含铁原料造粒粒度预测模型比较

含铁原料造粒粒度预测模型的分析研究,对于优化烧结生产工艺,促进烧结工业的持续高效发展具有重要意义。本文就国内外对造粒粒度预测模型基础研究及目前存在的主要问题进行讨论．根据建模的思路,造粒粒度预测模型可分为质量集合平衡模型和数群集合平衡模型,质量集合平衡模型又可分为单组元和多组元集合平衡模型．研究工作将在质量集合平衡模型的基础上,考虑造粒粒度分布对孔隙度的影响．     

基于Langmuir理论的平衡吸附量预测模型

为了实现对吸附反应的平衡吸附量的预测,建立了平衡吸附量预测模型.以高岭土、蒙脱土这两种黏土矿物吸附Ca2+为例,验证其等温吸附曲线符合Langmuir吸附方程.在Langmuir吸附等温式的基础上,建立了平衡吸附量预测模型,该模型应用于单组分吸附反应的平衡吸附量的预测.通过实验对该模型进行了验证,模型的计算结果与实验结果可以较好地吻合,证明该模型的可靠性较高.     

造粒粒度分布及其预测模型

以造粒粒度分布为研究对象,通过原料粒度及粒度分布、水分质量分数对造粒粒度分布影响的实验室研究,改进和优化烧结生产工艺,提出一套合理的烧结生产控制模型,以实现烧结生产的自动化控制和造粒粒度分布的预测。研究结果:在适宜的造粒水分范围内,随水分质量分数的增加,造粒粒度增加;但当水分质量分数过大时,造粒粒度反而减小。原料粒度对造粒粒度的影响是主要因素,而水分质量分数对造粒粒度的影响是次要因素。由造粒粒度分布数学模型得出的预测值与试验值之间有较好的一致性,原料粒度分布为正态分布时造粒粒度分布也为正态分布,并且造粒粒度分布的质量概率密度函数可由原料粒度分布的质量概率密度函数和原料粒度分割系数确定。     

包钢φ400自动轧管机组回送辊机架系列改造设计

应用液压基本传动理论和力学摩擦原理,建立回送辊及其平衡模型.利用该平衡模型计算相关的液压平衡参数,进行结构选择,从而证明液压平衡的实用性和液压传动的稳定性.     

串级萃取状态方程及多元稀土萃取分离工艺设计

本文在Underwood“数群”方法的基础上,讨论了恒定分离系数恒定混合萃取比串级萃取体系中级与级间的“数群”关系;提出了串级萃取状态参数和状态方程的概念;建立了设计多元稀土串级萃取分离工艺的方法。     

松比大、纯度高、球形团聚钼粉制备工艺研究

研究了松比大、纯度高、球形团聚钼粉的制备工艺过程,该工艺过程包括原料钼粉的喷雾造粒、喷雾造粒钼粉的脱脂、烧结(喷雾造粒—脱脂—烧结).结果表明:该制备工艺中,喷雾造粒是控制粉末的形貌和粒度的主要环节;脱脂温度是控制粉末纯度的重要参数;烧结是控制成品粉末物理性能及组织形貌的关键工艺;采用该工艺制备的团聚球形钼粉松比大、流动性好、纯度高,不仅适用于喷涂作业,还可用于精密器件的制备.     

国防专用高比重平衡器件新型制备技术的研究

本文通过研究粉体球磨混合技术及粉体造粒技术、新型粘结剂、高效脱除压坯件内粘结剂等技术确定国防专用高比重平衡件的生产工艺,规范了国防专用高比重平衡器件的产品标准.创新研制一套系统、高效、节能、安全的新型的国防专用高比重平衡件工艺技术.     

土壤湿度估计的理想同化试验研究

通过使用集合Kalman滤波,建立基于不同离散化方法的同化土壤湿度的理想试验.通过设置不同的初始状态,以集合预报的形式建立了openloop和模拟的理想"真值",并将来自不同离散化方法得到的理想"真值"集合生成多模型集合预报的理想"真值".分别使用单个的离散化方法同化来自各自理想"真值"和多模型集合预报的理想"真值",来检验通过同化表层土壤湿度后对整个湿度廓线的改进能力.结果表明,由于不同的离散化方法建立的土壤层之间的相关性不同,不同的离散化方法通过同化表层土壤湿度后土壤湿度廓线均有改进,但是改进的效率不同;当使用多模型的集合预报时,能够更有效地吸收观测,比任何单个模型的同化效果都要好.     

