蒸汽发生器是产生汽轮机所需蒸汽的换热设备，它将一回路冷却剂从堆芯带走的热量传递给二回路的工质水，使之变为蒸汽，蒸汽再驱动汽轮机做功发电。蒸汽发生器是高度复杂、非线性、时变的系统，并且其参数随运行条件变化而变化。核电站实际运行经验表明，它能否正常工作，直接关系到整个压水堆核动力装置能否安全而稳定地运行。因而，对其进行建模和仿真有着非常重要的现实意义。目前，单堆功率25万千瓦级高温气冷堆示范电站（HTR-PM）已在山东荣成石岛湾正式开建。作为核电站重要组成部分——高温气冷堆模拟机重大专项已逐步展开，本课题正是在此背景下提出的。本论文所做的工作是先对高温气冷堆(HTR)热工分析软件THERMIX系列程序中的蒸汽发生器模块BLAST进行分析，从中提取出蒸汽发生器的热工水力模型，进而建立适合模拟机实时仿真的直流蒸汽发生器数学模型。该模型将蒸汽发生器作为单管模型处理，根据水的状态将蒸汽发生器分为单相水段、两相段和过热段三大区，接着对这三区分别进行建模，并对模型进行数学处理，得到了相应的微分方程组。利用龙格库塔法对该微分方程组进行了求解，在求解过程中将蒸汽发生器沿流体流动方向划分了若干节点。最后，利用Fortran语言编写了相应的蒸汽发生器热工模拟程序，通过对典型工况的静态仿真计算得出了蒸汽发生器一、二次侧沿管长的压强分布和温度分布，并将该结果和由BLAST计算所得结果相对比，计算结果较为吻合，从而证明了该模型的正确性和计算结果的合理性。将高温气冷堆螺旋管式直流蒸汽发生器的计算模型从BLAST程序中提取出来，作为高温堆模拟机中的独立计算模块。在未来的工作中，还需根据HTR-PM蒸汽发生器的设计进行完善和细化模型，并改进计算方法。另外，本研究主要针对蒸汽发生器的稳态模拟计算问题，对于蒸汽发生器的动态计算，还有待进一步的研究。本文提出了处理瞬态方程组的方法，为进行蒸汽发生器的动态模拟计算提供了初步的思路和方法。
Steam generator (SG) is a circulatory heat exchanger which generates steam that flows into nuclear steam turbine. It transfers the heat from the nuclear reactor carried by primary side coolant to the water of secondary coolant system to make steam which drives the turbine to work. The SG is a highly complex, nonlinear and time-varying system and its parameters vary with operating conditions. According to actual operation experiences of nuclear plant, whether SG works normally or not is directly related to the safety of the whole nuclear power unit. Hence, to carry on the model and simulation of it is of great significance.Now a 250MW HTR-PM plant is being established in Shidaowang in Rongcheng of Shandong Province. As an important part of nuclear plant, the special project of HTR full scale simulator is being carried out. The object in this paper is proposed under this condition. The paper contains three parts, the first is to read the program of BLAST, and then get the thermal-hydraulic model and friction drag formulas and the heat transferring formulas from BLAST. The second is to establish a helical-coiled steam generator model. The steam generator is handled with single tube concept and is divided into three regions as subcooled region, boiling region, and superheated region. And these regions have their own conservation equations. The equations of mass, momentum and energy are solved by four order changing step Runge-Kutta method. And the OTSG is divided into several nodes along the moving direction of fluid. The last is to write program with Fortran90 language to get the pressure and temperature of the primary and secondary loops along the tube length. And then compare the results with that from BLAST, the comparison shows that the Runge-Kutta method is reasonable.Pick up the SG calculating model from BLAST program and make it as the independent calculating model of HTR full scale simulator. The paper uses the changing step Runge-Kutta method to simulate the moving boundaries of phase changing. Also, the paper only solves the steady state problem of the steam generator, and there is still much work to do for the dynamic calculation of steam generator. In this paper, a new method is proposed to solve the dynamic equations of steam generator which provides a preparatory thinking and method for the simulation of dynamic characteristic of SG.
