NUMERICAL ANALYSIS ON THREE-DIMENSIONAL FLOW FIELD OF TURBINE IN TORQUE CONVERTER

Three-dimensional flow field of turbine in torque converter is simulated by numerical calculation in order to improve the performance of torque converter. Calculation model of a torque converter is presented based on the mixing-plane technology. In the calculation of flow field, the 3D N-S equations are separated by finite-volume method and solved by semi-implicit method for pressure-linked equations（SIMPLE）. Based on flow field calculation, the flow field of turbine is simulated. The velocity and pressure in the flow field of turbine are analyzed. The external performance of the torque converter is also calculated. Results of flow simulation show that there are secondary flow, off flow and velocity gradient in turbine passage. The validity of numerical simulation is verified by comparing the results of numerical simulation with experiment data.

EXPERIMENTAL INVESTIGATION FOR THE EFFECT OF ROTATION ON THREE-DIMENSIONAL FLOW FIELD IN FILM-COOLED TURBINE

An experimental investigation of three-dimensional flow field in a film-cooled turbine model is carried out by using particle image velocimeter （PIV） in a low-speed wind tunnel. The effects of different blowing ratios （M=1.5, 2） on the flow field are studied. The experimental results reveal the classical phenomena of the formation of kidney vortex pair and secondary flow in wake region behind the jet hole. And the changes of the kidney vortex pair and the wake at different locations away from the hole on the suction and pressure sides are also studied. Compared with the flow field in stationary cascade, there are centrifugal force and Coriolis force existing in the flow field of rotating turbine, and these forces bring the radial velocity in the jet flow. The effect of rotatien on the flow field of the pressure side is more distinct than that on the suction side from the measured flow fields in Y-Z plane and radial velocity contours. The increase of blowing ratio makes the kidney vortex pair and the secondary flow in the wake region stronger and makes the range of the wake region enlarged.

Semi-Automatic Modeling Technique of Torque Converter Flow Passage

The modeling technique of hydrodynamic torque converter flow passage was investigated. The semi-automatic modeling technique of torque converter flow passage was proposed. The flow passage model of each converter wheel is considered as a revolution entity sliced by two curved surfaces. In order to generate the revolution entity, a new approximation method, condition optimum arc approximation, was proposed. The method was used to approximate the meridional streamlines of the inner and outer wall. As a result, the three-dimensional revolution entity can be conveniently generated. In order to create slice surfaces, the central stream surface of flow passage was approximated with a quadric surface. The normal vector of the quadric surface and the thickness/thickness-function of bade were used to calculate the discrete point coordinates of blade surfaces. Via the rotation transformation to the coordinates, the discrete point coordinates of slice surfaces were obtained. A parameterized program code used for the hydrodynamic torque converter design and semi-automatic modeling was developed. Modeling errors were calculated and analyzed. The flow passage model was generated in several minutes with the help of the program code, Auto CAD and Solidworks software. Finally, the model was inputted into Gambit, and the pre-processing task used for the numerical simulation of torque converter flow field was successfully completed. The investigation results show that the semi-automatic modeling not only can ensure the accuracy of modeling, but also librates the research and design workers of torque converter from the time-consuming modeling work, which paves the way for the numerical simulation of the complex flow field of the hydrodynamic torque converter.

SYSTEM FOR TORQUE CONVERTER DESIGN AND ANALYSIS BASED ON CAD/CFD INTEGRATED PLATFORM

A 3D torque converter design system is developed based on numerical investigation into flow field and CAD technology. The 3D steady-state flow field simulation is undertaken by using time averaged Reynolds equation and k-epsilon turbulence model, with mixing-plane boundary conditions at three section interfaces. The blades are designed according to the flow field characteristics by using a reverse design method in the system. The accurateness of numerical analysis and the validity of design system are verified by the fluid field experiment of desingn example of the torque converter. This kind of design and analysis system for torque converter based on integration of comput ationol fluid dynamics （CFD） and CAD is a powerful tool for torque converter manufacturing, but also a prettg important significance for research and development.

