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Fire Extinct Experiments with Water Mist by Adding Additives

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Journal of Thermal Science 2011年第6期20卷 563-569页

作者： lijun yang Jianbo Zhao School of Astronautics Beihang University Beijing 100191 China

The effects of fire extinguishment with water mist by adding different additives were *** of chemical substances (including alkali metal salt,dilution agent and surface active agent) were selected as additives due to their different extinct *** first the performance of fire extinguishment with single additive was studied,then the effects of the same kinds of chemical substances under the same mass fraction were compared to study their influences on the fire extinguishment factors,including extinct time,fire temperature and oxygen concentration from which the fire extinct mechanism with additives could be *** on this the experiments were conducted to study the cooperate effect of the complexity of different *** indicated the relations between different firefighting mechanisms and different additives were *** a large number of experiments the extinct mechanism with water mist by adding additives was concluded and an optimal compounding additive was selected.

关键词： fire extinguishment additives water mist

Calculation of fire extinguishment time with water mist in an enclosed room

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Journal of Thermal Science 2010年第6期19卷 561-566页

作者： lijun yang Jianbo Zhao Zhenyu Xu School of Astronautics Beijing University of Aeronautics and Astronautics Beijing 100191 China Naval Academy of Armament Beijing 100161 China

The fire extinguishment time is a major factor to evaluate the efficiency of fire extinguishment with water mist. In this paper the fire extinguishment time with water mist in an enclosed room is calculated. Before adding water mist, the chemical kinetics plays the role in combustion, where a dimensionless math model is established by us-ing the Semenov theory. After adding water mist, the diffusion plays the role instead. Then another math model containing water mist and dominated by oxygen concentration is established. The fire temperature is integrated from Tm to extinguishment temperature TB and the extinguishment time can be obtained. The calculated values are compared with the experimental data under different conditions. The results show that this model can predict the fire extinguishment time accurately. Besides, this model also can be used to determine the critical water mist flux and evaluate which fire extinguishment mechanisms dominate the extinguishment.

关键词： extinguishment time minimum flux water mist

Enhancement of pulsed laser ablation assisted with continuous wave laser irradiation

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Science China(Physics,Mechanics & Astronomy) 2019年第3期62卷 66-74页

作者： Ye Ding lijun yang MingHui Hong Key Laboratory of Micro-systems and Micro-structures Manufacturing Ministry of Education Harbin Institute of Technology Department of Electrical and Computer Engineering National University of Singapore School of Mechatronics Engineering Harbin Institute of Technology

Continuous wave(CW) laser irradiation is employed to enhance the pulsed laser ablation of silicon and stainless steel(316 L)samples. Different surface temperatures generated by the CW laser irradiation are set as the initial working circumstance for the pulsed laser ablation. The diameter and depth of laser-ablated craters are measured to study threshold fluence, pulse incubation coefficient and ablation rate under different surface temperatures. Numerical simulation employing Heat Transfer in Solid and Deformed Geometry Interface modules in COMSOL is performed to estimate ablation rate theoretically based on Hertz-Knudsen equation. The realized crater-related data are analyzed to further obtain their dependences on surface temperature. The parametric and morphological studies indicate that the weakened plasma shielding effect and thermal diffusion in the ablated region induced by the CW laser irradiation lead to the enhanced pulsed laser ablation significantly.

关键词： enhanced pulsed laser ablation CW laser irradiation Hertz-Knudsen equation parametric and morphological studies

Mesostructured carbon-based nanocages: an advanced platform for energy chemistry

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Science China Chemistry 2020年第5期63卷 665-681页

作者： Qiang Wu lijun yang Xizhang Wang Zheng Hu Key Laboratory of Mesoscopic Chemistry of Ministry of Education School of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China

The electrochemistry in energy conversion and storage(ECS) not only relies on the active species in catalysts or energy-storage materials, but also involves mass/ion transport around the active species and electron transfer to the external circuit. To realize high-rate ECS process, new architectures for catalysts or energy-storage electrodes are required to ensure more efficient mass/charge transport. 3 D porous mesostructured materials constructed by nanoscale functional units can form a continuous conductive network for electron transfer and an interconnected multiscale pores for mass/ion transport while maintaining the high surface area, showing great promise in boosting the ECS process. In this review, we summarize the recent progress on the design,construction and applications of 3 D mesostructured carbon-based nanocages for ECS. The role of the hierarchical architectures to the high rate performance is discussed to highlight the merits of the mesostructured materials. The perspective on future opportunities and challenges is also outlined for deepening and extending the related studies and applications.

关键词： carbon-based nanocages mesostructures energy conversion and storage enhanced mass/charge transport multifunction platform

Influences of Lateral Double-Layered Deflectors on Cooling Performance of Air-Cooled Condenser

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Journal of Thermal Science 2021年第6期30卷 2164-2177页

作者： HUANG Wenhui HUANG Xianwei yang lijun DU Xiaoze Key Laboratory of Power Station Energy Transfer Conversion and System of Ministry of Education School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing 102206China

The cooling performance of air-cooled condenser(ACC)is susceptible to adverse impacts of ambient *** this work,three kinds of lateral double-layered deflectors installed under the ACC platform are proposed to weaken the unfavorable effects of cross *** CFD simulation methods,the main parameters of thermo-flow performances of a 2×660 MW direct dry cooling system are obtained,by which it can be concluded that the deflectors can effectively reduce the inlet air temperatures while enhance the mass flow rates of upwind fans due to the guiding effect,especially at high wind speeds,while the improvement of cooling capacity of ACCs in the 0°wind direction is *** inclined-vertical deflectors are superior to others in performance improvement of ACCs for all cases,which can reduce the turbine back pressure by 12.15%when the wind speed is 12 m/s,so they can be applied to the performance enhancement of ACCs under windy conditions in practical engineering.

