关于分段函数若干问题的讨论

高等数学以函数为研究对象,其中分段函数又是函数中的一个难点.本文分析了分段函数的连续性、可导性、可积性,并通过例子说明如何处理分段函数的问题.     

焦炭实验转鼓与标准转鼓间相关性评定

我厂自建一台“7公斤试验焦炉”,因其产量微少,特配制了一台实验转鼓。其鼓径1m、转速25转/分、转数100转,长度1/4m,机械物理过程特性同米贡转鼓相似。其意在使小焦炉所炼焦炭通过实验转鼓显示的强度值能直接知道在大转鼓内的强度值,从而达到用小焦炉生产指导现场生产的目的。焦炭在两种转鼓内,因充满系数和鼓长不同而使焦块间的磨损、焦和鼓壁的接触及相对运动不同而有所影响。因此,不能直接以实验转鼓内强度值来代替“标准转鼓”内强度值。从而开展了两鼓间相关试验。     

Carrousel卷取机转鼓定位控制

攀枝花钢铁(集团)公司冷轧厂酸轧联机改造中,Carrousel卷取机转鼓定位控制采用ABB AC450集散控制系统,根据运动学理论计算定位过程中所需的减速度、减速点位置和最大定位速度后,对转鼓电动机进行控制。根据现场实际运行情况对控制程序进行改进后,解决了定位过程中转鼓与入口和出口夹钳碰撞的问题。实际应用表明,转鼓定位控制曲线与目标曲线一致,控制效果良好。     

浅谈加热炉汽化冷却装置汽包液位

从某热轧厂加热炉汽化冷却装置普遍存在的液位控制不好的情况出发,探讨了液位控制的重要意义。分析了排汽点的选择、液位计的选择、液位调节系统的选择等多个方面对改善液位控制效果的可行性,以保证汽化冷却装置的安全正常运行。     

基于响应曲面法的烧结孔隙优化

基于烧结生产实际工艺参数,采用响应曲面法对烧结矿孔隙率进行优化研究,以碱度(A)、燃料配比(B)、燃料粒度(C)为设计变量,以烧结矿孔隙率(Y1)和转鼓指数(Y2)为目标函数,建立数学模型,进行三因素的优化设计分析.研究结果表明,碱度和燃料配比对孔隙率和转鼓指数影响显著,燃料粒度的影响较小;碱度与燃料配比、燃料配比与燃...     

加热炉汽化冷却装置汽包液位控制问题研究

山西某热轧厂加热炉汽化冷却装置普遍存在液位控制不好的情况,为此探讨了液位控制的重要意义．分析了排汽点的选择、液位计的选择、液位调节系统的选择等多个方面对改善液位控制效果的可行性,以保证汽化冷却装置的安全正常运行。     

鞍钢Ф2300×L3000萘转鼓结晶机的热平衡分析

简单介绍了萘制片工艺过程与特点,建立了萘转鼓结晶机的热平衡分析计算模型,并对该转鼓结晶机进行了热平衡分析计算,计算值与实测结果基本吻合.     

基于PLC和WinCC的PID液位控制系统的研究

以PLC控制与WinCC组态技术为基础对单容水箱液位系统进行了研究,建立了液位系统的PLC控制模型,组建了系统的组态,并用WinCC进行了实时监控.系统具有图形显示直观,参数调试方便等优点.     

Co60辐射法结晶器液位自动控制系统在铸机上的应用

介绍了Co60辐射法结晶器液位自动控制系统的组成及工作原理。通过对原有系统硬件和软件进行分析,对结晶器液位控制进行了系统优化。应用表明,系统工作稳定,液位控制精度在±3mm以内,完全能满足连铸生产对结晶器液位控制的要求。     

用KMM调节器控制3^#锅炉自动上水功能

本文通过对3^#锅炉现状的分析指出：影响3^#锅炉给水控制的主要依据——汽包液位的因素为内扰因素是由于过冷水引起;外扰因素是锅炉内存贮热量的减少而引起的突然加剧沸腾而产生的虚假水位。为了便于良好控制,真实地反映汽包液位,从而更好地控制3^#锅炉给水系统,具体地分析和介绍了3^#锅炉采用KMM调节器的优点,无可置疑的好处,值得推广。     

