Combustion of single char particles in a turbulent fluidized bed

The combustion of single bituminous char particles (4-12 mm diameter) was studied in a turbulent fluidized bed operated at 1098 K using air as the fluidising medium. Results indicated that particles burn with constant density following a shrinking sphere model. Burning rates are much higher than those observed in a bubbling fluidized bed. The rate of transfer of oxygen to the particle surface is also higher than that observed in bubbling beds. A model is proposed to calculate the Sherwood numbers of the burning carbon particles. Experimental values of the Sherwood numbers agree well with those predicted from the model.     

Mass transfer between solid particles and liquid in a three phase fluidized bed

Particle-liquid mass transfer in a co-current three-phase fluidized bed of glass beads, water and air was studied with two measurement techniques. Both techniques measured the weight loss of a few particles coated with benzoic acid in a bed of inert glass beads. The effects of liquid and gas velocities, gas distribution and surface active agents on particle-liquid mass transfer in a three-phase fluidized bed were thus determined. In the absence of surface active agents in the liquid, particle-liquid mass transfer rates in a three-phase fluidized bed were up to 30% higher than in the corresponding liquid fluidized bed. When surface active agents were added to the liquid, the particle-liquid mass transfer rate was increased by up to about 100% in the three-phase fluidized bed, relative to the liquid fluidized bed. The particle-liquid mass transfer coefficient was found to be inversely proportional to the liquid hold-up in the three-phase fluidized bed.     

Zonal disintegration phenomenon in enclosing rock mass surrounding deep tunnels -- Elasto-plastic analysis of stress field of enclosing rock mass

The zonal disintegration phenomenon (ZDP) is a typical phenomenon in deep block rock masses. In order to investigate the mechanism of ZDP, an improved non-linear Hock-Brown strength criterion and a bi-linear constitutive model of rock mass were used to analyze the elasto-plastic stress field of the enclosing rock mass around a deep round tunnel. The radius of the plastic region and stress of the enclosing rock mass were obtained by introducing dimensionless parameters of radial distance. The results show that tunneling in deep rock mass causes a maximum stress zone to appear in the vicinity of the boundary of the elastic and the plas-tic zone in the surrounding rock mass. Under the compression of a large tangential force and a small radial force, the rock mass in the maximum stress zone was in an approximate uniaxial loading state, which could lead to a split failure in the rock mass.     

大体积混凝土温升与强度增长的试验研究

针对大体积混凝土结构构件实体强度与普通标准养护试块强度发展规律间的差别等问题,通过研究实际工程尺寸试件温度场的分布和实验室混凝土变温养护试验,以不同养护制度下的试块强度得出了大体积混凝土结构实体强度的发展规律,为工程施工提供了依据,成功地解决了工期与质量的矛盾,取得了较好的技术经济效果.     

强化两相混合的超临界技术制备聚乳酸微粒

针对商品化聚乳酸微球粒径分布较宽难于适用气溶胶给药要求的不足,采用水力空化混合强化超临界流体辅助雾化技术(SAA-HCM)制备聚乳酸(PLA)超细微粒.该技术主要特点是通过在超临界流体和液相进料处引入水力空化混合器,强化两相间的混合.考察SAA-HCM过程混合器压力、温度、沉淀器温度、进料中CO2与液体溶液质量流量比和溶液质量浓度等操作参数对微粒形态和粒径分布的影响,成功制备出球形度较好,粒径分布较窄(1～3μm)的PLA微球.经X射线衍射(XRD)分析和差示扫描量热(DSC)分析显示,与原料PLA相比,微球晶型及热曲线变化不大,但结晶度下降.同时把操作参数与相行为进行关联,探讨了影响颗粒形貌的机理.对比超临界流体辅助雾化法(SAA)的实验结果表明:水力空化的引入能有效强化混合器内的两相传质,混合更好,能制备出适用于气溶胶给药要求的超细微粒.     

