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9th International Symposium on Coal Combustion, ISCC 2019

作者： Zhao, Lei Wang, Chang’an Hu, Yueyi Sun, Ruijin Tang, Guantao Guo, Jin Jiang, Zhiming Du, Yongbo Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Guangdong Institute of Special Equipment Inspection and Research Foshan528251 China Shunde Institute of Inspection Guangdong Institute of Special Equipment Inspection and Research Foshan528251 China

ISBN: (纸本)9789811616563

Zhundong coal featuring high content of alkali metals induces severe slagging and fouling problems during its utilization in utility boilers. Oxy-fuel combustion technology can achieve a large amount of CO2 capture and reduce the NOx emission. Unfortunately, in-depth investigation has been seldom carried out on the process of ash deposition and slagging of high-alkali coal during oxy-fuel combustion. In the present study, the oxy-fuel combustion of high-alkali coals were experimentally studied using a non-cooled sampling probe in a drop tube furnace. The fouling and slagging mechanisms were investigated in various atmospheres, temperatures and different O2 concentrations. In addition, the slag samples were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectrometer (EDS). Experimental results indicated that under air and oxy-fuel conditions with the same O2 content, the types of elements and minerals were almost the same. With the temperature increased, the adhesion between the slag samples was strengthened and the pore structure slag was increased. The degree of slag melting and sintering was aggravated at the temperature of 1200 °C and the slag structure was complicated. As the oxygen concentration was increased, some of the spherical particles had completely melted on the surface of the massive ash, resulting in an uneven surface. The present work can provide new insights into the slagging and ash deposition of Zhundong high-alkali coal during oxy-fuel combustion. © 2022, Tsinghua University Press.

关键词： Coal

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An Operation Optimization of Cooling System for Reactor Shutdown in Pebble Bed Gas-Cooled Reactor

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SSRN 2024年

作者： Liu, Junfeng Wang, Chenglong Qiu, Suizheng Wang, Boyuan Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology Shaanxi Engineering Research Center of Advanced Nuclear Energy Xi’an Jiaotong University Xi’an710049 China Xi’an Thermal Power Research Institute Co. Ltd Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering China

For the emergency shutdown of a high temperature gas-cooled reactor pebble-bed module (HTR-PM) in its operation conditions, in the current design method with a low-flow auxiliary steam cooling technical solution, there are some security and economic issues, i.e. high thermal shock, long cooling time, and temperature drop rate exceeding the limit. To solve these problems, an optimized design method for the shutdown cooling system is presented. Through a simulation model of the shutdown cooling system based on Matlab/Simulink, the dynamic characteristics of the shutdown cooling system in its operation conditions are obtained, involving shutdown, low flow cooling, and water supply start-up stages. The results showed that with the optimized design method, the safety of the core and steam generator can both be ensured during the cooling process, and the cooling rate is significantly improved. Therefore, the optimized design method is feasible and advanced. © 2024, The Authors. All rights reserved.

关键词： Cooling

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Effect of Mixer Structure on Liquid Film Formation and Nox Conversion Efficiency in Selective Catalytic Reduction System

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SSRN 2022年

作者： Fu, Hang Huang, Zuohua Tang, Chenglong State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Selective Catalytic Reduction as an efficient technology to reduce NOx emission has been widely applied in exhaust aftertreatment system. However, the reductant injection causes inevitable impingement on the exhaust pipe and mixer surface and the liquid film will be generated. In this paper, the simulation of a double-blade mixer (Mixer 1) is verified by a bench test and other three kinds of mixer structures (baffle mixer: Mixer 2, blade-baffle mixer: Mixer 3, and blade mixer: Mixer 4) are simulated. The effect of the mixer structures on the liquid film formation, the pressure drop, the flow and temperature distribution after the mixers and ultimately the NOx conversion efficiency are investigated. Results show that the liquid film is prone to form and accumulate at the connection region between the mixer and exhaust pipe, and liquid film tends to develop with the flow direction. Mixer 2 and Mixer 4 shows smaller liquid film area about 15 cm2. The temperature distribution in four types of mixers shows negligible difference (within 4 °C). NH3 mass fraction distribution uniformity and pressure drop shows a trade-off relationship. For the vertical injection system, it is found Mixer 3 gets the worst NOx conversion efficiency, 57%, and Mixer 2 shows better NOx conversion efficiency, 78%. The paper are supportive to the SCR mixer selection and design. © 2022, The Authors. All rights reserved.

