不同转速的油罐旋转喷射搅油器数值模拟

为了研究旋转喷射搅拌器旋转速度对搅拌效果的影响,本文使用ANSYS15.0实现喷射搅拌全流场数值模拟,并以密度的标准差作为搅拌效果的评价参考。在模拟计算的设置中采用了滑移网格、混合模型和湍流的标准k-?模型。数值分析得出旋转速度过大会导致系统的搅拌效果变差;密度标准差随旋转速度的增大先逐渐减小再增大,旋转速度存在最佳值或最佳取值范围。     

行星式搅拌釜内固液混合时间的数值计算

行星式搅拌装置内搅拌桨的运动轨迹复杂,对固体颗粒与高黏度聚合物熔体的混合效果较好。混合时间是表征搅拌釜内流体混合状况、评定搅拌釜效率的重要参数之一。利用FLUENT软件数值模拟一种行星式搅拌釜内高黏固液两相混合过程,采用传统混合时间定义方法和体积分数法2种方法计算搅拌桨不同自转转速的混合时间,并将2种方法的计算结果进行比较;采用体积分数法计算搅拌桨不同安装高度时的混合时间。计算中采用欧拉模型,使用动网格技术,利用FLUENT的用户自定义函数确定搅拌桨的速度。数值计算结果表明,采用选取监测点计算混合时间的方法,不同监测点的混合时间有较大差异,为保证全釜内混合均匀,应选取混合时间最长的监测点;选取监测点和体积分数2种混合时间计算方法得到的混合时间基本相同;随着搅拌桨自转转速的提高,混合时间明显缩短;采用釜底加料方式,搅拌桨安装高度从20mm提高到60mm时混合时间缩短。     

双层桨搅拌浸出槽固液两相流场的数值仿真

在石煤提钒搅拌浸出槽的研究中,针对双层桨搅拌浸出槽固液悬浮特性以及混合浸出效果进行了研究.由于实验成本大、操作困难,提出了数值仿真的方法.运用计算流体力学(CFD)软件FLUENT对石煤提钒搅拌浸出槽进行流场仿真,用GAMBIT建立流场实体模型,采用k-ε湍流模型以及多重参考系法(MRF)处理搅拌桨区.探讨了双层桨同向旋转和双层桨异向旋转两种情况下的搅拌效果,结果表明在相同的情况下,双层桨异向旋转时湍动能分布更为合理,并且能够缓解底部沉积,搅拌混合效果更好.仿真结果对于研究搅拌反应容器内部流场规律,进而对搅拌反应容器的结构优化和浸出率的提高具有一定参考价值.     

用临界功率表征多相搅拌槽中搅拌效果

多相搅拌过程中常常根据临界搅拌转速表征搅拌效果。由于各种搅拌桨的功率准数不同,低临界转速的搅拌桨对应的搅拌功耗可能大于高临界转速的搅拌桨,因此,本文提出用临界功率作为表征手段。选取表面曝气和固体悬浮2个典型的多相搅拌过程进行了验证,结果表明:(1)在表面曝气过程中,达到临界曝气时六斜叶下推圆盘涡轮(PBRTD)桨的搅拌功耗比标准Rushton(RT)桨低,相同功耗下PBRTD桨的kLa也更高,与临界曝气转速的判定结果不同,临界功率法认为PBRTD桨更适合作表面曝气桨,这与表面曝气机理的认识相符;(2)下推折叶透平(PBTD)桨和三叶后掠(TBHA)桨的固体颗粒悬浮实验结果也表明TBHA桨的临界离底悬浮转速高但功耗更低,TBHA桨的整体循环能力更强,有利于固体悬浮。     

