A computational study on effects of fire location on smoke movement in a road tunnel

In this work, a numerical model of tunnel fire is developed and aimed to investigate the influence of cross-sectional fire locations on critical velocity and smoke flow characteristic. It is shown that the critical velocity for a fire next to the wall is obviously higher than that for a fire in the middle or on the left/right lane. The ratio is estimated to be 1.12. The predictions of critical velocity from ‘small-fire’ models show a good agreement with that for a fire in the middle or on the left/right lane from CFD. The tunnel height at the fire location is proposed to be instead of the hydraulic tunnel height in the ‘big-fire’ model of Wu and Bakar for a fire next to the wall. The smoke moves backward in a tongue like form as the ventilation velocity is lower than the critical velocity. The back-layering length of a fire in the middle is shown to be approximate twice than that on the left/right lane under the same ventilation velocity, although they share the same critical velocity. Whereas a relatively short back-layering length for a fire next to the wall under the velocity of 2.6 and 2.7 m/s. In addition, a snaky high-temperature profile on the top wall at the initial downstream is observed for a fire on the left lane and next to the wall, and finally a steady and layered smoke flow. The likely cause of this phenomenon is subsequently explained in this study.     

Overall photocatalytic water splitting on Na2ZrxTi6−xO13 (x = 0, 1) nanobelts modified with metal oxide nanoparticles as cocatalysts

In this work, we present the preparation of Na₂Zr_xTi_6?xO₁₃ (x = 0, 1) nanobelts through a rapid solvocombustion method. The phases exhibited stable photocatalytic activity for overall water splitting under UV light. Effect of the annealing temperature on the physicochemical properties and the catalytic performance of the materials were studied. Na₂ZrTi₅O₁₃ exhibited a higher rate of H₂ evolution compared to Na₂Ti₆O₁₃, and it was attributed to the incorporation of Zr⁴⁺ in the structure, which generates a distortion in the octahedral sites of the structure. This distortion promoted an enhanced charge transport and a reduction in the recombination of the free carriers and a higher photocatalytic activity. The nanobelts were superficially modified through the deposition of metal oxide nanoparticles as cocatalyst, MO (M = Ni, Cu). The incorporation of metal oxide nanoparticles improved the charge separation process and the overall efficiency. An integral study of the structural, morphological, textural, optical and photoelectrochemical properties of the materials is presented and a charge transference mechanism on the semiconductor interface is proposed. The highest catalytic activity was obtained by Na₂ZrTi₅O₁₃ modified with CuO (2909 μmol g?¹ h^?1), and corresponds to an increase of 13.6 times the activity of the bare photocatalyst. This was attributed to an improved charge separation at the interface of n-type Na₂ZrTi₅O₁₃ and p-type CuO semiconductors. For the best of our knowledge, the activity exhibited for overall water splitting of Na₂Zr_xTi_6?xO₁₃ (x = 0, 1) nanobelts prepared by solvocombustion method and modified with the addition of MO nanoparticles in this work is higher compared to the reported in previous works.     

Effects of buoyancy induced roof ventilation systems for smoke removal in tunnel fires

The present article highlights the performance of natural roof ventilation systems and its effects on tunnel fire flow characteristics. Numerical analysis is performed using Large Eddy Simulations (LES) to predict fire growth rate and smoke movement in tunnel with single and multiple roof openings. The smoke venting performance of ceiling vents are investigated by varying the vent size and fire source locations. The critical parameters such as mass flow rate through ceiling openings, smoke traveling time and fire growth patterns are presented. The ceiling openings are effective in transferring hot gases and reduces the longitudinal smoke velocity. The heat source and ceiling vent locations significantly affects the vent performance and smoke behavior in tunnel. The present results are in good agreement with the experimental results available in literature.     

滑坡落石灾害自动监测方案的探讨

以西部某客运专线的隧道施工监测为工程背景,探讨了铁路隧道所通过山体的稳定性自动监测问题,提出了一系列监测实施方案,可以为类似工程提供参考。     

山区高速铁路隧道内电气化过轨研究

接触网专业在山区高速铁路隧道内分区所、AT所设置的情况下需要设置大量的过轨管。本文结合云桂铁路隧道内分区所、AT所的设置方案．探讨隧道接触网过轨管的布置。     

挖掘式装载机运输槽改制

对挖掘式装载机的构件、作用及工作原理进行了简要介绍,并通过计算分析,着重对运输槽及运输槽刮板的改制方法进行了探讨,以提高挖掘式装载机的工作效率,满足其工况需求。     

谈工程量清单计价下的合同管理与结算的关系

对清单计价规范实施后,工程量计价模式下的工程合同管理与结算的关系进行了探讨,总结了加强工程量清单结算管理的措施和工程价款结算争议处理方法,最后指出加强施工合同的管理,对提高工程结算的效率和质量具有重要作用。     

复杂地形下人工挖孔灌注桩施工工艺研究

从传统人工挖孔灌注桩施工工艺角度入手，结合工程地质条件的复杂因素和现场环境恶劣的情况，对作业条件、施工技术可行性、环境制约因素，进行了深度技术分析，提出了经济的施工方案，采用新技术和自制简易机具，有效地解决了施工中的难题。     

煤矿巷道掘进工艺技术研究

基于巷道掘进中,地质条件不断变化的情况,掘进的施工和运行过程与现场安全、矿产能力密切相关。在越来越复杂的人机交互工作面,更要求施工掘进作业高效、安全,稳步进行。对煤矿巷道掘进工艺进行了探讨,具有有一定的借鉴作用。     

变频器在高速公路上的应用

变频器应用于高速公路收费站栏杆机、收费站和服务区供水系统、隧道通风系统.高速公路使用了变频器后,可提升自动化控制水平,并有一定的节能效果.