it is necessary to study the crystallization process of silica in combustion for the preparation of excellent rice husk ash. On the self-built fluidized bed experimental system, the combustion characteristics of rice husk and the pore characteristics of RHA under different excess air coefficients were studied. It was found that when the excess air ratio was between 0.8 and 0.9, the silica remained unchanged, and the specific surface area of rice husk ash is larger. Meanwhile, the furnace temperature is higher, which is conducive to the utilization of heat;when the excess air ratio is greater than 1, the crystallization of rice husk ash is more serious. In conclusion, it should be burned when the excess air ratio is less than 1 in order to prepare RHA with large specific surface area by direct combustion method. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Silica

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Experimental and modeling study on auto-ignition of DME/ n -butane blends under engine relevant pressure

Experimental and modeling study on auto-ignition of DME/ n -...

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SAE 2014 World Congress and Exhibition

作者： Jiang, Xue Zhang, Yingjia Pan, Lun Man, Xingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

In this study, the ignition delay times of DME/n-C4H 10 fuel blends (neat DME, 50/50 and neat n-C4H 10) diluted with argon were measured behind reflected shock waves. The experiments were performed in the temperature range of 1250 - 1600 K, at pressure of 2.0 MPa and equivalence ratios from 0.5 to 2.0. A latest kinetic mechanism NUIG Aramco Mech 1.3 was validated against the present ignition data and used to conducted chemical kinetic analysis. Different equivalence-ratio- dependent was exhibited at different temperature regimes for DME, n-C 4H10, and their blend. Fuel flux analysis, sensitive analysis and mole fraction analysis were carried out for understanding the interaction between the ignition chemistries of DME and n-C4H 10. Copyright © 2014 SAE International.

关键词： Shock waves

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Specific Heat Ratio of High Methane Fraction Natural Gas/Air in Confined Vessel

Specific Heat Ratio of High Methane Fraction Natural Gas/Air...

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SAE 2015 World Congress and Exhibition

作者： Tang, Chenglong Si, Zhanbo Zhang, Shuang Huang, Zuohua Pan, Shiyi Wang, Jinhua Gong, Jing Xi'An Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an710049 China

The specific heat ratio used in heat release calculation plays an important role and the mass fraction burned is also a crucial parameter in thermodynamics analysis for engine combustion. A research of high methane fraction natural gas was investigated in a constant volume combustion vessel at different initial conditions. Results show that with the increase of the initial pressure, the specific heat ratio is decreased, and the time of the mixture burned up is postponed, while the peak heat release ratio is increased. With the increase of the methane fraction, the parameters have the opposite behavior. With the increase of the initial temperature, the specific heat ratio is decreased, and the time when the mixture is burned up is accelerated, and the peak heat release ratio has no obviously difference. With the increase of the dilution ratio or the CO2/N2 ratio, the specific heat ratio is decreased, and the peak heat release heat ratio is decreased. Meanwhile, the time of mixture burned up is postponed with the increase of dilute ratio or CO2/ N2 ratio. Copyright © 2015 SAE International.

关键词： Specific heat

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Experimental study on premixed combustion of dimethyl ether-hydrogen-air mixtures

Experimental study on premixed combustion of dimethyl ether-...

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7th International Conference on Modeling and Diagnostics for Advanced Engine Systems, COMODIA 2008

作者： Chen, Gen Huang, Zuohua Chen, Chaoyang Miao, Haiyan Wang, Xibin Jiang, Deming State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The premixed flames of DME-hydrogen-air premixed mixture were studied by the outwardly expanding flame and schlieren photography. The influences from equivalence ratio, hydrogen addition and initial pressure on the flame speed and combustion characteristics are analyzed. The results show that the flame speed, the laminar burning velocity and the mass burning rate increase with the increase of hydrogen addition. Increasing the ratio of hydrogen to DME will shorten the combustion duration. In the case of small hydrogen addition, the Markstein length decreases with the increase of equivalence ratio, and this reveals that lean mixture has better flame front stability than of rich mixture. In the case of large hydrogen addition, the Markstein length increases with the increase of equivalence ratio, and this indicates that rich mixture has better flame front stability than that of lean mixture. The initial pressure has larger influence on the combustion pressure than that from hydrogen addition. The flame development duration decreases with the increase of hydrogen addition and/or with the increase of equivalence ratio. Addition of hydrogen into DME can improve the ignitability of the mixtures and fasten the combustion. Copyright © 2008 by the Japan Society of Mechanical Engineers.