Characteristic size research of human nasal cavity and the respiratory airflow CFD analysis

To study the airflow distribution in human nasal cavity during respiration and the characteristic parameters for nasal structure, thirty three-dimensional, anatomically accurate representations of adult nasal cavity models were reconstructed based on processed tomography images collected from normal people. The airflow fields in nasal cavities were simulated using the fluid dynamics with the finite element software ANSYS. The results showed that the difference of human nasal cavity structure led to varying airflow distribution in the nasal cavities and the main airflow passed through the common nasal meatus. The nasal resistance in the regions of nasal valve and nasal vestibule accounted for more than a half of overall resistance. The characteristic model of nasal cavity was extracted based on the characteristic points and dimensions deducted from the original models. It showed that either the geometric structure or the air-flow field of the two kinds of model was similar. The characteristic dimensions were the characteristic parameters of nasal cavity that properly represented the original model in research for nasal cavity.

Three-dimensional flow field simulation of steady flow in the serrated diffusers and nozzles of valveless micro-pumps

This paper presents a three-dimensional flow field simulation of the steady flows through diffusers and nozzles with straight or serrated-sided walls to analyze the effect of the channel structure on the flow characteristics.The pressure and velocity profiles in the diffusers and the nozzles as well as the net volumetric flow rate are determined.Our simulation demonstrates that the pressure and velocity profiles in the serrated diffuser/nozzles are more complicated than those with the straight-sided wall,while the net steady flow rate with the straight-sided wall increases monotonically with the increase of the pressure difference,the steady flow rate with serrated sided walls increases gradually to reach a maximum and then decreases with the increase of the pressure difference.The results suggest that the number of the sawteeth plays a significant role in optimizing the design of serrated diffusers and nozzles for improving the transport efficiency of valveless micro-pumps.

内外液流通道筒式磁流变制动器制动性能分析

针对传统磁流变制动器磁场利用率不高的问题,提出了一种具有内外液通道的筒式磁流变制动器;通过在缸筒和旋转套筒中增设非磁性器件,使得磁力线蜿蜒通过内外轴向液流通道的6段有效阻尼间隙,从而使该制动器在外形尺寸不变的前提下能产生较好的转矩性能;阐述了内外液流通道筒式磁流变制动器的结构和工作原理,并对有效阻尼间隙在磁场作用下的磁路进行分析;同时推导建立了制动转矩和温度场数学模型;基于COMSOL软件对磁流变制动器电磁场和温度场进行了仿真分析。由电磁场仿真可知,在外加电流为2.0 A、转速400 r/min时,制动转矩可达101.96 N·m,转矩动态可调范围由1.00增加至29.69;由温度场仿真可知,在多次紧急制动下最高温度为42.88℃,符合磁流变液正常工作范围。

EXPERIMENTAL MEASUREMENT AND NUMERICAL SIMULATION FOR FLOW FIELD AND FILM COOLING EFFECTIVENESS IN FILM-COOLED TURBINE

Numerical simulation of three-dimensional flow field and film cooling effectiveness in film-cooled turbine rotor and stationary turbine cascade were carried out by using the k- ε turbulence model, and the predictions of the three-dimensional velocities were compared with the measured results by Laser-Doppler Velocimetry （LDV）. Results reveal the secondary flow near the blade surface in the wake region behind the jet hole. Compared with the stationary cascade, there are the centrifugal force and Coriolis force existing in the flow field of the turbine rotor, and these forces make the three-dimensional flow field change in the turbine rotor, especially for the radial velocity. The effect of rotation on the flow field and the film cooling effectiveness on the pressure side is more apparent than that on the suction side as is shown in the computational and measured results, and the low film cooling effectiveness appears on the pressure surface of the turbine rotor blade compared with that of the stationary cascade.

