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Composite Hydrophobic Modification of Expanded Perlite

ACI MATERIALS JOURNAL 2022年第1期119卷 71-78页

作者： Yan, Qiuhui Wang, Haojie Luo, Jieren Lin, Ye Yang, Yaxin Xian Univ Architecture & Technol Xian Shaanxi Peoples R China Xian Univ Architecture & Technol Sch Bldg Serv Sci & Engn Xian Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

The hydrophobic agents polydimethylsiloxane emulsion (BS 1042) and sodium methyl silicate were used to modify expanded perlite (EP). The effects of the hydrophobic agents and modification methods on the water absorption, thermal conductivity, and bulk density of EP were investigated. First, the orthogonal experiments of the two hydrophobic agents on the modification of EP were designed, and the effects of the drying temperature, hydrophobic concentration, soaking time, and soaking temperature on the performance of EP were analyzed. The optimum modification conditions for the two hydrophobic agents were obtained. Second, under the optimum conditions, the EP was modified by BS 1042 under vacuum conditions and then modified by the atmospheric pressure with sodium methyl silicate, so the composite-modified EP with excellent hydrophobic performance was obtained. The results showed that the water absorption of the composite modified EP was significantly reduced, from 390.1 to 16.2%;the thermal conductivity increased from 0.0532 to 0.0555 w/(m center dot k), with a small increase of only 4.3%;and the bulk density increased from 51.6 to 59.2 kg/m(3), with an increase of 14.7%.

关键词： composite modification expanded perlite (EP) hydrophobic modification orthogonal test vacuum modification

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Application of a particle-grid hybrid method in multiphase flow calculation

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JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2020年第11期57卷 1199-1214页

作者： Zhang, Shengfeng Zhang, Bin Liu, Xiaoxing Shan, Jianqiang Xi An Jiao Tong Univ Sch Nucl Sci & Technol Xian Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China Kyushu Univ Dept Appl Quantum Phys & Nucl Engn Fukuoka Japan

In this paper, a new particle-grid hybrid method is used for numerical simulations of the gas-liquid two phase flow. In this method, the main area of the fluid is calculated via the constrained interpolated profile/multi-moment method (CIP/MM FVM), and the interface of the two phases is calculated by the finite volume particle method (FVP). In the numerical calculation, the particles are distributed in the dense one of the two phases, and only near the interface. Through calculations of the dam break, single bubble rise and bubble coalescence, the reliability and accuracy of the method in multiphase flow simulation have been verified.

关键词： Gas-liquid two-phase flow hybrid method CIP MM method finite volume particle method (FVP) dam break single bubble rise bubble coalescence

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Nanoporous Graphene Membrane for Gas Separation:Review and Our Progress

Nanoporous Graphene Membrane for Gas Separation:Review and O...

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2015欧亚经济论坛-2015第五届国际纳米科技大会

作者： Bofeng Bai Chengzhen Sun Boyao Wen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Graphene is a one-atom-thick sheet of graphite comprising sp2-hybridized carbon atoms arranged in the hexagonal honeycomb *** removing the honeycomb lattices and forming nanopores with specific geometry and size,nanoporous graphene has been demonstrated as a very high-efScient separation membrane,due to the ultrafast molecular permeation rate for its one atomic *** this presentation,we review the recent advances in nanoporous graphene membrane for the application of gas separation,including the recent theoretical and experimental works,the gas molecular transport mechanisms through the graphene nanopores and the advanced fabrication methods of this stateof-the-art ***,we give a brief introduction on our relevant *** proposed two mechanisms(direct mechanism *** mechanism) for the gas molecular permeation through nanoporous graphene *** quantified the relative contribution of the two mechanisms and showed that the direct flux can be described reasonably accurately using kinetic theory with an appropriate modification assuming steric molecule-pore *** identified an inhibition effect of non-permeable components on the permeation of permeable component,caused by the relatively weakening adsorption on the graphene surface and the blocking effect of non-permeable *** also reported an asymptotically pressure-dependent gas permeation flux owing to the isothermal adsorption *** addition,we demonstrated the potential of nanoporous graphene membranes in natural gas processing to efficiently separate CO2,H2 S,N2,H2 O and others from CH4 with high permeability and selectivity.

关键词： Graphene Nanoporous Graphene Membrane for Gas Separation:Review and Our Progress

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Study on the Radiation Distribution in A Fluidized Tubular Reactor for Heterogeneous Photocatalytic Hydrogen Production

Study on the Radiation Distribution in A Fluidized Tubular R...

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2011 International Conference on Energy and Environment(ICEE 2011)

作者： Zhao Liang Fan Liangliang Jing Dengwei Liu Wenxu Cao Fei Zhu Xule Yang Junyin Zhang Hailong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Radiation distribution study is of importance for the design and the optimization of fluidized photocatalytic tubular reactor which has been developed for photocatalytic hydrogen production under direct solar light. In the present study, the radiation distribution in such reactor was successfully simulated by adopting Monte Carlo method and the six-flux radiation absorption-scattering models. Both the incident angles of light around the reactor and the concentration distribution of photocatalyst were taken into account. Our analysis indicates that the angles and the intensity of the incident rays significantly affect the radiation distribution. Moreover, it was also found that the equilibrium radiation distribution has a close relationship with the density distribution of the photocatalysts. The simulated results are expected to be helpful for obtaining the optimal operating parameters for solar photocatalytic hydrogen production.

