HFCVD衬底三维温度场有限元法模拟

热丝化学气相沉积(Hot filament chemical vapor deposition,HFCVD)方法制备金刚石薄膜设备简单,成本低廉,适合大面积金刚石膜的产业化生产,其中衬底温度是沉积高质量CVD金刚石膜的重要参数之一.基于此,首先分析大面积HFCVD系统的热交换过程,建立大面积HFCVD系统衬底温度场的三维有限元模型.与传统纯热辐射模型相比,本模型更加接近实际系统,并较好符合试验测定的结果.根据三维有限元模型开展对大面积HFCVD系统衬底温度场的有限元仿真研究,得到HFCVD系统衬底温度场的三维分布规律,并讨论热丝直径、热丝温度、热丝根数、热丝-衬底距离和水冷散热系数等对衬底温度大小及均匀性的影响.仿真结果表明,在适宜金刚石膜生长的参数范围内,热丝参数和衬底接触热阻对衬底温度大小有显著影响,由于衬底内部的三维热传导使得衬底温度场更加均匀,各参数对衬底温度场的均匀性影响不大.研究结果为高质量制备金刚石膜提供理论基础.     

Method for measuring thermal contact resistance of graphite thin film materials

Thermal contact resistance (TCR) is an important parameter in thermal analysis of materials. Because of many influential factors, it is difficult to find a general model or computational formula to calculate the TCR of a solid interface. In many engineering applications, TCR values are usually obtained through experiments. Unlike extensive research focusing on ordinary columnar materials, this paper aims at measuring the TCR values of graphite thin film materials. The technical challenge is that it is not convenient to embed thermocouples into such materials. To overcome this challenge, a steady-state method using a copper heat flux meter is developed, which provides a useful tool for indirect TCR measurement. In our experiments, the TCR values of the graphite thin film materials are successfully measured under different temperature and pressure levels. The results provide a valuable guideline for the use of this type of material in high-temperature, high-pressure applications.     

Experimental and CFD analysis of heat sinks with base plate for CPU cooling

Experimental and theoretical investigations of the thermal performance of a variety of heat sinks have been made. The heat sinks investigated were: straight finned, elliptical finned, small pin finned, circular disc finned, elliptical disc finned, frustum finned and double base straight finned. Realistic, manufacturable geometries are considered for minimizing thermal resistance at low velocity. The experimental results of several of the simple geometry heat sinks have been compared to those predicted by a commercially available computational fluid dynamics code fluent. The parameters such as fin geometry, fin pitch and fin height are optimized primarily in this paper and a second task is carried out to optimize base plate thicknesses, base plate materials and modify design of heat sink for improving the thermal performance in the next generation. Although the performance of heat sink is good, the temperature of heat sink at center is high. In this research work, the best heat sink geometry is selected and modified in order to reduce maximum temperature distribution and hot spots of heat sink at center by changing the geometry design and adding one more base. It is observed that flow obstructions in the chassis and the resulting air recirculation affect the heat sink temperature distribution.     

Calculation analysis of thermal loss and temperature field of in-wheel motor in micro-electric vehicle

To improve the efficiency and life of in-wheel motor in micro-electric vehicle, thermal loss and temperature field are calculated and analyzed. The mathematical model of thermal loss and temperature field was established, the equivalent model of stator winding was adequately handled, convection heat transfer coefficients was calculated, and the heat distribution of in-wheel motor was analyzed. Winding copper loss, stator and rotor core loss and eddy current loss of permanent magnet were calculated, which were coupled to the temperature field as the heat sources. This paper effectively simplified and dealt with the inner complex radiating coefficient. Three-dimensional finite element model of temperature field was established, and static and transient state temperatures were simulated and analyzed. Overall temperature of the stator region is higher than that of the rotor region. Temperature of stator iron core is basically accord with the temperature of equivalent insulating film, but both are less than the temperature of equivalent winding. The conformity of the measurement results with the final simulation results shows that three-dimensional finite element method is accurate and feasible to analyze thermal loss and temperature distribution of in-wheel motor, which can afford a theoretical basis to optimize the in-wheel motor.     

栅板式换热器的传热性能研究

建立了栅板式换热器板内流体流动的二维物理模型,通过数值模拟和冲渣水试验,分析了回收余热的栅板式换热器的传热性能。模拟了板间距和入口流速对流动和流阻的影响;试验测试了栅板式换热器的压降,分析栅板式换热器传热和流阻特性,并拟合出其传热和压降准则关系式。     

空调列车室内三维紊流流场和温度场数值模拟

基于计算流体动力学对某列车车厢内部的速度场与温度场的分布进行了数值模拟。采用稳态不可压缩雷诺平均N-S方程,紊流模型选择两方程模型,应用有限体积法计算了车厢内气固耦合传热问题。研究了送风方式和送风速度对空调列车室内流场的影响,以及送风温度对列车室内温度场的影响,为空调列车室内气流组织优化设计及舒适性研究提供依据。     

新型动静压混合润滑机械密封流场数值研究

以流体膜为研究对象,建立了新型动静压混合润滑密封端面的三维模型,并利用流体力学软件FLUENT对端面流场进行数值模拟,得出端面液膜的压力分布及速度分布.通过与静压和动压式密封对比,分析了操作参数(如封液压力、转速)对密封性能的影响规律.结果表明,该密封兼有动压与静压两种密封形式的特点,泄漏量小,液膜刚度大,适合于低速非接触密封.     

