Numerical Investigation on the Flow and Temperature Fields in an Inductively Coupled Plasma Reactor

This paper gives a numerical study on the flow and temperature fields in an induced plasma reactor, which worked in 0.5 ATM with air as a working gas. We employed a two-dimensional mode of an inductively coupled plasma to calculate the temperature and flow field of the reactor as well as the generator. The algorithm is based on the solutions of the two-dimensional continuity, momentum, and energy equations in term of vorticity, stream function and enthalpy. An upwind finite-difference scheme was adopted to solve those equations with appropriate boundary conditions. The computed results show that there is a flat region with little parameter change in the reactor, that the diameter of the region is not much larger than that of the generator and that a deep change of parameter exists in the outer side of the region.

Fluid Flow and Solidification Simulation in Beam Blank Continuous Casting Process With 3D Coupled Model

Based on turbulent theory, a 3D coupled model of fluid flow and solidification was built using finite difference method and used to study the influence of superheating degree and casting speed on fluid flow and solidification, analyze the interaction between shell and molten steel, and compare the temperature distribution under different technological conditions. The results indicate that high superheating degree can lengthen the liquid-core depth and make the crack and breakout possible, so suitable superheating should be controlled within 35℃ according to the simulation results. Casting speed which is one of the most important technological parameters of improving production rate, should be controlled between 0. 85 m/min and 1.05 m/min and the caster has great potential in the improvement of blank quality.

Coupled Modeling of Electromagnetic Fleld,Fluid Flow,Heat Transfer and Solidification During Conventional DC Casting and Low Ftequency Electrmagnetic Casting of 7xxx Aluminum Alloys

A comprehensive mathematical model has been developed to describe the interaction of the multiple physics fields during the conventional DC casting and LFEC (low frequency electromagnetic casting) process. The model is based on a combination of the commercial finite element package ANSYS and the commercial finite volume package FLUENT, with the former for the calculation of the electromagnetic field and the latter for the calculation of the magnetic driven fluid flow, heat transfer and solidification. Moreover, the model has been verified against the temperature measurements obtained from two 7XXX aluminum alloy billets of 200mm diameter, cast during the conventional DC casting and the LFEC casting processes. In addition, a measurement of the sump shape of the billets were carried out by using addition melting metal of Al-30%Cu alloy into the billets during casting process. There was a good agreement between the calculated results and the measured results. Further, comparison of the calculated results during the LFEC process with that during the conventional DC casting process indicated that velocity patterns, temperature profiles and the sump depth are strongly modified by the application of a low frequency electromagnetic field during the DC casting.

Study on application and numerical simulation of the airflow temperature distribution rule in drifting tunnel

According to the law of conservation in the state of turbulent flow, the differential equation describing the airflow temperature distribution in drifting tunnel is derived, By theoretical analysis and field measurement of the airflow and thermal process in mine, theoretical analysis and systematic flow are developed. By PHONENICS program, the numerical simulation is processed, and the changing rule of airflow temperature with various parameters in drifting tunnel is derived. The airflow temperature in drifting tunnel decreases as the airflow velocity increases in a way of negative power exponent, and elevates linearly as the temperature of the incoming airflow elevates.

Design and Enhancement of Thermal Flow Characteristic in an Annular Diffuser under Turbulent Flow

The annular diffuser is an expansion area, which, despite its simple structure, is very important in some engineering and thermal applications. In the present research, numerical simulations were performed to investigate the temperature field and flow structure characteristics in an annular diffuser. The hub of the annular diffuser consisted of a straight semi-dimpled tube SSDT. Three different diffuser wall angles (α) 1.8°, 3.6° and 5.4° with inlet Reynolds number 1.5 × 104?were studied in details with air as a working fluid. The computational fluid dynamics CFD was used to simulate the model in a turbulent flow. The standard k-ε turbulence model was used to complete the governing equations. The numerical results, mainly the temperature distribution, pressure drop and velocity distribution for the airflow in the annular diffuser fitted with SSDT for different diffuser wall angles α were obtained and compared. It was observed that as the wall diffuser angle α increases, the enhancement of the temperature distribution and the velocity distribution decrease while the pressure drop rate increases. The maximum temperature distribution and velocity distribution were completed by diffuser wall angle α1 = 1.8° whereas, the highest pressure drop achieved by diffuser wall angle α3 = 5.4°.

