【作者】 刘军涛；

【导师】 吴俊飞；

【作者基本信息】 青岛科技大学 ， 化工过程机械， 2008， 硕士

【摘要】 层板包扎结构作为承压设备的一种,是高压容器中常见的和通常被认为是不会破坏的结构形式,但目前已发生多起这类容器的灾难性事故,因此如何对尿塔的剩余寿命作出有效的评估就成为了目前迫切需要解决的问题。为了建立现实可行的层板包扎高压容器的剩余寿命试验评价技术和对其中缺陷进行有效检测的技术,青岛科技大学和其他三个单位联合申报了国家863项目“层板包扎高压容器剩余寿命试验评价技术”并获得批准。本文主要进行层板包扎容器的应力场、温度场等的数值模拟分析,为剩余寿命估算和评价提供数据基础。考虑数值模拟时建模多、难度大,尤其是层板间隙时建立接触对手工操作非常困难。本文以ANSYS为平台,开发了层板包扎尿素合成塔有限元参数化分析程序,将建模、划分网格、加载求解等各功能融入系统,通过输入少量参数就能快速完成尿素合成塔有限元数值分析,大大减小了分析的工作量和难度。利用开发的分析程序对尿塔进行了详细的有限元分析,并与实验结果进行了对比。结果表明,数值模拟和P.G.Pimshtein计算出的应力呈相同的单调下降的变化趋势,数值吻和较好,而Lame公式的计算结果则偏离较大。随着层板间隙的增大,不承受内压的外部层板不断增多,承受内压的内部层板发生破裂的可能性也越来越大。因为间隙的存在,多层板连接的环焊缝部位应力场最为复杂,越靠近焊缝层板两侧拉、压应力越大,从而在层板间隙与深环焊缝相交的部位产生一个尖角,应力集中最易发生的部位是层板间隙顶端的深环焊缝融合线处。分析也表明坡口角的变化对深环焊缝融合线应力场的分布产生一定的影响。因此,层板间隙、焊缝形式等对多层包扎尿塔应力场的分布有很大影响。尿素合成塔应变测试结果也表明,尿素合成塔层板之间存在间隙对尿素合成塔的应力分布具有较大的影响,实测应变值与理论值基本吻合较好。所以,在进行多层包扎尿素合成塔设计时,应考虑间隙的存在所引起的应力集中对尿素合成塔整体强度的影响。在对尿塔结构进行线弹性数值模拟时,发现深环焊缝焊趾部位局部应力已经超出材料的屈服强度,因此对尿素合成塔进行了弹塑性有限元分析,结果表明,盲板层和第一层板两侧焊趾处von Mises应力最大,说明在实际操作条件下,内衬层、盲板层及内筒之间间隙对应的深环焊缝焊趾部位可能会发生局部屈服。因为尿塔操作温度较高,最后还进行了热-结构耦合分析,结果表明,在操作温度下,温度载荷对尿素合成塔整体应力场的影响不大。更多还原

【Abstract】 To high pressure vessel, multi-layer wrapped structure as kind of pressurized equipment is common and supposed can’t be damaged. But now this kind of vessel has induced many disastrous accidents. So how to evaluate the wrapped layer vessel’s remaining life became an urgent problem. In order to establish a feasible test to evaluate wrapped layer vessel’s remaining life and detect the defect efficiently, Qingdao University of Science &Technology with other three units apply for the 863 project named test evaluation for wrapped layer vessel’s remaining life. This article mainly worked on wrapped layer vessel’s numerical simulation in aspects of stress field and temperature field to estimate and evaluate wrapped layer vessel’s remaining life.When performing numerical simulation, I had to establish lots models, and it was very difficult especially presented a model of contact through manual operation when considering the layer gap. So based on ANSYS, I developed a finite element parametric analysis program in wrapped layer urea converter, and integrated modeling&division grid&load solution and so on various functions into the system. Then I can complete the urea converter finite element numerical analysis quickly through inputting few parameters. All of these reduced the analysis work load and the difficulty greatly.I carried out a detailed finite element analysis for urea reactor by using parametric program, and analyzed with the experimental results. The results showed that the calculation stress of numerical simulation and P.G.Pimshtein Formula have the same trend, the data are in good agreement with each other, but the result of Lame Formula has a greater deviation. With the Laminate’s gap increasing, the external laminates number that doesn’t bear pressure is growing and Laminates rupture possibility occurred more easily. Multilayer girth weld connecting is the most complex parts of Stress distribution since the existence of laminate’s gap. The more around the both sides of welding seam, the more pull stress and the compression. Shelf space and deep girth weld parts intersect produce a cusp, the most vulnerable stress parts is the top laminates gap and deep girth weld fusion line. Analysis also shows that change in the Slope angle has a certain impact to the distribution of stress field of deep girth weld fusion line.Therefore, the layer gap and the welded joint form and so on have the very tremendous influence to the multi-layer wrapped urea converter stress field’s distribution. The urea converter strain test result also indicated that gaps between the urea converter layers have the tremendous influence to the urea converter stress distribution. And there is a basically good agreement between the actual strain value and the theoretical value. So, when carrying on the multi-layer wrapped urea converter design, should consider the stress concentration’s influence which caused by gaps to urea converter overall intensity.I found that the Local Stress at deep seam weld toe ring site has already exceeded the yield strength while I was doing structure linear elastic numerical simulation of urea reactor, Therefore I did a elastic-plastic finite element analysis for urea reactor. The results showed that it has the largest von Mises stress at Blind and both sides of the first layer. It can prove that lining layer, blind lamellar gap between the inner core and the corresponding deep seam weld toe Central location may be a limited yield under actual operating pressure.Because urea reactor’s operating temperature is high, I got thermal- structure coupling analysis at last. The result showed that temperature load on urea reactor has little affection on stress field under the operating temperature.更多还原