装载机管片式散热器流动与传热特性数值分析

应用CFD软件对装载机管片式散热器空气侧流场、压力场和温度场进行了CFD研究。根据不同的空气质量流速,采用k-ε湍流模型对空气流动阻力和散热器换热系数进行数值模拟。与试验结果相比,CFD分析的空气流动阻力和散热器换热系数的平均误差小于10%,计算精度较高,该CFD模型可直接用于工程设计。     

撞击流反应器的流场测量及数值模拟研究

为更好地了解撞击流反应器的流场特性,通过实验对撞击流反应器内流体的压力场进行测量,并使用数据采集系统应用脉冲-响应法对速度场进行测量.结果显示在撞击面的中心部分存在一个撞击区,此区域关于撞击面对称,基本上为轴对称,区域内压力较高而流速很低.围绕此区域有一个强烈湍动的区域,能够促进混合及反应的进行.同时使用FLUENT软件对反应器中的流场进行数值模拟,数值模拟结果与实验测量结果吻合较好.     

燃油锅炉配风器流动特性数值模拟研究

采用κ-ε模型,对配风器内回流区分布特性进行CFD模拟研究,以优化配风器结构,达到最优回流区分布.研究结果表明:入口角度减小,回流区尺寸减小,配风器沿程压损减小;入口速度降低,回流区尺寸减小,配风器沿程压损减小;压力增大,回流区尺寸增大,压损增大;流场温度增大,回流区增大,压损减小.     

纵向通风地下道路火区风压损失分析及应用

为了解决地下道路纵向通风系统设计中计算火灾工况下的火区风压损失问题,基于热力学平衡关系建立了火区风压损失模型,并得到了半经验计算公式,利用模型实验和数值模拟对公式的有效性做了初步验证,并以工程实例展示了火区风压损失对隧道内压力与风速分布的影响. 结果表明:在临界风速下,火区的风压损失与对流热释放速率成正比,与上游风速和隧道断面积成反比;提出的计算公式与隧道火灾实验拟合公式得出的规律一致且结果接近,具有明确的理论基础和风速取值;为使地下道路通风系统阻力计算准确可靠,进而制定有效的应急通风运行方案,有必要考虑火区的风压损失,提出的风压损失公式经深入验证后可用于设计计算.     

基于PMAC控制器的成型砂轮数控技术研究

分析以PMAC运动控制器为基础的任意母线砂轮修形机的原理和功能,借助PMAC中的驱动接口数据库Pcomm32PRO和执行程序PEwin32PRO开发工具,开发砂轮修改机的用户软件,在PLC程序支持下实现控制面板的快捷功能通过对PID参数的优化减少自身误差.试验证明,该系统可以实现砂轮的数控成型砂轮修形.     

纵向磨削砂轮堵塞的试验研究

本文研究了纵向外圆磨削中,工件转速,修速速度,走刀量,磨削厚度及冷却液对硝轮堵塞深度和而积的影响。初步探讨了纵磨时,砂轮堵塞的基本规律。     

Numerical computation and analysis of unsteady viscous flow around autonomous underwater vehicle with propellers based on sliding mesh

The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment, which realizes the multi-motion modes of the autonomous underwater vehicle (AUV) such as vectored thruster and wheeled movement. In order to study the interactional principle between the hull and the wheel propellers while the AUV navigating in water, the computational fluid dynamics (CFD) method is used to simulate numerically the unsteady viscous flow around AUV with propellers by using the Reynolds-averaged Navier-Stokes (RANS) equations, shear-stress transport (SST) k-w model and pressure with splitting of operators (PISO) algorithm based on sliding mesh. The hydrodynamic parameters of AUV with propellers such as resistance, pressure and velocity are got, which reflect well the real ambient flow field of AUV with propellers. Then, the semi-implicit method for pressure-linked equations (SIMPLE) algorithm is used to compute the steady viscous flow field of AUV hull and propellers, respectively. The computational results agree well with the experimental data, which shows that the numerical method has good accuracy in the prediction of hydrodynamic performance. The interaction between AUV hull and wheel propellers is predicted qualitatively and quantitatively by comparing the hydrodynamic parameters such as resistance, pressure and velocity with those from integral computation and partial computation of the viscous flow around AUV with propellers, which provides an effective reference to the study on noise and vibration of AUV hull and propellers in real environment. It also provides technical support for the design of new AUVs.     