基于剪切-挤压模式的磁流变制动器流动与传动性能分析

针对现有加压式磁流变制动器结构复杂的问题,提出一种利用楔形间隙自挤压强化的盘式磁流变液制动器。此制动器通过在转子壁面上布置4个矩形槽的结构,利用矩形槽与圆盘面之间的间隙产生的挤压力对磁流变液进行挤压,使它在提高工作性能的同时,结构更加紧凑。基于有限单元法对磁场进行分析,得出不同电流下磁流变液的磁学与力学性能;基于计算流体动力学对磁流变液进行流场分析,得到挤压应力沿周向分布的云图;基于Navier-Stokes方程和挤压强化模型,推导出磁流变液的流动方程,并得到制动器产生的转矩与电流、液体挤压应力的关系。结果表明:楔形间隙使得液体挤压应力产生周期性的变化,磁流变液在挤压强化后,剪切屈服应力显著增加,当输入电流为2.0 A时,磁流变液剪切屈服应力最大值为67.7 kPa,制动转矩为24.8 N·m,相较于未挤压状态,制动转矩提升了约46.2%。

基于粒子图像测速技术的液力变矩器涡轮内流场测试与分析

液力变矩器是自动变速器的主要部件,其在乘用车、载重汽车、公共汽车和机车上的应用广泛。液力变矩器内部流动特性影响其外部性能,为了深入研究其内部流动特性,基于粒子图像测速(particle image velocimetry,PIV)技术对液力变矩器涡轮内流场进行试验研究。采用帧频为1 000帧/s的CCD高速相机,在不同工况下(输入与输出的转速比分别取0、0.3、0.5、0.7)采集不同粒子直径、不同粒子浓度下的流动图像,经过图像预处理,对连续两帧图像进行互相关计算,获得涡轮径向切面的速度场和涡量场。通过对流场分布结构和流动区域上复杂流动现象的对比分析,发现投入流场中粒子浓度越高(1 500mL蒸馏水中投入2.4 g粒子)、粒子直径越小(10μm)时,识别并提取流动区域上的流动参数越丰富,流速场和涡量场信息越可靠。液力变矩器内部高梯度流场分布结构和非均匀流速场分布导致出现多尺度涡旋和反向流等复杂流动现象,造成液力变矩器内部流动能量损耗,随转速比提高,涡轮流场结构趋于规律,能耗逐渐降低。该文试验测量与分析结果对于液力变矩器结构优化和性能提升提供了参考。

液力变矩器导轮流场数值模拟与试验

利用CFD分析软件对W305型液力变矩器的内部流场进行了仿真计算。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。基于仿真计算结果,重点分析了导轮内流场的速度和压力分布情况,并将导轮内流场计算结果与试验结果进行了对比分析,结果表明流场计算结果具有较高的精度。

基于Fluent的液力变矩器内流场数值计算

为了找出影响液力变矩器传动效率的原因,为进一步改善变矩器的性能和设计制造水平提供理论依据,通过Fluent对变矩器内流场进行数值模拟。采用分离求解器,绝对速度方程,标准k-ε模型,标准壁面函数,二阶迎风离散格式,SIMPLE算法,压力进口和压力出口,并使用混合平面模型。通过数值计算,得到了不同工况下内流场的分布情况,并计算出变矩器的原始特性,最后将计算结果与实验结果对比,最大误差不超过5%,证明了三维计算的正确性。

