Inherently consistent temperature function for interaction parameters demonstrated for the Mg–Si assessment

A new inherently consistent temperature function for interaction parameters, L, is proposed. It is designed for the unconstrained application of any optimization software, such as PanOptimizer or PARROT, to avoid artifacts, for example inverted liquid miscibility gaps or re-stabilization of liquid well below solidus. Without introducing additional system-dependent adjustable parameters, the new function automatically excludes both the exaggerated negative values of L at low temperature and the exaggerated positive values of L at high temperature. The viability of the new function is demonstrated by a complete Calphad re-assessment of the Mg–Si system, which is the prime example of the most challenging systems pertinent to both artifacts. For the first time the calculated Mg–Si phase diagram from 0 K to very high temperature is presented. The new assessment also includes the quantitative solidus data of (Si) and other previously not considered original experimental data.     

通用Gibbs反应器的机理建模和求解方法

Gibbs反应器是一种虚拟设备;它不考虑具体的反应过程和机理;只考虑在达到热力学平衡;即达到质量平衡和能量平衡时Gibbs自由能最小的状态。Gibbs反应器非常适用于反应机理复杂;反应过程众多或者反应机理耦合严重的情况。利用机理建模技术和传统优化方法拉格朗日-牛顿法建立通用的Gibbs反应器模型;用于描述煤制甲醇生产过程硫回收工段的反应过程;并将其结果同Aspen Plus中标准Gibbs反应器的计算结果进行了比较。     

模拟甲基叔丁基醚反应精馏的过程

为揭示反应精馏过程的耦合特性,从而为进一步开发新的反应精馏设计方法提供理论支持,采用Gibbs自由能平衡级模型,应用Aspen Plus软件模拟分析MTBE的反应精馏过程,研究了回流比与理论板数对反应和分离效果的影响。结果表明由于反应和精馏的相互作用,在固定回流比改变理论板数(或固定理论板数改变回流比)的情况下,存在最佳理论板数(或回流比)使产品组成最高,这种特性与普通精馏有所不同。     

The thermodynamics of several elements at high pressure

We have used the CALPHAD-compatible equation of state (EOS) based on the explicit Gibbs free energy concept for the solid state of ten important elements: V, Nb, Ta, Mo, W (groups VB and VIB), Pd, Pt (group VIIIB) and Cu, Ag and Au (group IB). The new formulation uses SGTE data for ambient pressure and converges to the quasi-harmonic model at the limit of extreme pressure to calculate the Gibbs free energy as a function of pressure and temperature. The model is based on the available pressure-volume-temperature (PVT) data on the elements and can be usefully extrapolated to extreme pressures. When compared to shock wave data, the modeled EOS holds well, but the fit is not totally satisfactory in the ultrahigh-pressure range. A great advantage of this formulation is that it can be used to calculate thermodynamic properties such as the heat capacity and entropy at very high temperatures and pressures.     

科学计算可视化及其在相图中的应用研究

科学计算可视化是一种把数据信息转换成可视信息的新兴技术,是分析与理解数据的有力工具。本文介绍了VISC工具和应用状况的基础。提出了一种通过科学计算利用吉布斯最小自由能绘制相图的方法。本方法通过计算来获得体系在某一状态下的准确数据,甚至可以获得体系的内部情况,这是传统的表面重建所不能比拟的。     

甲烷部分氧化合成燃气过程能量耦合工艺的研究

从反应温度、压力和进料量(CH_4、CO_2、H_2O和O_2)等6个变量中固定任意5个,优化剩下的一个变量的方案,研究甲烷部分氧化合成燃气含水蒸气、二氧化碳重整的能量耦合工艺(即平衡时体系的热效应为零)。建立为能量耦合的双层优化模型,即内层通过求解吉布斯自由能的最低限度得到平衡组成;外层通过改变进料组成实现体系的能量耦合。结果表明:0．1 MPa下反应体系的最佳操作温度范围为1 050～1 150 K;固定其他条件,总可通过优化O_2的量使反应体系实现能量耦合,且平衡时加入的O_2可以反应完全;平衡组分中H_2/CO比值主要取决于进料中H_2O/CO_2比值,与O_2量关系不大;另外还得出了能量耦合时变量间的关系和消炭条件。石英管反应器的热中性温度下的实验结果与本文计算结果基本一致。     

德士古水煤浆气化过程的建模与优化分析

根据德士古水煤浆气化工艺的操作特性和装置特点,采集实际工业运行数据,基于Aspen Plus软件平台,建立了气化炉和水洗过程的模型,模拟结果与实际生产较吻合。基于所建立的模型,进行了水煤浆浓度、气化反应温度对气化结果的灵敏度分析,并讨论了过程的节水,分析了高温汽提冷凝液对废水排放与合成气水汽比的影响。结果表明:在现有工况下,提高水煤浆浓度和反应温度,有效合成气收率会提高;适当减少高温、汽提冷凝液,有利于装置的废水排放和提高合成气水汽比。     

The thermodynamic analysis of Guinier–Preston zones in aged supersaturated Al–Cu alloys

Being the structural cause of hardening, Guinier–Preston (GP) zones in many alloys still attract much interest. The expression of energy for GP zones in the Al–Cu alloy is established by combining the essential Gibbs energy with the interfacial energy and the strain energy. Based on the equilibrium between GP zones and the surrounding matrix, a quantitative analysis on the sizes, concentrations, aging temperatures and their relationships can be predicted. The size and the concentration of GP zones calculated with defined composition and aging temperature accord with the experimental results well.     