模拟加速方法的设计和验证

为在直升机旋翼气动性能数值模拟时简化建模过程、缩减计算时间,利用用户自定义函数（User Defined Function,UDF）设计混合模型盘激励模型和线激励模型,并对简单旋翼的悬停工况进行模拟.与风洞试验结果的对比表明：所设计的混合模型在简化旋翼模型的同时,能有效地计算旋翼的气动特性,模拟旋翼悬停时的流场,具有正确性和可行性;盘激励模型作为定常计算模型能够较快地计算得到旋翼的气动性能,缺点是不能体现每个桨叶对流场的单独作用;所设计的线激励模型在计算时由于所用的诱导速度为平均值,所以计算结果中旋翼效率比实际值偏高;通过与粒子图像测速（Particle Image Velocimetry,PIV）测量结果对比发现,线激励模型能较好地模拟出桨尖涡的分布.     

基于改进直线涡元诱导速度模型的旋翼自由尾迹计算方法

通过设置涡核模型的角度条件,使涡核模型在极限状态下仍保持收敛,进而改进了利用Biot-Savart定律计算直线涡元对空间任意一点诱导速度的模型;桨叶气动模型采用Weissinger-L升力面理论模拟;自由尾迹的求解采用PIPC松弛迭代算法结合具有二阶精度的CB2D时间步进算法.利用上述模型和算法对某型号旋翼的尾迹进行数值计算,结果显示:利用改进涡核模型计算的桨尖涡径向位移收缩更加明显,这与实际情况更加接近;利用改进涡核模型得到的自由尾迹结果与实验数据吻合的更好.上述结论可以证明,新建立的旋翼自由尾迹模型提高了原有模型的准确性.     

板翅式换热器平直翅片的数值模拟

利用CFD的方法建立了简单、准确计算板翅式换热器平直翅片在层流和湍流区域性能的数值模型。在湍流区域使用低雷诺数湍流模型来替代壁面函数的方法,f因子的平均绝对误差从22.7%降低到7.9%;并用湍流普朗特数模型代替FLUENT软件中默认的湍流普朗特数常量(0.85)使得j因子平均绝对误差从17.9%降低到6.9%;通过以上两个措施使得CFD方法能够更准确预测平直翅片性能。对18种具有不同几何结构参数的平直翅片进行数值模拟;计算结果表明:翅片间距、高度对性能有较大影响而翅片厚度影响较小。同时,回归了j和f因子关联式。     

多相流搅拌器流场数值模拟软件

为对搅拌器多相流体间的最终乳化结果进行模拟,结合FLUENT与ANSYS软件,以VB为前台程序开发搅拌器流场数值模拟软件.用VB开发用户交互界面,通过后台调用ANSYS的APDL完成前处理模块,实现搅拌器叶片、筒体的建模,网格划分和组元创建;通过后台调用FLUENT运行日志文件实现流体流场仿真运算与结果后处理,并以图形...     

液-固-固三相流搅拌槽内流动特性研究

采用计算流体动力学方法,通过欧拉多相流模型对螺杆-挡板搅拌槽内的某液-固-固三相流进行速度场、密度场和各相体积分数分布进行研究。结果表明,在原始的螺杆-挡板式搅拌桨作用下,多相流整体流动性和湍流特性均不太明显,近壁区易形成高密度聚集现象。增设辅助螺杆桨后,湍流现象明显增强,促进了各区域流体的混合对流;近壁区各相体积分数偏离设定值较小,偏差为±5%;中间区域各相体积分数相对稳定,且与设定数值更接近,偏差为±2%,整体而言,混合均匀化效果更好,有效避免了搅拌死角。研究结果对多相流流动特性分析和搅拌装置优化设计具有一定的参考意义和理论价值。     