波纹翅片管换热器空气侧流动换热的三维数值模拟

基于有限容积法建立波纹翅片管换热器流体流动与传热的计算模型,在不同送风速度工况下,分别对6种不同波纹倾角结构换热器内流体的流动及传热进行了数值模拟,分析了流道内的温度场、压力场及速度场的变化规律,得到了换热量、压降以及出口温度随入口风速变化的规律。结果表明,换热量、压降以及出口温度均随波纹倾角的增加而增大;换热量随着送风速度的加快而增加,压降及出口温度随着送风速度的加快而降低;翅片板间流体的流动与传热存在比较明显的不均性,导致换热管背风侧存在明显的传热"死区"。     

发动机叶栅的实验研究和数值预测

在暂冲式跨音速平面透平叶栅风洞上对某叶栅进行了吹风试验。通过数值预估实验叶栅流场,提供了流场大体结构,设计了实验方案。为选择压力传感器量程和布置测点位置提供了依据。实验测量得到了设计安装角及变工况下叶片表面压力、叶片表面等熵马赫教及波系结构随叶栅进口气流角的变化,并对叶栅内部及出口流场进行了纹影照相。数值预测与试验结果相比较,在大部分情况下,吻合得很好,说明了计算程序的可靠性。反过来,试验结果又可用于检验和改进N.S方程计算程序。     

达里厄风力机恶劣工况下气动特性的数值模拟

以一台具有三个叶片的达里厄风力发电机为例,分析了不同相位叶片的受力特点;基于Fluent软件,采用雷诺时均N-S方程和k-ωSST模型,结合MRF旋转坐标系技术对垂直轴风力发电机进行了二维数值模拟,研究了该垂直轴风力机的风轮扭矩的周期性变化规律,确定了一个旋转周期内的恶劣工况。通过对恶劣工况下不同来流风速和转速时的瞬态数值模拟获得了其流场特征。研究表明:叶片之间的干扰和风轮的气流泄露将在不同程度上影响风力机的性能,并模拟计算了增加叶片后的扭矩变化规律。     

并列行驶两辆汽车外流场的数值模拟

以国际标准的MIRA模型为研究对象,采用移动地面边界条件,对单车和两车并列行驶情况下的汽车外流场进行了数值模拟研究.将两辆车车体周围的速度分布、车身表面的压力分布情况与单车外流场进行了比较.在并列行驶情况下,车体周围的速度和车身表面压力分布与单车不同,呈不对称分布,并且在两车的内侧出现了低压区,两车具有相互靠近的趋势.通过计算,两车的气动阻力有所增加,侧向力有了很大程度的增加.     

液力变矩器泵轮内流场的数值分析

利用流体分析软件STAR CD对W305型液力变矩器内部流场进行了数值计算。采用混合平面理论处理旋转速度不同的各叶轮之间的相互作用。基于计算结果重点分析了泵轮内流场的特性,对泵轮进出口平面的速度和压力分布进行了研究,并与相关公开实验数据进行了定性对比,同时还对外特性进行了计算。将计算结果与试验数据进行对比表明了流场计算是十分准确的。     

蒸汽发生器致畸变入流对核主泵流动性能的影响

为了探究由蒸汽发生器（SG）引起的畸变入流对核主泵（RCP）流动性能的影响,采用计算流体力学方法,建立核主泵与下封头的联合计算模型;利用多参考坐标系模型和滑移交界面技术,开展运行工况下的全三维稳态和瞬态数值模拟;采用入流畸变度和平均偏流角公式定量表征畸变入流的流场速度分布,通过正则化螺旋度法捕捉核主泵叶轮的涡流流动特征. 研究结果表明：与均匀入流相比,畸变入流复杂化了核主泵进口流场,导致核主泵的湍动能和湍耗散增大,降低了主泵的水力效率;在泵的进口流场形成了明显的非对称分布的涡核区域,引起叶轮各流道流态产生差异,造成叶轮内部压力和速度分布不均;导致各流道流量分配不均,加剧叶轮受载波动;降低其运行的稳定性和安全性.     

发电机组流场数值模拟及优化分析

发电机组在运行过程中会产生较大热量,其散热性能不好会直接影响使用性能和寿命。文章以某发电机组为研究对象,采用流体力学计算方法,利用STAR-CCM+软件对其流场特性进行数值模拟分析。流场分析发现,机组内发动机各冷却风道风量分配不均匀和消声器局部区域存在速度死区,不利于散热。依据流场分析结果提出相应的结构优化方案,优化后机组发动机各冷却风道风量分配得到明显改善,消声器表面平均速度得到明显提升,不存在速度死区,变频器、定子及发动机表面速度分布更均匀。发电机组流场分析及优化结果为后续整机产品开发和系统级热管理匹配提供了参考。     