关键词： radiation distribution,fluidized tubular reactor,nanometer catalyst,compound parabolic concentrators

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Sensitive detection of iodine by low pressure and short pulse laser-induced breakdown spectroscopy (LIBS)

Sensitive detection of iodine by low pressure and short puls...

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作者： Zhang, Xiaobo Deguchi, Yoshihiro Wang, Zhenzhen Yan, Junjie Liu, Jiping State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China Graduate School of Advanced Technology and Science University of Tokushima Tokushima 770-8501 Japan

In this study, Laser-Induced Breakdown Spectroscopy (LIBS) technology was applied to detect iodine, an essential element for human body. Iodine in buffer gases of N2 and air was detected using nanosecond and picosecond breakdowns of CH3I at reduced pressure. Compared with the conventional methods of iodine measurement, LIBS technology without sample preparation shows the merits of fast response, real-time detection and enhanced detection limit. The measurement results of iodine demonstrated that low-pressure LIBS is the favourable method for trace species measurement in analytical applications. The plasma generation processes of multi-photon ionization and electron impact ionization can be controlled by pressure and laser pulse width for the larger ionization and excitation processes of iodine, which was discussed by the intensity ratio of iodine emission at 183 nm to nitrogen emission at 174.3 nm. The detection limit of iodine measurement in N2 was 60 ppb in nanosecond breakdown at 700 Pa. Iodine in air as the buffer gas was also detected using nanosecond and picosecond breakdowns to examine the effect of oxygen. This journal is © the Partner Organisations 2014.

关键词： Impact ionization

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Experimental study of combustion characteristics and ash-related issues of ammonia co-firing with high alkali pulverized coal in a 4 MW boiler

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PROCEEDINGS OF THE COMBUSTION INSTITUTE 2024年第1-4期40卷

作者： Pu, Yang Jia, Zixiu Wang, Zhichao Yao, Bin Lou, Chun Li, Yuhang Huazhong Univ Sci & Technol Sch Energy & Power Engn State Key Lab Coal Combust Wuhan 430074 Hubei Peoples R China Xian Thermal Power Res Inst Co Ltd Shaanxi Engn Res Ctr Coal Fired Boiler Environm Pr Xian 710054 Shaanxi Peoples R China Huazhong Univ Sci & Technol Sch Energy & Power Engn Wuhan 430074 Hubei Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Co-firing ammonia with coal is a promising solution for reducing carbon emissions from coal power plants. In this study, we conducted experimental research in a 4 MW pilot boiler and successfully achieved stable operation of full ammonia combustion and co-firing. The effects of the ammonia co-firing ratio and combustion method on the combustion characteristics and alkali- and ash-related issues of co-firing ammonia with Zhundong (highalkali) coal were mainly discussed. The results showed a positive correlation between NOx emissions and the ammonia co-firing ratio. However, although a 20 % (thermal ratio) fuel-staged combustion can lower NOx emissions compared with pure coal burning, this may have an adverse impact on CO emissions. The distance at which ammonia was injected into the furnace positively affected both NOx and CO emissions. The spectral diagnosis results indicated that co-firing ammonia significantly reduced the particle radiation of the flame in the furnace. When the co-firing ratio was 60 %, the particle radiation in the boiler upper area was reduced by approximately 50 %. A 20 % ammonia co-firing ratio in the main combustion zone (including staged combustion with 40 % ammonia) effectively reduced the gas-phase sodium content leaving the furnace area. A co-firing ratio of 20 % was the best working condition in terms of the NOx emission ratio and alkali release. Compared to pure coal combustion, co-firing has no significant impact on the chemical properties of ash and slag and does not become a bottleneck in the utilization of ammonia for power plants. However, considering that the introduction of ammonia reduces the amount of ash entering the furnace, this may be beneficial for the promotion and utilization of Zhundong coal.

关键词： Ammonia/Zhundong coal Co-firing NOx emission Spectral analysis Ash and slag

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Leakage flow-induced excitation behavior and rotor instability in the high-speed supercritical CO2 scallop damper seals

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PHYSICS OF FLUIDS 2024年第3期36卷 036122-036122页

作者： Zhang, Enbo Li, Yuzhe Lai, Zitian Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

As an innovative type of damper seal, the scallop damper seal (SDS) has shown greatly improved sealing performance for the high-compactness supercritical CO2 (S-CO2) turbomachinery, but leakage-induced excitation forces have an impact on the rotor stability. In this research, we improve the rotordynamic solution based on the multi-frequency elliptic whirling model for the S-CO2 seals and investigate the leakage-induced excitation behavior of SDS depending on seal geometry and operating condition. By comparing the results of a labyrinth seal and a full-partition pocket damper seal, we prove that SDS has better rotordynamic performance for the S-CO2 compressor. The results show that increasing the pressure drop favors greater direct stiffness and effective damping of the SDS. Inlet preswirl changes the direction of fluid-response force to coincide with the rotor motion, which is detrimental to rotor stability. Changing the cavity depth has no significant effect on the dynamic characteristics of the SDS, but shortening the cavity length reduces the direct stiffness to below zero. Supplementing the number of circumferential cavities increases the direct stiffness and effective damping but results in SDS not being able to be machined directly by milling cutters. The design with 12 circumferential cavities is recommended for the 100-kW-class S-CO2 compressor.

