轮胎噪声仿真分析专用球声源的研制

介绍轮胎噪声重放专用球声源的研制。球声源系统硬件包括扬声器、功放电路和电脑。扬声器球壳上均匀分布小孔,球体外部声场的波阵面呈球面波,声波无指向性,球面上声源的辐射声级基本相同。本研制专用球声源结构简单,实用性强,性价比高,在轮胎噪声测试分析中具有较高的应用价值。     

三通管二维湍流数值模拟

正确计算出三通管内流体交汇附近的流场、温度场和压力场的分布情况,对于管路的设计具有重要作用。本文以石油工业中常见的三通管为例,应用计算流体力学(CFD)技术,研究三通管管内流体各个流态参数,使用了FLUENT软件的标准k-ε模型对管内流体进行了二维模拟。在此过程中采用了不同流体介质和不同状态参数,并对模拟结果进行了分析,得出了用FLUENT进行模拟,效果良好。     

给水排水过程中三通管湍流数值模拟

正确计算出三通管内流体交汇附近的流场、温度场和压力场的分布情况,对于管路的设计具有重要作用。以给排水暖通常见的三通管为例,应用计算流体力学技术,研究三通管管内流体各个流态参数,使用了FLUENT软件的标准模型对管内流体进行了二维模拟。在模拟过程中采用了水的状态参数,得到了相应参数下三通管内流体交汇处的流场,温度场,压力场的分布情况。     

环氧乙烷装置T形三通管件故障原因分析与改进

环氧乙烷（EO）是重要的石化产品,该产品易燃易爆,同时也是一种有毒的致癌物质。山东某化工厂EO生产装置T形三通管件材料与焊缝质量合格、管内介质无腐蚀性,但是频繁出现裂纹故障导致介质泄漏。T形三通裂纹故障原因不明导致该厂几乎半年更换一次T形三通管件,造成了严重的经济损失。为了解决该厂T形三通频繁失效问题,必须准确查明T形三通故障原因,分析T形三通故障机理成为解决问题的关键。本文运用流场分析软件,结合T形三通管线现场故障情况,分析该厂T形三通内部流场特性及故障机理：T形三通管件内部流场存在两个对称的漩涡,导致T形三通流场速度、压力分布不稳定,形成了大范围低于汽化压力的低压区,液体汽化形成了大量气泡,气泡在三通内壁破裂产生巨大的压力冲击,导致汽蚀破坏,使贫水管线T形三通产生裂纹。基于T形三通故障机理,本文提出了3种改进建议,使用Y形三通、圆弧形三通和球形三通3种三通结构代替T形三通结构,并分析这3种三通结构流场特性。数值计算结果表明：提出的3种三通结构能减小三通管件汽蚀破坏,其中Y形三通有微弱的流体漩涡产生,产生低压区体积最小,但管道入口方向需要改变;圆弧形三通结构不改变原来入口方向,流场压力、速度分布更稳定;球形三通流场绝对压力高于Y形和圆弧形,其结构出口及下游流场压力最稳定。本文为解决T形三通裂纹故障提供了新思路,为保障化工厂三通管件的安全提供了技术支撑。     

基于四极子声源的轮胎管腔共振噪声研究

基于流固耦合仿真,应用计算气动声学方法对轮胎管腔共振噪声进行研究。滚动轮胎引起周围流体微粒间的相互作用被视为分散的四极子声源,基于Lighthill理论进一步求解并分析近场噪声和声学特性。通过对比接地前端、接地后端和胎侧位置声源的声辐射结果和频谱特性,验证了轮胎管腔共振噪声的产生机理。     

循环流化床气固流动行为的数值模拟

采用欧拉-欧拉双流体模型,在Fluent数值模拟平台上对循环湍动流化床进行了研究。采用Gidaspow模型分段描述密相湍动和稀相循环输送区气固的相互作用,考察了反应器内压力、颗粒浓度等气固湍动特性参数的变化。计算流体力学(CFD)的模拟结果表明:反应器中压力分布较为均匀;固体颗粒相和气体相间隙成絮状分布,在轴向中心区域颗粒浓度分布较为均匀;边壁区域颗粒浓度变化较大,存在强烈的气固相互作用。     

XJM-S8型浮选机数值模拟及湍流特性分析

利用计算流体力学方法通过数值模拟分析了XJM-S8型浮选机的液流运动状态和湍流运动特征,得出如下结论：XJM-S8型浮选机槽内湍动能、湍流强度、湍流耗散率关于叶轮中心呈对称分布;XJM-S8型浮选机的搅拌区域在槽体下部0.7m以下,在0.7m以上部分是相对平稳的浮选分离区域,搅拌区域的湍流强度约为分离区域的6倍,这表明该浮选机的结构合理,矿浆运动状态符合浮选过程要求。     