关键词： Hydrogen

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Shock Tube Experimental and Modeling Study of MTHF Ignition Characteristics at High Temperatures

Shock Tube Experimental and Modeling Study of MTHF Ignition ...

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JSAE/SAE 2015 International powertrains, Fuels and Lubricants Meeting, FFL 2015

作者： Wang, Jingshan Wang, Xibin Fan, Xiangshan Yang, Kangkang State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an710049 China

High temperature ignition delays of 2-methyltetrahydrofuran(MTHF) were measured behind a reflected shock tube under conditions of pressures from 1.2 to 10 atm, temperatures from 1050 to 1800 K, equivalence ratios from 0.5 to 2.0, and fuel concentrations of 0.25%, 0.5% and 1.0% diluted in argon. Results showed that the ignition delay of MTHF decreases with the increase of pressure, temperature, fuel concentration and increases with equivalence ratio. The trend is less notable at higher fuel concentrations and equivalence ratios. Based on sensitivity and pathway analysis at pressure of 10 atm, fuel concentration of 1.0%, equivalence ratio of 1.0 and temperature of 1550K, it was found that the most sensitive reaction of MTHF at high temperature is H+O2=O+OH, and the main consumption way is fuel decomposition instead of H-abstraction. Finally, ignition delays of MTHF were compared with THF both on experimental and kinetic analyses, and MTHF has lower ignition delays than THF. To our knowledge, it is the first time to present the ignition delays of MTHF under these conditions. © 2015 SAE Japan.

关键词： Shock tubes

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Numerical investigations on cluster characteristics in the supercritical water circulating fluidized bed riser

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Particuology 2024年第11期94卷 281-293页

作者： Kenan Xi Runqing Li Xiazhi Li Mei Li Xiudong Xu Yu Zhang Hao Wang Youjun Lu Northwest Institute of Nuclear Technology Xi'an710024China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an710049China Xi'an Institute of Applied Optics Xi'an710065China

There are currently no reports about clusters in the supercritical water circulating fluidized bed(SCWCFB).Simulations were conducted to investigate the numbers,diameters,aspect ratios,circularity,and orientation angles of cluster in the riser of SCWCFB via two-fluid model across different flow velocities,solid circulation rates,pressures,and *** results show that cluster numbers are mainly between 10 and 80 per *** are more at the bottom but less at the top,and more near the wall but less at the *** diameters are mainly between 0.2 and 0.5 times the bed *** are large at the bottom but small at the top,and large at the center but small near the *** aspect ratios are mainly between 0 and 1,indicating that most clusters have shorter width than their ***-like clusters are more likely to appear near the walls,and clusters at the center of the riser are more likely to be *** circularity is mainly between 0.2 and 0.4,suggesting that the shapes of clusters are far from the *** absolute values of cluster orientation angles are mainly between 75°and 90°,indicating that most clusters move in the vertical *** fluid velocities may facilitate cluster coalescence.

关键词： Supercritical water Circulating fluidized bed Cluster Two-fluid model Riser

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Polyacrylate modified Cu electrode for selective electrochemical CO_(2) reduction towards multicarbon products

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Science Bulletin 2024年第15期69卷 2395-2404页

作者： Yuchuan Shi Kaini Zhang Chung-Li Dong Ta Thi Thuy Nga Miao Wang Daixing Wei Jialin Wang Yiqing Wang Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049China Department of Physics Tamkang UniversityNew Taipei City 25137China

Highly selective production of value-added multicarbon(C^(2+))products via electrochemical CO_(2) reduction reaction(eCO_(2)RR)on polycrystalline copper(Cu)remains ***,the facile surface modification using poly(α-ethyl cyanoacrylate)(PECA)is presented to greatly enhance the C^(2+)selectivity for eCO_(2)RR over polycrystalline Cu,with Faradaic efficiency(FE)towards C^(2+)products increased from30.1%for the Cu electrode to 72.6%for the obtained Cu-PECA electrode at-1.1 V *** hydrogen electrode(RHE).Given the well-determined FEs towards C^(2+)products,the partial current densities for C^(2+)production could be estimated to be-145.4 mA cm~(-2)for the Cu-PECA electrode at-0.9 V *** in a homemade flow ***-situ spectral characterizations and theoretical calculations reveal that PECA featured with electron-accepting-C≡N and-COOR groups decorated onto the Cu electrode could inhibit the adsorption of^(*)H intermediates and stabilize the^(*)CO intermediates,given the redistributed interfacial electron density and the raised energy level of d-band center(E_(d))of Cu active sites,thus facilitating the C-C coupling and then the C^(2+)selective *** study is believed to be guidable to the modification of electrocatalysts and electrodes with polymers to steer the surface adsorption behaviors of reaction intermediates to realize practical eCO_(2)RR towards value-added C^(2+)products with high activity and selectivity.

