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Guo W.,Nanjing University of Technology | Guo W.,Jiangsu Key Laboratory of Urban and Industrial Safety | Yue T.,Nanjing University of Technology | Yue T.,Jiangsu Key Laboratory of Urban and Industrial Safety | And 8 more authors.
Procedia Engineering | Year: 2012

Water curtain could dilute leaking poisonous gas or obstruct the diffusion of the poisonous gas to the sensitivity regions safely, efficiently and quickly. So it was very important to understand diffusion mechanism of the heavy gas diluted by water curtain and explore pattern of the effect of water curtain's setting parameter on the diffusion capacity of heavy gas diluted with water curtain. In this paper, experiments of fan water curtain and cone water curtain diluting CO2 in open space were done. According to experiment results, dilution mechanism of fan water curtain and cone water curtain were obtained. The protective screen formed by fan water curtain could obstruct heavy gas diffusion effectively, and fan water curtain could also disperse heavy gas upwards through the mechanical effect. Cone water curtain would atomize the water and mix the heavy gas and air intensively with the help of air entrainment to dilute the heavy gas clouds. On this basis, it was concluded that when water curtain was opened before heavy gas passed through water curtain and the cone water curtain was installed in front of the fan water curtain, dilution effect was better. When water curtain was opened after heavy gas passed through water curtain and the fan water curtain was installed in front of the cone water curtain, dilution effect was better. © 2012 The Authors. Published by Elsevier Ltd.


Zhao D.,Nanjing University | Zhao D.,Jiangsu Key Laboratory of Urban and Industrial Safety | Jiang J.,Nanjing University | Jiang J.,Jiangsu Key Laboratory of Urban and Industrial Safety | And 3 more authors.
Modern Tunnelling Technology | Year: 2015

Aimed at the problem of not being able to fully guarantee safe evacuation in case of urban tunnel fires with semi-open natural ventilation, the Fire Dynamic Simulation (FDS) software and a wind tunnel experimental platform were used to carry out a numerical simulation and experimental study on how smoke diffuses under natural ventilation and hybrid ventilation modes. The results show that natural ventilation used in a semi-open urban tunnel is unable to solve the problems of fire safety, but hybrid ventilation can effectively control smoke when the exhaust coefficient reaches 3.3, which assures the safe evacuation of personnel and vehicles. Additionally, the exhaust coefficient presented in this paper and applied in the study of the hybrid ventilation mode for semi-open urban tunnels may provide a theoretical basis for similar tunnels regarding safety during fires. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.


Hua M.,Nanjing University of Science and Technology | Hua M.,Nanjing University of Technology | Hua M.,Jiangsu Key Laboratory of Urban and Industrial Safety | Xu D.,Nanjing University of Technology | And 6 more authors.
Procedia Engineering | Year: 2012

The movement process of superfine powder extinguishing agent would be affected by temperature gradient, hot smoke and thermal radiation existed in fire. Numerical simulation was used to make a comparative research on superfine powder extinguishing agent movement released in non-fire room and fire room. The results showed that when superfine powder extinguishing agent was released in non-fire room, particles were mainly controlled by drive gas and moved to the bottom of the fire room firstly. And then particles moved to the side walls of the room after they impacted the bottom. Finally, total flooding condition was formed from the bottom to top. When fire was located at the middle ground, particles moved to both sides of the room at early time after release. And then particles reached the flame region from the sides and top of the flame. Finally total flooding condition was formed from the top to the bottom, and the total flooding time was pretty much exactly the same as non-fire condition. When fire was located at the left bottom corner, particles were mainly controlled by eddies, which led to irregular trajectory and uneven concentration distribution of particles. Under this condition, particles were mainly entrained into flame region by eddies, and it took more time to form total flooding condition. © 2012 The Authors. Published by Elsevier Ltd.


