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Release and Transformation of Potassium during Combustion of Biomass

Energy Procedia 2017年 142卷 401-406页

作者： Lei Deng Jiaming Ye Xi Jin Tao Zhu Defu Che State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

To investigate the release and transformation of fuel K during combustion of biomass, wheat straw and corn stalk are burnt in a fixed-bed reactor system during 400−1000 °C, and weight measurement, elemental composition analysis, and chemical fractionation analysis are performed. The influences of fuel type, combustion temperature, and water washing pretreatment are discussed. The results show that wheat straw has a higher K release ratio than corn stalk, especially when combustion temperature is above 500 °C. For both biomass fuels, the released K is far less than the water-soluble K. For wheat straw, some of the other occurrence modes of K turn into the insoluble K gradually. For corn stalk, the water-soluble and ion-exchangeable K turn into HCl-soluble and insoluble K. Water washing removes all the water-soluble K of corn stalk and reduces the K release from 3.26 to 0.27 mg g -1 at 1000 °C.

关键词： Potassium release Transformation Biomass combustion Water washing

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The liquid film behaviors created by an inclined jet impinging on a vertical wall

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PHYSICS OF FLUIDS 2022年第11期34卷 1-13页

作者： Liu, Chuansheng Yu, Jun Tang, Chenglong Zhang, Peng Huang, Zuohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Xian Aerosp Prop Inst Xian 710100 Peoples R China City Univ Hong Dept Mech Engn KongKowloon Tong Hong Kong Peoples R China

Liquid films created by inclined jet-wall impingement are commonly seen in industrial applications. We investigated the liquid film behaviors created by an inclined jet impinging on a vertical glass wall using a brightness-based laser-induced fluorescence method. It was found that the typical liquid film by an inclined jet-wall impingement consists of the thin layer zone, the raised zone, the liquid node, and the trailing edge. The liquid film expands with higher impingement velocity but keeps the same elliptical shape. A normalized linear correlation is proposed to estimate the liquid film thickness. Based on the continuity equation and the empirical convection model, the Reynolds number distribution is deduced from the film thickness distribution. The Reynolds number in the thin layer zone is less than the critical Reynolds number. The surface waves in the thin layer zone are divided into the ripple waves and the disturbance waves. The disturbance waves have a larger wavelength and amplitude than the ripple waves. The quantitative measurement of the disturbance waves shows that the wavelength and amplitude increase linearly along the radial distance. The smaller impingement velocity does not change the growth rate of the wavelength but accelerates the development of the amplitude. Published under an exclusive license by AIP Publishing.

关键词： Liquid films

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Numerical study of collision behavior of melt drops during fuelcoolant interaction

Numerical study of collision behavior of melt drops during f...

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2020 International Conference on Nuclear engineering, ICONE 2020, collocated with the ASME 2020 power Conference

作者： Wen, Panpan Li, Gen Gao, Jinchen Li, Yupeng Yamaji, Akifumi Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Cooperative Major in Nuclear Energy Waseda University Tokyo169-8555 Japan

ISBN: (纸本)9780791883785

The collision dynamics between two droplets plays an important role in various disciplines of nature and practical interests, such as fuel-coolant interaction (FCI), fuel combustion in engines, and various spraying process. FCI presents in nuclear reactor severe accident when the melt relocates into the coolant in the lower head with violent disturbance and vigorous heat transfer. The purpose of this study is to investigate the collision behavior of melt droplets during fuel-coolant interaction. The collision of two equal-sized droplets has been simulated in 3D by using the volume of fluid (VOF) and adaptive mesh refinement method. The numerical simulations of tetradecane droplet collision were carried out to validate the numerical methods. The results showed good agreement with the experiments. Furthermore, the simulations of uranium dioxide (UO2) droplets collision in coolant were carried out. The results showed that the contact area between droplets and coolant increased with time first and then decreased. With the increase of Weber number, the contact area of maximum in the droplet collision increased. Break happened in the later period and many child droplets formed. The number of child droplets increased with the increase of Weber number. In addition, the size distribution of little droplets was investigated. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Coolants