2种高剪切搅拌器流动特性的CFD模拟

采用计算流体力学模拟方法对2种用于分散混合过程的高剪切搅拌器的流动特性进行研究分析,分别是转子定子搅拌器(RS)和多级叶轮式搅拌釜(CF)。本文从流场细节和功率消耗方面对其进行考察研究,从而为解释搅拌器中气泡的分散混合过程提供理论依据。模拟结果表明,在RS中流体大致呈周向流动,且剪切速率分布相对较为均匀,较高剪切速率不仅出现在转子到壁面的径向间隙处,而且出现在转子与定子之间的轴向间隙处:而在CF中,流体呈现较为明显的旋转流动,且剪切速率分布没有RS均匀,较高的剪切速率只出现在叶轮与壁面的径向间隙处。在相同转速下,虽然这2种搅拌器所形成的平均剪切速率差别不大,但CF中所形成的最大剪切速率大于RS,这也意味着相同操作条件下CF中所能形成的气泡尺寸更小,这与实验结果是一致的。对于这2种搅拌器,在层流区功率准数与搅拌雷诺数都成反比,且CFD模拟计算得到的结果与根据实验得到的关联式的结果基本一致。然而CF的功率消耗高于RS的功率消耗。     

Sensitivity analysis of artificial neural networks for just-suspension speed prediction in solid-liquid mixing systems: Performance comparison of MLPNN and RBFNN

Just-suspension speed (Njs) is an important parameter for stirred tank design using a solid-liquid mixing system in the chemical process industry. However, current correlations for Njs suffer from uncertainty from limited experimental databases and limitations due to many parameters that play an important role in Njs determination. A comprehensive computation of the radial basis function neural network (RBFNN) was developed based on solid-liquid mixing experiments, which contain 935 datasets for the prediction of Njs. The Njs values were obtained experimentally using Zwietering correlation with different solid loading percentages, solid particle density, solid particle diameter, mixing solvent density, number of impeller blades, impeller diameter, impeller blade hub angle, impeller blade tip angle, the width of the impeller blade and the ratio of the clearance between the impeller and the bottom of the tank with the tank diameter. The RBFNN proved to have a much better ability to accurately predict the desired Njs compared to MLPNN even after decreasing the number of input variables from 11 to 8. Thus, the computational RBFNN model results will be useful for extending the application of a solid-liquid mixing system for estimating the just-suspension speed for stirred tank design.     

CRONE control based anti-icing/deicing system for wind turbine blades

This paper presents an application of CRONE control, a robust control based on fractional order differentiation, to an anti-icing/deicing system for wind turbine blades. The deicing system uses an electrically conductive polymer paint applied on the blade at ice formation areas. The voltage applied to the paint leads to its heating. Based on a temperature measure provided by various sensors placed on the blade, a control system can thus be used to prevent the blade icing up during wind turbine operation or to deice the blade after a rest time. To design the control system, a thermal model of the blade with the paint was developed and its associated parameters were identified using tests in a climatic wind tunnel. A CRONE controller was then designed and its performance evaluated both on blade subparts in the climatic wind tunnel and on a floor-standing real blade.     

Computer-aided measurement plan for an impeller on a coordinate measurement machine with a rotating and tilting probe

This paper presents a computer-aided measurement plan (CAMP) for an impeller on a coordinate measurement machine (CMM) with a rotating/tilting probe. The blade surfaces of a machined impeller were measured exactly to secure the machining tolerance and surface finish of the impeller. CMM with a rotating and tilting probe is commonly used for this measurement. However, it is not easy to evaluate all the points on the impeller surfaces due to the time-consuming nature of the CMM measurement. In addition, many points cannot be easily accessed by the CMM probe due to the interference between the probe and the impeller blades. Furthermore, the inherent complexity of the existing teaching operation of a probe using a joystick suggests the necessity of developing a new method for the measurement planning of an impeller. Thus, this paper proposes a CAMP for effectively gauging the inspection points based on the ruled line information of the impeller blade surfaces. The proposed plan partitions the surfaces into several measurement regions based on the ruled lines of a blade surface and the approach vectors of the probe. Finally, a case example for an impeller is presented to demonstrate the effectiveness of the proposed strategy.     

