Dynamic pressure induced by a methane–air explosion in a coal mine

The hazardous effect of dynamic pressure and strong gas flows induced by a methane–air mixture explosion in underground coal mines is studied. The dynamic pressure effect of a methane–air explosion was analyzed by numerical simulation, in a duct and tunnel. Compared to the overpressure generated by an explosion that can act on a body, the dynamic pressure caused by the high-speed flow of the gaseous combustion products can cause serious damage as well. At the structural opening of a coal mine, the destruction caused by the dynamic pressure induced by a methane–air explosion is more serious than the overpressure. For a tube or tunnel partially filled by a methane–air mixture, the dynamic pressure is lower than the overpressure in the region occupied by the flammable mixture. Beyond the premixed region, the dynamic pressure is of the same order of magnitude as the overpressure.     

间接蒸发冷却新风机组净化室内PM2.5特性

为有效降低室内PM2.5,指导间接蒸发冷却新风机组的设计选型,推导了新风机组净化效力和净化能效评价指标的数学表达式,并利用自行研制的间接蒸发冷却新风机组,分析了2种过滤器在不同运行工况下净化PM2.5的特性。结果表明,MERV 7+16和MERV 7+13的计数效率均随颗粒物粒径增加而提高,且前者的计数效率高于后者;由于滤材的不同,MERV 7+16的初阻力更小。MERV 7+16的渗透系数更小,其净化效力也要大于MERV 7+13;由于PM10在室内的自然沉降作用更显著,过滤器对PM10的净化效力明显大于PM2.5和PM1。将室内新风负荷作为新风机组能耗的一部分,在对比天津和南宁地区新风机组的净化能效时发现,由于两地区冬季室外温度存在明显差异,导致处于天津地区的新风机组若要在冬季获得同等的洁净空气量,需付出更多的能耗代价。     

无上部抽吸装置储罐区人工龙卷风风场模拟

为了减少因储罐泄漏位置不确定造成的人员伤亡,指导应急疏散,提出利用人工龙卷风定向控制气体流动方向的模型。首先基于Fluent软件建立了储罐区域人工龙卷风数值模型,分析切向速度和压强沿径向变化规律,发现与经典Rankine涡模型切向速度沿径向分布规律一致,证实可在储罐区以射流相切的方式形成人工龙卷风风场。其次研究了涡流比和进风量对风场控制气流特性的影响,即分析形成的龙卷风风场最大切向速度、压强差变化规律,结果表明,涡流比越大,形成的龙卷风风场中切向速度和压强差越小,即气流向中心汇聚能力越弱;进风量越大,形成的龙卷风风场中切向速度和压强差越大,即气流向中心汇聚能力越强。研究表明,用人工龙卷风控制储罐泄漏气流方向是可行的。     

Hybrid H2/Al dust explosions in Siwek sphere

Explosion indices and explosion behaviour of Al dust/H₂/air mixtures were studied using standard 20 l sphere. The study was motivated by an explosion hazard occurring at some accidental scenarios considered now in ITER design (International Thermonuclear Experimental Reactor). During Loss-of-Vacuum or Loss-of-Coolant Accidents (LOCA/LOVA) it is possible to form inside the ITER vacuum vessel an explosible atmosphere containing fine Be or W dusts and hydrogen. To approach the Be/H₂ explosion problem, Be dust is substituted in this study by aluminium, because of high toxicity of Be dusts. The tested dust concentrations were 100, 200, 400, 800, and 1200 g/m3; hydrogen concentrations varied from 8 to 20 vol. % with 2% step. The mixtures were ignited by a weak electric spark. Pressure evolutions were recorded during the mixture explosions. In addition, the gaseous compositions of the combustion products were measured by a quadruple mass-spectrometer. The dust was involved in the explosion process at all hydrogen and dust concentrations even at the combination ‘8%/100 g/m3’. In all the other tests the explosion overpressures and the pressure rise rates were noticeably higher than those relevant to pure H₂/air mixtures and pure Al dust/air mixtures. At lower hybrid fuel concentrations the mixture exploded in two steps: first hydrogen explosion followed by a clearly separated Al dust explosion. With rising concentrations, the two-phase explosion regime transits to a single-phase regime where the two fuel components exploded together as a single fuel. In this regime both the hybrid explosion pressures and pressure rise rates are higher than either H₂ or Al ones. The two fuels compete for the oxygen; the higher the dust concentration, the more part of O2 it consumes (and the more H₂ remains in the combustion products). The test results are used to support DUST3D CFD code developed at KIT to model LOCA or LOVA scenarios in ITER.     