雾化造粒钼粉烧结过程研究

研究了喷雾造粒钼粉脱脂、烧结过程,结果表明:该制备工艺中脱脂温度是控制造粒钼粉碳含量的重要参数;烧结过程直接影响造粒钼粉组织形貌、霍尔流速及松装密度;采用该工艺制备的造粒钼粉具备良好流动性、大松装密度,是近净成形钼精密器件及喷涂行业理想的原材料。     

旋流沉淀池的调节容量与水量平衡

突破传统设计方式，针对目前冶金工厂各循环水处理系统普遍存在的水量不平衡问题，从建立旋流沉淀池泵房吸水井水量平衡的数学模型入手，找到了水泵启动周期公式，并通过对该公式的分析，解释了目前水量不平衡问题的现象和产生的原因，探讨了解决该问题的有效途径，并在工程实践中得到验征。     

Application of two population balance models in predicting multi size bubbly flow in continuous casting mold

Accurately predicting the flow characteristics of multi scale bubble flow in continuous casting mold is of great significance for cleaning molten steel and improving slab quality. To consider the influence of bubble coalescence, breakage, and other microscopic phenomena on the macroscopic characteristics such as bubble size, number density, and gas void fraction, two mathematical models based on population balance equation, MUltiple SIze Group (MUSIG) model and Average Bubble Number Density (ABND) model, were employed to simulate the multi size bubbly flow in the mold. The predicted results have been compared with the water model experiments. Results show that the two population balance models can accurately capture the liquid flow pattern, bubble size and void fraction distribution characteristics of the multi size bubble flow in the mold, especially the " intermediate peak" and "outlet peak" distribution characteristics of void fraction in the submerged entry nozzle（SEN）. Compared with the MUSIG model, the ABND model is more accurate in predicting the bubble size distribution near the SEN. The two population balance models contribute to expanding the applicable scope of the two fluid model with a single size bubble and provide the theoretical fundament and mathematical framework for studying the multi size bubbly flow.     

2种群体平衡模型在连铸结晶器多尺寸泡状流中的应用

摘要：准确预测连铸结晶器内多尺寸泡状流的流动特性对洁净钢水和提高铸坯质量至关重要。为了考虑气泡聚并、破碎等微观现象对气泡尺寸、数密度、含气率等宏观参量的影响,分别采用2种基于群体平衡方程的数学模型—多气泡组质量传递模型（MUSIG）与平均气泡数密度模型（ABND）,对连铸结晶器内的多尺寸泡状流进行了数值模拟,并与水模型实验结果进行了对比研究。结果发现：2种群体平衡模型均可以较准确地捕捉到结晶器多尺寸泡状流中的液相流型、气泡尺寸以及含气率分布特征,尤其是较好地预测了浸入式水口内部含气率的“中间峰”和“出口峰”分布特征;相比于MUSIG模型,ABND模型对靠近水口处气泡尺寸分布的预测结果更加准确。2种群体平衡模型扩展了传统单一粒径双流体模型的适用范围,为结晶器内多尺寸泡状流研究提供了理论基础和数学框架。     

Behaviour of Oxide Inclusions in Liquid Steel: Multi‐QMOM Simulation

The topic of this paper is the study of inclusion properties and behaviour inside a ladle containing liquid steel. A new numerical tool tracks the size and the composition of inclusions during the oxygen removal and the steel refining. Commercial CFD codes (Fluent?), home‐made thermo‐kinetics code and population balance model have been associated to follow oxide precipitates. The long‐term scientific goal of this study consists in proposing actuators to prevent or to eliminate harmful inclusions based on results predicted by the numerical model.     

The number of self-incompatibility alleles in a finite, subdivided population

The actual and effective number of gametophytic self-incompatibility alleles maintained at mutation-drift-selection equilibrium in a finite population subdivided as in the island model is investigated by stochastic simulations. The existing theory founded by Wright predicts that for a given population size the number of alleles maintained increases monotonically with decreasing migration as is the case for neutral alleles. The simulation results here show that this is not true. At migration rates above Nm = 0.01-0.1, the actual and effective number of alleles is lower than for an undivided population with the same number of individuals, and, contrary to Wright's theoretical expectation, the number of alleles is not much higher than for an undivided population unless Nm < 0.001. The same pattern is observed in a model where the alleles display symmetrical overdominant selection. This broadens the applicability of the results to include proposed models for the major histocompatibility (MHC) loci. For a subdivided population over a large range of migration rates, it appears that the number of self-incompatibility alleles (or MHC-alleles) observed can provide a rough estimate of the total number of individuals in the population but it underestimates the neutral effective size of the subdivided population.     

