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341.
342.
G. Vachon P. Louka J-M. Rosant P.G. Mestayer J-F. Sini 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):127-140
A full scale experiment has been performed in a streetcanyon, the Rue de Strasbourg in Nantes (France). Thiscampaign, the Nantes'99 experiment, provided a detaileddata base documenting, amongst others, the production ofturbulent kinetic energy (TKE) by vehicles within thestreet. Airflow and CO concentration measurements have beenanalysed during days with low wind perpendicular to thestreet axis, i.e. for conditions expected to greatly favourthe enhancement of the turbulence produced by traffic onflow and dispersion within the street canyon. It is shownthat traffic is associated with an increase in turbulentkinetic energy at the lowest levels of the street,especially at the leeward side of the street. It issuggested that turbulent kinetic energy increases with thenumber of vehicles up to a threshold value and thendecreases when vehicles form a `block' shape that limitsthe additional production of turbulence. Moreover, it issuggested that traffic-produced turbulence affectspollutant dispersion reducing CO concentration at the lowerlevels of the leeward side of the street from a thresholdvalue of TKE equal to about 0.15 m2 s-2. On the other hand, high traffic density generates less turbulencewhich in turn leads to a lower pollutant dispersion. 相似文献
343.
在高原格尔木地区对箱式装备集装箱内部环境条件如温度、大气温度、太阳辐射强度及风速等数据进行了测试,利用模糊系统分析的方法,建立了非线性数学模型,预测出该地区集装箱内部最恶劣的温度范围,为危险军用物资集装箱安全储运提供了理论依据并提出相应的建议和对策。 相似文献
344.
S. Radandt Jianye Shi A. Vogl X. F. Deng S. J. Zhong 《Journal of Loss Prevention in the Process Industries》2001,14(6):495-502
Height to diameter (H/D) ratio is one of the important parameters affecting premixed particle–air combustion characteristics. This paper focuses on the behavior of cornstarch combustion in closed vessels with changed H/D ratios and fixed volumes; and a combustion model is employed to simulate the experiments. An Eulerian–Lagrangian approach for two-phase flows was used in the model and conservation equations of unsteady turbulent two-phase reacting flows were solved in two-dimensional domains. Heat loss to the vessel walls was taken into consideration in the model. The simulation results have a good agreement with those of experiments. Further simulations were carried out for higher H/D ratios from 8 to 15. These results show that H/D=8 is a changing point. When H/D<8, the maximum pressure and the rate of maximum pressure rise decrease with increasing H/D ratios. While H/D>8, the both have an increasing tendency with increasing H/D ratios. 相似文献
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347.
With the production of crude steel, China produces several million tons of sintering dusts which contain a great deal of valuable metals such as, K, Na, Zn, Pb. If discharged directly without adequate treatment, these elements can lead to adverse effects on the environment. Therefore, it is very necessary to determine how to separate these elements from the dust before discharge. Several physical and chemical detection methods were used to study the basic properties of sintering dust. At the same time, preliminary experiments on the recovery of the potassium resources from the sintering dust were carried out. The mean particle size of the electrostatic precipitator (ESP) dust determined by a laser granulometer was 41.468 μm. Multi-point BET and single-point BET analysis showed that the surface area of the ESP dust was 2.697 m2/g. XRD measurements detected the following phases in the ESP dust: Fe2O3, Fe3O4, KCl and NaCl, and Fe2O3, Fe3O4 and SiO2 in the water-washed dust. SEM-EDS results proved that in the ESP dust, K mostly existed in the form of KCl particles without being coated. Leaching experiments showed that the KCl in the ESP dust could be separated and recovered by water leaching and fractional crystallization. Through the recovery experiments, the yield of K-Na vaporized crystalline salt was 18.56%, in which the mass fractions of KCl, NaCl, CaSO4 and K2SO4 were about 61.03%, 13.58%, 14.03% and 9.97%, respectively. This process is technically viable and considerable in economic benefit. There was almost no secondary pollution produced in the whole recovery process. 相似文献
348.