本钢7号高炉水渣系统转鼓转速PID控制的研究

讨论了PID控制器的原理,并以转鼓转速控制系统为例,介绍了一个以PID控制器为基本调节单元的转鼓转速控制系统,同时讨论了转鼓转速的速度曲线以及PID参数的调整过程。     

A two-dimensional heat and fluid-flow model of single-roll continuous-sheet casting process

Single-roll continuous-sheet casting process has been simulated using a mathematical model based on considerations of fluid flow, heat transfer, and solidification. The principal model equations include momentum and energy balances which are written for various zones comprising the process. The flow of liquid metal in the pool is taken to be a two-dimensional recirculatory flow. The concepts of vorticity and stream function are used to reduce the number of equations and number of unknowns, respectively. Model equations and boundary conditions are written in terms of dimensionless variables and are solved, using an implicit finite difference technique, to give stream functions and velocity fields in the metal pool, temperature fields in the metal pool, sheet, and caster drum, and the final sheet thickness for various operating parameters. The parameters examined are: (1) rotational speed of the caster drum, (2) liquid metal head in the tundish, (3) superheat of the melt, (4) caster drum material, and (5) cooling conditions prevailing at the inner surface of the caster drum. The final sheet thickness decreases with increasing rotational speed of the caster drum and melt superheat, but it increases with increasing standoff distance and metal head in the tundish.     

可双向多次剪切的转鼓式飞剪设计

介绍了单向剪切转鼓式飞剪的结构现状,结合双向多次剪切转鼓式飞剪的工艺设计需求分析,从中归纳出双向多次剪切功能实现的基本要求,在此基础上重点讨论了双向多次剪切转鼓式飞剪的结构设计及其控制方法,并依托飞剪的能量转化模型对飞剪的力能参数进行了计算。分析表明,这种新型的转鼓式飞剪结构合理,不仅能满足炉卷和中厚板组合生产线双向、每向多次剪切的功能要求,同时能满足生产线的快速生产节奏的工艺需求。通过设计讨论,为双向多次剪切的转鼓式飞剪设计研究提供一些思路和方法,同时为轧钢工艺人员的选型应用提供参考。     

柔性挡轮在烧结混合机上的应用

介绍了能适应大型化设备和高产能的一种新型烧结圆筒混合机的柔性挡轮装置的结构、工作原理和实践应用效果。混合机运行更加平稳,柔性挡轮能够有效减少作用于挡轮上的冲击负荷,防止了筒体轴向窜动、后移以及造成的挡轮支撑轴等零部件的损坏,优化了挡轮调整方式。     

超声搅拌和气体搅拌去除夹杂物

 通过水模型实验，对同一容器内相同比搅拌功率条件下，超声搅拌和气体搅拌对去除夹杂物的影响进行了对比研究。结果表明：超声搅拌的空化作用可产生的大量小气泡增大了吸附面积，延长了气泡的上浮时间，有利于夹杂物的去除，可以充分发挥容器器壁粘附夹杂物的作用，保护液体不受外界污染；气体搅拌时，夹杂物去除速率快、效率高。两种搅拌方式去除夹杂物的效率均随比搅拌功率的提高而增大，但比搅拌功率对气体搅拌的影响更加显著。     

Understanding the Agglomeration Behavior of Selected Copper Ores Using Statistical Design of Experiments

