板坯连铸结晶器内钢液流场的数值模拟

以计算流体力学理论为基础,利用Fluent软件建立了连铸结晶器内钢液流动的三维数学模型,运用模型低雷诺数方程对板坯结晶器内钢液的流场进行了模拟研究.通过数值计算研究了水口浸入深度、拉坯速度等上艺参数对结晶器内钢液流动状态的影响,为优化结品器内的钢液流场分布、合理设计连铸结晶器装置和指导实际生产提供了依据.     

横管降膜过程中液膜内流动和传热特性分析

横管降膜流动过程中,液膜速度和温度及其分布是影响传热传质的关键因素,由于实验研究方法的局限性,实验研究结果一般只是液膜内各参数的平均值,而液膜内部的速度和温度具体分布特性却很难得到。借助FLUENT软件,利用VOF模型研究了橫管外液膜速度和温度及其分布特性。通过建立三维数理模型,模拟研究了常温常压下,橫管外液膜无相变条件下横管液膜的传热过程,并从边界层的角度解释了液膜波动对传热过程的影响。     

火焰筒内环向多孔径向射流的流场研究

环向径向射流对燃烧室火焰筒内的流场有着重要的影响。本文采用三雏标准k-￡湍流模型详细模拟了燃烧室火焰筒内外的等温流场，给出了火焰筒不同截面位置的轴向速度和径向速度分布。并对数值模拟结果与实验数据进行了比较，结果符合较好，同时还分析了数值模拟结果与实验数据的差异。研究了火焰筒内多孔径向射流的流场特性，并比较了不同环向径向射流流量对火焰筒内流场的影响。研究结果表明：在射流孔附近，火焰筒内轴向速度和径向速度沿径向的梯度增大；而在火焰筒外，轴向速度沿径向的梯度变化不大，径向速度变化较大，但随着流体的流动，火焰筒外径向速度很快趋于均匀。当射流流量增加时，火焰筒内射流孔中心截面的两对称旋涡逐渐增大。     

基于大涡模拟方法的二冲程发动机缸内冷态流场的模拟研究

应用大涡模拟方法对一台二冲程发动机缸内冷态湍流流场进行了三维瞬态数值分析。探索缸内流场的速度、压力及温度的变动情况,并与PIV流场测试结果进行了对比。三维模拟的缸压曲线与试验及一维模拟均吻合较好,但在速度概率密度函数方面与试验存在一定差异。模拟结果表明:本文建立的三维模型能够自然再现缸内冷态流动的随机大尺度涡流情况,模型可靠有效。模拟能够较好地反应火花塞位置附近速度随机波动情况,其结果对于后续研究缸内大尺度涡流对燃烧循环变动的影响机理具有一定的指导意义。     

微喷管内气体流动的实验研究与数值模拟

通过实验和数值模拟来研究气体在渐缩微喷管内流动,基于连续介质模型研究了二维微喷管内的流场及推力特性,研究分析了流量和气体入口温度对微喷管流场结构和喷管性能的影响。研究结果表明,随着流量的不断增加,气体稀薄效应相应减小,粘性力对喷管流动的影响降低,边界层逐渐变薄,马赫数不断增大,微喷管的推力大小近似与流量成线性变化,但流量变化对微喷管流场结构影响并不显著。当温度增大时,粘性损失对喷管影响较大,导致边界层变厚,影响了微喷管推进性能,流场马赫数和微喷管推力随温度的升高而下降,说明低温气体有利于提高微喷管的推进性能。     

水─汽浸没凝结射流两相流动的数值研究

本文对水－汽浸没凝结射流两相流动采用单流体模型及ｋ－ε－ｇ湍流模型进行了数值研究。得到了速度、温度、密度和气相体积分数等物理量的分布以及穿透区（含气区）的形状。穿透区的长度与相关的由实验得到的经验公式符合得很好。计算结果表明水的汽－液浸没凝结射流经历了气相流动、气液两相流动和液相流动等不同流动型态的变化，具有复杂的流场结构。     

风力机二维翼型的PIV实验研究与数值仿真

通过PIV实验研究和非定常CFD数值计算相结合的办法,对风力机二维翼型(NREL S809)的流动参数和流场结构开展研究.利用PIV系统对在一定的雷诺数、不同攻角下翼型的流场进行测量,获得了丰富的流场信息;同时采用CFD软件对相应的流场进行了数值模拟,实验值与计算值吻合很好.该文着重比较了在不同攻角下实验和计算所获得的速度矢量图以及升力和阻力等气动参数,并结合实验数据分析了不同攻角下涡的分布及附面层的分离现象.     