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Optimal electrical conductivity and interfacial polarization induced by loaded nanoparticles on carbon nanotubes for excellent electromagnetic wave absorption performance

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JOURNAL OF COLLOID AND INTERFACE SCIENCE 2022年 626卷 759-767页

作者： Wen, Bo Zhang, Juantao Yang, Guorui Jing, Dengwei Yin, Xiancheng Fan, Lei Nasir, Muhammad Salman Ding, Shujiang Xi An Jiao Tong Univ Sch Chem Xian Key Lab Sustainable Energy Mat Chem Xian 710049 Peoples R China CNPC Tubular Goods Res Inst State Key Lab Performance & Struct Safety Petr Tub Xian 710077 Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Univ Agr Faisalabad Dept Struct & Environm Engn Faisalabad 38040 Pakistan

Carbon materials have aroused wide attention in the field of electromagnetic wave absorption because of their advantages of good electrical conductivity, low density and adjustable structure. To obtain enhanced performance of electromagnetic wave absorption, the elaborate design of structures for carbon materials has become essential. In this work, the nitrogen-doped and large diameter carbon nanotubes modified with cobalt nanoparticles (M-Co/C-CNTs) composites were successfully prepared by adsorption and carbonization of the gases generated by organic matter pyrolysis. It is concluded that the enhanced conduction loss and polarization loss are attributed to the interfacial electronic engineering induced by the sensibly loaded cobalt nanoparticles and nitrogen doping. As a result, the samples achieved a broad effective absorption bandwidth of 4.56 GHz, and a strong reflection loss of -52.2 dB with a thin thickness of 2.1 mm. This work proposes a tailored way to fabricate the large diameter carbon nanotube composites and enhance electromagnetic wave absorption through novel structural modulation. (c) 2022 Elsevier Inc. All rights reserved.

关键词： M-Co C-CNTs composites Polarization loss Electromagnetic wave absorption

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On the Relation between Nucleation Site Density and Critical Heat Flux of Pool Boiling

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HEAT TRANSFER engineering 2018年第17-18期39卷 1498-1506页

作者： Wang, Ke Gong, Shengjie Bai, Bofeng Ma, Weimin China Univ Petr Beijing Key Lab Proc Fluid Filtrat & Separat Beijing Peoples R China KTH Dept Phys Stockholm Sweden Shanghai Jiao Tong Univ Sch Nucl Sci & Engn Shanghai Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

It is traditionally accepted that the critical heat flux (CHF) decreases with increasing nucleation site density (NSD). However, such a CHF-NSD relation was no longer observed in the BETA-B experiment performed on nano-film heaters;instead the increase of NSD resulted in a gain in CHF. To address this seeming contradiction in the relation between critical heat flux and nucleation site density, the present work employed probabilistic analysis to reveal the different tendencies. A concept of effective NSD was proposed, which concerns the active nucleation sites appear within a bubble lifetime, and the resulting bubbles have the chance of direct interaction. We assumed that the boiling crisis on a heater surface is mainly induced by two mechanisms: dry spot expanding in isolated bubble regime for low-NSD surface, coalescence of dry spots under multiple bubbles in fully developed nucleate boiling regime for high-NSD surface, or a combination of the two in the transition regime for medium-NSD surface. Accordingly, we estimated the critical heat flux of each boiling regime at which the boiling crisis occurs. The result indicated that there is a threshold of nucleation site density below which the increase of NSD is contributing to CHF enhancement, while the trend is inverted beyond the threshold.

关键词： Heat flux

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On the origin of spanwise vortex deformations during the secondary instability stage in compressible mixing layers

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PHYSICS OF FLUIDS 2023年第3期35卷 1-16页

作者： Bai, Yuping Yan, Peiwen Yu, Yifei Zhao, Quanbin Chong, Daotong Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Univ Calif Los Angeles Dept Mech & Aerosp Engn Los Angeles CA 90095 USA Univ Texas Arlington Dept Math Arlington TX 76019 USA