关键词： Computational fluid dynamics

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Numerical Investigation on the Radiation Performance of a Crisscross Liquid Droplet Radiator in Space Under Different Operating Conditions

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SSRN 2022年

作者： Zhu, Maoguo Sha, Zhaoyang Zhao, Quanbin Chong, Daotong Chen, Weixiong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China

Crisscross liquid droplet radiator (LDR) is a promising solution for the heat dissipation of large-power space structures. In this study, a three-dimensional steady numerical simulation of the radiation performance of crisscross LDR in space under different operating conditions was conducted. Significantly, the radiation interaction between adjacent droplet planes was introduced into the radiation model to accurately compute the energy radiated by the crisscross droplet sheet. Simulation results indicated the radiation performance of crisscross droplet sheet deteriorated with an increase in the nonuniformity of droplet planes arrangement and hence droplet planes uniformly arranged were required for a good crisscross LDR. Moreover, there existed a critical droplet sheet angle of 72° where the pressure disturbance frequency almost had no influence on the radiation performance of crisscross LDR. For certain pressure disturbance frequency, decreasing the droplet sheet angle can expand the available operational pressure difference range. The radiation performance of crisscross LDR with high initial droplet temperature was more sensitive to the changes in droplet sheet angle than that with low initial droplet temperature. Finally, the optimal working medium collocation scheme and droplet sheet configuration for crisscross liquid metal LDR were proposed. Given the lightweight and efficiency of crisscross liquid metal LDR, the collocation scheme of working medium including tin and lithium can be adopted and the droplet sheet angle should be designed as 15°. The present work can provide significant guidance for selecting suitable operating conditions for droplet generators to optimize the thermal design of a crisscross LDR. © 2022, The Authors. All rights reserved.

关键词： Drops

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Experimental Investigation on Separation Characteristics of Gas-Liquid Two-Phase Flow Around the Perforated Tube

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SSRN 2022年

作者： Wang, Jinzhi Xie, Xiangdong Wang, Yechun Xu, Qiang Wang, Jiang Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The flow around cylinder is widely used in industrial applications. In this study, the separation characteristics of gas-liquid two-phase flow around a perforated tube are investigated experimentally. The interface fluctuation process of the gas pocket and liquid slug periodic separation around the perforated tube is presented intuitively using a high-speed camera. The mean value and standard deviation of the void fraction in the wake region are independent of the inlet liquid flow rate. When the flow pattern is plug flow, the air separation efficiency first decreases and then increases with an increase in the inlet void fraction;the separation efficiency increases monotonically when the flow pattern is slug flow. The separation purity and total pressure drop increase with increasing inlet void fraction. Based on the principle of minimum kinetic energy, methods for predicting the void fraction in the wake region, separation purity, air separation efficiency and pressure drop have been developed. The new correlations are based on the Weber number and liquid-phase Reynolds number that are also controlling dimensionless group in determining the void fraction, separation efficiency and pressure drop. The prediction accuracies of the void fraction and separation purity are within ±10% and the prediction accuracies of the separation efficiency and pressure drop are within ±20%, which provides an accurate prediction of the separated flow around the perforated tube. © 2022, The Authors. All rights reserved.

