Construction of a Minimum Energy Path for the VT Flash Model by the String Method Coupled with the Exponential Time Differencing Scheme
Construction of a Minimum Energy Path for the VT Flash Model by the String Method Coupled with the Exponential Time Differencing Scheme
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DOI：
10.4208/cicp.oa-2021-0024
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发表时间：
2021-06
影响因子：
3.7
通讯作者：
Yuze Zhang
中科院分区：
文献类型：
--
作者：
Yuze Zhang
.闪速计算在石油和化学工业的各个方面发挥着重要作用。自1982年Michelsen提出他的里程碑式的研究以来，经过几十年的发展，目前的研究重点已从精确性转向效率性，但最终的目标仍然是准确确定给定条件下的平衡相数量和组成。另一方面，找到过渡路线及其相关的鞍点通常对于理解Crachash模型的整个能量景观至关重要，这将为设计数值算法或优化现有算法提供新的见解。本文将弦方法与指数时间差分（ETD）方法相结合，发展了一种有效的数值方法，研究了Peng-Robinson状态方程VT-半经验模型的最小能量路径和一阶鞍点.作为传统方法的一种有前途的替代方法，VT Escherash在体积和温度的新变量规格下计算相平衡。采用Rosenbrock型ETD格式来减小模型系统高刚度引起的计算困难。所提出的ETD弦方法成功地计算了具有强刚度的单组分和双组分VT湍流模型的最小能量路径。数值计算结果也表明了平衡相含量和组成计算的可行性和准确性。
. Flash calculation plays significant roles in various aspects of petroleum and chemical industries. Since Michelsen proposed his milestone studies in 1982, through several decades of development, the current research interests on flash calculation have been shifted from accuracy to efficiency, but the ultimate goal remains the same; that is accurate determination of equilibrium phase amounts and compositions at a given condition. On the other hand, finding the transition route and its related saddle point is often crucial to understand the whole energy landscape of flash models, which would provide new insights for designing numerical algorithms or optimizing existing ones. In this study, an efficient numerical approach is developed by coupling the string method with the exponential time differencing (ETD) scheme to investigate the minimum energy paths and first-order saddle points of VT flash models with Peng-Robinson equation of state. As a promising alternative to the conventional approach, VT flash calculates phase equilibria under a new variable specification of volume and temperature. The Rosenbrock-type ETD scheme is used to reduce the computational difficulty caused by the high stiffness of the model systems. The proposed ETD-String method successfully calculates the minimum energy paths of single-component and two-component VT flash models with strong stiffness. Numerical results also show good feasibility and accuracy in calculation of equilibrium phase amounts and compositions.