The three-dimensionality of turbulence initiates with spanwise vortex deformations associated with the amplification of three-dimensional disturbance modes. However, the origin of spanwise vortex deformations is still not well understood. In this paper, compressible mixing layers are performed via direct numerical simulation (DNS). Two typical types of secondary instabilities producing spanwise vortex deformations are of consideration: fundamental instability and subharmonic instability. Based on the fast Fourier transform and DNS data, a low-rank velocity model v(0) is obtained to demonstrate that spanwise vortex deformations are originated from a linear superposition of fundamental norm mode, a pair of fundamental or subharmonic oblique modes, and the mean mode. Through observing flow structures of the above norm and oblique modes, a striking feature is found that the velocity model v(0) containing deformed spanwise vortices can be decomposed into three new velocity models v(1), v(2), and v(3) containing relatively simplified counterparts (spanwise or oblique vortices). Then, the instability mechanism of the latter vortices is explored by analyzing the position relationship between the function of the generalized inflection points and cores of relatively simplified vortices. We find that an inviscid inflectional instability mechanism is responsible for the formation of spanwise and oblique vortices. Based on the above findings, a view is first proposed that spanwise vortex deformations with aligned and staggered patterns are a joint result of the parametric resonant mechanism and the inviscid inflectional instability mechanism.

关键词： Vortex flow

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Continuous solid solutions of Na_0.5La_0.5TiO₃-LaCrO₃ for photocatalytic H₂ evolution under visible-light irradiation

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RSC ADVANCES 2016年第57期6卷 51801-51806页

作者： Shi, Jinwen Zong, Shichao Hu, Yuchao Guan, Xiangjiu Luo, Jiaying Shang, Yi Li, Guoxing Liu, Dongyu Wang, Xin Guo, Penghui Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn MFPE IRCRE 28 West Xianning Rd Xian 710049 Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn Dept New Energy Sci & Engn 28 West Xianning Rd Xian 710049 Peoples R China

A series of continuous (Na0.5La0.5TiO3)(1-x)(LaCrO3)(x) solid solutions with orthorhombic-phase perovskite structure and with LaCrO3 contents (x) in the range from 0 to 1.0 were synthesized by a facile polymerized complex method, and were employed as photocatalysts for H-2 evolution under visible-light irradiation. It was found that photocatalytic activities of the solid solutions significantly increased with the increase of x to 0.3, and reached the highest H-2-evolution rate of 238.2 mu mol h(-1) g(cat)(-1) on (Na0.5La0.5TiO3)(0.7)(LaCrO3)(0.3), because the narrowed bandgaps of samples enhanced the generation of charge carriers and the increased lattice distortion of samples could promote the separation and migration of charge carriers. Nevertheless, photocatalytic activities of the solid solutions gradually decreased with the further increase of x from 0.3, since both the bandgaps and lattice distortion rarely changed but Cr6+ and defects gradually increased and thus accelerated the recombination of charge carriers.

关键词： Solid solutions

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Calculation method of friction coefficient on flat plate in supercritical water laminar boundary layer flow

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PHYSICS OF FLUIDS 2023年第5期35卷 053613-053613页

作者： Li, Peitong Wang, Huibo Li, Xiaoyu Guo, Liejin Jin, Hui Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Peoples R China

In supercritical water (SCW) gasification reactor, understanding the interaction of SCW with wall surfaces and the boundary layer situation is significant to gasification efficiency improvement. This paper wishes to find a convenient way to calculate the friction coefficient on flat plate in SCW laminar flow with a pseudo-critical incoming state. The velocity profiles characteristics in the SCW boundary layer would be studied using direct numerical simulation (DNS) method, and they would be applied to variable separation of friction coefficient expression. Then, a semi-analytical formula for plate friction applied to the SCW fluid field would be derived, and it would be found to be the extended form of that derived from the Blasius's theory. In this formula, the effects of the unique properties variation around critical points had been isolated as dimensionless parameter G(mu)*, dependent on pressure and temperature boundary conditions. The method of obtaining G(mu)* by DNS will be given, and two details in the processes will be explained. Finally, the dependence between G(mu)* and boundary conditions would be derived by numerical experiments. By the semi-analytical formula and diagram of G(mu)*(T-w)|(in), the friction coefficient on one side of the plate in SCW laminar flow could be quickly calculated. The applicable inflow states are five pseudo-critical points of 23-27 MPa, the wall temperature is 645-673 K, and the Reynolds number range is above 1 x 10(5). The accuracy of this method has been proved by comparing the results obtained by it with DNS results.

