沉淀搅拌槽三维流场数值模拟

使用计算流体动力学软件FLUENT对沉淀搅拌槽内的流场进行了数值模拟,分析了桨叶离底高度对三维流场的影响,进而利用模拟出的数据计算出搅拌轴的功率。结果表明:提高搅拌桨离底高度,有利于提高混合效果。     

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。     

多层桨搅拌槽内的液相流场研究

针对多层桨搅拌槽的结构配制问题,对多层Rushton桨搅拌槽内的液相湍流流场采用计算流体动力学方法进行了数值模拟研究。首先分析了一个高径比为H/T=1.4的双层Rushton桨搅拌槽内的流型,通过与实验结果的对比,验证了模拟方法的可靠性;随后分析了底层搅拌桨的离底高度、桨间距、桨径比、以及搅拌桨数目对一个高径比为1.6的Rushton桨椭圆底搅拌槽内流型、湍动能和搅拌功耗的影响。研究结果表明,对于所研究的搅拌槽,采用桨径比D/T=0.48、底层桨离底高度C1=0.4T的双层Rushton桨配置为最佳选择,相同雷诺数的条件下,具有湍动均匀度高、搅拌功耗低的优势。     

基于FLUENT的磨损试验机磨料流场模拟和试验验证

为了研究磨损试验机搅拌机构混合磨料的均匀度问题,应用计算流体力学软件FLUENT对磨损试验机磨料流场进行了模拟,直观显示了工作区内的流场特性和速度分布规律。对桨叶直径分别为10,15,20 cm及桨叶转速分别为450,600,750 r/min等不同参数下的磨损试验机磨料流场进行了模拟。结果显示,桨叶直径为20 cm,桨叶转速为750 r/min时为最佳工作状态。通过调节桨叶的转速及更换不同直径的桨叶,对实际搅拌的面粉和麸皮混合磨料进行了对比试验,试验结果与模拟结果基本吻合。     

搅拌浸出槽固液两相流场的数值模拟

运用Fluent对石煤提钒搅拌浸出槽进行流场模拟,用GAMBIT建立流场实体模型,采用k-ε湍流模型、欧拉一欧拉多相流模型、以及多重参考系法处理搅拌桨区。对搅拌槽在直桨式和旋桨式两种桨型下的流场以及装有挡板或导流筒后的流场情况进行了比较研究,结果表明在同等条件下旋桨式搅拌桨搅拌效果较好,轴向速度比直桨式搅拌桨平均高出120%,在搅拌槽中设置挡板和循环筒有利于改善流场速度分布,从而加强混合效果,但挡板的改善效果更为显著。     

立式捏合机桨叶间隙、螺旋角对搅拌扭矩和功率特性的影响

以1 L两桨叶立式捏合机为研究对象,采用CFD方法系统性地研究立式捏合机桨叶结构参数（间隙、螺旋角）对搅拌牛顿流体（玉米糖浆）的搅拌扭矩和功率消耗的影响关系。立式捏合机仿真模型与试验数据进行对比验证,确保了模型的可信度。研究结果表明,减小桨叶间隙或增大桨叶螺旋角可增大桨叶搅拌扭矩和功率消耗。减小桨叶螺旋角可增加桨叶捏合作用时间,减小桨桨间隙或增大桨叶螺旋角可增大桨叶捏合作用强度。一定范围内,桨桨间隙c₁=3.0 mm、螺旋角β_k=35°时,空心桨平均扭矩取得最小值0.046 93 N·m;桨桨间隙c₁=1.0 mm、螺旋角β_k=55°,空心桨平均扭矩取得最大值0.068 73 N·m。搅拌牛顿流体时,立式捏合机功率准数N_pM与雷诺数R_eM为线性关系,并且桨桨间隙对立式捏合机功率特性曲线的影响大于桨叶螺旋角的影响。     

基于FlUENT的单层直叶搅拌槽混合时间的数值模拟

搅拌槽广泛应用于化工、医药、废水处理领域,充分了解搅拌槽内部的流场信息、搅拌效果具有一定的实际的意义。针对广西某环保企业的搅拌槽模型,采用滑移网格模型(Mesh motion)、示踪剂浓度法、标准k-ε湍流模型对单层直叶桨式搅拌槽的混合时间和流场进行数值模拟。模拟结果表明:桨叶安装高度设置在距离罐高的1/2H位置时,流场分布均匀,加快罐内的介质混合且混合时间最短。     

一种高效节能型轴流式搅拌桨功率曲线测定及分析

新近开发的一种高效节能型轴流式搅拌桨--JH-2型轴流式搅拌桨是一种空间扭曲板材型搅拌桨,该桨型设计时考虑了桨叶背面的曲面形状对流场的影响,减低了桨叶尾部的流体脱附,大大降低了能耗.在标准搅拌实验台上对JH-2桨进行功率实验,给出了JH-2型扭弯叶片轴流式搅拌桨的功率曲线及其关联式,并在同等实验条件下与三折叶桨进行功率对比分析,表明JH-2型搅拌桨比三折叶桨至少可节省20%～30%的功率.     

曲面型叶片轴流式搅拌器数值模拟研究

采用计算流体动力学(CFD)软件FLUENT、利用多重参考系法(MRF)对曲面型叶片轴流式搅拌器的流场进行数值模拟.首先分析研究了不同扭角下曲面型搅拌器槽内流场特性和搅拌功率,表明:当扭角为10°时,槽内湍流强度强的区域更大,且搅拌功率最高;其次还分析了不同桨叶数的曲面型轴流式搅拌器的时均速度分布和搅拌功率,可知槽内时均速度、搅拌功率随着桨叶数的增加而增加.     

桨式搅拌器安装高度对搅拌效果的数值模拟

搅拌器安装高度对搅拌效果的影响一般采用实验研究方法,运用数值模拟技术系统的研究较少.通过FLUENT软件系统地研究了桨式搅拌器在不同安装高度下搅拌槽内流场的湍流强度分布、流速分布以及在不同安装高度下搅拌功率的大小.结果表明,搅拌器在合适的安装高度下,搅拌功率随着安装高度的增加有细微的减小;在不合适的安装高度下,搅拌效果会受到影响,功率会增加.     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

基于多目标非支配解提取法的电力系统无功优化

针对传统的电力系统多目标粒子群优化算法采用权重系数法将多目标转化为单目标,从而忽视了各目标函数间的竞争关系这一问题,提出将非支配解提取法运用到电力系统多目标无功优化中,并设定了一套提取规则,以电力系统中的有功网损、电压偏差和电压稳定裕度为目标,使目标在充分竞争的情况下得出Pareto最优解,利用IEEE-14节点系统对多目标非支配解提取法的电力系统无功优化进行了仿真测试。研究结果表明,该算法一次运行可以得出多组非支配解,既有偏向单个目标的解也有兼顾所有目标的解,克服了权重系数法的盲目性和单一性,可使电力决策者根据实际问题选择最优解,具有较好的灵活性与多样性。     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Robust Impedance Control of Robots Using an Adaptive Interaction Force Observer

For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type ...     

Research on key techniques of expendable conductivity temperature depth measuring system

This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.