旋转对梯形扰流柱通道流动及换热的影响

采用数值模拟的方法,对在旋转情况下的有弦向出流的梯形扰流柱通道内的三维流场进行了模拟研究。重点研究了在固定出流比的情况下,不同转速对扰流柱通道内的流动情况及端壁平均换热系数的影响。计算结果表明：R_o不为0时,通道内的流场与静止时相比有较大变化,在扰流柱区域内的扰动强度明显增大,流动更加紊乱,在扰流柱区域和无柱区域内均有涡旋现象发生；当Re数一定时,通道的压降和端壁的平均换热系数随着旋转数R_o的增大而增加；旋转对扰流柱通道的压降和端壁换热系数有明显影响,旋转对扰流柱通道流动及换热的影响随通道数Re数的增大而增强。     

电弧等离子体点火器湍流燃烧流场传热与流动数值模拟

对燃气轮机燃烧室电弧等离子体点火器内湍流燃烧流场,进行了传热与流动数值模拟。采用了RNGk-ε湍流模型、扩散燃烧模型和离散传播辐射DTRM模型。计算域包括点火器内的等离子体发生器和点火器主体。将计算结果与未考虑辐射的温度场和流场进行了比较。结果表明辐射模型对其温度场有影响,对速度场影响不大;在点火器出口处的径向温度分布是均匀的。     

燃气轮机燃烧室燃烧流场的数值计算

对某型燃气轮机燃烧室的燃烧流场运用FLUENT软件进行了数值模拟.在模拟过程中采用了标准k-ε湍流模型、"简单化学反应系统"模型和"快速化学反应"假设,用SIMPLE算法进行压力一速度耦合求解,分析了不同负荷情况对燃烧效率、出口平均温度、过量空气系数及火焰长度的影响.计算结果能够很好地反映燃烧室燃烧流动的特点,对预测燃烧室内的燃烧流动及燃烧室的优化有一定参考价值.     

直流电弧炉精炼期内熔池流场和温度场的数值模拟

数值模拟直流电弧炉精炼期内熔池部分的流体流动和电磁现象有重要的理论意义和实用价值.在对直流电弧炉内电弧等离子体进行数值模拟的基础上,使用一个二维时变磁流体力学模型来描述电弧炉精炼期内熔池部分电磁场、速度场和温度场的分布情况,同时,研究了炉底电极大小对炉内熔池部分流场的影响.仿真结果可为直流电弧炉的合理化设计和冶炼过程的优化提供参考依据.     

Study on the wiping gas jet in continuous galvanizing line

In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating thickness is generally influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. The flow charact...     

Modelling of the flow at the rotor disc in a geothermal turbine of 110 MW

To elucidate an excessive erosion damage produced by solid particles in the fourth stage rotor disc of a 110 MW double flow geothermal turbine, a bi-dimensional modelling investigation has been conducted. The study was based on a set of results from a computational model using a Reynolds stress, RSM, turbulence model. The predicted results confirmed characteristic flow conditions that may play a main role in the serious erosion of the fourth stage rotor disc governor side, which has been detected in periodic overhauls. The results show a jet of vapour that hits the disc transition radius surface at velocities around 112 m/s. These conditions are produced by the flow outgoing from the labyrinth seal, which passes through a drastic cross-section reduction in the last seal strip. The flow was then simulated introducing specific changes to the geometry and the grid in order to modify the flow patterns favourably. Actually, the suggested changes have been envisaged indeed to be practically feasible of being implemented. The new results showed that it is possible to reduce the erosion process up to 86% by increasing the distance from the labyrinth seal to the rotor disc, which produces a 38% velocity reduction of the vapour flow in that zone. The design proposed in this work produces a flow pattern of a lower velocity on disc surface together with a modified angle of flow incidence. Furthermore, the proposed design also reduces a recirculating flow at the exit of the last seal strip. Based on these results, an analysis of erosion against velocity demonstrates that the redesigned rotor disc proposed here leads to the duplication of the time period used at present between maintenance repairs.     

浮法玻璃熔窑熔化池底部横向宽度对熔化池温度场影响的研究

基于计算机数值模拟方法,以460 t/d浮法玻璃熔窑为模拟对象,分析研究了不同熔化池底部横向宽度对玻璃熔窑的生产能力以及熔窑内玻璃液温度场的影响。结果表明,适当减小熔化池底部横向宽度不会明显改变卡脖和冷却部的玻璃液状况,从而不影响熔窑的生产能力。但不同的熔化池底部横向宽度将导致熔化部玻璃液温度场发生改变,中轴面处玻璃液温度降低,而胸墙处玻璃液温度升高,导致窑内玻璃液横向温度梯度发生相应变化,加剧玻璃液横向对流,有助于玻璃液均化和澄清。     

Experimental and Computational Studies on Coanda Nozzle Flow for the Air Knife Application

To control the film thickness of zinc in the process of continuous hot-dip galvanizing,it is known from the earlydays that the gas wiping through an air knife is the most effective one.The gas wiping using in galvanizing proc-ess brings about a problem of splashing from the strip edge for a certain high speed of coating.So,in the presentstudy,the effects of the deflection angle of Coanda nozzle on jet structure and the distribution of impinging pres-sure at the plate surface are investigated numerically and experimentally.In numerical analysis,the governingequations consisted of three-dimensional time dependent full Navier-Stokes equations,standard k-ε turbulencemodel to solve turbulent stress and so on are employed.In experiment,16 channel pressure scanning valve and3-axis auto traversing unit are used to measure the impinging pressure at the strip surface.As a result,it is foundthat the smaller the deflection angle for the same nozzle slit of air knife is,the larger the impinging pressure is.Toreduce the size of separation bubble and to enhance the cutting ability,it is recommendable to use an air knifewith the Coanda nozzle.     

