细水雾抑制瓦斯爆炸的实验研究

对内径68 mm,长1 200 mm的密闭管内甲烷爆炸的细水雾抑制效果进行了实验研究,分析了不同喷雾量对瓦斯爆炸最大爆炸压力及最大压力上升速率的影响。实验结果表明,喷雾量较小时,瓦斯爆炸的最大爆炸压力及最大压力上升速率都出现增大,达到压力峰值的时间缩短。随着喷雾量的增加,最大爆炸压力及最大压力上升速率会随着下降,达压力峰值的时间延长。这表明细水雾的喷雾量较大时,对瓦斯爆炸的抑制作用比较明显。     

钢管控制冷却物理模拟平台的建立及传热边界条件的确定

目前关于钢管控制冷却的研究没有专门针对其关键问题传热边界条件进行深入分析。为此基于钢管热机械控制工艺实际,建立钢管控制冷却全尺寸物理模拟平台,测定28CrMoVNiRE油井管在水量11.4 L/min、气压0.2 MPa,水量11.4 L/min、气压0.3 MPa和水量18.0 L/min、气压0.3 MPa三种不同气雾控制冷却条件下的冷却曲线,通过反传热法计算钢管表面的热流密度和换热系数,分析钢管在气雾控制冷却条件下的传热边界条件。结果表明,影响钢管气雾控制冷却传热的关键因素是气水混合比,其最佳值为6～7;换热系数随温差ΔT的下降依次经历高温慢速增加阶段、中温稳定阶段和低温快速增加阶段。采用有限元正算法,验证了反传热计算结果的可靠性。钢管控制冷却后细化的微观组织验证了气雾控制冷却物理模拟技术的可行性。钢管控制冷却传热边界条件的确定对于实现钢管在线气雾控制冷却工艺具有重要的指导意义。     

神经外科颅骨磨削温度场预测新模型

基于恒定热流密度的温度场理论计算值与实际温度值的误差较大,是当前磨削温度场理论研究的瓶颈。建立了不同冷却条件下的对流换热系数及材料内部的热传导模型,通过实时采集动态磨削力,利用高次高斯函数拟合建立了动态热流密度模型,并以此为基础建立了神经外科骨磨削温度场预测新模型。在干式磨削、喷雾式及纳米粒子射流喷雾式冷却条件下对骨磨削温度场进行了数值分析,并采用与人体颅骨力学性能最相近的新鲜牛股骨密质骨,采用羟基磷灰石纳米粒子及生理盐水进行了试验验证。结果表明,与试验测得温度值相比,采用基于恒定热流密度的温度场模型计算的温度值误差为18.8%,而采用新模型计算的温度值误差为6.6%,理论分析与试验结果吻合,即骨磨削温度场预测新模型更符合实际工况。     

人造云雾对电视制导武器影响的半物理仿真研究

综述了国内外研究现状,分析了人造云雾技术和模拟导引头的特点,设计了半物理仿真模型,描述了测试与评估流程,总结了研究意义。     

Experiment and prediction of fire extinguishment with water mist in an enclosed room

The correlation between oxygen concentration and fire temperature when fire was extinguished with water mist was theoretically studied. The Semenov theory was applied to analyze the critical condition when fire was extinguished with water mist, from which the correlation could be obtained. The water mist experiments were carried out by varying the fire size, atomizer number, ceiling height, system pressure, and pre-burn time in an enclosed room. The oxygen concentration near the edge of the liquid pool and the fire temperature above the center of the liquid pool were measured. A comparison of the experimental data with the correlation was made under different conditions. The results showed that fire extinguishment was a stochastic process which could be affected by many factors. This theoretical model could predict the correlation between fire temperature and oxygen concentration when fire was extinguished with water mist in an enclosed room and it can also be treated as a critical condition for fire extinguishment.     

Suppression of hydrogen/oxygen/nitrogen explosions by fine water mist containing sodium hydroxide additive

Complementary sets of experiments, consisting of burning velocity measurements and vented explosion tests, have been undertaken for a wide range of hydrogen–oxygen–air test compositions using fine water mist with NaOH additive (SMD ∼ 4 μm). In contrast to pure water mists, burning velocity measurements identified a critical mist concentration (for a given gas composition) above which a sudden large decrease in burning velocity is observed. The critical concentration was also found to correspond to an inerting concentration during vented explosion testing. Prior to reaching the critical concentration, the NaOH additive had a negligible effect on both the burning velocity measurements and explosion tests. This clearly indicates that the NaOH additive is acting as a chemical inhibitor. The inhibiting effect is generally considered to occur due to homogeneous gas phase mechanisms and it is thought likely that only the fraction of the entire mist (with droplet diameter < 2.5 μm) would evaporate sufficiently quickly to allow vaporised NaOH to take part in the inhibition. The experimental data obtained have enabled the construction of an inerting map to facilitate the design of a practical mist inerting system.     

Sulfuric Acid Mist: Generation,Suppression, Health Aspects,and Analysis

Sulfuric acid mist, which is generated in electrowinning tankhouses, poses corrosion problems to the tankhouse structure and adverse health effects to employees. The literature pertaining to the generation of acid mist from bursting bubbles as film and jet droplets is reviewed. In addition, various methods of suppressing acid mist, such as the use of surfactants, balls, and hoods, are presented and discussed. The occupational exposure limits in various countries are presented and the commonly accepted methods of sampling acid mist are reviewed. Data on acid mist from a survey of 25 zinc and copper tankhouses are summarized.     

铝箔轧制油雾的在线回收及循环利用

结合铝箔轧制加工设备及工艺特点,阐述了制约加工成本和环境污染的轧制油油雾在线回收及循环利用系统原理、工艺流程、实施方案及节能降耗效果.     

Sodium Mist Behavior in Cover Gas Space of LMFBR Out-Pile Experiment

Sodium mist behavior in argon cover gas space over sodium pool was investigated experimentally using of a test vessel having cover gas volume of ～100l. Mass concentration and gravitational settling flux of the mist (i.e. sodium aerosol) were determined between pool temperature range of 290～520°C. Apparatuses used for the concentration determination were a He-Ne laser mist concentration meter (LCM) and mist traps, which were developed specifically for the present experiment. The mist gravitational settling flux φ was determined by using of collection plates, which were exposed to the mist entrained cover gas over sodium pool.

The experimental results revealed that the concentration C was very high from 0.15 to 20g/m³. It increased with pool temperature. The mist particle radii, which were determined from the gravitational settling flux φ and decay curve of the concentration, were from 1.5 to 13 μm in the range of the present experiment. The vapor evaporation rate φe from the pool surface, which were also determined from the experimental φ data, were found to increase with saturated vapor pressure P_s at pool surface. This rate did not depend so strongly on experimental geometries and cover gas flow convection pattern over sodium pool. Evaluations of transient C changing and steady state C fluctuation indicated that the mist formation was occurred near the pool surface.