离心泵叶轮内流动的油膜法测试

为了理解离心泵内部复杂的流动机理,揭示其内部的流动规律,以一叶轮形式为半开式的小型离心泵为例,采用表面油膜显示法,对其叶片及叶轮后盖板表面的流动情况进行了可视化试验研究。通过调整试剂成分比例,共设计6个试验方案,对比了不同油膜试剂的显示效果,并根据叶轮表面的流线分布对叶轮表面附近的流动情况进行了分析。试验结果证明了油膜显示法捕捉离心泵表面流动特征的可行性,为进一步理解离心泵内部复杂的流动机理提供依据。     

Comparison of different mixing phenomena in anaerobic digestion using food waste and sewage treatment plant for green biofuel through simulations of velocity contours

Three-dimensional computational fluid dynamics models have been developed for the comparison of diffuser-based biogas recirculation and impeller mixed anaerobic reactors with unmixed reactors for food waste co-digested with sewage treatment plant sludge for enriched with 60–73% of biogas. Enhanced biogas yield was observed in diffuser mixing, intensity of 2 L/min (0.28–1.180 L/g VSr), compared to impeller mixing of 200 rpm. pH of 5.94 from the feed slurry pH range of 7.0–8.4 shows sheathe-broken microbial SEM structure.     

Impeller power draw during turbulent operation in solid‐liquid suspensions

Experimental measurements with six impeller types in solid‐liquid suspensions indicate that impeller power draw in the turbulent regime is approximately proportional to the solid‐liquid suspension density when the solids are distributed throughout the liquid; however, the accuracy of this approach is limited and there are clear differences in the behaviours of the various impellers. In general, power draw increases are less than suspension density increases for impellers with large blade‐trailing vortices, while power draw increases are equal to or greater than suspension density increases for impellers with smaller blade‐trailing vortices. The power draw data is well‐described using linear relations between the impeller power number and the density difference correlating parameter proposed by Micheletti et al.,^[9] with the slope of the relation being dependent on impeller type. More extensive testing with a pitched‐blade turbine, using a greater variety of solids, found that the relation between the impeller power number and the density difference correlating parameter is independent of particle size for particles as large as 1 mm (1000 microns). For particles larger than 1.7 mm (1700 microns), in addition to suspension density, the solid volume fraction affects the pitched‐blade turbine power number; however, it is difficult to determine if this effect exists at all scales or if it is a result of the large particle size relative to the impeller dimensions in the experimental system. For large particles, the power draw is increased by the addition of neutrally‐buoyant particles that do not change the suspension density, with the magnitude of the increase being dependent on impeller type.     

三叶后掠-HEDT组合桨搅拌釜内流场的模拟及实验

对应用于聚乙烯聚合反应中的三叶后掠-HEDT组合桨的搅拌釜内流场进行了模拟研究,分析组合桨的离底距C ₁、桨间距C ₂以及转速N的变化对搅拌釜内流场的影响,利用PIV实验对模拟结果进行了验证;将该组合桨与三叶后掠-六直叶圆盘涡轮组合桨进行了模拟对比研究。结果表明：当桨间距与釜内径的比为0.35时,釜内桨叶间的流体流动效果最好,该条件下能够改善搅拌釜上层流体的速度分布;当离底距与釜内径的比值为0.29时,组合桨下方出现了整体的环流,有利于釜底流体的混合;桨叶转速N=90 r/min时釜内流体速度分布均匀,同时上层HEDT桨叶产生的射流方向趋于水平。两种组合桨的对比研究表明：二者流型相近,但前者搅拌功率能够得到明显降低。研究结果可为三叶后掠-HEDT组合桨在聚乙烯聚合反应釜中的工程应用提供参考。     

Cavern Boundary Determination with Pseudoplastic Fluid Based on the Apparent Viscosity Method

The cavern characteristics of xanthan gum solutions stirred by impellers of a perturbed six-bent-bladed turbine (6PBT) were investigated numerically using computational fluid dynamics (CFD) with laminar flow model. The apparent viscosity method was proposed to determine the boundary of the cavern. The cavern sizes predicted by apparent viscosity were in good agreement with the calculated results, and this method was not influenced by speed and impeller configuration. However, the predicted results of the cavern by the traditional speed method usually displayed a great deviation, especially at high speed. Therefore, it is feasible to determine the cavern boundary with the apparent viscosity, i.e., 0.25 times the yield viscosity of a pseudoplastic fluid, as the unified standard.     

PTA装置扩产氧化母液罐挖潜——搅拌器改造

上海石化0.4 Mt/a PTA装置扩产改造中,TJ-302氧化母液罐处理量不能满足需求,需要大幅度加快循环速度,在原有设备上增设搅拌器是最经济的选择。增设搅拌器后,又出现新问题,由于循环速度加快,设备中原有的固体含量增加,必须进行再改造。经充分的分析研究以及计算,增设了罐内轴滑动轴承,从而解决了上述问题。     

Performance Evaluation of Two High‐Shear Impellers in an Unbaffled Stirred Tank

High‐shear impellers (HSIs) are mixers used in industrial stirred tanks to incorporate powders into liquids and break down particle agglomerates. A detailed numerical study of two commercial ring‐style HSIs of laboratory scale was carried out and their performance was compared with the Rushton turbine (RT). It was found that power and pumping numbers or their ratio cannot be simply connected for properly selecting an impeller in applications where highly localized viscous dissipation is desirable. The ratio of the average viscous dissipation in the impeller swept volume to the mean in the entire volume at two constant values of power input turned out to be lower for HSIs compared to that evaluated for RT. However, at higher power input, the dimensionless average viscous dissipation in the blade swept volume was found to be similar for the HSI of two rings and the RT, corroborating the high local viscous dissipation of this HSI when operated at higher speeds.     

基于Pro/E的汽车电机叶轮冲压成形工艺分析

为了准确制定合理的冲压成形工艺方案,借助Pro/E软件,基于汽车电机叶轮对于平衡性的高要求,模拟分析了最合理的冲压工艺方案,从而保证了较好的产品质量,提高了经济效益。     

电弧喷涂防磨技术在电站锅炉排粉机叶轮上的研究与应用

借鉴电弧喷涂在引风机等类似部件上的应用经验，结合排粉机叶轮特殊的工作环境，综合运用电弧喷涂和火焰喷焊的优点，通过一系列试验研究，使电弧喷涂技术和火焰喷焊技术有效的应用于较引风机叶轮的服役环境更为恶劣的排粉机叶轮上，并取得良好的效果。