3D FEM simulation of flow velocity field for 5052 aluminum alloy multi-row sprocket in cold semi-precision forging process

Based on the design of the multi-row sprocket with a new tooth profile,a cold semi-precision forging process for manufacturing 5052 aluminum alloy multi-row sprocket was presented.Through simulating the forging process of 5052 aluminum alloy sprocket billet with 3D rigid-viscoplastic FEM,both the distributions of flow velocity field in axial(U_Z),radial(U_R) and circumferential(U_θ) directions and the curves of velocity component in different deformation regions were respectively obtained.By comparison and analysis of the velocity varying curves,the velocity component relation conditions for filling the die cavity were clarified.It shows that when the die cavity is almost fully filled,the circumferential velocity U_θ increases sharply,implying that U_θplays a key role in fully filling the die cavity.

Numerical calculation of flow field inside TiAl melt during rectangular cold crucible directional solidification

Numerical investigations on the flow field in Ti-Al melt during rectangular cold crucible directional solidification were carried out. Combined with the experimental results, 3-D finite element models for calculating flow field inside melting pool were established, the characteristics of the flow under different power parameters were further studied. Numerical calculation results show that there is a complex circular flow in the melt, a rapid horizontal flow exists on the solid/liquid interface and those flows confluence in the center of the melting pool. The flow velocity v increases with the increase of current intensity, but the flow patterns remain unchanged. When the current is 1000 A, the vmax reaches 4 mm/s and the flow on the interface achieves 3 mm/s. Flow patterns are quite different when the frequency changes from 10 kHz to 100 kHz, the mechanism of the frequency influence on the flow pattern is analyzed, and there is an optimum frequency for cold crucible directional solidification.

Confluence and cold shut computation based on time field in casting simulation

Numerical simulation technology has been widely used in the foundry industry to analyze and improve casting processes.During the casting filling process,many filling-related defects form easily at the confluences of liquid metal streams.The main filling-related defects are cold shut defects.To calculate the positions of casting defects,the characteristics of liquid metal confluences were analyzed.The flow front of liquid metal was captured by the volume-of-fluid algorithm to obtain a time field,which was used to calculate the time derivatives of the liquid front position and the confluences of liquid metal streams.To distinguish small confluences from the main confluences,the concept of confluent scale was developed,which was used to filter the small confluences based on a threshold.The calculation process was demonstrated through the post-processing of numerical simulation.A "W" shaped casting and a steering wheel casting were calculated to validate the accuracy of the method developed in this study.The positions of cold shut defects were predicted by calculating the confluences of liquid metal streams.The method was proved to be practical by comparing the calculation results with the positions of cold shut defects in an end cover casting.The computation of confluences and cold shut defects can improve the analysis efficiency and provide assurance for the optimization of a casting process plan.

Numerical study on surrounding rock mass temperature field of Kangding tunnel no.2 considering wind flow

Based on the Kangding Tunnel No.2 project,this study analyzes the heat exchange between air and the rock mass surrounding the tunnel under wind flow by the finite difference method.The influence of factors on the temperature field of a tunnel in cold regions,including ventilation and initial conditions,is investigated.The results show that:1)The lower the air temperature,the greater the wind speed,the larger the rock mass temperature influence circle and the greater the frozen depth;2)When the wind speed is less than 3 m/s,its change has an obvious impact on the rock mass temperature;3)For every drop of 5C in air temperature,the frozen depth increases by about 5 m,indicating that the air temperature is an essential factor affecting the rock mass temperature regime;4)The higher the initial rock mass temperature is,the smaller the influence circle on the rock mass is.And to a certain extent,it determines the temperature distribution in the rock mass within a specific range from the wall surface.