Hua M.,Nanjing University of Science and Technology | Hua M.,Nanjing University of Technology | Hua M.,Jiangsu Key Laboratory of Urban and Industrial Safety | Xu D.,Nanjing University of Technology | And 4 more authors.
Nanjing Li Gong Daxue Xuebao/Journal of Nanjing University of Science and Technology | Year: 2014

In order to research the interaction between superfine powder extinguishing agents (SPEA) and fire plume, the injection and movement characteristics of SPEA particles are numerically simulated in fire at different driving pressures. The interaction process of injection velocity model, discrete phase model, and fire model on the particles release, flow, and fire is numerically simulated. The simulation results indicate that the converging nozzle can enhance the capacity of extinguishing agent particles to penetrate fire plume, and its penetration capacity is directly proportional to the driving pressure value. When the fire interacts with the particles, the height decreases and the width increases. The larger the driving pressure becomes, the shorter the time for particles to enter into fire source area becomes. Particle concentration value in fire source area is relatively higher at 1.2 MPa and smaller at 1.0 MPa. Larger driving pressure can accelerate the motion time of particles to fill the extinguishing room. Eddies, which appear more easily at lower driving pressure, can also drive particles to fill the extinguishing room quickly, but with uneven distribution.


Xu D.-Y.,Nanjing University of Technology | Xu D.-Y.,Jiangsu Key Laboratory of Urban and Industrial Safety | Hua M.,Jiangsu Key Laboratory of Urban and Industrial Safety | Hua M.,Nanjing University of Science and Technology | And 3 more authors.
Procedia Engineering | Year: 2014

When the nozzle of release device directly faces the protected object, it is necessary for the superfine powder extinguishing agents (SPEA) to penetrate fire plume, so that SPEA can reach the fire source to extinguish fire effectively. Numerical simulation was used to make a comparative study on SPEA motion released at different driving pressures in fire. The simulation results indicate that the converging nozzle will enhance the capacity of extinguishing agent particles to penetrate fire plume, and its penetration capacity is directly proportional to the driving pressure value. When interacting with particles, the flame height decreases and flame width increases. The larger the driving pressure, the shorter time for particles to enter into fire source area. Particle concentration value in fire source area is relatively higher at 1.2MPa and it less changes at 1.0MPa. Larger driving pressure can accelerate the motion of particles to fill the extinguishing room. Eddies, which appear more easily at lower driving pressure, can also drive particles to fill the extinguishing room quickly, but with uneven distribution. © 2014 Published by Elsevier Ltd.


Wei Z.,Nanjing University of Technology | Wei Z.,Jiangsu Key Laboratory of Urban and Industrial Safety | Jiapeng H.,Nanjing University of Technology | Jiapeng H.,Jiangsu Key Laboratory of Urban and Industrial Safety
2011 International Conference on Electric Technology and Civil Engineering, ICETCE 2011 - Proceedings | Year: 2011

In order to study the effect of common smoke control model, the numerical simulation combined with the full size experimental have been used to analyze effect of several modes, which composed with the smoke screen, mechanical smoke and air curtain, and the smoke temperature distribution, concentration distribution, and smoke down time between these model is compared. The results show that smoke preventing air curtain and pressurization in atria, with two smoke vents in aisle has the best mode of smoke control effect, which has exhaust efficiency about 74.52%. It not only can let smoke out timely, but also can guarantee safe evacuation environment in atria. © 2011 IEEE.


Ye C.,Nanjing University of Technology | Ye C.,Jiangsu Key Laboratory of Urban and Industrial Safety | Hua M.,Nanjing University of Technology | Hua M.,Jiangsu Key Laboratory of Urban and Industrial Safety | And 6 more authors.
Journal of Loss Prevention in the Process Industries | Year: 2016