Xue Bai Qinhe Zhang Jianhua Zhang Dezheng Kong Tingyi Yang 《Journal of Manufacturing Processes》2013,15(4):474-482
Powder mixed near dry electrical discharge machining (PMND-EDM) is a novel electrical discharge machining (EDM) process. It is proposed to further improve the machining efficiency of dry EDM. The principle of material removal in PMND-EDM is illustrated and its deionization principle is proposed. The influence of residual heat on MRR is analyzed. The concept of superfluous residual heat is proposed. The material removal rate (MRR), the main index of machining efficiency for PMND-EDM process, is researched. Single factor experiments are performed to get effect of peak current, pulse on time, pulse off time, flow rate, tool rotational speed, air pressure and powder concentration on MRR under different material combinations of tool electrode and workpiece electrode. Thermal phenomena in PMND-EDM are illustrated. Effect of each process parameter on MRR of PMND-EDM is gotten and analyzed based on the deionization principle of PMND-EDM. Differences in MRR under different material combinations are found out. Brass tool electrode and W18Cr4V workpiece gain higher MRR under most of discharge conditions, while the superiority of copper tool electrode and 45 carbon steel workpiece in MRR arise when there is improper heat dissipation. The difference is analyzed based on the deionization principle of PMND-EDM. 相似文献
349.
目的研究密封剂的施工工艺环境对其剥离强度的影响。方法采用正交实验法,分别从待密封表面清洗、密封剂厚度、密封剂混合比、密封剂施工温湿环境等4个影响因素研究对剥离强度的影响,找出影响因素的主次关系和各自影响趋势。结果对密封剂剥离强度影响程度由大到小顺序依次为表面清洁度、涂覆厚度、温度/湿度、密封剂混合比。剥离强度与待密封表面清洗程度、密封剂厚度大小成正相关,与密封剂温/湿环境大小成反相关。结论在密封剂施工工艺环境规范内,了解各环境因素的影响特点,能有效提高密封剂的剥离强度大小。 相似文献
350.
Jaffee A. SuardinRuifeng Qi Benjamin R. CormierMorshed Rana Yingchun ZhangM. Sam Mannan 《Journal of Loss Prevention in the Process Industries》2011,24(1):63-75
An LNG pool fire is considered one of the main hazards of LNG, together with LNG vapor dispersion. Suppression methods are designed to reduce the hazard exclusion zones, distance to reach radiant heat of 5 kW/m2, when an LNG pool fire is considered. For LNG vapor dispersion, the hazard exclusion zone is the distance travelled by the LNG vapor to reach a concentration of 2.5% v/v (half of the LNG lower flammability limit).Warming the LNG vapor to reach positive buoyancy faster is one way to suppress LNG vapor dispersion and reduce evaporation rate (thus fire size and its associated radiant heat) and that is the main objective in LNG pool fire suppression. Based on previous research, the use of high expansion foam has been regarded as the primary method in suppressing LNG pool fires. However, in 1980, another method was introduced as an alternative pool fire suppression system, Foamglas®. The research concluded that 90% of the radiant heat was successfully reduced. Currently-called Foamglas® pool fire suppression (Foamglas® PFS) is a passive mitigation system and is deployed after the leak occurs. Foamglas® PFS is non-flammable, and has a density one-third of the density of LNG, thus floats when an LNG pool is formed.This paper describes the study and confirmation of Foamglas®PFS effectiveness in suppressing LNG pool fires. In addition, while Foamglas® PFS is not expected to suppress LNG vapor dispersion, further investigation was conducted to study the effect of Foamglas®PFS on LNG vapor dispersion. An LNG field experiment was conducted at Brayton Fire Field. The experimental development, procedures, results and findings are detailed in this paper. 相似文献