3-D temperature and stress distributions of strip in preheating furnace of continuous annealing line

The cold-rolled steel sheets produced by continuous annealing line (CAL) exhibit a significant phenomenon of warping during punching process. The phenomenon of warping is attributed to the non-uniform residual stress of steel strip, which may result from the non-uniform distributions of the temperature and plastic deformation along both the width and thickness of strip when it passes through the rolls in the CAL. In this study, only the distributions of the temperature and thermal stresses of strip in the preheating zone, one of several zones in CAL, are investigated first. Both the thermal and mechanical analyses are performed by using the finite element code ANSYS to investigate the effects of heating conditions in the preheating furnace. The equivalent emission of radiation of the strip corresponding to the complicated furnace environment is evaluated inversely with the aid of strip temperature estimated by energy balance model. Moreover, three-dimensional (3-D) distributions of the temperature and deformation of strip are then iteratively evaluated by the energy and mechanical models due to their coupling effect until a satisfied convergence in numerical solutions is obtained. The results show that the taper rolls tend to introduce a significantly non-uniform distribution of the temperature along the width. This temperature pattern might lead to an unfavorable consequence of enormously non-uniform distribution of stress along the width.     

低能耗机械镀锌技术及应用

机械镀锌是一种在常温常压下利用化学吸附和机械碰撞使金属锌粉沉积在工件表面形成镀层的工艺,与传统的热镀锌、电镀锌相比,具有生产过程能耗低、对环境污染小等优点,是一种清洁低耗镀锌技术。简要介绍机械镀锌工艺及设备,将机械镀锌、热镀锌和电镀锌的性能、特点、环境影响进行了对比,探讨了机械镀锌技术的发展及应用前景。     

涡轮增压器蜗壳形状对其喷嘴出口速度场的影响

用心形线表征了一种涡轮增压器无叶蜗壳梨形流道横截面轮廓，用有限差分法计算了涡轮增压器蜗壳流场，分析了无叶喷嘴出口气流速度和气流角的分布，经与测量结果比较，两者吻合较好。在此基础上，研究了三种不同蜗壳型线对喷嘴出口速度场的影响。结果表明，C型线蜗壳喷嘴出口的总速度v和气流角α分布均匀，A，B型线蜗壳喷嘴出口的总速度v和气流角α分布不均匀。     

Magnetized squeezed flow of time‐dependent Prandtl‐Eyring fluid past a sensor surface

The present numerical investigation describes the influence of a transverse magnetic field on the heat and mass transfer characteristics of time‐dependent squeezed flow of Prandtl‐Eyring fluid past a horizontal sensor surface. The current physical problem is modeled based on the considered flow configuration. Also, the present problem is analyzed under the influence of Lorentz forces, to explore the impact of a magnetic field on the flow behaviour. The considered physical problem in the present study gives highly nonlinear coupled time‐dependent, two‐dimensional partial differential equations. The governing flow equations are reduced to the system of nonlinear ordinary differential equations by imposing the suitable similarity transformations on the laws of motion. Due to the inadequacy in the analytical methods, the present problem is solved by using the Runge‐Kutta fourth order integration scheme with shooting method. The flow and heat transfer behaviour of various control parameters are studied and presented in terms of graphs and tables. From the current investigation it is noticed that, the increasing magnetic parameter enhances the velocity field and diminishes the temperature profile in the flow region. Also, the magnifying permeable velocity parameter decreases the temperature field. The present similarity solutions are found to be in good agreement with previously published results.     

Longitudinal residual warpage of strip in continuous annealing line

After the heat treatment in continuous annealing line (CAL), the strip always exhibits phenomenon of residual warpage during punching process. This geometric defect is mainly attributed to the residual stress induced in the line and has a close relation with the temperature history of the strip. It becomes more serious for the wider strip and may significantly degrade the quality of the products. The contents of this study are mainly composed of establishing the energy model of the strip and roll to estimate the temperature distributions of the strip and the surface temperature of the roll, estimating the emissivity and equivalent heat transfer coefficient of the strip in each section of CAL, and establishing mechanical model of the strip to evaluate the distributions of contact pressure and residual stress of the strip especially along the width direction. Finally, the longitudinal residual warpage was calculated accordingly by virtual layers method (VLM). It was found that the residual warpage at both sides is larger than the central region. Moreover, the numerical results of strip warpage are well consistent with the experimental data which demonstrates the accuracy and reliability of the proposed method.