新型动静压混合润滑机械密封结构参数优化

以流体膜为研究对象,建立了新型动静压混合润滑密封端面的三维模型,并利用流体力学软件FLUENT对端面流场进行数值模拟,得出主要结构参数(动压槽深度、静压槽深度、动压槽宽比、静压槽宽比)对端面开启力、两侧泄漏量等密封性能的影响规律。通过分析得出各结构参数的大致范围,从而对新型动静压混合润滑机械密封结构进行了优化。     

基于热四极法的涂层刀具切削温度分布研究

为研究涂层在切削过程中对刀具温度分布的影响,建立了涂层刀具的三维瞬态热传导分析模型,发展了基于热四极法的切削过程涂层刀具三维温度场求解算法,得到了涂层刀具的瞬态温度分布。研究了涂层厚度、热对流以及界面热阻对涂层刀具切削温度分布的影响,为切削加工中涂层厚度的确定、切削液的选择以及涂层刀具的失效诊断提供了理论依据。     

3D Two-way coupled TEHD analysis on the lubricating characteristics of thrust bearings in pump-turbine units by combining CFD and FEA

The thermal elastic hydro dynamic(TEHD) lubrication analysis for the thrust bearing is usually conducted by combining Reynolds equation with finite element analysis(FEA). But it is still a problem to conduct the computation by combining computational fluid dynamics(CFD) and FEA which can simulate the TEHD more accurately. In this paper, by using both direct and separate coupled solutions together, steady TEHD lubrication considering the viscosity-temperature effect for a bidirectional thrust bearing in a pump-turbine unit is simulated combining a 3D CFD model for the oil film with a 3D FEA model for the pad and mirror plate. Cyclic symmetry condition is used in the oil film flow as more reasonable boundary conditions which avoids the oil temperature assumption at the leading and trailing edge. Deformations of the pad and mirror plate are predicted and discussed as well as the distributions of oil film thickness, pressure, temperature. The predicted temperature shows good agreement with measurements, while the pressure shows a reasonable distribution comparing with previous studies. Further analysis of the three-coupled-field reveals the reason of the high pressure and high temperature generated in the film. Finally, the influence of rotational speed of the mirror plate on the lubrication characteristics is illustrated which shows the thrust load should be balanced against the oil film temperature and pressure in optimized designs. This research proposes a thrust bearing computation method by combining CFD and FEA which can do the TEHD analysis more accurately.     

Simulation of the continuous casting process by a mathematical model

A computational three-dimensional (3D) heat transfer model has been developed and applied to calculate the temperature distribution and solid shell thickness profile of a continous cast slab in a steel plant. This developed model includes non-linear material properties of specific heat and thermal conductivity as well as phase changes during solidification. A general thermo-fluidmechanics computer program, PHOENICS, was employed to numerically solve the heat transfer equation with the associated source terms. The thermal profile and solid shell thickness calculated by mathematical model agree with those predicted by an industrial model and experimental measurements. The model could also be used to predict the optimum process parameters on casting speed, heat removal rates and associated water flow rates and roll force. These parameters could be monitored by suitable sensors and controlled through a feed back system that interfaced with the mathematical model and the sensors.     

大偏心下滑动轴承热弹流润滑状态及特性*

滑动轴承在大偏心条件下工作时，热效应及弹性变形使得油膜润滑状态发生变化，进而影响摩擦特性。为此建立耦合轴瓦弹性变形、轴颈轴瓦粗糙峰接触、油膜温度分布及黏温-黏压关系的滑动轴承混合润滑模型，采用有限差分法求解得到不同工况下油膜压力场、温度场分布，分析热效应及弹性变形对润滑状态转变及轴承各特性参数的影响；搭建实验台测量试件内表面温度分布，测试结果验证了计算模型的正确性。结果表明：大偏心时热效应和弹性变形使得油膜润滑状态出现转化；粗糙峰的接触使摩擦热增加，且在最小油膜处形成温度峰值；热效应和轴瓦弹性变形使得接触压力峰值集中在轴承两端，承载能力和摩擦力均有所下降。     

Study on the convection heat transfer coefficient of coolant and the maximum temperature in the grinding process

Grinding fluid is typically applied in order to achieve reduced surface grinding temperatures, improved workpiece surface integrity, and extended wheel life compared to that which can be achieved in the dry situation. This paper presents the results of an investigation concerned with methods to determine the value of the convection heat transfer coefficient. The work is based on the theory of fluid dynamics and heat transfer that are used to describe the heat transfers within the grinding zone under different grinding conditions. The simulation research is made by means of the FEM for the wet grinding temperature distribution, and the three-dimensional topology map of the temperature distribution is obtained. Temperature is measured with the clamped thermocouple in different grinding conditions. The experimental result is approximately suitable to the simulated result. The simplicity and accuracy of the method allow the application to a wide range of grinding regimes from shallow-cut to high-efficiency deep grinding.     