关键词： Stiffness

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Particle dispersion in turbulent mixing layer at supercritical pressure

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POWDER TECHNOLOGY 2022年 412卷

作者： Pei, Binbin Zhao, Kunpeng Luo, Zhengyuan Zhao, Liang Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The heterogeneous structures of particles are generated due to the significant temperature changes when cold particles-dilute jet injects into a supercritical water fluidized bed, which is unfavorable for the reaction of coal particles. We expect to promote the particle dispersion by entrainment mechanism of large-scale vortical structures. The Eulerian-Lagrangian point-source method is used to numerically investigate the dynamics of dilute particles in mixing layer sustained by supercritical water with different temperatures. The effects of density ratio and velocity ratio between two streams are analyzed. In addition to the smaller particle numbers at high-density side, the particle clustering in the vortex core regions is found due to the inhibition of vortical structures by increasing density ratio. With increasing velocity ratio, however, the enhanced vortex stretching promotes the entrainment of particles. As a result, the increase in particle number density at high-density side is up to 26% compared with the constant-property flow.

关键词： Particle dispersion Mixing layer Vortical structure Variable-density

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Influence of thermal effects on the cavitation of orifices in nuclear power plants

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NUCLEAR engineering AND DESIGN 2022年 398卷 1页

作者： Xu, Bo Yang, Kuang Chen, Qiuxiang Wang, Haijun Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Orifices are widely used as throttling devices in nuclear power plants. The pressure drop is not the only driving parameter of cavitation when the fluid is operating at its critical temperature, and the thermal effects cannot be neglected owing to the phase change. This study aims to extend a cavitation model to investigate the impact of thermal effects by modeling the water cavitation flow in an orifice. The thermal effects on the mass transfer process are considered using the Zwart-Gerber-Belamri cavitation model, and the effect of the two-phase flow on the turbulence viscosity is considered in the turbulence model. The numerical results reveal that the period of the variation in vapor volume is shorter under thermal cavitation than under isothermal cavitation. The pressure downstream of the orifice fluctuates with the heat transfer during thermal cavitation. The thermal cavitation model can reproduce the instability downstream of the orifice, which is caused by cavity shedding. The shedding cavities become mushy and frothy during thermal cavitation. The thermal effect term plays a dominant role during vaporization. The influence of thermal effects is positively correlated with the vapor volume fraction, and as the free-stream temperature and velocity increase, the ratio of the thermal effects term to the pressure difference effect term increases during the phase change process.

关键词： Orifice Cavitation Thermal effects Simulation

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Effect of laser spot diameter on oxygen bubble behavior in photoelectrochemical water splitting

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JOURNAL OF ELECTROANALYTICAL CHEMISTRY 2023年 935卷

作者： Xu, Qiang Tao, Leqing She, Yonglu Ye, Xingmiao Wang, Mengsha Nie, Tengfei Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The detrimental effect caused by the long-term adhesion of bubbles on the gas production efficiency has been the main bottleneck limiting the efficiency improvement of photoelectrochemical water splitting. The evolu-tion of oxygen bubbles on the fixed photoelectrode surface of TiO2 films was observed in-situ using a combi-nation of a synchronized high-speed microscopic camera and an electrochemical workstation. The effect of oxygen bubble evolution on the current during the photoelectrochemical reaction was investigated under dif-ferent laser spot diameters. When the spot diameter increased 1.68 times from 700 mu m to 1176 mu m with a laser power of 5 mW, the bubble detachment diameter and growth period increased 2.7 times and 20.2 times, respectively, yet the gas production efficiency decreased by 34.7%. Meanwhile, the peak current caused by the bubble detachment gradually increased. However, the valley current at the nucleation waiting stage of the bubble did not have obvious changes. The model for the gas evolving based on supersaturation was adopted. It illustrated that the concentration gradient of dissolved gas perpendicular to the photoelectrode sur-face increased with the increase of spot diameter, leading to an increase in the bubble surface tension gradient, and causing the Marangoni force to inhibit the detachment of bubbles. A force balance model was developed to evaluate the Marangoni forces and the buoyancy forces. The growth rate of the Marangoni force was found to be proportional to the spot diameter. Therefore, reducing the laser spot diameter is a means to effectively remove the bubbles from the photoelectrode surface.

关键词： Photoelectrochemical water splitting Laser spot diameter Bubble evolution Marangoni effect Photocurrent

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