Cold-state Experimental Study on Flow Characteristics of Multi-nozzle in Natural Gas Reburning Burner

Based on the prototypes of a 130 t/h boiler, constant proportional cold-state test bench is established, flow characteristics of multi-nozzle in natural gas reburning burner and its influence on the covering effect for the upflow in the furnace are researched. Numerical simulations of this process are also made with standard ?turbulence model. The results show that air flow fullness in furnace is better in the case of the reburning zone with 8 nozzles compared to 4 nozzles and also coverage effect of the reburning flow for the updraft gas in the furnace is better. In the condition each nozzle airflow velocity is constant, the effect of reburning flow on coverage of up-secondary air is best when the incident angle for four corners is 14.17?, while Center of the furnace wall is 84.57. And while the best incident angle is invariable, the effect of reburning flow on coverage of up-secondary air is best when the speed of reburning gas in the corners of furnace is 51 m/s, the same to the center of the furnace wall’s.

Numerical prediction of vortex flow and thermal separation in a subsonic vortex tube

This work was aimed at gaining understanding of the physical behaviours of the flow and temperature separation process in a vortex tube. To investigate the cold mass fraction’s effect on the temperature separation, the numerical calculation was carried out using an algebraic Reynolds stress model (ASM) and the standard k-ε model. The modelling of turbulence of com-pressible, complex flows used in the simulation is discussed. Emphasis is given to the derivation of the ASM for 2D axisymmet-rical flows, particularly to the model constants in the algebraic Reynolds stress equations. The TEFESS code, based on a staggered Finite Volume approach with the standard k-ε model and first-order numerical schemes, was used to carry out all the computations. The predicted results for strongly swirling turbulent compressible flow in a vortex tube suggested that the use of the ASM leads to better agreement between the numerical results and experimental data, while the k-ε model cannot capture the stabilizing effect of the swirl.

Flow zone distribution and mixing time in a Peirce-Smith copper converter

Peirce-Smith copper converting involves complex multiphase flow and mixing.In this work,the flow zone distribution and mixing time in a Peirce-Smith copper converter were investigated in a 1:5 scaled cold model.Flow field distribution,including dead,splashing,and strong-loop zones,were measured,and a dimensionless equation was established to determine the correlation of the effects of stirring and mixing energy with an error of<5%.Four positions in the bath,namely,injection,splashing,strong-loop,and dead zones,were selected to add a hollow salt powder tracer and measure the mixing time.Injecting a quartz flux through tuyeres or into the backflow point of the splashing wave through a chute was recommended instead of adding it through a crane hopper from the top of the furnace to improve the slag-making reaction.

TASCflow软件包技术特点分析与应用研究

引进加拿大先进的三维流动数值分析软件包TASCflow ,深入研究软件包物理模型 ,分析总结功能模块的技术特点。开展应用研究工作 ,以元宝山电厂 2号炉试验模型为研究对象 ,数值模拟炉内冷态流场 。

寒冷地区电液制动器的油液黏度-时间模型及制动特性研究

针对寒冷地区电液制动器制动力和制动力矩不足等导致水闸制动系统发生溜车问题,基于液压油Vogel黏温模型以及当地温度变化数据,构建了油液黏度随时间变化的黏度-时间模型,并基于该模型对电液制动器制动过程中油液流动特性进行了研究,然后对电液制动器制动性能进行了定量分析。结果表明:在制动过程中,电液制动器液压油压力主要分布在活塞底腔,且随着黏度增大而逐渐增大,当油液黏度为662.4 Pa·s时,压力达到1.455×10^(-3)MPa,电液制动器液压油在叶轮中心轴部位会出现涡流循环,其循环强度随着油液黏度的增加而逐渐增加;在给定工况下,该电液制动器的最小制动力为1098 N,最小制动力矩为274 N·m。而这一制动力矩已低于该电液制动器工作力矩范围,此时可以通过更换该月份黏度更小的液压油或增设预加热系统等措施来提高其制动力和制动力矩,从而实现正常制动。