Natural gas is a kind of clean, efficient green energy source, which is used widely. Liquefied natural gas (LNG) is produced by cooling natural gas to,-161,°C, at which it becomes the liquid. Once LNG was released, fire or explosion would happen when ignition source existed nearby. The high expansion foam (Hi-Ex foam) is believed to quickly blanket on the top of LNG spillage pool and warm the LNG vapor to lower the vapor cloud density at the ground level and raising vapor buoyancy. To identify the physical structure after it contacted with LN2 and to develop heat transfer model, the small-scale field test with liquid nitrogen (LN2) was designed. In experiment, three layers including frozen ice layer, frozen Hi-Ex layer and soft layer of Hi-Ex foam were observed at the steady state. By characterizing physical structure of the foam, formulas for calculating the surface of single foam bubble and counting foam film thickness were deduced. The micro heat transfer and evaporation model between cryogenic liquid and Hi-Ex foam was established. Indicating the physical structure of the frozen ice layer, there were a certain number of icicles below it. The heat transfer and evaporation mathematical model between the frozen ice layer and LNG was derived. Combining models above with the heat transfer between LNG, ground and cofferdam, the heat transfer and evaporation mathematical model of LNG covered by Hi-Ex foam was developed eventually. Finally, LN2 evaporation rate calculated by this model was compared with the measured evaporation rate. The calculated results are 1.2-2.1 times of experimental results, which were acceptable in engineering and proved the model was reliable. © 2016 Elsevier Ltd.


Xu D.-Y.,Nanjing University of Technology | Xu D.-Y.,Jiangsu Key Laboratory of Urban and Industrial Safety | Zhang C.-F.,Nanjing University of Technology | Zhang C.-F.,Jiangsu Key Laboratory of Urban and Industrial Safety | And 4 more authors.
Tunnelling and Underground Space Technology | Year: 2014

A natural ventilation scheme was proposed for large underground spaces based on the top cover design. This is regarded as a design towards 'green' or 'sustainable' building. The main factors influencing the natural smoke extraction efficiency were studied by using orthogonal design method and CFD technique. A new model was built to estimate the feasibility of the natural ventilation scheme in case of fire accidents. Results show that when fire occurs in underground part of the building, smoke can be exhausted to the interlayer, which is added between the underground part and its top cover, and then the smoke spread along the ceiling of the interlayer to its open boundaries. When working together with smoke shafts, smoke screens can limit the spread of smoke and improve the smoke exhausting efficiency of shafts. In addition, whether the smoke can be vented above specified safety height both in underground part and in the interlayer can be theoretically estimated by the judging model constructed. In order to ensure safety smoke layer height, the size of the underground part is limited when the fire power is determinate. And it showed linear relationship between critical underground part size and critical fire power. The slop of the line decreases when smoke screens are added. © 2014 Elsevier Ltd.


Mao G.,Nanjing University of Technology | Jiang J.,Nanjing University of Technology | Jiang J.,Jiangsu Key Laboratory of Urban and Industrial Safety | Dou Z.,Nanjing University of Technology | And 2 more authors.
Shiyou Xuebao, Shiyou Jiagong/Acta Petrolei Sinica (Petroleum Processing Section) | Year: 2015

To study the natural oxidation tendency of sulfur corrosion products in oil tank, the sulfuration experiment equipment was built. Through the experiment of oxidizing reaction with O2 of simulated sulfur corrosion products in gasoline, diesel and high sulfur crude oil storage tanks, the law of the natural oxidation process was explored. The experimental results showed that the sulfur corrosion products in the gasoline tank were produced slowest for the longest cycle among these in the three tanks. When the oxygen volume fraction was between 7.8%-18.2%, the oxidation process of the sulfur corrosion products in high sulfur crude oil tank could be divided into three stages, which were primary oxidation stage, the secondary oxidation stage and the deep oxidation. When the oxygen volume fraction was below 13.2%, the oxidation of the sulfur corrosion products in diesel fuel tank only stayed in primary oxidation stage, while the oxidation risk of sulfur corrosion product in the gasoline tank was relatively small. The higher oxygen volume fraction, the greater combustion risk of sulfur corrosion products. © 2015, Editorial Office of Acta Petrolei Sinica. All right reserved.

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