New statistical tests of neutrality for DNA samples from a population

The purpose of this paper is to develop statistical tests of the neutral model of evolution against a class of alternative models with the common characteristic of having an excess of mutations that occurred a long time ago or a reduction of recent mutations compared to the neutral model. This class of population genetics models include models for structured populations, models with decreasing effective population size and models of selection and mutation balance. Four statistical tests were proposed in this paper for DNA samples from a population. Two of these tests, one new and another a modification of an existing test, are based on EWENS' sampling formula, and the other two new tests make use of the frequencies of mutations of various classes. Using simulated samples and regression analyses, the critical values of these tests can be computed from regression equations. This approach for computing the critical values of a test was found to be appropriate and quite effective. We examined the powers of these four tests using simulated samples from structured populations, populations with linearly decreasing sizes and models of selection and mutation balance and found that they are more powerful than existing statistical tests of the neutral model of evolution.     

液相烧结过程中粉末粒径分布演化模拟研究

液相烧结过程中, 粉末颗粒的熟化长大和聚并同时发生。利用群体平衡模型定量预测了相邻颗粒聚并效应作用下的粒径分布演化规律, 提出了一种基于欧式范数的方法以确定液相烧结过程是否达到稳态, 研究了从瞬态到稳态的转变过程中的粒径上限及其变化率, 发现颗粒瞬态粗化之后将得到稳态粒径分布。模型计算得到的粒径分布和实验数据之间吻合良好, 表明本数值模型具备定量预测能力。通过引入布朗粗化频率描述液相烧结过程中的聚并现象, 模拟结果表明颗粒的聚并行为显著延缓了瞬态向稳态的转变过程, 甚至可能导致最终得到非稳态粒径分布。     

An explicit method for numerical simulation of wave equations: 3D wave motion

In this paper, an explicit method is generalized from 1D and 2D models to a 3D model for numerical simulation of wave motion, and the corresponding recursion formulas are developed for 3D irregular grids. For uniform cubic grids, the approach used to establish stable formulas with 2M-order accuracy is discussed in detail, with M being a positive integer,and is illustrated by establishing second order (M=l) recursion formulas. The theoretical results presented in this paper are demonstrated through numerical testing.     

Numerical Modeling of Type I Circular Sedimentation Tank

A numerical model for Type I circular sedimentation tanks (center feed) has been developed to provide useful information for circular tank operation. The unsteady flow process in circular sedimentation tanks is divided by numerous time intervals in which flow and sediment transport are considered to be steady. The other feature for this model is that particle size distribution of raw water is nonuniform. A numerical experiment based on the proposed model is carried out, and the results were compared with results from other models. The comparison shows that this model can provide more information, such as variations of water elevation, overall removal efficiency, bottom sludge thickness, and particle size distribution at outlet. In addition, this model had the advantage of optimizing the tank dimensions based on the sludge raking frequency and preferred removal efficiency. After simplification of the model, this model is practical in determining the overall removal efficiency and dimension of the tank based on different inflow situations for tank design.     

The free-surface shape and temperature distribution produced in liquid metal droplets by heating coil pulses in the TEMPUS electromagnetic levitation facility

We present the results of analytical and numerical calculations of the free-surface shape and temperature distribution produced in liquid metal droplets processed in the TEMPUS electromagnetic levitation facility. The mathematical models were developed to predict the behavior of liquid metal droplets in containerless experiments used to measure thermophysical properties aboard the Space Shuttle Columbia during the IML-2 mission in July 1994. A normal stress balance model was used to numerically calculate the equilibrium free-surface shapes for various samples produced by a number of induction coil voltages. Analytical and numerical calculations were performed to model the heat transfer in the liquid metal droplets during and following the heating coil pulses. The work illustrates the use of mathematical modeling in the design of microgravity experiments and is applicable to industrial processes such as casting and skull melting.