新型双筒体旋风分离器的分离性能和流场

为降低普通逆流式旋风分离器的阻力,设计了一种双筒体旋风分离器(简称双筒体分离器),即在筒体内部增加一个同心内筒、进口移至筒体下端、升气管插入内筒一段长度。通过冷模对比实验和数值模拟研究了该双筒体分离器的分离性能和流场。结果表明:双筒体分离器的效率在低入口气速区低于PV型高效旋风分离器(简称PV型分离器),但当入口气速高于28 m/s时则高于PV型分离器;双筒体分离器的效率总是高于环流式除尘器;压降与环流式除尘器相近但比PV型分离器低约50%。双筒体分离器耦合了常规逆流和直流旋风分离器中的2种旋涡流动,克服了逆流式分离器气体流路长和顶灰环的缺陷,同时还增加了部分细颗粒循环再分离的机会,效率高于直流式旋风分离器,是一种具有较低阻力和较高分离效率的新型旋风分离器,对于入口颗粒稍粗的分离应用具有显著的节能优势。

电站锅炉SCR脱硝系统导流板的设计与优化

为了优化某燃煤电厂选择性催化还原(SCR)脱硝系统的流场,研究不同导流装置的设计对该系统内流场的影响.基于fluent软件,对SCR脱硝反应器的流场进行数值模拟,应用可实现(Realizable)k-ε双方程模型计算气体的湍流运动,采用物质输运方程预测烟气组分的混合,研究反应器原设计方案下的速度场和浓度场信息,并通过优化导流装置对SCR脱硝系统结构进行优化.研究表明:优化后可以保证系统内烟气速度标准偏差小于10%,浓度流场小于5%;有利于减少SCR系统的压降,优化后压降小于800Pa;同时将数值模拟结果和试验数据进行对比,得到了较好地吻合.

四角切向燃烧锅炉烟道烟速偏差的实验研究与数值模拟

在对 6 0 0MW四角切向燃烧锅炉进行冷态模化实验的基础上 ,对四角切向燃烧锅炉炉内流场及水平烟道内速度偏差进行了数值模拟 ,分析了炉内气流流动特性和水平烟道烟气速度偏差的形成机理 ,提出了减小水平烟道烟气偏差的措施。模拟结果与冷态实验结果符合较好。

猕猴桃冷库内流场的CFD模拟

以一间实际装配式猕猴桃冷库为研究对象,建立了该冷库的三维物理模型和标准k-ε湍流数学模型。应用SIMPLE算法求解微分方程,对冷库进行三维数值模拟,获取冷库内部三维温度场、速度和压力场的信息,通过分析特定截面,模拟结果与实测值大致吻合。另外,通过改变冷风机条件和货物堆放方式,模拟其温度场的变化,讨论了这些因素对冷库温度场变化的影响情况。研究表明,CFD数值模拟在猕猴桃冷库内流场设计中的应用是切实可行的。

基于STAR-CCM+的拖拉机发动机舱三维仿真分析

拖拉机作业环境恶劣承受负荷大产热量高等问题,所以对拖拉机的外形,机舱内零部件布置,以及系统内单体性能都有着特殊而又严格要求,从而优化和解决拖拉机工作时所出现的上述问题,与此同时改善整机的动力性、经济性、和排放性等其他重要参数指标。利用STAR-CCM+软件建立某款拖拉机整车三维数值模型,通过计算获得舱内压力、速度、温度分布云图,进而分析得出拖拉机在工作时动力机舱内冷热流场分布情况。仿真结果表明:发动机舱内零部件布局合理,舱内气流平顺,无明显热流囤积,冷却系统各单体流场分布合理,为整车热管理系统的开发提供了相应的参考依据,也为拖拉机发动机舱前期开发提供了新的技术思路。

计算流体力学在冷库优化中的应用研究进展

对中国冷库的发展进行论述并列举冷库运行中存在的一些问题,对计算流体力学技术在冷库中的应用研究进行综述,介绍国内外该技术在冷库模拟中所取得的进展,尤其是如何使气流均匀、不同货物最适储存温度和湿度、货物储存中合适的堆码形式和堆码尺寸等方面的研究成果,并对今后计算流体力学技术在冷库中的进一步应用进行展望。

