Way to simulate the airflows’ motion in subway constructions during fires

It is examined how the airflows move in subway constructions during fires. The motion is simulated by means of marker and cell methods and also with the help of Patankar??s simpler method. By taking into account the thermal resistance and inertial forces depression, we obtain an analytical relationship between the gas flow dynamics in the tunnel and the sources of forced and free convection. It is revealed that, in several cases, the period of the ventilation??s stabilization and the time needed for the passengers?? evacuation out of the tunnel are commensurable, and this fact causes an additional danger for passengers?? safety. It is found out that the air??s maneuvers during the evacuation can spoil the thermal and gas conditions in the tunnel. That is why it is necessary to choose the emergency conditions only if we know the results of such activity by considering the duration of the stabilization period. The presented model that describes the 2D gas flow in subway service rooms makes it possible to investigate the velocity field at different positions and sizes of arbitrary heat sources both in the presence and absence of forced ventilation. Such a numerical method for simulating 2D gas flows can be used to describe a rolling stock fire in tunnels and to predict smoke plumes?? behavior during fires.     

汽车模型风洞研究

汽车缩比模型风洞对汽车空气动力学性能的正向开发、造型设计起着至关重要的作用。对国内外多座先进的模型风洞技术能力进行深入研究,对这些模型风洞的风洞结构、流场品质和试验能力进行了详细总结。结合模型风洞基本理论,提出先进的模型风洞技术指标。     

利用红外热成像技术分析搅拌摩擦焊隧道型孔洞形成机制

隧道型孔洞是搅拌摩擦焊焊接厚板的过程中最为典型且危害性最大的一种缺陷,并贯穿于整个焊缝。研究隧道型孔洞的形成机制,通过红外热成像仪拍摄摩擦焊接过程中无轴肩搅拌针温度实时变化情况,分析搅拌针附近金属的流动情况和隧道型孔洞形成位置,利用倒锥形搅拌针急停实验验证隧道型孔洞形成位置。根据红外热成像仪拍摄数据分析搅拌针前进侧后端温度最低,说明此处金属流动性最差,隧道型孔道易在此处形成,并结合急停实验对上述推论进行实验验证。同时实验发现在搅拌摩擦焊搅拌针旋转一周这个周期内,金属温度的传递可为三种形式:摩擦产热、流动传热与扩散传热。在前端半个周期内进行摩擦产热,在后端半个周期内进行温度的传递。     

小型风洞放气特性的数值计算及试验研究

为了研究小型风洞瞬时放气的工作性能,通过数值计算和试验对风洞的放气特性进行研究。建立了风洞放气模型,并进行了数值计算,结果表明:在声速放气过程中,容器内压力以指数方式减小,风洞出口质量流量梯度较大;在亚声速放气时,容器内压力以近似二次曲线减小,风洞出口质量流量近似线性减小。在风洞试验段内设置试验模型进行放气试验研究,试验结果与数值计算结果吻合良好,验证了数值计算的正确性。     

Corrosive effects of smoke with different concentrations from PVC on 304 stainless steel and 6061 aluminium alloy

Three hundred and four stainless steel and 6061 aluminium alloy samples were exposed to different concentrations of smoke generated by polyvinyl chloride in high humidity. The corrosion kinetics of 304 stainless steel and 6061 aluminium alloy under smoke were found to obey the power function and a linear rule, respectively. Pitting corrosion in smoke became increasingly obvious with exposure time. Surface morphology and chemical compositions of corrosion products were analysed by scanning electron microscope, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Possible corrosion mechanisms were proposed and compared. All the analysis helps to provide basic information for the determination of smoke damage and timely rescue after fire.     

Influence of gas flow rate on the microstructure and mechanical properties of hydroxyapatite coatings fabricated by gas tunnel type plasma spraying

Gas tunnel type plasma torch was used to spray hydroxyapatite (HA) coatings on 304 stainless steel substrate at different plasma gas (Ar) flow rates (100-170 l/min). Microstructure was observed by scanning electron microscope and phase analysis by X-ray diffraction. The mechanical properties such as hardness and abrasive wear resistance of HA coatings sprayed at different gas flow rates were investigated. The results showed that the gas flow rates affect greatly the microstructure and mechanical properties of HA coatings. Crystallinity increased and porosity decreased as the gas flow rate increased. Hardness and abrasion resistance increased as the gas flow rates increased.     