关键词： Void fraction

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Research on Artificial Neural Network for Geometric Design and Optimization of Three-Stage Segmented Thermoelectric Generators

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SSRN 2024年

作者： Zhang, Yin Guo, Kailun Wang, Chenglong Zhang, Jing Wang, Yulu Tian, Wenxi Su, Guanghui Qiu, Suizheng School of Nuclear Science and Technology Shanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechatronic Engineering Xianyang Vocational Technical College Xi’an712000 China

More green and environmentally friendly electricity production is the driving force for the development of thermoelectric generators. In addition to high-performance thermoelectric materials, optimizing the geometric shape of thermoelectric generators can also maximize thermoelectric efficiency. This work applies artificial neural networks to the design and optimization of a three-stage segmented thermoelectric generator. After verifying the thermoelectric numerical model of COMSOL, this work generated 3000 sets of simulation data for neural network training. After hyperparameter and particle swarm optimization, the trained neural network can exhibit extremely high prediction accuracy. By coupling the genetic algorithm and artificial fish swarm algorithm, the trained artificial neural network can optimize eight geometric parameters of a three-stage segmented thermoelectric generator under different temperature differences. Compared with COMSOL optimization results, the conversion efficiency optimized by GA has increased by 1.42% and 2.48% in cases 1 and 2, respectively;The conversion efficiency optimized by AFSA has increased by 3.61% and 2.86% in cases 1 and 2, respectively. By obtaining almost identical optimization values, the neural network can achieve geometric design optimization within 5 minutes under different temperature differences. This method provides a new and economical avenue for rapid prediction and design of thermoelectric generators. © 2024, The Authors. All rights reserved.

关键词： Genetic algorithms

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An Experimental Study on Ash Deposition Problem of Low-Low Temperature Flue Gas System 9th

An Experimental Study on Ash Deposition Problem of Low-Low T...

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9th International Symposium on Coal Combustion, ISCC 2019

作者： Yan, Yu Jiang, Jiahao Guo, Jin Li, Yuesheng Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Guangdong Institue of Special Equipment Inspection and Research Foshan528251 China Guangdong Institue of Special Equipment Inspection and Research Shunde Institue of Inspection Foshan528300 China

ISBN: (纸本)9789811616563

In order to achieve the ultra-clean emission standards, many power plants in China have completed the installation of low-low temperature flue gas system. However, during the operation of this system, many problems have emerged, such as the ash deposition problem in the heat exchanger and dry ESP (electrostatic precipitator). In this paper, the fixed adsorption system and entrained flow experimental system were built to study the ash deposition characteristics in low-low temperature flue gas system under different temperatures and particle sizes. The repose angle was measured to evaluate the flowability and adhesion capacity of ash particles. The results show that as the increase of adsorption time, the particle size increased gradually, and the agglomeration effect is attenuated after the particles have reached adsorption saturation. The time at which the ash particles began to agglomerate with each other was defined as the agglomeration threshold. As the adsorption temperature decreased, the particle size growth rate increased. The smaller the size of ash particles, the more significant the agglomeration effect. Large particles were easy to adsorb small particles, but the agglomeration effect between large particles was weak. In addition, in the initial stage of particle agglomeration, it was mainly included the adhesion between smaller particles and the adhesion of smaller particles on the surface of large particles. The followability of the ash particles was greatly reduced after the adsorption and agglomeration process. The repose angle of the ash particles increased as the temperature of the flue gas decreased. The smaller the particle size, the larger the repose angle changes, and the more pronounced the repose angle is influenced by the adsorption temperature. The flue gas temperature cannot be blindly dropped in pursuit of high sulfur oxide removal efficiency and dust removal efficiency. © 2022, Tsinghua University Press.

关键词： Particle size

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Co_(2)N Nanoparticles Anchored on N-Doped Active Carbon as Catalyst for Oxygen Reduction Reaction in Zinc–Air Battery

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Energy & Environmental Materials 2022年第3期5卷 935-943页

作者： Xianli Wu Guosheng Han Hao Wen Yanyan Liu Lei Han Xingyu Cui Jiajing Kou Baojun Li Jianchun Jiang Research Center of Green Catalysis College of ChemistryZhengzhou University100 Science RoadZhengzhou 450001China National Engineering Laboratory for Biomass Chemical Utilization Institute of Chemical Industry of Forest ProductsChinese Academy of ForestryNanjing 210042China College of Science Henan Agricultural UniversityZhengzhou 450002China Davidson School of Chemical Engineering Purdue University480 Stadium Mall DriveIN 47906United States State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University28 Xianning West RoadXi'an 710049China

