Discharge Characteristics of Polydisperse Powders through Conical Hoppers. Part 2: Predictions for Coarse, Granular, Free Flowing Powders

Discharge characteristics of coarse polydisperse granular powders through a conical hopper are experimentally investigated. The average discharge rates of four different powder types are systematically measured for seven different diameters of hopper orifice under gravity flow conditions. Each powder type is a mixture of some sub-sizes (smaller than 3 mm) of same powder material. Effects of orifice diameter of hopper and size distribution of polydisperse powders on discharge characteristics are experimentally determined. The measured discharge data are compared with discharge values predicted by using modified forms of the well-known Beverloo correlation. The volume-moment-mean diameter, d_VM, and the 50% weight fraction diameter, d₅₀, cited in available literature are both checked to characterize the coarse polydisperse powders and used throughout the predictions. Comparisons implied that both d_VM and d₅₀ diameters can be successfully used to characterize polydisperse test powders, and discharge rate predictions are in good agreement with experimental data, with mean deviations lower than ±4.04%.     

Product distribution modelling in the thermal pyrolysis of high density polyethylene

The thermal fast pyrolysis of high density polyethylene (HDPE) has been carried out in a conical spouted bed reactor in the 450-715 degrees C range, and individual products have been monitored with the aim of obtaining kinetic data for the design and simulation of this process at large scale. Kinetic schemes have been proposed in order to explain both the results obtained in the laboratory plant and those obtained in the literature by other authors operating at laboratory and larger scale. Discrimination has been carried out based on the contribution of the variance of model parameters (stepwise regression) to the total variance explained by the model. The models based on that of Westerhout et al. [R.W.J. Westerhout, J. Waanders, W.P.M. Van Swaaij, Recycling of polyethene and polypropene in a novel bench-scale rotating cone reactor by high-temperature pyrolysis. Ind. Eng. Chem. Res. 37 (6) (1998) 2293-2300] do not adequately predict the experimental results, especially those corresponding to aromatics and char, which is probably due to the very short residence times attained in the conical spouted bed and, consequently, to the lower yields of aromatics and char. The model of best fit is the one where polyethylene degrades to give gas, liquid (oil) and wax fractions. Furthermore, the latter undergoes secondary reactions to give liquid and aromatics, which in turn produce more char.     

圆锥形零件成形时极限承载能力的确定

根据圆锥形零件成形时破裂危险断面处的应力状态，并综合考虑几何尺寸、各向异性、材料硬化等因素的影响，经力学分析得出了圆锥形零件成形时危险断面处的承载能力，以此可作为判断成形过程能否顺利成形，确定极限变形程度的依据。     

修形直齿锥形齿轮啮合特性研究

为了避免直齿锥形齿轮发生边缘接触和降低对安装误差的敏感性,对小轮进行齿向弧线修形和齿廓抛物线修形.采用假想齿条的方法,模拟齿条与被加工齿轮的啮合运动关系,推导出齿轮齿面的数学模型,根据两齿面在啮合过程中的连续切触条件,建立了齿轮接触分析模型.仿真表明,修形后的直齿锥齿轮副,对安装误差的敏感性降低,且没有发生边缘接触,改...     

一种圆锥面无键联接接触压力和应力的解析计算方法

推导了计算圆锥无键联接的接触压力的解析公式,给出了心轴和套筒轴的径向应力、轴向应力、切向应力、Mises等效应力以及压入轴向力的方程。对解析解与等效直径的圆柱面无键联接近似解法、有限元法的计算结果进行了比较。在不考虑端部应力集中时,3种方法计算出的接触压力和Mises等效应力结果差别不大。进一步验证了近似解法的可行性,并为计算圆锥联接传递的扭矩和胀紧套的应力分析提供了依据。     

Application of the scaling law for swept shock/boundary— layer interactions

An experimental study providing additional knowledge of quasi-conical symmetry in swept shock wave/turbulent boundary-layer interactions is described. When a turbulent boundary layer on the flat plate is subjected to interact with a swept planar shock wave, the interaction flowfield far from fin leading edge has a nature of conical symmetry, which topological features of the interaction How appear to emanate from a virtual conical origin. Surface streakline patterns obtained from the kerosene-lampblack tracings have been utilized to obtain representative surface features of the flow, including the location of the virtual conical origin. The scaling law for the sharp-fin interactions suggested by previous investigators has been reexamined for different freestream Mach numbers. It is noticed that the scaling law reasonably agrees with the present experimental data, however, that the law is not appropriate to estimate the location of the virtual conical origin. Further knowledge of the correlation for the virtual conical origin has thus been proposed.     

锥形螺旋轴流血泵流场三维数值模拟与分析

利用ProE软件对血泵的不同结构进行三维建模,应用计算流体力学(Computational fluid dynamics, CFD)中非定常三维N-S方程,基于非结构网格的有限体积法以及k-ε湍流模型方法数值模拟血泵的全三维内流场。着重计算和分析旋转叶轮转速和锥度变化对血泵流场的影响。仿真试验表明,锥形螺旋轴流血泵转速和锥度都不应过大,否则将会使得流场变得紊乱。转速过大,泵的性能会降低;锥度不应过大,否则不能保证流场平稳。     

圆锥浮环动静压轴承动态特性理论研究

对一种新型结构的滑动轴承——圆锥浮环动静压轴承的动态特性进行理论分析和数值计算。首先给出内、外膜的动态雷诺方程和边界条件,应用有限元得到内外膜36个刚度系数和阻尼系数,在此基础上分析该轴承的稳定性,计算其稳定性参数。结果表明该轴承具有稳定性好,易于实现主动控制的优点,在高速旋转机械领域有广泛的应用前景。     

基于Solidworks的锥形橡胶弹簧的参数化设计系统开发

介绍了基于Solidworks平台的锥形橡胶弹簧计算机辅助设计,给出在Solidworks平台下实现该橡胶弹簧计算机辅助设计及三维造型的程序和相应实例.