加氢反应器瞬态温度场数值模拟

Numeric simulation of transient temperature field on hydrogenation reactor

加氢反应器开停车或变工况时引起的过大交变热应力会危及设备的安全运行。为了研究加氢反应器在此种情况下的热应力场,利用ANSYS有限元软件对加氢反应器上半部进行了瞬态温度场分析,首先对空间域进行离散,采用泛函建立有限元的一般格式,得到一阶常微分方程组;然后对时间域进行离散,采用差分格式求解,得出各载荷步、时间子步的温度分布等值线图,实现了温度分布与热流方向的动态显示。利用瞬态温度场分析结果进行了热应力计算,得出瞬态热应力随时间的变化状况。结果表明,加氢反应器上半部接管法兰区温度梯度最大,壳体内部的热流方向基本是从筒体、封头到法兰,温度分布极不均匀;最大热应力发生在瞬态温度场的某一时段,而不是瞬态温度变化的最终状态。

The excessive alternating thermal stress caused by startup/shutdown and off-design condition can endanger the safe operation of the hydrogenation reactor. In order to study the stress field in this state, the instantaneous temperature field analysis on the top of the equipment is done by using the finite-element analysis software ANSYS. Firstly, disperse the spatial domain, establish ordinary finite-element format using functional analysis, and obtain the first-order ordinary differential equations. Then, disperse the time domain, make solutions by difference format, and obtain the contour line diagram of multi-step loading and time stepping by analyzing instantaneous temperature field. Real-time dynamic display of temperature distributing and heat transmitting is carried out. For studying the diversification of instantaneous thermal stress along with time, analysis and calculation of thermal stress are brought out by using the result of instantaneous temperature field. The result shows that it is feasible to analyze the instantaneous temperature field by partial dispersion cables; the temperature gradient on the top of hydrogenation reactor appears on the region of tube and flange; the direction of heat flow in shell is from shell to head and to flange; the maximum thermal stress appears in a period of time, but not in final state, and its value is sizeable.