压力比对高压SF_6断路器喷口中冷态气流场影响的研究

为了辅助高压SF6断路器灭弧室的设计和优化,以拉法尔喷口结构为基础,对3种长度喷口结构下的冷态SF6气流场进行了数值计算和分析.通过对比压力与马赫数的变化特点,研究了上、下游压力以及喷口长短对气流场分布的影响.确定了3种长度喷口对应的临界压力比值,并着重分析了压力比与激波产生和运动之间的关系,讨论了物性参数所引起的计算误差.结果表明:不同长度的喷口结构,临界压力比不同,当上下游压力比低于临界值时,喷口中产生激波,反之则无激波产生;激波的位置随着压力比以及喷口的长度而变化;当喷口下游气体始终处于超音速流动时,出口压力与设定值无关,仅随着入口压力的增加而增大.此外,有效地导入气体属性能够降低数值仿真中的误差,提高仿真结果的精度.

中储式热风送粉W型火焰锅炉炉内空气动力场实验研究

针对引进美国FW公司的配备双旋风分离式煤粉燃烧器的W型火焰锅炉 ,在相似模化的基础上建立冷态模型 ,利用热线风速仪与示踪法测量了不同工况下炉内的空气动力场 ,得出了不同工况下炉内流场的矢量图、火焰长度、炉内主气流在炉深方向上的分布曲线以及主气流充满度变化曲线 ,通过实验结果对炉内空气动力特性进行了分析 ,研究结果表明 ,沿水平方向高速送入炉内的三次风对炉内空气动力特性有显著影响。

旋流燃烧锅炉炉内流场的数值研究

某电站2×600 MW机组锅炉采用了轴向旋流燃烧器,前后墙布置,对冲燃烧。为了更好地了解旋流燃烧锅炉的性能,采用数值模拟的方法对该锅炉炉膛内的流场进行了分析计算。结果表明:采用旋流燃烧器,在锅炉炉膛出口沿宽度的流场分布相对较均匀,仅在两侧速度稍大。另外停投不同层的燃烧器时,对炉内空气动力场及炉膛出口流场影响不大。

LPP低污染燃烧室冷态流场与油雾特性

为了研究某贫油预混预蒸发(Lean premixed prevaporized,LPP)低污染燃烧室冷态流场和油雾特性,本文采用粒子图像测速仪(Particle image velocimetry,PIV)首先试验研究不同进口空气流量对燃烧室冷态流场的影响,其次分别在单开值班级喷嘴、主级喷嘴以及同开主级和值班级喷嘴时,分析了燃油流量分配和值班级喷嘴位置对燃烧室油雾特性的影响。试验结果表明:在LPP燃烧室头部流场存在中心回流区、角落回流区和唇口回流区,中心回流区宽度随着距燃烧室头部距离的增加先逐渐增加,而后逐渐减少,且进口空气流量对燃烧室回流区形状影响不大;单开值班级喷嘴时,供油量增加,燃烧室油雾特性变差;单开主级喷嘴时,主级供油量增加,燃烧室油雾特性得到改善;主级和值班级喷嘴同时打开时,随着主级供油量增加,值班级供油量减少,燃油雾化特性得到改善;值班级喷嘴位于喉道处时燃油雾化效果优于值班级喷嘴在旋流器出口处。

环形中心钝体驻涡燃烧室进气方式研究

采用FLUENT软件对两种驻涡腔进气方式时环形中心钝体驻涡燃烧室的冷态流场进行了数值模拟,并对两种驻涡腔进气方式时环形中心钝体驻涡燃烧室驻涡腔内的旋涡结构、平均流动参数以及燃烧室总体性能等进行了对比分析。结果表明:两种进气方式时,环形中心钝体驻涡燃烧室驻涡腔内均能形成相对稳定的涡系结构,进气方式由后钝体中心逆流进气变为前钝体中心顺流进气时,驻涡腔内涡系结构由单对涡转变为双对涡;与后钝体中心逆流进气相比,前钝体中心顺流进气时,燃烧室总压损失系数、驻涡腔平均静压和总压分别增加约1.345%,8.207%和6.479%,驻涡腔平均速度降低约48.423%;驻涡腔进气方式的变化对燃烧室出口气流参数沿流道高度方向的变化趋势影响不大。