关键词： air-cooled condenser lateral double-layered deflectors cooling capacity turbine back pressure wind speed and direction

Thermo-flow characteristics and air flow field leading of the air-cooled condenser cell in a power plant

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Science China(Technological Sciences) 2011年第9期54卷 2475-2482页

作者： ZHANG WanXi yang lijun DU XiaoZe yang YongPing Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education School of Energy Power and Mechanical Engineering North China Electric Power University Beifing 102206 China

Special A-frame geometry of the air-cooled condenser cell and the complicated flow field at the exit of the axial flow fan bring on the air mal-distribution on the surface of the finned tube bundles and the deteriorated thermo-flow performances of a condenser cell. It is of benefit to the design and operation optimization of the direct dry cooling system in a power plant to investigate the thermo-flow characteristics of the condenser cell and propose the flow leading measures of cooling air. On the basis of the representative configuration of the air-cooled condenser cell in a 600 MW direct dry cooling power plant, the computa- tional models of the air side fluid and heat flows are built, in which the actual fan blade geometric details are considered. Various flow field leading ways of cooling air are presented and the thermo-flow characteristics in the A-frame condenser cell and through the finned tube bundles are compared. Results show that the flow field leading measures can result in the increased volumetric flow rate and heat rejection, thus bringing on the improved performance of the condenser cell. The improvement of thermo-flow oerformances depends upon the geometric details of the flow guiding device.

关键词： air-cooled condenser axial flow fan t'mned tube bundle flow and heat transfer characteristics flow field leading

Ageing characteristics and lifetime model of oil-paper insulation for oil-immersed paper condenser bushing

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High Voltage 2021年第2期6卷 278-290页

作者： Sihang Gao lijun yang Tingjing Ke Key Laboratory of Industrial Internet of Things and Networked Control Ministry of EducationChongqing University of Posts and TelecommunicationsChongqingChina State Key Laboratory of Power Transmission Equipment and System Security and New Technology Chongqing UniversityChongqingChina State Grid Chongqing Electric Power Company Chongqing ChongqingChina

This study extensively investigated the ageing characteristics and lifetime model of oil-paper insulation for oil-immersed paper condenser *** accelerated thermal and electrothermal ageing experiments of oil-immersed paper condenser bushing were con-ducted *** properties of oil-paper insulation during the ageing process were *** showed that descending speed of degree of polymerization of the innermost and the outermost layer paper was higher than that of middle layer paper,the difference in water content on different paper layers caused varying deterioration *** aluminium foil contributed to a surge in aluminium dissolution in oil,further accelerating the ageing of *** on the obtained degree of polymerization data under thermal ageing at 90°C,100°C and 130°C,the lifetime model of oil-paper insu-lation for condenser bushing model was *** addition,the surface breakdown of the scale model of bushing occurred after 133 days ageing,the properties of bushing decreased gradually during the ageing process and sharply after the *** of polymerization deviation of different paper layers in bushing between calculated value according to the above lifetime model and actual value of bushing after the breakdown was less than 6%,further verifying the validity of lifetime model.

关键词： lifetime immersed insulation

Indoor and outdoor particle concentration distributions of a typical meeting room during haze and clear-sky days

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Science China(Technological Sciences) 2017年第3期60卷 355-362页

作者： LI YanLong JIN XinMing yang lijun DU XiaoZe yang YongPing Key Laboratory of Condition Monitoring and Control for Power Plant Equipments of Ministry of Education School of Energy Power and Mechanical Engineering North China Electric Power University Beijing 102206 China

Air quality has increasingly been a great concern all over the world,and the good command of indoor and outdoor air qualities is of

关键词： indoor and outdoor environment particle concentration mass concentration PM2.5 in-situ measurement

Study on heat transfer enhancement of discontinuous short wave finned flat tube

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Science China(Technological Sciences) 2011年第12期54卷 3281-3288页

作者： FENG LiLi DU XlaoZe yang YongPing yang lijun School of Energy and Mechanical Engineering North China Electric Power University Beijing 102206 China

The typical configuration adopted by air-cooled condenser(ACC) in coal-fired power generating unit is the wave finned flat tube. The development of boundary layer between wave fins along long axis of flat tube can suppress the air-side heat transfer enhancement to a great extent. It has been proved that the serrated fins can enhance heat transfer obviously by breaking the development of boundary layer periodically. In the present study,the discontinuous short wave fin was introduced to the flat tube to enhance the air-side heat transfer of ACC. Two different types of arrangements,i.e. staggered and in-line for discontinuous short wave fins on the flat tube,were designed. By numerical simulation,the heat transfer and flow performances of short wave fins were studied under different arrangements(in-line,staggered) ,and the influences on heat transfer and flow characteristics of rows of short wave fin and interrupted distance between discontinuous short wave fins were revealed numerically. The results indicated that,compared with the original continuous wave fin,the discontinuous short wave fin effectively improved the air-side heat transfer of flat tube under the air flow velocities in the practical application of engineering. Moreover,the increment of pressure loss of air-side flow was restricted for the discontinuous short wave fins because of the reduction of contact areas between the air flow and fin surface.

关键词： fiat tube discontinuous short fin heat transfer enhancement direct air-cooled condenser