Experiment and numerical simulation of chaotic mixing performance enhanced by perturbed rigid-flexible impeller in stirred tank

To eliminate the isolated mixing regions in the stirred tank, factors associated with chaotic mixing performance were studied, including flow field structure and fluid velocity of rigid RT impeller (R-RT), perturbed rigid RT impeller (PR-RT) and perturbed rigid-flexible RT impeller (PRF-RT). The maximum Lyapunov exponent (LLE) and multi-scale entropy (MSE) were calculated by using Matlab software programming, and the differences in flow field structure and fluid velocity of the three blade systems were studied through computational fluid mechanics. The experimental and computational results showed that perturbed rigid-flexible RT impeller could destroy the boundary of the mesostatic flow field in the isolated mixing regions and the symmetry flow in the process of fluid mixing through the random disturbance of the flexible blade, eliminating the isolated mixing regions. At 90 r/min, the LLE of the perturbed rigid-flexible RT impeller is larger than that of rigid RT impeller and perturbed rigid RT impeller. The LLE of the rigid-flexible RT impeller compared with the rigid RT impeller and perturbed rigid RT impeller increases 13.29% and 7.25% respectively and the MSE of the perturbed rigid-flexible RT impeller is also larger than that of rigid RT impeller and perturbed rigid RT impeller. The perturbed rigid-flexible RT impeller enhances the flow field instability, forms an asymmetric flow field structure, and reduces the distribution range of isolated mixing regions. The perturbed rigid-flexible RT impeller enhances the energy dissipation of the blade, improves the fluid velocity at the bottom and top of the tank and the wall of the tank, and reduces the mixing time.     

整体叶轮展成电解精加工成型规律及运动设计

为提高整体叶轮精加工展成运动设计效率和加工精度,对精加工阴极表面进行离散化处理,研究其成型规律,建立了成型规律的数学模型,提出以叶片拟合型面母线的法向偏置线为基准进行展成运动轨迹设计.利用得到的数学模型对展成运动的合成进给速度进行优化设计,从而控制加工中去除材料的厚度.实验证明,以该数学模型为基础的展成运动设计方法可以...     

Mixing Time Studies in Multiple Impeller Agitated Reactors

Mixing time studies have been carried in a 0.3m diameter and 0.9m tall vessel equipped with three impellers. Conductivity measurement technique has been used for the measurements of mixing time. Effect of the various parameters i.e. tracer density, tracer volume, speed of rotation and impeller combination on mixing time has been studied for two impeller combinations used viz. PTD‐PTD‐PTD and PTD‐PTD‐DT. A compartment model (with one fitted parameter, the exchange flow rate Q_E) with single compartment per agitation stage has been used to predict the conductivity response and the exchange coefficients are calculated from the model parameter. An attempt has been made to explain the experimental results on the basis of the liquid phase axial dispersion coefficient and cell residence time, calculated from the model parameter Q_E     

低比转速离心泵叶轮几何参数多目标优化

低比转速离心泵的效率与泵的损失、汽蚀余量和扬程曲线的稳定性有关.以能量损失最小、汽蚀余量最小及消除驼峰为目标,采用线性加权组合的方法,建立低比转速泵叶轮几何参数的多目标优化函数,并应用超传递近似法进行多目标优化.实例优化证明,采用该方法,设计者可根据实际经验对各目标函数的重要性进行模糊评价,合理确定各目标的权值,对泵的效率、汽蚀和稳定性等性能进行设计优化,以得到更为科学的设计方案.     

实验室用3．0L单槽式浮选机的设计

分析了实验室用浮选机的结构特点、作用及在设计过程中需要考虑的主要问题,并结合选矿工艺、生产实践、实验中得出的参数和要求,新设计了3．0L浮选机,以提高实验室选矿效率和处理量。     

圆柱形叶片潜油离心泵流场的三维数值分析

采用CFD方法研究了潜油离心泵的内部流场，讨论分析了3种不同工况下叶轮和导轮的数值计算结果。数值模拟捕捉到了离心泵内部许多不良流动现象，探讨了影响离心泵效率的原因。泵在设计工况有着良好的流动性能，在非设计工况出现了不良流动现象，影响了泵的效率。计算结果还显示：潜油泵叶轮有较好的水力性能，而潜油泵导轮的水力性能是不完善的，效率较低。     

基于分层制造和三轴铣削的叶轮原型制造

针对叶轮原型的低成本快速制作需要,研究了利用分层制造与三轴数控铣削相结合的分层铣削工艺制作叶轮原型的方法.实验结果表明,该方法在没有专用夹具的条件下,仅利用三轴数控铣床就能够经济快速地制作叶轮原型.     

水泵叶轮在激光选区熔化成型加工中的几何误差研究

以316L不锈钢金属粉末为原料,利用激光选区熔化成型技术试制某潜水泵用叶轮。针对水泵叶轮激光选区熔化成型加工中出现的几何误差,分析水泵叶轮出现几何误差的原因。通过设计工艺试验,探究水泵叶轮在激光选区熔化成型加工中几何误差的产生规律,建立水泵叶轮的几何误差模型,确定引起水泵叶轮成型精度的主要因素有:切片处理产生的误差、激光深穿透产生的误差、外边框凸起产生的误差、材料收缩变形产生的误差、粉末的杂质引起误差和成型缸升降产生的误差,采用后处理和补偿成型缸位移量,解决水泵叶轮几何误差。研究结果表明:当成型缸位移量为0.02823 mm时,所成型的水泵叶轮加工精度符合制造要求。     

叶片数和叶轮外径对微型风扇性能影响的实验研究

对不同叶片数和不同叶轮外径的微型风扇,以及同一款风扇在几种转速下进行实验测试,分别得到其流量-压力性能曲线。结果表明,针对同一类型的风扇,在相同转速下叶片数多的风扇性能更好,风量更大。从不同叶轮外径的风扇性能曲线来看,叶轮外径大的风扇性能较叶轮外径小的风扇性能更优。同时,计算并绘制了在相应工况下风扇的无因次性能曲线,其变化趋势与流量-压力性能曲线基本相同。最后,测试了同一款风扇在不同转速下的性能曲线,提高转速能明显增加微型风扇的风量。     

日本6WTB-142型离心泵叶轮车削节能改造

介绍了泵叶轮车削的基本原理以及车削尺寸的确定方法，并以6WTB-142型泵为例，验证了这一方法的实际效果。