The development of efficient catalytic electrode toward oxygen reduction reaction(ORR)is still a great challenge for the wide use of zinc–air ***,Co_(2)N nanoparticles(NPs)anchored on N-doped carbon from cattail were verified with excellent catalytic performances for *** onset and half-wave potentials over the optimal catalyst reach to 0.96 V and 0.84 V,*** retention rates of 96.8%after 22-h test and 98.8%after running 1600 s were obtained in 1 M methanol *** functional theory simulation proposes an apparently increased electronic states of Co_(2)N in N-doped carbon layer close to the Fermi *** charge density,favorable adsorption,and charge transfer of intermediates originate from the coexistence of Co_(2)N NPs and N atoms in carbon *** superior catalytic activity of composites also was confirmed in zinc–air *** novel catalytic property and controllable preparation approach of Co_(2)Ncarbon composites provide a promising avenue to fabricate metal-containing catalytically active carbon from biomass.

关键词： catalytically active carbon Co2N nanoparticles N-doping oxygen reduction reaction zinc–air battery

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Experimental Study on Frost Crystal Morphologies and Frosting Characteristics Under Different Working Pressures

SSRN

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SSRN 2022年

作者： Lai, Tianwei Liu, Xue Dong, Xiaojun Qiang, Mingchen Yan, Shaohang Hou, Yu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Frost usually grows on the cooling surface of heat transfer equipment which often operates under different working pressures. In such conditions, one of the fundamental influencing factors of frosting, the diffusion coefficient of water vapor around the cooling surface is different from that in the normal atmosphere pressure. In order to investigate the pressure effect on frosting, a test rig for frosting visualization is designed. The role of working pressure around the cooling surface on the frost crystal morphologies and frost layer characteristics are evaluated under different air parameters and temperatures of cooling surface. The vertical growth and lateral distribution of frost crystals are related strongly to working pressure around the cooling surface. More frost crystal morphologies and faster growth rate of frost layer are presented at a lower pressure. The frost thickness, frost accumulation and density reduce with higher pressure. The dimensionless correlation of frost thickness is proposed considering working pressure around the cooling surface, humid air parameters, and temperature of cooling surface. © 2022, The Authors. All rights reserved.

关键词： Working pressure

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Improving sampling depth of laser speckle imaging by topical optical clearing:A theoretical and in vivo study

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Journal of Innovative Optical Health Sciences 2020年第2期13卷 33-43页

作者： D.Li Y.Zhang B.Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049P.R.China

The effect of optical cleaning method combined with laser speckle imaging(LSI)was discussed to improve the detection depth of LSI due to high scattering characteristics of skin,which limit its clinical application.A double-layer skin tissue model embedded with a single blood vessel was established,and the Monte Carlo method was used to simulate photon propagation under the action of light-permeating agent.808 nm semiconductor and 632.8 nm He–Ne lasers were selected to study the e®ect of optical clearing agents(OCAs)on photon deposition in *** show that the photon energy deposition density in the epidermis increases with the amount of tissue°uid replaced by *** with glucose solution,polyethylene glycol 400(PEG 400)and glycerol can considerably increase the average penetration depth of photons in the skin tissue,thereby raising the sampling depth of the *** the action of glycerol,PEG 400,and glucose,the average photon penetration depth is increased by 51.78%,51.06%,and 21.51%for 808nm,68.93%,67.94%,and 26.67%for 632.8 nm lasers,*** vivo experiment by dorsal skin chamber proves that glycerol can cause a substantial decrease in blood°ow rate,whereas PEG 400 can signicantly improve the capability of light penetration without a®ecting blood velocity,which exhibits considerable potential in the monitoring of blood°ow in skin tissues.

关键词： Laser speckle image topical optical clearing imaging depth Monte-Carlo simulation dorsal skin experiment

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