一种应用于隔爆试验装置中的新型自动配气系统

针对应用于隔爆试验装置中的传统配气方法存在配气速度慢、系统体积较大的问题,设计了一种基于质量流量法的自动配气系统。该系统采用质量流量控制器精确控制多种不同气体的流量,输出的多种气体经混合装置均匀混合后,由O2分析仪和H2分析仪实时监测混合气体的体积分数。测试结果表明,该配气系统配气速度快、结构简单,配制的多种气体体积分数精度能满足GB 3836.2—2010的要求。     

Mixed convection heat and Mass transfer in a vertical channel with film evaporation

Numerical results are presented for effects of latent heat transport associated with film vaporization on laminar mixed convection heat and mass transfer in a vertical channel with a half channel width b = 0.01 m. The influences of the inlet liquid mass flowrate and wall temperature on the film vaporization and the associated heat and mass transfer characteristics are examined for air-water and air-ethanol systems with gas Reynolds number Re_g = 2000. Predicted results obtained by including transport in the liquid film are contrasted with those where liquid film transport is neglected, showing that the assumption of an extremely thin film made in Lin et al. (1988) and Yan and Lin (1989) is only valid for systems having small liquid mass flow rates. Additionally, it is found that the interfacial heat flux is predominantly determined by latent heat transfer connected with film evaporation.     

基于边缘敏感的SLIC和二次密度聚类的GGO分割

针对磨玻璃肺结节(Ground Glass Opacity,GGO)边界对比度低、大小各异和灰度不均匀等造成分割准确率低的问题,提出一种基于边缘敏感的SLIC和二次密度聚类相结合的分割算法。将图像边缘检测结果与SLIC超像素算法相结合,并将其中含有边缘的超像素块用区域质心代替其原始聚类中心,改善SLIC边界黏连性较差的问题;针对密度聚类不能完整分割GGO的问题,提出二次密度聚类的方法,对密度聚类定位到的簇及其邻域簇进行二次密度聚类。实验结果表明,该算法分割GGO的平均准确率达90.17%,灵敏度达84%。     

大型抽水蓄能电站地下厂房围岩变形时效特征和反馈分析

丰宁抽水蓄能电站地下厂房洞室群的施工期围岩变形具有量值大、时效特征明显、不同深度围岩均可能发生变形的特点。为研究该地下厂房围岩变形时效特征,基于工程地质条件和监测数据,开展围岩变形机制研究。分析结果表明:地下厂房围岩变形的分布特征和时效特性,既与围岩在开挖卸荷后所出现的岩体质量下降、围岩强度减小、岩体蚀变现象有关,也与围岩内存在节理裂隙或断层等不连续地质结构在开挖卸荷作用下易发生张开或错动有关。采用由伯格斯流变模型与带拉伸截止限的摩尔-库伦塑性屈服准则组合而成的复合黏弹塑性模型,进行围岩流变力学参数反演,获得了与监测值吻合较好的围岩变形和变形时程曲线计算结果。根据洞室群围岩开挖支护稳定性分析结果,可知截至主厂房第V层开挖支护完毕,洞周围岩局部变形和塑性区深度均较大,且塑性区贯穿主厂房和主变室洞间岩柱,围岩稳定性总体较差。因此,主厂房在第V层开挖完毕后暂停继续下挖,专门进行洞室群的系统性加强支护是必要的。     

大型地下洞室上层爆破开挖对下层围岩振动特性的影响

某地下实验厅采用上、下层同时爆破开挖,最后进行贯通的开挖施工方案。采用现场爆破试验监测的手段,研究了上层水平钻孔爆破开挖时下层围岩的质点峰值振动速度及频率特性,分析了上层爆破开挖对下层围岩动力稳定的影响。研究结果表明,大型地下洞室上层水平钻孔爆破开挖时,爆炸地震波能量主要向下层岩体传播,致使下层洞室顶拱处的振动速度大于上层底板相同距离处的振动速度;爆破振动主要以剪切波(SV波)的形式向下层岩体传播,下层洞室围岩在平行于炮孔纵轴向(实验厅纵轴向)方向上的振动速度最大;由于上层的爆破振动以体波的形式在岩体内向下层传播,下层围岩的振动频率更高。