A closer look at BLEVE overpressure

The overpressure produced by the boiling liquid expanding vapor explosion (BLEVE) is still not well understood. Various methods have been published on the overpressure modeling in the far field. They mostly differ by the modeling of the expansion energy, used to scale the distance to the source where the overpressure needs to be calculated. But these methods usually include a experimentally fitted reduction factor, and are mostly overestimating the overpressures. Today there is a growing interest in modeling the BLEVE overpressure in the near field, for studying the blast effect on critical infrastructure such as bridges and buildings. This requires a much better understanding of the BLEVE blast. This paper goes deeper in the understanding of the physical phenomenon leading to the BLEVE blast wave generation and propagation. First, mid-scale BLEVE experiments in addition to new experimental data for near field blast from a small scale supercritical BLEVE are analyzed. And second, an analysis method of the shocks observed in the experiments is presented based on fundamental gas dynamics, and allows the elaboration of a new modeling approach for BLEVE overpressure, based on the calculation of the initial overpressure and radius of the blast.     

多器件联合L波段强电磁脉冲防护模块仿真设计

目的 设计针对L波段射频前端敏感器件的强电磁脉冲防护模块,利用瞬态电压抑制二极管、气体放电管和发夹型微带带通滤波器进行联合仿真设计。方法 瞬态电压抑制二极管具有快速响应时间,气体放电管具有高功率容量,而微带带通滤波器可分离噪声信号,并保留有效信号。通过结合这些器件进行防护设计,可以充分发挥各自优势,提高系统稳定性和强电磁脉冲防护能力。结果 该模块设计工作频段为1.3~ 1.7 GHz,带内插入损耗小于1.5 dB,在70 dBm功率注入的情况下,防护效果可以达到42.5 dB,具有良好的防护效果。结论 通过分析研究不同器件的特性和优化设计,实现了对L波段频谱的防护,具有重要的实用价值和广阔的应用前景。     

随机振动加速度响应谱及与冲击等效性分析

目的 获得随机振动的加速度响应谱,提升随机振动与冲击的等效性分析精度。方法 首先,基于维纳-辛钦定理,推导单自由度系统在随机振动基础激励作用下加速度响应均方值的通用表达式;其次,分别推导单自由度系统在理想白噪声和限带非均匀谱随机振动基础激励作用下的加速度响应均方值;再次,基于3σ准则,推导限带非均匀谱随机振动的3σ加速度响应谱;最后,基于加速度响应等效,通过将装备随机振动条件的3σ加速度响应谱与冲击条件的冲击响应谱进行等效性分析,对GJB 150.18A—2009中的冲击试验剪裁条件进行精细优化。结果 精细优化后,可有效改善冲击试验剪裁条件的工程实施精度。结论 获得了限带非均匀谱随机振动的3σ加速度响应谱,并基于此对GJB 150.18A—2009中的冲击试验剪裁条件进行了精细优化,对于装备合理剪裁冲击试验具有借鉴意义。     

垃圾焚烧中抑制二恶英二次生成的方法探讨

根据生活垃圾焚烧技术中二恶英的生成机理,余热锅炉的烟气在低温区急冷可以避免二恶英在低温区的再次合成,但目前在余热锅炉烟气低温区急冷是不可行的。提出一种从垃圾焚烧系统设计上进行烟气的急冷,从而抑制二恶英低温区二次生成的新方法。     

酸化冲击对低pH厌氧发酵系统性能的影响

为了研究酸化冲击对厌氧发酵有机废水能源回收系统的影响,利用自制的厌氧内循环反应器（anaerobic internal circulation reactor,AICR）,以模拟糖蜜废水为底物,逐步提高进水容积负荷以模拟高容积负荷下出现的酸化冲击。研究了反应器酸化前后运行参数,并利用高通量测序检测了酸化后系统微生物群落结构。结果表明：酸化会导致颗粒污泥解体,产气速率和COD去除率下降,产甲烷活性严重抑制,同时发酵类型也发生转变。反应器酸化以后,发酵类型从丁酸型发酵类型转变为混合酸发酵类型,在进水负荷不变的情况下,总产气速率下降约50%,从2 100 mmol·（L·d）-1下降至1 056 mmol·（L·d）-1。酸化后的系统中,非产氢发酵细菌为优势细菌（54.7%）,而产氢细菌所占比例较少（37.3%）,未检测到产甲烷细菌。     

Experimental study on the inhibition of methane/air explosion by modified attapulgite powder