FLASK-SG: A program to compute chemical equilibria in metamorphic petrology

Chemical equilibrium calculation program for metamorphic petrology, FLASK-SG, was written for Unix variants (Linux, IRIX, Tru64 UNIX). It is also ported to Windows 95/98. The user specifies a temperature, pressure, and substance amounts (in moles of any chemical formula in C–H–O–Si–Al–Ti–Fe–Mn–Mg–Ca–Na–K system) to this program, then it calculates the stable mineral assemblage, mineral amounts, and gas composition under the given conditions using Gibbs free energy minimization method with the Holland and Powell (1990) data set. Searching algorithm for the stable mineral assemblage is the Metropolis Monte Carlo method. The coding language is C++, and experimental object oriented programming style is adopted to make the main program part as a class library. Model-dependent functions such as fugacity coefficients and activities are implemented as virtual methods of the “systems” class, so they can be easily changed as methods of inherited class from the “systems” class. These characteristics are aimed for a future “simulation kit”.     

SiC高温氧化的热力学研究

本文运用自由能最小法研究了Ａｒ－Ｃ－Ｈ－Ｏ－Ｓｉ体系的化学平衡，以国际流行的广义简约梯度软件ＧＢＧ２为优化模型编制了求解复杂化学平衡的软件ＺＧＲＧ计算表明ＺＧＲＧ具有很好的收敛性能，对Ａｒ－Ｃ－Ｈ－Ｏ－Ｓｉ体系的计算表明，ＳｉＣ从活性氧化向惰性氧化的转变分压（Ｐｏ２，ＰＨ２Ｏ）随温度的增加而增加，同时本文还将计算结果与其他研究者的实验结果进行了比较，并对造成计算值与实验值差异的原因进行了分析。     

一种适用于真实人体数据能有效消除Gibbs伪影的MR重建新算法

Gibbs振铃是在磁共振成像中常见的主要存在于组织边缘处的一种伪影,它是在采用部分k空间数据进行图像重建时产生的.Gegenbauer重建方法能够有效消除Gibbs环状伪影并能保持图像高分辨率,但重建时间长且参数的选择对重建结果影响很大.文中引入逆多项式方法对Gegenbauer重建方法进行了改进,同时以Chebyshev多项式替代Gegenbauer多项式,免去了参数的人为选择,提高了重建精度并加快了速度.由于上述方法是针对连续区间讨论的,因此如何通过边缘检测准确地划分连续子区间显得尤为重要.文中提出的频域滤波边缘检测法能得到准确的边缘检测结果,有效地提高了文中方法对具有复杂组织结构的真实人体MR数据重建的精度,使其更具实用性.     

Simulation of combustion by vortex method

In this paper, we present a simple and efficient technique that uses a vortex method to predict the quantities of the combustion products; however, this technique uses no chemical equations. This technique incorporates the concept of chemical equilibrium into a vortex method. By using this technique, the products of a chemical system are determined by minimizing the Gibbs free energy, which is subject to the conservation of the chemical elements involved in the combustion process. The amount of gas (a mixture of fuel and oxygen) that is used for the calculation of chemical equilibrium is estimated by the eddy-dissipation model. In order to avoid increasing the number of species of particles, a single particle is provided with five physical properties - vorticity, turbulent energy, dissipation rate, amount of fuel, and amount of oxygen. To meet this condition, the motion equations of these properties are modified. For the sake of simplicity and low computational load, the presented technique does not focus on achieving higher order accuracy in the solutions. Nevertheless, the simulated results for the temperature and the main products for the premixed methane/air jet turbulent flame are in good agreement with the experimental results. In some cases, the data from the simulation concerning the intermediate products disagree with that from the experiment due to the slow reaction speeds in actual combustion. The convergence of the algorithms is also examined.     

易挥发弱电解质体系化学及相平衡计算的遗传算法

基于Gibbs自由能最小化原理,提出用遗传算法计算易挥发弱电解质体系化学及相平衡问题。首先建立了易挥发弱电解质体系Gibbs自由能的计算模型,将含化学反应平衡和相平衡计算问题转化为有约束的最优化问题．并应用遗传算法求解;其次在算法实施时提出两点改进,即通过对优化变量采取动态边界的可行域编码方法来处理问题约束和引入反应平衡常数来提高低含量组分的计算精度;最后对两个算例进行了计算。计算表明,本文计算结果与文献值相吻合,并且简单易实施,是这类问题计算的有效方法。