NUMERICAL SIMULATION OF MOLTEN POOL AND CONTROL STRATEGY OF KISS POINT IN A TWIN-ROLL STRIP CASTING PROCESS

Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten pool, corresponding control strategy is also proposed.

Development and application of coupling model of aluminum thin-gauge high-speed casting

Based on the analyses of aluminum melt flow, solidification, heat transfer during the process of twin-roll casting, a coupling mathematical model of aluminum thin-gauge high-speed casting was developed, which included the casting roller shell. At the same time, Galerkin method was adopted to solve the coupling model. The fluid field and temperature field of aluminum melt in casting zone, the temperature field and thermal stress field of roller shells were simulated by the coupling model. When the casting velocity is 7m/min, and the thickness of strip is 2mm, the circumfluent area comes into being in the casting zone, and the mushy zone dominates the casting zone, while the temperature of melt decreases rapidly as it approaches the rollers. The temperature of the roller shell varies periodically with the rotation of roller, and reaches the highest temperature in the casting zone, while the temperature of roller shell decreases gradually as it leaves the casting zone. The difference of thermal stress between the inner surface and outer surface of the roller shell is very large, and the outer surface suffers tensile-compressive stress.

致密气井筒热流耦合高压气水两相温度场动态特性

分析井筒气水两相管流温度的动态分布对保障致密气井连续稳定安全开采和实现智能计产具有重要意义。综合井筒流体、油管、环空、套管、水泥环和地层之间热流耦合传热,将井筒流体的焓、焦耳-汤姆逊系数、温度梯度、传热速率等热力学和两相流动力学进行统一,提出适用于致密气井筒气水两相流态温度场分布预测方法,从而通过数值模拟和井场测试更全面和准确地分析致密气井筒温度分布随产量、管径、地层温度、导热率等动态变化情况。结果表明:在气水两相流热耦合作用下,提高致密气井产量、缩小油管内径、提升地层温度和降低地温梯度会增大井筒内单位质量流体承载的热量,并有助于井筒保温和有效抑制水合物的生成,且深井处井底温度的影响较大;改变油管、环空和套管以及水泥环导热率会影响井筒传热系统的总热阻、松弛距离与无因次时间,并改变井筒整体温度的分布;与产量和地层温度相比,总传热系数对井筒温度的影响较小。

基于电-热流场双向耦合的直流继电器温升特性仿真研究

高压直流继电器体积小、散热能力有限,长期工作下存在局部过热的风险,发热严重时甚至影响到接触稳定性和继电器工作寿命。针对200 A直流继电器,综合考虑导体回路通电下欧姆损耗发热,在大空间的自然热对流、热传导以及热辐射、材料电阻率随温度变化等因素,建立继电器在额定工况下电-热流场双向耦合模型,设置电阻率随温度变化函数,进行耦合计算。最后,搭建对应的样机测温平台,对仿真正确性进行验证。结果表明双向耦合结果比单向耦合结果高约5.1%,与实验测量值误差小于6.2%,验证了电热流场双向耦合的有效性。

油气输送管道甜腐蚀传质规律

含CO_(2)的“甜”腐蚀已成为油气输送管道面临的重要问题。为预测和防范腐蚀危害,很多一维腐蚀预测模型被提出。但这些模型对于管内复杂流动的考虑不足。为此本文构建了多场耦合有限元模型,讨论输送管道中的腐蚀传质规律。综合考虑CO_(2)水溶液中化学反应、腐蚀电化学反应及腐蚀产物形成的过程,电化学腐蚀的模型被耦合在流动计算中,从而模拟研究直管流动中CO_(2)腐蚀传质。结果显示管内流动腐蚀的传质边界层厚度小于流动边界层的1/10,流动增大了腐蚀传质速率,形成高流动腐蚀速率。流动腐蚀下,管道表面H+并未完全消耗。这使得腐蚀传质中H+舍伍德数(Sh)随雷诺数(Re)的变化在不同pH下规律不同。考虑管内的实际流动,研究得到预测油气管道流动腐蚀的传质经验关联式。