关键词： Laminar flow

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Mo-doped Pr_0.6Sr_0.4Fe_0.8Ni_0.2O_3-δ as potential electrodes for intermediate-temperature symmetrical solid oxide fuel cells

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ELECTROCHIMICA ACTA 2017年 227卷 33-40页

作者： Lu, Xiaoyong Yang, Yang Ding, Yanzhi Chen, Yonghong Gu, Qingwen Tian, Dong Yu, Weili Lin, Bin Huainan Normal Univ Huainan Engn Res Ctr Fuel Cells Anhui Key Lab Low Temp Cofired Mat Huainan 232001 Peoples R China Anhui Univ Sci & Technol Sch Chem Engn Huainan 232001 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Sch Energy & Power Engn Xian 710049 Peoples R China

Mo-doped Pr0.6Sr0.4Fe0.8Ni0.2O3-delta(PSFNM) perovskites are synthesized by a modified Pechini method and evaluated as both anode and cathode for intermediate -temperature symmetrical solid oxide fuel cell (SSOFC). The influence of Mo-doping on structure, conductivity, thermal expansion coefficient and electrochemical performance of Pr0.6Sr0.4Fe0.8Ni0.2O3-delta (PSFN) electrode are investigated. The results indicate that PSFNM exhibits a cubic perovskite structure and shows a good reversibility. After heated at 800 degrees C for 10 h in humidified H-2, some new phases of SrPrFeO4, Pr2O3, and Fe-Ni alloy in PSFNM are identified by powder X-ray diffraction analysis. Although the conductivity of Mo-doped sample is slightly decreased, the thermal expansion compatibility and hydrogen oxidation reaction (HOR) activity are gradually improved. The maximum power density of SSOFC increase from 435 mW/cm(2) to 500 mW/cm(2) at 800 degrees C, and the corresponding polarization resistance decrease from 0.102 ***(2) to 0.070 ***(2), respectively. In addition, the SSOFC with PSFNM electrode shows a robust stability after operating at 700 degrees C for 100 h. These results demonstrate that PSFNM is a promising electrode for SSOFC at intermediate temperatures. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Symmetrical solid oxide fuel cell Pro(0.6)Sr(0.4)Fe(0.7)Ni(0.2)MO(0.1)O(3-delta) Interfacial polarization resistance Robust stability

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Experimental research on liquid-vapor two-phase flow separation of zeotropic mixtures at an impacting T-junction

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2017年 89卷 140-152页

作者： Zheng, Nan Zhao, Li Wei, Jinjia Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Shaanxi Peoples R China Tianjin Univ MOE Key Lab Efficient Utilizat Low & Medium Grade Ene Tianjin 300072 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Impacting T-junctions could work as a partial vapor-liquid separators by enhancing the mal-distribution of phase that occurs naturally therein. Previous studies have mainly concerned the phase splitting of air-water and pure refrigerants but here the performance of a vertical impacting T-junction using zeotropic mixtures as test fluids is reported. Experiments were conducted to investigate the effect of parameters, including inlet mass velocity, vapor quality, splitting ratio, outlet branch diameter and circulating composition of mixtures, on the liquid separation efficiency, based on mixtures R134a/R245fa and R290/R600a. The inlet flow patterns of each test fluid were also identified by using a high-speed camera under various test conditions. It was found that the mixture composition had an obvious effect on phase splitting at high separation loads, but the separation efficiency would not change linearly versus the R134a mass fraction in mixture R134a/R245fa. Overall, pure refrigerant showed better separation performance than zeotropic mixtures, under the same inlet and outlet conditions. Besides, the vaporization due to pressure drop at T-junction was also discussed by conducting a comparison study between air-water mixture and organic fluids. Calculation results indicated that an increase in pressure drop would promote mass transfer from liquid to vapor phase at the impacting T-junction.

关键词： Impacting T-junction Phase separation Zeotropic mixture Circulating composition Pressure drop

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