湍动流化床过渡段固含率分布特征的实验及数值模拟

在湍动流化床中,过渡段对于包括甲醇制烯烃在内的气固催化快反应有着重要的作用。采用PV6D反射型光纤探针对内径95 mm的湍动流化床内过渡段的固含率分布和脉动参数进行了测量,分别考察了表观气速和静床高的影响,并采用修正的基于颗粒动力学的三段曳力双流体模型进行模拟。实验表明,湍动流化床过渡段中固含率的轴向分布呈现S型和指数型两种类型,固含率轴向与径向分布都在过渡段内出现最大梯度,表明过渡段中固体浓度分布比稀相段和密相段更不均匀。表观气速和静床高的变化将导致S型和指数型分布的相互转变,并且对过渡段底部与壁面附近的固体高浓度区影响最为显著。局部固含率脉动概率密度分布表明,在静床高较小时,随着气速的增大,床层下部气含率最大值位置将从中心区移动至环隙区,呈现气含率的双峰型分布。本文提出的修正三段曳力模型考虑了颗粒团聚的影响,对过渡段中分布板影响区之外的固含率分布均能较好地模拟。     

非充气塑料轮胎对整车气动性能的影响

以SAE(美国机动车工程师学会)汽车模型为载体,分别装载普通轮胎、蜂窝式塑料轮胎和辐板式塑料轮胎,采用计算流体力学数值模拟的方法研究轮胎对整车气动性能的影响.通过比较3种模型的气动阻力、气动升力、速度场、压力场和湍流动能,分析造成差异的原因.结果显示,塑料轮胎对整车的气动阻力影响较小,但能够减小气动升力,尤其是辐板式塑料轮胎减小升力达13.27％.     

搅拌槽内湍流流场的数值模拟

搅拌槽在过程工业中的应用非常广泛,对搅拌槽内流场的研究具有十分重要的意义。实验研究方法具有局限性,基于计算流体动力学的数值模拟方法是研究流场的重要方法。文中介绍了搅拌流场的数值模拟方法和湍流模型,分析了各自的特点及其应用情况,总结了搅拌模拟时边界条件的处理情况,并指出了未来的发展方向。     

Investigation on the flow characteristics of a novel multi-blade combined agitator by time-resolved particle image velocimetry and large eddy simulation

We investigated the flow characteristics in a tank of H/T = 1.5 stirred by a novel multi-blade combined agitator (MBC) by using time-resolved particle image velocimetry and large eddy simulation approach. The predictions were assessed by Y⁺ values, Taylor microscale and power spectrum analysis, as well as experimental validation of velocity distributions. Results demonstrate that the MBC agitator can load the energy into the system effectively with a power number of 12.5 in a turbulent regime, resulting in improved axial and radial mass exchange. The upper and lower short blades produce an axial down-flow in the top half and an axial up-flow in the bottom half, respectively. Part of axial flows change to radial flows by the radial pumping of the long blades, meanwhile, the impingement of two axial flows improves the axial mass exchange. These flow characteristics lead to an obvious improvement in the turbulent kinetic energy distribution uniformity with higher turbulent intensity.     

开孔形式对盘环形挡板汽提器特性影响的模拟分析

采用CFD方法对安置盘环挡板的汽提器进行了模拟计算,对比了盘环挡板上有无开孔情况下的颗粒流动分布。结果表明,在盘环挡板上进行开孔可有效减少“气垫”区域,使气体与颗粒更顺利地穿透挡板进行高效接触。此外,通过对比不同开孔形式下的催化剂颗粒流动与气泡分布特性,可以发现均匀开孔时,随着开孔尺寸的增加,气相流动阻力下降,可以携带颗粒更加均匀地穿过盘环挡板,使得挡板以下的“气垫”区域减小,颗粒在汽提器内分布更加均匀,有利于汽提蒸汽与催化剂颗粒之间的接触。但是,随着开孔尺寸增加,汽提器内气泡的平均尺寸有所增加,气泡数量减小,气泡所占的总体积及气泡所能提供的相界面积有所减少。对比均匀开孔与非均匀开孔的颗粒流动与气泡特性,结果表明,在盘形挡板顶部附近开孔12mm,其他区域均匀开孔9mm的非均匀开孔形式在确保催化剂颗粒流动的均匀性分布、汽提蒸汽与催化剂颗粒之间的接触效果的同时,容易产生更小的气泡,可以提供更高的气固相界面积,更加有利于汽提器性能的改善,因此是比较优选的开孔方式。本文关于挡板开孔形式影响的模拟分析对设计高性能的汽提器内构件具有重要意义。     

搅拌萃取塔内单相流动不同雷诺平均湍流模型结果的比较

The flow field of liquid phase (water) of agitated extraction columns is simulated with the help of computational fluid dynamics (CFD). Four kinds of Reynolds-averaged turbulence models, i.e. the standard k-ε model, the RNG (renormaiization group) k-ε model, the realizable k-ε model and the Reynolds stress model, are compared in detail in order to judge which is the best model in terms of the accuracy, less CPU time and memory required. The performance of the realizable k-ε model is obviously improved by reducing the model constant from c2 = 1.90 to c2 = 1.61. It is concluded that the improved realizable k-ε model is the optimal model.     