屏蔽套形变对环形间隙轴向流阻的影响研究

针对核主泵屏蔽电机中内冷回路上下支路流量分配的预测问题,研究了屏蔽电机定子屏蔽套变形规律及其对间隙环流轴向流阻的影响规律。采用有限元方法计算了内冷介质高压作用下定子屏蔽套轮廓的圆角沟槽状变形特征,并进行了实验验证。采用计算流体动力学方法研究了界面非圆轮廓形变对间隙流场的影响,通过变参数分析与数学拟合,建立了核主泵屏蔽电机定子屏蔽套形变后的间隙环流轴向流动阻力系数修正模型。该模型的计算结果表明,在屏蔽式核主泵的额定工作状态,驱动电机定子界面轮廓相较于理想状态存在11%的变形,这种变形会导致电机定转子间隙流动轴向沿程压降值下降到无形变间隙的83%左右。     

管侧流量分布均匀性对水平管降膜蒸发器换热的影响

研究水平管降膜蒸发器的管侧物流分配对总换热性能的影响,建立水平管降膜蒸发器水侧流动的湍流数学模型,并借助计算流体力学软件,对额定负荷为600 kW的水平管降膜蒸发器进行水侧速度场及压力场的模拟计算.计算结果表明,水侧的流量分配存在着严重的不均匀,从而产生不均匀的压力场,进而增大干斑的产生比例,恶化了传热.经过计算,流量...     

NUMERICAL SIMULATION OF FLOW FIELD BETWEEN FRICTIONAL PAIRS IN HYDROVISCOUS DRIVE SURFACE

The flow field of the oil film between frictional pairs in the hydroviscous drive test rig is investigated. A three-dimensional Navier-Stokes（N-S） equation considering viscous force and inertial force rather than Reynolds equation or modified Reynolds equation is presented to model the flow field. Pressure and temperature distribution in radial and circumferential direction under three different conditions, i.e., isothermal, that considering viscosity-temperature characteristic as well as shear thinning non-Newtonian fluid are simulated, respectively, by utilizing the commercial computational fluid dynamics（CFD） software FLUENT. The results reveal that the grooves on the driven plate make the pressure, temperature distribution present periodic variation. The oil temperature and shear rate have important effects on the flow field between frictional pairs, and the oil temperature is more important parameter. The simulation results lay a theoretical foundation for the reasonable designs ofhydroviscous drive.     

微管道散热器换热性能的有限元分析

利用伽辽金有限元公式计算了微管道散热器中的管道表面温度分布、流体温度分布及流动阻力系数和换热系数等。与现有的分析方法对比发现，利用有限元方法可对热负荷任意分布工况下的微管道散热器进行传热性能分析，而且使用范围比现行的大型CFD软件更广，也可用于分析微管道散热器的几何参数对散热器传热性能的影响。     

Thermometric design considerations for temperature monitoring in machine tools and CMM structures

Temperature measurement is an essential element in monitoring and studying the thermal deformation response of machine tools and CMM structures. In this context, temperature measurement is required for model verification, for control purposes and for determining the thermal contact resistance and other thermal boundary conditions. In these applications, where heat flux and temperature rise levels are relatively low, a proper thermometric design is a must to ensure accurate and precise results. This paper addresses the problem of thermometric design in the case of temperature measurement inside a solid body and on its surface. Results and recommendations regarding the interactions between neighbouring thermocouples, the effect of the distance between the thermocouple and the contact interface (i.e. the heat input surface), and the effect of heat flow along the thermocouple wires on the measurement error are presented. The issue of the effect of the unknown thickness and thermal conductivity of the surface paint on the uncertainty in surface temperature measurement is also addressed.     

承压热冲击瞬态下反应堆压力容器下降环腔内三维热工水力分析

以压水堆核电厂承压热冲击分析评定技术研究(PTS确定性分析方法研究项目)为背景,针对核电厂PTS瞬态下RPV下降环腔内热工水力分析问题,基于通用计算流体动力学软件Fluent,采用合适的对流换热分析和湍流模型,建立了RPV下降环腔内的三维热工流场分析模型,模拟分析RPV下降环腔内的三维流动与换热情况。重点模拟得到了RPV下降环腔内的三维流场分布和RPV内壁面的温度分布,并且在某些瞬态时刻得到了典型的热工水力现象即羽流(Plume)现象。得到的RPV下降环腔内详细的热工流场数据和羽流现象,为PTS下RPV应力分析和完整性提供了热工数据。