多声道超声流量计在弯管段安装的适应性研究

针对在不具备直管段安装条件时,如何合理地选取多声道超声流量计的声道数量、测量断面及安装角度,本文从数学建模、误差分析、数值计算仿真与试验分析等方面,对DN400多声道超声流量计在弯管中的适应性进行了综合研究.利用高斯-雅克比数值积分法,给出了试验数据处理与数值仿真的数学模型,并分析了模型误差及横流的影响,提出利用双断面测量可减小横流的影响,并在数值仿真和试验中得到了验证.通过对声道数量、测量断面、安装角度进行数值仿真和试验表明,安装角度对低流速测量影响显著,最佳安装角应为0°;高流速测量应选用双断面,可根据测量精度的要求选用8声道或18声道.仿真结果与试验结果得到了很好的吻合,为进一步指导试验奠定了理论基础.     

基于数字散斑相关法的弯管残余应力测量系统

为了测量圆形管件在弯曲后产生的残余应力的情况,提出了一种新的基于数字散斑相关法(DSCM)的残余应力测量方法并且搭建了对应的测量系统.利用该系统对90.弯管外圆弯曲处的残余应力进行了测量.使用电测法作为参考,验证了基于数字散斑相关法的测量方法能够有效测定弯管内残余应力的值.实验结果表明,该方法在保证一定的测量精度的同时能够大幅度地提高测量效率,为进一步研究残余应力对弯管工艺的影响提供了基础.     

一种弯管特殊形式坡口的加工方法

介绍了一种弯管特殊形式坡口的加工方法,重点从操作控制方法、参数设置、控制流程等方面做了说明,使得这种特殊形式的坡口在有限的加工条件下得以实现.这种特殊形式坡口可以将由过渡台阶产生的负面影响(即引起的流体渐变流或急变流产生的外力和对管体的更大的冲击)转移到距离焊缝50mm之外平滑过渡,能使管道相对比较薄弱的焊缝更好地得到...     

Two-phase slug flow across small diameter tubes with the presence of vertical return bend

This study examines the two-phase slug flow across small diameter tubes with the presence of vertical U-type return bends. The translational velocity of the air slug across return bend usually peaks at an angle of π/2-3π/4. The increase of translational velocity is especially pronounced when flow enters at the lower tube with a smaller curvature ratio. An approximately twofold increase of the slug velocity is observed at a curvature ratio of 3. Dimensionless correlations for flowing upwards and downwards with a mean deviation of 18.7% and 24.5% are proposed that can describe the variation of translational velocity within the return bend.     

Experimental study and numerical investigation of particle penetration and deposition in 90° bent ventilation ducts

Particle deposition in a ventilation duct is a severe problem as it can pose health hazards. This is more evident in 90° bent ventilation ducts. The exposure of particle deposition location in bend section is important and useful in understanding and dispelling particle contamination. This paper investigated particle penetration and deposition in 90° bent ventilation ducts numerically and validated using experimental and previous research data. In the numerical study, particle penetration and deposition in a 2D 90° bend turbulent flow were analyzed. The Renormalized Group (RNG) k-<epsilon > model and Lagrangian particle tracking model were utilized to characterize turbulent gas flow and particle behavior, respectively. Particle turbulent dispersion was introduced by adopting the eddy lifetime model with the near wall fluctuating velocity corrected to take turbulence anisotropy into account. In the experimental validation, particle pollution collected from an actual ventilation duct was observed. The particle penetration rates in a test duct at 6 different Stokes numbers were measured for validation. The numerical results were consistent with both the experimental study and the data obtained from previous research.     

A computational investigation of particle distribution and deposition in a 90° bend incorporating a particle–wall model

This paper investigates the particle flow movement and deposition in a 90° bend after a straight duct, utilizing the Lagrangian particle-tracking model incorporated with a particle–wall collision model. Particle turbulent dispersion is introduced by employing the ‘eddy lifetime’ model, and particle deposition velocity in the bend is proposed by counting the number of deposited trajectories in a time period. The developed models are validated for both airflow and particle flow by previous experimental data. Particle distribution and deposition behavior at five size groups (1, 3, 5, 9, and 16 μm) are investigated. The simulation results show that, compared with traditional ‘Trap’ model, the particle–wall collision model postpones the emergence and slows the increase of the ‘particle free zone’ as the particle diameter increases. Particle deposition velocity in the duct bend is also generally predicted by the proposed estimation equation under the simulated conditions. This reveals that adopting the particle–wall collision model obtains a reasonable prediction of particle distribution and deposition in the duct bend. This work will benefit the understanding and application of microparticle flow in curved duct systems.     

腹板间距对改向滚筒应力应变的影响

改向滚筒作为带式输送机的关键部件,其可靠性和使用寿命都直接影响着输送机的性能。根据改向滚筒的结构类型、材料属性和载荷工况,利用ABAQUS进行有限元分析。以1m改向滚筒为例,进行了腹板间距对改向滚筒应力应变影响的研究。研究表明,腹板间距为900～1000mm比较合理,与实际1m改向滚筒腹板间距950mm一致,有效减少了筒体和滚筒轴所受的应力和应变,为改向滚筒的设计提供了有力的理论依据。     

增强砂浆混凝土的弯曲性能

对钢纤维和聚丙烯纤维混杂的砂浆混凝土的弯曲性能进行了分析,探讨这种钢纤维和聚丙烯纤维混杂增强复合材料是否有较高的初裂强度和较高的韧性,试验结果表明,混杂纤维增强砂浆混凝土的弯曲性能比单一纤维增强砂浆混凝土的弯曲性能明显地得到改善,这种混杂纤维增强砂浆混凝土的复合材料性能很好地发挥出了钢纤维和聚丙烯纤维各自增强砂浆混凝土的优点。     

高速动车组箱体类铝合金挤压型材性能研究

本文主要研究高速动车组箱体类铝合金型材的组织及性能。利用直读光谱仪、电子万能试验机、多功能硬度计和光学显微镜等设备,对型材的合金成分、拉伸性能、布氏硬度、弯曲性能、高倍组织等进行检测分析。研究表明,铸锭温度480~510℃,挤压速度1.7~2.2 m/min,强风冷却淬火,模具温度440~500℃,淬火后温度低于80℃,人工时效170℃×6 h,可得到力学性能和弯曲性能良好的高速动车组箱体类铝型材,且能耗低,生产效率高。     

NUMERICAL INVESTIGATION ON FLOW CHARACTERISTICS IN RIBBED BEND

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｇａｓ ｐａｒｔｉｃｌｅｆｌｏｗｉｎｃｕｒｖｅｄｄｕｃｔｓｈａｖｅｂｅｅｎｗｉｄｅｌｙａｐｐｌｉｅｄｉｎｅｎｇｉｎｅｅｒｉｎｇ .Ｒｅｓｅａｒｃｈ[2 ] ｓｈｏｗｓｔｈａｔｔｈｅｅｒｏｓｉｏｎｅｆｆｉｃｉｅｎｃｙｏｆｂｅｎｄｉｓ 5 0ｔｉｍｅｓｈｉｇｈｅｒｔｈａｎｔｈａｔｏｆｓｔｒａｉｇｈｔｐｉｐｅ .Ｔｈｅｒｅｆｏｒｅ ,ｉｍｐｒｏｖｉｎｇｔｈｅａｂｉｌｉｔｙｏｆｂｅｎｄｅｒｏｓｉｏｎｐｒｏｔｅｃｔｉｏｎｉｓａｎｕｒｇｅｎｔｔａｓｋ .Ｔｈｅｐｒｅｖｉｏｕｓｒｅｓｅａｒｃ…