空气幕对城际铁路地下车站火灾烟气控制数值分析

为将空气幕作为城际铁路地下车站控烟措施提供理论依据,进而为地下车站防灾控烟设计提供新思路,以某典型城际铁路地下车站岛式站台层为依托,采用火灾动力学三维模拟软件FDS建立全尺寸火灾模型,对比单吹式、吹吸式空气幕布置于站台与轨行区间时楼梯及站台处温度及可见度分布规律,并分别对单吹式、吹吸式空气幕的射流风速、射流角度进行了参数优化研究。结果表明:单吹式、吹吸式空气幕均可保证火灾下楼梯区域可见度和温度的安全性要求;单吹式在射流风速为12 m/s且射流角度为10°时,吹吸式在射流风速为8 m/s时,防烟效果良好且趋于稳定;采用单吹式的最小站台危险区域较吹吸式长15 m,建议在城际铁路地下车站中选用吹吸式空气幕。     

特长隧道风仓接力通风关键参数及其效果研究

通过长斜井进入正洞施工的特长隧道,往往面临独头通风距离过长、工作面风量不足等问题,造成污染物难以在规定时间排出洞外。以衢宁铁路鹫峰山隧道风仓接力施工通风为依托,采用数值模拟方法研究了风仓长度、隔板长度及风机布置方式对轴流风机通风效率的影响,分析了原压入式通风和风仓接力通风洞内CO运移特性。结果表明,风仓长度从10 m增至25 m时,轴流风机通风效率大幅提高,风仓长度大于25 m时,对轴流风机通风效率的影响不大。设置中隔板会影响空气在风仓内的分流并产生较多旋流,从而降低风机通风效率;轴流风机远离斜井端对称布置,风仓内部风流的引流速度和引流范围最大,风流运动路径最优,通风效率最高。由于压入式通风受限于斜井断面尺寸及现场布置方式,当通风距离超过3 000 m后,无法满足洞内作业环境规定的条件。在正洞与斜井交叉部位设置密封的风仓,形成接力通风,能大幅度延长通风距离,提高通风效率,改善洞内空气质量。     

多能硫杆菌1,5-二磷酸核酮糖羧化酶/加氧酶的酶学特征及基因检测

从固体平板的生长情况及RubisCO酶活性测定结果，表明多能硫杆菌是通过卡尔文循环固定的CO2，并具有该循环的关键酶──1，5－二磷酸核酮糖羧化酶／加氧酶．进一步将多能硫杆菌染色体DNA用各种限制性内切酸酶切，Southern转移到硝酸纤维素滤膜上，与光合细菌Rhodobactersphaeroides的RubisCO基因（rbcL－rbcS）探针杂交，显示出杂交带型，说明多能硫杆菌具有R．sphaeroides同源的羧化酶基因，并初步将该基因定位在3．0kb的PstⅠ片段内．     

天空蓝色饱和程度与城市空气质量等级的相关性

以大气散射理论为基础,结合颜色学、大气环境监测及城市空气质量日报等相关原理,从理论分析与实证研究2个方面证实了天空蓝色饱和程度与城市空气质量等级之间存在着显著的负相关性,即:天空蓝色饱和程度越低,空气污染等级越高,空气质量状况越差;天空蓝色饱和程度越高,空气污染等级较低,空气质量状况越好;通过相关及回归分析与检验,制得“城市空气质量等级目测色卡”,适用于晴朗天气肉眼观察天空颜色,进而目测估计空气质量等级状况,以采取必要防护措施。     

长江口柱状沉积物中有机质C/N比的研究

对长江口四个站位沉积物中有机质的C／N比在垂向上的分布进行了研究，在影响沉积物中有机质C／N比的环境因素中，上覆水体的水深、盐度、密度以及浊度对其有一定的影响．在研究沉积物中有机质C／N比的分布及其影响因素的基础上，进一步估算了陆源输入和海洋自生有机碳在这四个站位沉积物有机碳中所占的比例，结果表明，海洋自生组分占沉积物总有机碳的比例分别为：53．57％(8号站位)、20．34％(11号站位)，12．28％(17号站位)和32．73％(26号站位)．     

大气污染源监测采样技术

依据气态污染源共同的排放特性及平均排放浓度，排放速率的概念，导出气态污染源监测中常用的三种采样方法：积分法、分部积分法、有限加合近似法。根据分析化学的要求，提出样品采集时间的设计方法。由此得出不同类型排放源的监测时间和采样频率确定方法。