考虑地面积尘时置换通风的数值模拟

引言 置换通风系统始于北欧,较多应用于工业通风.近几年来,由于其合理的温度分布、较高的通风效率和明显的节能特性,置换通风系统已经越来越多地应用到民用建筑中.在北欧新建的办公建筑中,约有50%～70%的部分采用了置换通风系统[1].     

湍流促进器强化微滤过程的实验与CFD模拟研究(英文)

This paper reports experimental and computational fluid dynamics(CFD) studies on the performance of microfiltration enhanced by a helical screw insert.The experimental results show that the use of turbulence pro-moter can improve the permeate flux of membrane in the crossflow microfiltration of calcium carbonate suspension,and flux improvement efficiency is strongly influenced by operation conditions.The energy consumption analysis indicates that the enhanced membrane system is more energy saving at higher feed concentrations.To explore the intrinsic mechanism of flux enhancement by a helical screw insert,three-dimensional CFD simulation of fluid flow was implemented.It reveals that hydrodynamic characteristics of fluid flow inside the channel are entirely changed by the turbulence promoter.The rotational flow pattern increases the scouring effect on the tube wall,reducing the particle deposition on the membrane surface.The absence of stagnant regions and high wall shear stress are respon-sible for the enhanced filtration performance.No secondary flow is generated in the channel,owing to the streamline shape of helical screw insert,so that the enhanced performance is achieved at relatively low energy consumption.     

高固含搅拌槽内临界离底悬浮转速的数值模拟

使用计算流体软件CFX5.5.1对固液搅拌槽内颗粒的临界离底悬浮转速进行了数值模拟. 搅拌槽直径D=0.476 m,搅拌桨为三叶CBY螺旋桨. 桨叶安装高度h=D/3. 固液两相为玻璃珠-水,固体体积浓度为15%~50%. 对临界离底悬浮的速度判据进行了修正,并利用浓度判据与修正的速度判据得到颗粒临界离底悬浮转速Njs,模拟计算结果与实验数据的误差在工业允许的范围内. 同时,对临界离底悬浮状态槽底部不同浓度下的流体湍流动能的分布情况以及大小进行了预测,并对2种固体临界离底悬浮机理进行了验证.     

A computational fluid dynamics study of supercritical antisolvent precipitation: Mixing effects on particle size

Supercritical fluids have been extensively used for particle production of many natural and pharmaceutical substances providing useful alternatives for pharmaceutical and nutraceutical particulate system formulation. Among the different methods, the gas or supercritical antisolvent (GAS or SAS) process and its variants, have received a considerable interest due to the wide range of materials that can be micronized. Controlling particle formation in order to nucleate small particles is a key issue in GAS and SAS processes and this is directly related to mixing at all scales. In this work, we focus on numerical simulation of the process, emphasizing mixing modeling. Different mixing devices characterized by different nozzles are analyzed, to get an insight into mixing dynamics and its influence on the final particle size distribution. Results show that mixing is determinant in obtaining small particles, and that mixing at the microscale is a significant parameter to account for in the proper design of precipitators. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Numerical and experimental analysis of forced convection in rib-roughened channels with moisture-permeable walls

Ribbed features can promote mixing and improve convective heat and mass transfer in channels. This can be beneficial in certain exchangers, such as Energy Recovery Ventilators (ERVs), which employ moisture-permeable membranes to transfer both latent and sensible heat. In this work, a computational fluid dynamics model with experimental validation was used to study angled rib mixing features in compact channels. Results show that, relative to a smooth channel, the ribs increase the channel Sherwood and Nusselt numbers by a larger fraction than the corresponding increase in friction factor. For a typical commercial grade ERV, total effectiveness can be improved by over 10% for an equal pressure drop by adding ribs and slightly increasing the channel height. A custom test stand and rib-forming technique were developed to validate the simulation predictions. The experiments confirm the net benefit of ribbed channels and agree with the simulation results within experimental uncertainty.     

不同推进式桨叶对搅拌反应器内气液两相混合特性的影响

为了研究不同推进式桨叶对搅拌反应器内气液两相混合特性的影响,以某搅拌反应器的推进式桨叶为研究对象,将搅拌聚合物简化为含5%气体的清水介质,基于螺旋桨叶片设计方法和CFD流场仿真技术,采用VOF多相流模型和RNG k-ε 湍流模型,对四种推进式桨叶内部气液两相流动进行数值分析,实现了推进式桨叶参数设计和性能优化。分析设计转速在400 r/min时的径向速度、0~18 s的时间范围内气体体积分数的变化、无量纲气体体积分数以及无量纲轴向速度,来评价四种推进式搅拌反应器搅拌性能的剪切、混合、分散。研究结果表明：变螺旋角(FDC-450-γ)非对称桨叶的流动更均匀、混合速率更快和剪切分散能力能强。通过对四种不同推进式桨叶的比较分析,为后续的研究和工程实践奠定了基础。