关于叶轮集成化智能CAM系统的研究

针对叶轮五坐标ＣＡＭ技术，本文在统一的产品信息模型基础上， 运用智能工程技术，建立了一个并行分层式集成化ＣＡＭ系统，此系统可有效地解决叶轮零件的图形输入，几何设计、叶片及叶轮的造型、曲线及曲面求交、加工刀心轨迹的求解等，并以ＤＮＣ方式控制数控机床进行加工，实现了软硬件的集成。     

Reverse engineering approach to appearance-based design of metallic and pearlescent paints

We propose a new approach to interactive design of metallic and pearlescent coatings, such as automotive paints and plastic finishes of electronic appliances. This approach includes solving the inverse problem, that is, finding pigment composition of a paint from its bidirectional reflectance distribution function (BRDF) based on a simple paint model. The inverse problem is solved by two consecutive optimizations calculated in real-time on a contemporary PC. Such reverse engineering can serve as a starting point for subsequent design of new paints in terms of appearance attributes that are directly connected to the physical parameters of our model. This allows the user to have a paint composition in parallel with the appearance being designed.     

Rendering Pearlescent Appearance Based On Paint-Composition Modelling

We describe a new approach to modelling pearlescent paints based on decomposing paint layers into stacks of imaginary thin sublayers. The sublayers are chosen so thin that multiple scattering can be considered across different sublayers, while it can be neglected within each of the sublayers. Based on this assumption, an efficient recursive procedure of assembling the layers is developed, which enables to compute the paint BRDF at interactive speeds. Since the proposed paint model connects fundamental optical properties of multi-layer pearlescent and metallic paints with their microscopic structure, interactive prediction of the paint appearance based on its composition becomes possible.     

基于Patran和MSC Nastran的某空压机第1级叶轮强度分析及结构优化

基于Patran和MSC Nastran,采用三维有限元法分析某型空压机第1级叶轮在工作转速下的强度,并优化叶轮结构.研究结果表明：原叶轮在叶片进气边分别与轴盘和盖盘的焊接处出现高离心应力区域;原叶轮设计模型的最大应力为970 MPa,与材料抗拉强度试验平均值1 066 MPa相差9%,安全裕量不足.优化设计后的叶轮模型的最大应力为864 MPa,与材料抗拉强度试验平均值1 066 MPa相差19%,安全裕量提高1倍.     

A computer-aided design procedure for radial and mixed flow compressors

A technique is described for the analytical representation of the geometry of radial and mixed flow compressor impellers constructed of radial or non-radial blade elements. A similar analytical expression is used to describe the hub, shroud, and camberline curves; if required, the angle of inclination of the blade elements from the radial direction is also described. These analytical expressions lend themselves to rapid manipulation, enabling the designer to apply established two- and three-dimensional fluid dynamic analysis procedures to a wide range of possible design configurations.The analytical expressions completely specify the impeller passage geometry from which computer graphics output can be obtained to give isometric, plan and side views of the impeller. For manufacturing, the computer graphics subroutine supplies a series of flow passage sections on a large scale at any number of axial stations specified by the designer. These passage sections are used in the construction of templates from which the impeller is manufactured using copy milling techniques. The analytical specification also gives a detailed co-ordinate specification of the impeller for use with numerically controlled machines.     

On the optimal design of the form of hydroturbine impeller blades

When designing a hydraulic turbine, a machine of better performance characteristics and primarily of the highest possible efficiency should be created. In the process, a designer is given a numer of restrictions concerning dam height, impeller diameter, etc. The turbine efficiency can be increased by varying the impeller blade profile or the angular velocity of the impeller rotation and by some other design techniques.The problem of optimization of hydroturbine parameters has been investigated in a number of works (see e.g. Fedorov 1983, 1984; Klimovich and Fedorov 1984; Kazachkov and Provad 1989). This paper presents some optimum decisions obtained for one-and two-dimensional axisymmetrical flow models. The turbine efficiency and local cavitation coefficients are accepted as the goal functionals. Necessary optimizing conditions are described, and calculated optimum characteristics of blade systems are given.