The drum agglomeration of two different crushed copper ores (I and II) has been optimized using Taguchi's L₁₆ (4⁵) orthogonal array design to determine the optimum conditions for maximizing the average agglomerate size and minimizing the amount of fines. The effects of controllable operating factors including moisture content (ore I: 9.6–11.1%; ore II: 12.8–14%), retention time (2–4 min), drum speed (15–45% critical), drum load (ore I: 13–32%; ore II: 6–24%) and acid concentration (6.5–90 g/L) on the performance of the agglomeration process were studied. For ore I, the maximum average agglomerate size and minimum percent fines (?1 mm) occurred under the conditions: drum load (22.75%), moisture (10.35%), time (4 min), drum speed (30% critical), and acid concentration (41 g/L), whereas for ore II, the same conditions occurred under the drum load (18%), moisture (13%), time (3 min), drum speed (30% critical), and acid concentration (30 g/L). Under the conditions studied for ore I, the most effective parameter for maximizing average agglomerate size and minimizing the amount of fines was found to be drum load. For ore I, time and acid concentration had a measurable effect on maximizing average agglomerate size, whereas moisture had a statistically significant effect on minimizing the amount of fines. For ore II, the most effective parameter for maximizing average agglomerate size and minimizing the amount of fines was found to be acid concentration. Time had a measurable effect on maximizing average agglomerate size, whereas the other variables did not affect the responses significantly for ore II.     

采煤机机电传动系统调速动态特性分析

为研究滚筒调速的可行性及调速对传动系统动态性能的影响,采用MATLAB/Simulink搭建了采煤机截割-牵引耦合机电传动系统动力学模型.针对截割部过载工况,综合考虑采煤机可靠运行和高效生产,制定了4种调速降载方案,并提出了通过截割电机电流计算目标切削厚度、依据目标切削厚度选择调速方案的方法.最后通过仿真对比了各种调速方案下电机和传动系统的动态响应特性,结果表明:当截割电机过载倍数较小时,采用滚筒调速方案能够在降低系统负载的同时使采煤生产率不受影响;当过载倍数较大时,采用牵引调速方案可获得较高的系统可靠性,而采用牵引-滚筒顺序调速方案可获得较高的采煤生产率.     

A simple fluid mechanical model for planar flow casting melt-spinning

A math model for melt-spinning based on a two-dimensional steady-state condition has been developed. Because of the complexity of the processes involved, the solution of the full governing nonlinear partial differential equations and boundary conditions is not sought. Instead, the problem is analyzed using a control volume approach. In this approach, overall conservation laws for mass, momentum, and energy are satisfied for each of the zones into which the flow field can be conveniently subdivided. The zones are the reservoir, the nozzle, the liquid pool, and the solidified thin metal sheet. The conservation laws can be solved to yield the thickness of the sheet with the reservoir pressure, the ambient pressure, the nozzle/drum gap, the drum speed, and the geometry as input parameters. Because the model contains all the essential parameters, it can be used to optimize operation of the process or its dependence on any of the geometric or physical parameters.     

A simple fluid mechanical model for planar flow casting melt-spinning

A math model for melt-spinning based on a two-dimensional steady-state condition has been developed. Because of the complexity of the processes involved, the solution of the full governing nonlinear partial differential equations and boundary conditions is not sought. Instead, the problem is analyzed using a control volume approach. In this approach, overall conservation laws for mass, momentum, and energy are satisfied for each of the zones into which the flow field can be conveniently subdivided. The zones are the reservoir, the nozzle, the liquid pool, and the solidified thin metal sheet. The conservation laws can be solved to yield the thickness of the sheet with the reservoir pressure, the ambient pressure, the nozzle/drum gap, the drum speed, and the geometry as input parameters. Because the model contains all the essential parameters, it can be used to optimize operation of the process or its dependence on any of the geometric or physical parameters.     

提高钒钛磁铁精矿配比对烧结的影响

为了探索钒钛磁铁精矿配比变化对烧结的影响,研究了不同钒钛磁铁精矿配比对混合料制粒、混合料液相生成特性、烧结性能、烧结矿矿物组成、烧结矿冶金性能的影响,结果表明:钒钛磁铁精矿配比在46%~67%时,随着精矿配比的升高,烧结矿中TiO2含量增加,混合料的透气性指数略有降低,烧结速度明显减慢,利用系数降低,转鼓强度略有降低;总体上液相量逐渐变少,矿物结构的粘结性与结晶性变差;滴落温度明显升高,软熔区间变宽,软化温度和熔融温度在一定范围内有所波动;混合料液相生成温度升高,生成量降低,成矿性能变差。