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。

椭圆底封头十字形挡板搅拌釜内流场研究

以底部椭圆形封头十字形挡板搅拌反应釜为研究对象,采用Fluent软件分析搅拌桨流型、离底高度、直径、底部加装挡板及其高度和长度对该搅拌釜内流场的影响,利用标准k-ε湍流模型对其在单相流体水中产生的流场进行模拟。开展搅拌轴转矩的试验研究,并与模拟值进行对比。研究表明,径向流搅拌桨更适合于底部加装挡板搅拌釜流场的研究。与六直叶圆盘涡轮搅拌桨相比,六直叶开启涡轮搅拌桨更有利于反应釜内物料的悬浮及混合。搅拌桨离底高度取0.7倍液面高比0.6倍更合适。搅拌桨直径越大,轴向速度越大,反应釜中心部位形成的螺旋向上轴向流越明显。在十字形挡板高度或长度固定时,搅拌桨下部区域中心部位的轴向速度比其他部位大,搅拌釜内上桨、下桨叶区将形成一个循环。同等条件下,随着搅拌转速不断增大,搅拌轴转矩随之增大。搅拌轴转矩的模拟值与试验值的相对误差在10%左右,两者具有很好的一致性。

基于三维流场计算的液力变矩器特性预测方法

为了改进液力变矩器特性计算方法,应用CFD软件对液力变矩器内流场进行数值计算,根据得到的内流场速度与压力信息,计算液力变矩器叶轮转矩,得到变矩器性能参数,从而预测所设计变矩器性能.为验证性能预测准确性,将W350液力变矩器基于三维流动数值解的性能计算结果与试验结果进行对比、分析,二者在数值上有良好的吻合,表明基于三维流场数值解的液力变矩器特性预测方法比传统的一维束流理论预测精确度更高,可以应用于工程实际.

液力变矩器泵轮流场数值分析

应用计算流体动力学 (CFD)方法 ,采用非结构网格和稳态交互面技术 ,模拟了液力变矩器三维内流场 ,并与试验相对照 ,验证了数值模拟的正确性。分析了泵轮进口、中弦面、出口面速度场和压力场 。

液力变矩器流道网格生成及内流场数值分析

采用映射法划分变矩器流道网格,利用流体分析软件FLUENT对YB-200型液力变矩器内部流场进行仿真研究,湍流模型选择标准k-ε模型,较精确地得到了速度、压力分布,最终计算出变矩器的叶轮轴转矩。计算结果与试验数据相符合,表明数值分析对变矩器的优化设计具有指导意义。

不同扁平率无内环液力变矩器设计与性能分析

提出一种扁平化无内环液力变矩器,研究不同扁平率和有无内环对其性能的影响。采用基于椭圆的扁平循环圆设计方法,设计3种不同扁平率的无内环循环圆且叶形为空间扭曲的扁平化液力变矩器。利用CFD软件对不同扁平率的无内环变矩器进行数值模拟,分析了内部流场的压力和速度分布,得到了扁平率和有无内环对变矩器流场和性能的影响规律。

基于CFD的液力变矩器内部流场分布特征研究

为提升液力变矩器性能,需要进一步研究液力变矩器内部流动,获取流动特征规律。针对某型液力变矩器进行不同速比下内部流场的CFD数值模拟,并分析其流动现象,得出该变矩器内流场中流动状态的速度、漩涡的分布规律。结果表明,流体的相对速度随速比升高有下降趋势,漩涡结构随速比增大而增大。相同速比下,不同叶轮中、不同弦面的流体出现不同类型二次流。通过CFD研究发现二次流主要出现在泵轮和导轮中,其中叶轮进出口处漩涡湍动能较高,能量损失较大。流场分布规律研究可以指导液力变矩器设计,使流场分布合理并且减少二次流等现象,对提高液力变矩器的效率有重要意义。

越野车液力变矩器流场分析与实验研究

为深入了解液力变矩器内部流场,提高工作效率,利用CFD软件对越野车W 305液力变矩器流场进行数值计算.基于计算结果,分析了液力变矩器各工作轮流场特性,研究其流场分布规律,力求找到影响液力变矩器效率的因素.为验证CFD计算准确性,利用激光多普勒测速系统(LDA)对导轮流场进行测试.将计算结果与实验结果进行对比分析,并与理论计算相比较,表明流场计算结果准确、可靠,CFD计算可以指导液力变矩器的设计.