FIELD-NETWORK MODEL FOR MINE FIRE SMOKE MOVEMENT

ＦＩＥＬＤＮＥＴＷＯＲＫＭＯＤＥＬＦＯＲＭＩＮＥＦＩＲＥＳＭＯＫＥＭＯＶＥＭＥＮＴ①ＪｉａｎｇＪｕｎｃｈｅｎｇ，ＷａｎｇＸｉｎｇｓｈｅｎＤｅｐａｒｔｍｅｎｔｏｆＭｉｎｉｎｇＥｎｇｉｎｅｒｉｎｇ，ＣｈｉｎａＵｎｉｖｅｒｓｉｔｙｏｆＭｉｎｉｎｇａｎｄＴ...     

个性化送风模式下客舱火灾阴燃排烟控制模拟

为有效控制飞机客舱火灾阴燃阶段烟雾和有毒气体在客舱内的扩散范围,以火灾阴燃阶段对人体危害较大的CO为研究对象,建立Boeing737经济舱模型,模拟发生小范围火灾阴燃时,普通送风模式与个性送风模式下,CO扩散范围的控制效果。采用NEV作为排污效率评价指标,得出在增加个性送风后,可以将火灾阴燃产生的烟雾和有毒气体控制在阴燃源附近的结论。所得结论为飞机客舱内发生小范围火灾阴燃时控制局部区域的烟雾和有毒气体提供参考。     

消防水炮喷嘴流场数值模拟研究

消防水炮是消灭大型火灾的关键工具,正在向大流量、远射程和高射高等方向发展。喷嘴作为消防水炮的核心部件之一,其设计直接决定射流性能的优劣。采用Fluent对3种不同内轮廓线结构的消防水炮喷嘴进行流场数值模拟,分析结构形式对射流压力、速度和湍动能的影响,从而确定消防水炮喷嘴的最佳内轮廓线结构。通过实验结果可知,在流量为40、50、60和80 L/s的情况下,采用正弦形式的喷嘴内轮廓曲线的射程高于国标规定射程15%以上。以上研究可为提高消防水炮射流性能提供参考。     

Progressive fracture processes around tunnel triggered by blast disturbances under biaxial compression with different lateral pressure coefficients

To investigate the progressive fracture processes around a tunnel triggered by static stress and dynamic disturbance, experiments and numerical simulations were performed. The results show that the spatial distributions of acoustic emission (AE) events become very different as lateral pressure coefficients change. The combined effect of static stress and dynamic disturbance causes the damage around the tunnel, and initial stress conditions control the damage morphology. The blast disturbance cannot fundamentally change the damaged area but will deepen the extent of damage and accelerate the failure speed. The more significant the difference between the vertical and horizontal stresses is, the higher the impact on the tunnel by the dynamic disturbance is. The AE activity recovers to a relatively stable state within a short time after the blast and conforms to power-law characteristics.     

隧道式热风循环电热干燥炉及其应用

本文介绍了一种干燥效率高、节能降耗、温差小、干燥产品质量高的隧道式热风循环电热干燥炉.该炉采用多点分区控温,各均温区为一个热风循环组元,实现炉内双侧纵横双向热风循环,热风循环组元根据干燥传热学按干燥第一阶段、第二阶段在干燥炉长度方向间距不同布置.可根据产品规格和工艺需要,实现严格的温度曲线,同时也便于调整.热风循环装置应用于隧道式干燥炉,能强化对流换热,均匀炉温,提高干燥质量.推广应用结果表明:本炉型非常适合于规模化生产高质量树脂磨具,比箱式炉可节能约40%.     

基于CFD的液氮消防喷嘴两相流数值分析

为了研究液氮消防喷嘴的射流特性,对氮气和水混合喷射的两相流喷嘴建立数学模型和几何模型,利用计算流体力学的方法对气液两相流射流流场的速度、压力、密度等物性参数进行数值模拟仿真分析。并改变喷嘴的入口、出口以及总长度等参数进行仿真,对比不同参数时的射流速度,从而得到喷嘴的最佳尺寸参数。压力仿真云图的结果表明,喷嘴弯折处易出现负压,因此在设计时应将喷嘴设计成曲线型。     

水力自摆移动式消防水炮结构设计及数值模拟研究

设计一种水力自摆移动式消防水炮,采用阀控缸系统作为水力自摆控制系统,利用自身水压力驱动水液压缸带动水炮炮头摆动,并采用机械反馈装置使其自动换向.采用Fluent流场仿真软件对水炮流道结构进行仿真,具体分析了不同进水口压力和不同炮身直径对出口速度的影响规律,结果表明:所设计的消防水炮水力学性能较好,结构比较合理.初步实验验证了该水炮能满足灭火覆盖范围和射程的要求.其相关结论也可为其他规格类型的消防水炮设计提供参考.     