基于声学层析成像的温度场和流速场重构

为有效重构三维管道内液体的温度场和流速场,提出了一种超声飞渡时间计算表征,并基于此求解温度场和流速场反演模型。同时考虑温度梯度导致的声线弯曲效应,采用正四面体前向展开法,追踪超声弯曲路径;开展“华龙一号”反应堆主管道冷却剂温度场和流速场重构实验。实验结果表明,所提方法能有效重构管道冷却剂温度场和流速场,且考虑弯曲效应能进一步提高重构精度。

冶炼电孤炉多物理场耦合仿真分析及结构优化

针对某项目贵金属冶炼电炉耐火材料损耗过快,极大影响生产效率的问题,通过构建三维多物理场耦合仿真模型,对电弧炉内电磁场和温度场进行模拟分析,明晰冶炼电弧炉内的传热机制并优化其水冷设计。通过Maxwell与Comsol两种电磁场仿真软件计算结果的对比,保证了计算的准确性。仿真结果表明,熔池电极以上部分,电极两侧磁感应强度最大,由内向外逐渐减小;熔池电极以下部分,磁感应强度由内向外逐渐增大。加热功率密度主要集中在电极区域,熔池内加热功率约占总加热功率的98%,炉壁温度随炉壁与熔池距离的增加而逐渐减小。针对铜水套上部外壁面温度过高的问题,提出了优化铜水套设计的解决方案。通过增加相邻铜水套之间的距离,炉壁局部过高点温度由452℃降低为277℃,水套冷却水进出口温差增大了9.45%,降低了耐火材料消耗,提高了生产效率。

基于CEL模型的AZ91D镁合金搅拌摩擦焊材料流动行为数值模拟

基于耦合欧拉-拉格朗日(CEL)方法,利用Johnson-Cook本构模型建立了AZ91D镁合金搅拌摩擦焊热力耦合有限元模型。利用粒子示踪技术并结合温度场、应变场和欧拉场探究了焊接过程的材料流动行为。结果显示,高温区域位于后退侧的搅拌针后方,焊核区后退侧的温度高于前进侧约40℃;峰值温度随旋转速度的增加和焊接速度的减小而升高,高温区域面积也相应增加;焊接速度对峰值温度的影响小于旋转速度;等效应变场与温度场的分布规律基本一致,高温区域塑性应变相应较大。轴肩影响区的材料在轴肩的挤压及剪切共同作用下在后退侧形成飞边。焊核区材料从搅拌针前方移动到后退侧,并在前进侧搅拌针后方完成回填。当旋转速度增加到950 rpm时,热输入过高,材料流失,会在前进侧底部形成隧道缺陷。

50MVar凸极调相机冷却技术研究与创新

近期研制的新型分布式凸极调相机,转子热负荷大幅超出设计经验范围,若沿用常规散热方式,热点温度将远超绝缘耐热限值,不能满足技术要求。本文提出该电机转子空内冷技术解决方案,并通过开展三维热-流场仿真、转子全电流温升试验等研究,消除了重大技术风险,为产品研制提供了关键技术保障。

掘进巷道风流温度分布规律的数值模拟

根据紊流状态下的守恒原理 ,导出了描述掘进巷道风流紊流流动和温度分布的微分方程。通过对矿内风流流动及热力过程的理论分析及现场实测 ,系统地开展矿内风流流场和风流温度场的分布规律及其耦合作用机理的理论分析与研究 ,并利用PHOENICS程序进行数值模拟 ,初步得出了矿井掘进巷道风流温度与各种参数的变化规律。掘进巷道风流温度随风速提高呈负幂函数规律降低 ,随入风流温度升高而线性升高。