关键词： Electrochemical CO_(2)reduction Polymer modification Electron transfer C_(2+)products

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Evaluation of droplet drag force model on spray and atomization behaviours of R134a flashing spray 14

Evaluation of droplet drag force model on spray and atomizat...

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14th International Conference on Liquid Atomization and Spray Systems, ICLASS 2018

作者： Zhou, Zhi-Fu Lu, Guan-Yu Zhang, Lu Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Flashing spray is of great importance in a variety of engineering fields, which occurs as the pressurized liquid is released into a low-pressure environment below its saturation pressure. This paper conducts a systematically numerical study on the spray and thermal characteristics of R134a flashing spray with high volatility and low saturation temperature, using a modified sprayFoam solver in the open source tool OpenFOAM-2.4.0. key physics involved in the complex process, including droplet flash boiling, evaporation, droplet transport, breakup, heat transfer and interaction between droplet and gas phases are taken into consideration. The emphasis is put on the droplet drag force model and nozzle diameter on flashing spray including spray morphology, droplet diameter, velocity and temperature. The result indicates that most of the drag force models have little effect on droplet diameter, velocity and temperature distributions in flashing spray, except the Khan-Richardson (K-R) model. The K-R model predicts lower temperature, higher velocity and larger size of droplet, compared to other models. The nozzle diameter greatly affects R134a spray morphology and tip penetration, that smaller diameter contributes to a larger radial expansion at the near nozzle region while leading to a much smaller penetration distance. This research give a useful guidance that how people choose the appropriate drag force model for simulation of flashing spray. © 2018 Solar Turbines Incorporated.

关键词： Morphology

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Catalytic combustion of methane over a highly active and stable Ni0/Ce02 catalyst

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Frontiers of Chemical Science and engineering 2020年第4期14卷 534-545页

作者： Xiuhui Huang Junfeng Li Jun Wang Zeqiu Li Jiayin Xu School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093China Shanghai MCC20 Construction Co.Ltd Shanghai 201999China

In the last decades,many reports dealing with technology for the catalytic combustion of methane(CH4)have been ***,attention has increasingly focused on the synthesis and catalytic activity of nickel *** this paper,a NiO/CeO2 catalyst with high catalytic performance in methane combustion was synthe-sized via a facile impregnation method,and its catalytic activity,stability,and water-resistance during CH4 com-bustion were investigated.X-ray diffraction,low-tempera-ture N2 adsorption,thermogravimetric analysis,Fourier transform infrared spectroscopy,hydrogen temperature programmed reduction,methane temperature programmed surface reaction,Raman spectroscopy,electron paramag-netic resonance,and transmission electron microscope characterization of the catalyst were conducted to determine the origin of its high catalytic activity and stability in *** incorporation of NiO was found to enhance the concentration of oxygen vacancies,as well as the activity and amount of surface *** a result,the mobility of bulk oxygen in CeO2 was *** presence of CeO2 prevented the aggregation of NiO,enhanced reduction by NiO,and provided more oxygen species for the combustion *** results of a kinetics study indicated that the reaction order was about 1.07 for CH4 and about 0.10 for O2 over the NiO/CeO2 catalyst.

关键词： methane combustion NiO/CeO2 catalyst interaction oxygen vacancy kinetic study

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Ventilation and cooling of wind generator: A numerical study and experimental verification 7

Ventilation and cooling of wind generator: A numerical study...

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7th International Conference on power engineering, ICOPE 2019

作者： Ao, Yunjin Li, Na Zhou, Qulan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In the wind generator, a large amount of heat is generated during the operation, which usually causes severe temperature rise and decrease of efficiency. By coupling fluid dynamics and heat transfer, a numerical method has been developed to calculate the velocity filed and temperature distribution of a common air-cooled doubly-fed wind generator. The numerical results have been verified by the experiments. The results show that the flow resistance is higher in the center in the axial direction, thus the temperature is much higher than the ends. In the height direction, there locate the most dangerous points and the temperature rise is about 110K. In the circumference direction, there are regularity of fluctuation and can assist in finding the dangerous points. The variations of heat source and cooler power as well as rotation speed all affect the temperature rise of the generator. The regularity and method of this study can be applied to similar generators or generators of other forms, thus advice can be given for the design, manufacture, operation and maintenance of wind generators. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Temperature distribution

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