隐伏溶洞对隧道围岩稳定性的数值模拟研究

为分析隐伏溶洞对隧道围岩稳定性的影响,本文以辽宁某在建隧道为工程背景,采用MIDAS/GTS NX有限元数值模拟方法对不同溶洞跨度、不同隧道与溶洞之间距离进行数值模拟研究,分析了不同工况下隧道的拱顶、拱底、边墙的位移变化情况,并对隧道周围岩体的拉压应力分布进行了分析.结果表明:隧道拱顶沉降位移、拱底隆起位移、左边墙收敛...     

隧道衬砌火灾损伤程度的超声波检测试验研究

在对隧道衬砌混凝土和构件进行实际试验基础上，探讨了衬 高温作用后残余强 讧民超声波速之间的关系，以及超声检测技术用于测试隧道火灾损伤的适用性和可靠性。     

基于CFD的调节阀内流场流动特性研究

针对某调节阀,建立其三维流场模型。应用CFD方法对调节阀内部流体流动特性进行仿真,得到该型号调节阀内流场流动特性的三维可视化结果。根据仿真结果分析调节阀内部流场的流动特性,得到在阀芯不同开度下调节阀的理想流量特性曲线以及相同开度下流量和压降的关系曲线,为后续的阀门故障诊断及流动性能优化等研究提供参考。     

整体叶盘叶栅通道电解加工工具电极进给方向优化设计

整体叶盘叶栅通道的加工是在叶片型面精加工至满足设计要求之前不可缺少的工艺步骤。设计了工具电极径向进给加工叶栅通道的模式,为了提高整体叶盘叶栅通道余量分布的均匀性,还提出了电极进给方向的优化策略。分析了通道型面在进给方向上的前后遮挡情况,比较所有采样点在与进给方向垂直的方向上坐标分量的差值,得到不同进给方向的余量差。以通道叶盆、叶背型面余量均匀、余量差均衡为准则,搜索出最优进给方向。在电解加工机床上展开试验研究,结果表明,采用优化后的进给方向进行加工,可获得余量更均匀、两侧型面余量差较均衡的叶栅通道。     

不同分布脉冲微射流对圆射流外部流场的影响

根据圆射流的射流条件建立了流场的CFD模型,并通过计算流体动力学的有限元软件ANSYS,对湍流射流外部流场流动特性进行了数值模拟。通过在外部流场入口处加入脉冲微射流,对原本处于层流状态的射流外层边界层进行扰动并得到模拟结果,从而分析在径向脉冲微射流的影响下,外部流场的变化特性。在改变微射流的脉冲频率的情况下,得到不同脉冲频率下的外部流场流动特性。通过对比,得到的射流流场数值模拟结果与实验结果趋势一致,并且与前人所得实验结果相吻合。     

水下隧道穿越管道保护效果测试评价

本文通过对四川气田北干线涪江隧道穿越管道阴极保护电参数的现场测试，取得了实际可信的基础数据，验证了处于水下隧道洞内的穿越段管道，能得到陆上强制电流阴极保护系统的有效保护，保护电流所必经的岩石层和锚喷钢筋混凝土层对保护电流没有构成屏蔽的结论，对管道工程设计和运行管理具有指导作用。     

TBM分体式刀座系统设计方法及力学性能分析

硬岩隧道掘进机(TBM)通过刀盘上的滚刀破碎剥离岩石开挖,刀座系统是连接滚刀与刀盘之间的桥梁,其联接可靠性和承载能力性能好坏直接关系到设备开挖效率及施工维护成本,刀座系统设计理论及标准的缺乏已无法满足TBM安全、高效发展需求。总结刀座系统的结构设计基本原则,基于系统受载特性分析及轴式滚刀基本结构尺寸,建立了分体式刀座和整体式刀座的结构参数化设计方法。通过对轴式滚刀-刀座系统进行静力学建模,分析额定负载工况、不同螺栓预紧力下、不同工作载荷下的静力学特性,找出了各类刀座的应力分布特性、危险区域,揭示了工程中刀座部分区域开裂、压溃现象的力学原因。此研究可为工程中刀座优化设计提供参考。