工作频率及装置结构对射频感应等离子体特性影响的数值研究

为研究射频感应等离子体(RFICP)受等离子体发生器装置结构及工作频率的影响效应,以期可以为装置的正常工作提供参考,首先建立了射频感应热等离子体的湍流模型,然后利用商业软件ANSYS FLUENT对等离子体发生器装置内的纯氩气热等离子体温度及流场分布进行了计算,并研究了工作频率及装置结构的变化对射频感应等离子体传热及流动特性的影响。研究结果表明:提高装置的工作频率、增大等离子体炬内半径、增加射频线圈匝数并减小两匝线圈间距均能使发生器装置内的等离子体轴向速度减小,等离子体温度显著增加,并对等离子体炬内的流场分布产生较大的影响。因此可以通过改变相应的装置结构及工作频率来控制等离子体发生器装置内的温度和流场分布,以便使装置能够稳定运行。

空调客车室内三维紊流流动与传热数值研究

空调车室内空气的速度场、温度场研究是空调车室内气流组织设计及车室内舒适环境评价与研究的基础．空调客车运行环境恶劣，太阳辐射作用及复杂的车室内部结构等直接影响客车室内的温度场与空气速度场分布．采用κ－ε紊流模型及贴体坐标，应用整体求解法计算了空调车室内气固耦合传热问题，采用ＭｏｎｔｅＣａｒｌｏ法分析计算了太阳透射辐射在车室内各固体表面引起的附加热流变化，并以此作为能量方程的附加源项，对空调客车室内三维空气流场与温度场分布进行了数值模拟研究。

掘进巷道风流温度场分布规律的研究

从质量、能量和动量守恒原理出发,导出了描述掘进巷道风流紊流流动和温度分布的微分方程。通过理论分析和现场实测,系统地开展矿内掘进巷道风流流场和风流温度场的分布规律及其耦合作用机理的理论分析研究,并采用SIMPLE算法、利用PHOENICS程序进行数值模拟,初步得出了掘进巷道风流温度随风速提高呈负幂函数规律降低、随入风流温度升高而线性升高的变化规律,对矿井掘进工作面高温治理具有一定的指导意义和使用价值。

基于耦合场的金属氧化物限压器的温度计算与特性分析

为改善金属氧化物限压器(MOV)本体结构的散热能力,利用有限体积法,建立了用于MOV本体冷却结构流场、温度场直接耦合计算的3维分析模型。建立了简化的验证实验模型,计算了其流场、温度场,并通过实验验证了计算结果的准确性。在此基础上,对影响MOV温度特性的主要因素进行了分析。结果表明:在t<300s时段内,对MOV冷却结构起主导作用的是金属导电环的传导散热,加大入口风速对MOV散热效果的影响并不明显,增大冷却通道半径反而消弱了导电环的传导散热能力;在满足约束条件的前提下,增加导电环的厚度,选用热导率大的金属材质,可以得到更好的散热效果;在t>300s时段内,对MOV冷却结构起主导作用的是对流换热,加大入口风速和增大冷却通道半径可明显增强MOV的冷却效果。

3MW双馈风力发电机传热特性数值研究

随着风力发电机容量的增加,电磁负荷不断提高,电机的发热问题成为影响机组性能和经济指标的主要因素之一。为了解决该难题,以一台3MW双馈风力发电机为例,根据流体力学以及传热学理论,结合发电机通风性能以及结构特点,建立了发电机三维流动与传热耦合求解的数学模型与物理模型;并给出基本假设与相应的边界条件,采用有限体积法对三维流体场和温度场控制方程进行耦合计算。最后,对发电机内部的流体流动性能、传热特性以及发电机定转子铁心、定转子绕组以及绝缘的温升分布进行了分析,得到端部气体流动不规律以及二次冷却热能力较强等,为更大容量风力发电机综合物理场的准确计算提供了理论依据。