In order to explore the influence of attapulgite powder on the methane explosion, a small-size semi-closed visual explosion experiment platform was built, and experiments were carried out. The effect of spraying powder on the whole process of methane explosion was studied when methane concentration was 7%, 8%, 9.5%, 11% and 12%, respectively. When the methane concentration was 11%, the maximum explosion overpressure dropped by modified spraying attapulgite powder was as high as 33.26%, and at the same time, the reduction rate of flame propagation velocity reached the maximum value of 36.65%. Furthermore, when the methane concentration was 9.5%, the experimental results when the powder spraying amount of modified attapulgite was 120 mg, 160 mg, 200 mg, 240 mg and 280 mg showed that when the powder spraying was 240 mg, the maximum explosive overpressure decreased by 33.14%, and the reduction rate of the peak flame propagation velocity reached the maximum value of 33.73%. Through the video images recorded by the high-speed camera, the flame structure, shape, color, etc. Were analyzed. The characterization analysis illustrated that the modified attapulgite powder has a small particle size, relatively large porosity and specific surface area. Also, it has a high weight loss rate. Combined with the results of characterization analysis, the explosion suppression mechanism of modified attapulgite powder was discussed. It was found that the modified attapulgite powder could effectively absorb the active free radicals generated in the explosion, and the modified new chemical components have a better thermal decomposition and endothermic effect and a better suppression of methane explosions.     

开敞空间可燃气云爆炸冲击波超压及灾害动力响应研究评述

为了进一步梳理和分析开敞空间可燃云爆炸冲击波超压传播规律及灾害动力响应方面的各项研究成果,推进可燃气体爆炸安全防控,减少人员伤亡和经济损失。在分析现有研究的基础上,总结开敞空间可燃气云爆炸冲击波超压传播规律及灾害动力响应研究等方面存在的不足,提出开敞空间多元混合气体爆炸冲击波超压传播规律研究、多影响参数下可燃气云爆炸冲击波超压传播规律定量分析、基于可燃气云爆炸冲击波超压作用下的承载体动力响应等未来研究的关键技术问题。     

低浓度Pb2+、Cd2+对鲫鱼肝脏组织中 HSP70诱导的影响

以鲫鱼(Carassius auratus)作为实验对象,经过40 d Pb2+、Cd2+不同浓度的暴露后,运用SDS-PAGE和Western Blotting方法检测鱼肝脏组织内应激蛋白HSP70的诱导表达情况.结果表明,在实验浓度下,与对照组相比,Pb2+、Cd2+对鱼肝脏内HSP70有显著的诱导(P＜0.05),但在Cd2+浓度为0.2 mg/L有停止表达HSP70的现象,可能是由于浓度过高造成了组织病理损伤而破坏了诱导表达机制.实验还发现,在实验浓度低于国家渔业用水标准时,HSP70仍然表现为明显诱导(P＜0.05),充分说明运用分子生物学指标要比传统的环境检测指标敏感,具有对污染物早期预警的作用.     

进料频率对餐厨垃圾与剩余污泥中温共发酵系统稳定性的影响

考察系统负荷(以COD计)为11.36 g·(L·d)-1时,6种不同进料频率下,餐厨垃圾和剩余污泥中温厌氧共发酵过程中产气量、气体组分、SCOD、pH和挥发性脂肪酸(VFAs)的变化,旨在明确进料频率对系统稳定性的影响,同时结合单一VFA的产甲烷动力学特性,探明系统不稳定的原因。结果表明,进料频率较高时,进料周期内系统的气体组分、SCOD和pH无明显变化,产气量呈线性增长,且基本无VFA积累。随着进料频率降低,进料初期过快的水解酸化导致SCOD和VFAs浓度呈现明显的先升高后逐渐降低的趋势,从而导致pH和甲烷含量波动明显。当进料频率为1 次·d-1时,系统中pH降至7.5,甲烷含量降至45.4%,丙酸占总有机酸的比例最高可达87.9%。相比乙酸而言,丙酸在甲烷化过程中存在的延滞期(1.21 h)及较低的甲烷化速率(5.01 mL·h-1)可能是导致存在丙酸积累的低频进料系统中稳定性较差的原因之一。     

采用TSF技术改善电力变压器运行的安全性

分析了无功功率和高次谐波对电力变压器的危害,介绍了晶闸管投切滤波器(TSF)装置的特点、结构原理．提出了TSF装置在工厂实际应用中的主电路结构,操作及控制方案。实践证明,TSF晶闸管投切滤波器装置起到了高效节能、优化电能质量的作用,保证了电网的安全运行。