【摘要】 目的研究火电厂空冷系统排汽管道应力分布情况,确定用于设计的最不利应力分布模式.方法以火电厂空冷岛为例,采用《钢制压力容器分析设计标准》(JB4732-1995)中计算薄膜应力的方法,考虑将基本载荷、地震荷载及风荷载进行组合,形成各种组合工况,应用ANSYS对某300 MW火电厂空冷岛系统的排汽管道进行大量的仿真分析,并对计算结果进行整理.结果各工况结果中管道应力最大的区域发生在三通,该处一次局部薄膜应力最大值为236 MPa,小于应力限值SⅡ=259 M Pa;除三通外其他区域在各种荷载工况下的最大薄膜应力均较小.其中与-X方向风荷载组合的各计算工况中,管道应力水平比之没有风荷载作用的相对较高,说明风荷载对管道应力影响较大,原因是管道属于高耸结构,且上部结构迎风面积较大.薄膜应力与弯曲应力求和后最大值为280 MPa,该应力为一次应力加二次应力,远小于限值SⅣ=518 M Pa.结论管道应力最大的区域为三通,三通区域的应力水平远高于其他区域,最终得出危险荷载工况作用下管道支座、三通、下部三通、折角以及盖板的应力分布,为300 MW直接空冷排汽管道提供设计依据.更多还原

【Abstract】 Mechanical behavior of exhausting steam pipe in air-cooled system of thermal power plant under complex loads was analyzed to determine the worst stress distribution pattern. Taking an example of the air-cooled island in a thermal power plant,using the proposed calculation method of membrane stress by the code "Stress Analysis Design Standard of Steel Pressure Vessel"JB4732-1995,taking into account of loading combinations including basic load,seismic load,and wind load,simulation analyses for mechanical behavior of the exhausting steam pipe in air-cooled system of a 300 MW thermal power plant with ANSYS were carried out. Stress distributions in pipe supports,tees,lower tees,knuckle and cover plate under the dangerous load case were obtained. It is found that the maximum value of local membrane stress is 236 MPa,which locates in the lower tee region of the pipe system. But it is less then the stress limit SⅡ= 259 MPa. The largest membrane stress value of other locations is relatively small. The overall stress level of the pipe under X-direction wind load is higher than that without wind load. That is because the pipe system is a tall structure and the upper structure windward area is larger. The maximum sum of membrane stress and bending stress is 280 MPa,it is far less than the limit value of SⅣ= 518 MPa. Conclusion is that the maximum stress occurs at the lower tee region. It is far higher that that of other regions of the pipe system. The results provide some references for design of exhausting steam pipe with 300 MW Unit.更多还原