ELID镜面磨削热源和热量分配模型

针对ELID超精密磨削的特点，对ELID磨削热产生的机理进行了分析，建立了ELID磨削热源模型和热量在工件、砂轮、电解液及磨屑间分配的模型，并进行了数值计算，计算结果表明：ELID磨削热量主要由磨粒与工件的耕犁和摩擦作用产生，磨削热量在各部分的分配是随磨削区内位置改变的分布函数，电解液和砂轮带走绝大部分的磨削热量。     

中央扩散型精矿喷嘴空气动力学特性数值模拟

为了解决在加大给料速度时中央扩散型喷嘴生产过程中存在冶炼不完全、气粒混合不佳等问题,采用Fluent 6.3.26建立中央扩散型喷嘴控制模型,实验验证模型的有效性,仿真研究分散风和给料速度变化对喷嘴出口附近区域流场、颗粒运动轨迹和颗粒浓度场等的影响.结果表明:仿真模型可靠,最大误差为6.3%.工艺风气流占主导作用时,颗粒分布集中于反应塔中心;分散风可调节炉内颗粒的分散及分布情状况,工艺风和中央氧环形气流下方颗粒分布较多;相同工艺风和分散风条件下,给料速度对炉内颗粒分散和分布状况影响较小.     

Fundamental studies on enhancing heat transfer in contact zone during high efficiency grinding

On the basis of research on the thermal effect in grinding contact zone during high efficiency grinding, an idea of enhancing heat transfer in contact zone using high pressure water jet impinging is advanced. Fundamental heat transfer experiments on enhancing heat transfer with high pressure water jet impinging were completed. The maximum speed of jet impinging reaches 110m/s. The experimental results of transient and steady-state experiment prove that the critical heat flux and the heat-transfer coefficient of water jet impinging are 70 and 30 times those of the pool boiling, respectively. Furthermore, a new grinding fluid supply system was employed to enhance heat transfer in grinding zone by high-pressure water jet impingement during creep feed grinding. The experimental results show that high-pressure water jet impinging has remarkable cooling effect. The temperature of the workpiece surface can be steadily kept below 100℃, while the workpiece is badly burnt with conventional coolant supply. The stu     

缝洞型油藏裂缝-溶洞中流体运动特征研究

用数值计算和实验的方法研究单个裂缝-溶洞中单相流动问题.从流体运动基本方程出发,建立裂缝溶洞之间流动的数学模型,采用投影差分格式求解,得到流体在缝洞模型中流动时流场的分布规律,给出压力和速度的空间分布.数值模拟和实验表明:当溶洞足够大,裂缝到溶洞中流动与"射流"相似.     

影响钢坯修磨因素初探

以建立在磨削几何学分析之上的金属切除率数学模型为基础，分析讨论了磨削工艺参数（修磨压力、砂轮圆周速度。砂轮直径、工件进给速度）对金属切除率、磨削力比的影响，并对钢坯修磨机理进行了初步探讨，揭示了高效修磨的特点和规律．从而为提高钢坯修磨生产效率，降低修磨成本提供了理论参考依据．     

Development of an aero-thermal coupled through-flow method for cooled turbines

The influence of complicated interaction between the flow field and heat transfer in cooled turbines becomes more and more significant with the increasing turbine inlet temperature. However, classical through-flow methods did not take into account the influence of the interaction caused by air cooling. The aerodynamic design and cooling design of cooled turbines were carried out separately, and the iterations between the aerodynamic design and cooling design led to a long design period and raised the design cost. To shorten the design period and decrease the design cost, this paper proposes a concise aero-thermal coupled through-flow method for the design of cooled turbines, taking into account the influence of the complicated interaction between the flow field and heat transfer in cooled turbines. The governing equations, such as energy equation and continuity equation in classical through-flow method are re-derived theoretically by considering the historical influence of cooling with the same method that deals with viscous losses in this paper. A cooling model is developed in this method. The cooled blade is split into a number of heat transfer elements, and the heat transfer is studied element by element along both the span and the chord in detail. This paper applies the method in the design of a two-stage axial turbine, of which the first stator is cooled with convective cooling. With the prescribed blade temperature limitation and the knowledge of the flow variables of the mainstream at the turbine inlet, such as the total pressure, total temperature and mass flow rate, the convergence of the calculation is then obtained and the properties of the flow field, velocity triangles and coolant requirement are well predicted. The calculated results prove that the aero-thermal coupled through-flow method is a reliable tool for flow analysis and coolant requirement prediction in the design of cooled turbines.