离心泵叶轮轴面图的优化设计

在叶轮轴面投影图绘制方法的基础上,用正交设计方法完成对流道型线进行反复检验-调整、修改的优化,以取得较为理想的叶轮轴面投影图.     

离心泵叶轮轴面流线分点的二分法

本文从离心泵计轮轴面流线分点的基本原理出发,介绍了用数值分析中解非线性方程的二分法实现对叶轮轴面流线进行分点的方法。该方法避免了繁复的公式推导。具有概念清晰,计算编程简单,运算精度高的特点。     

离心泵叶轮轴面中间流线绘制的二分法

介绍了一种用二分法绘制叶轮轴面中间流线的方法。当给出叶轮轴面图中各过流截面形成线的端点坐标、过端点坐标切线的交点坐标、过流截面形成线圆弧半径及过流截面积后即可绘制数目为n(包含前后盖板流线,一般取n为奇数)的任意条中间流线,可大大提高叶轮绘型的效率和精度。     

汽轮机直叶片级叶轮轴向推力计算研究

为了解决提高冲动式汽轮机直叶片压力级的叶轮轴向推力计算精度的问题,利用CFD方法对叶栅及间隙流的流场进行计算,研究一维计算方法中的假设条件对叶轮轴向推力计算结果的影响.结果表明:间隙流假设为理想的等熵流动对叶轮轴向推力计算的相对误差减小到约3％,方差减小到0.02;叶根反动度关系式的选取对叶轮轴向推力一维计算的精度影响...     

三型面联接的力学特性及加工测量方法

本文以三型面轮轴和轮毂为研究对象,借助有限元分析方法探讨三型面联接的接触应力分布特点,并使用三坐标测量检测仪对三型面加工样件进行测量分析。研究结果表明,三型面联接的接触应力近似呈三角形分布,轮轴承受压应力作用,轮毂承受拉应力作用。研究发现,保证三型面轮轴、轮毂接触面的表面光洁度是减小接触应力的有效措施;设计过程中将轮毂结构设计在转动惯量较小、离心力较小的零件上,可以提高三型面联接方式的使用寿命。将三坐标检测仪的测量数据结果拟合成曲线后发现,现代数控技术加工的三型面轮轴、轮毂可以满足使用要求。     

用流道中线法绘制离心泵叶轮轴面图的改进

通过多个算例,验证了在离心泵叶轮轴面图绘制的流道中线法中用四次方程曲线构造流道中线的不尽合理之处.提出了在流道中线函数式中加入指数项或用洛仑兹曲线作流道中线的改进,得到比较好的结果.     

红外热成像技术在回转窑托轮轴温度监测中的应用

<正>0引言回转窑托轮作为支撑窑运转的支点,承受着热负荷、物料负荷和窑自重三大载荷,托轮轴作为主要支撑,其运行稳定性直接关系着回转窑的安全可靠运行,托轮轴瓦发热在回转窑运转中时有发生,因此实时监测托轮轴温度,及时发现托轮轴温度变化是确保回转窑安全稳定运行的关键因素之一。本文以4000t/d新型干法水泥生产线回转窑托轮轴温度的在线监测的成功案例,阐述该项技术的技术原理、技术背景、设计方案、实施效果等,并对方案进行一定的分析,对同类回转窑托轮轴面温度监测的推广有积极的借鉴和参考作用。     

轮胎滚动阻力试验设备定位误差的补偿

介绍轮胎滚动阻力试验设备定位精度的要求及定位偏差对滚动阻力的影响.给出了定位误差的补偿方法,主要介绍在给定校准负荷情况下产生的轮轴力作为校准值,试验时用此校准值对轮轴力进行修正.分析表明,采用此方法进行补偿得到净轮轴力,可消除定位误差对试验结果的影响.     

回转窑支承系统构件等寿命模糊优化研究

以支承系统各构件疲劳寿命相当为优化目标,考虑接触应力、滚圈变形、托轮、托轮轴配合面不脱开等约束条件的模糊因素,建立了支承系统构件等寿命模糊优化模型,并引入广义最大最小法,对模型进行求解.结果表明:优化后滚圈、托轮、托轮轴的疲劳寿命比较接近,且载荷大于2000kN时,滚圈疲劳寿命有较大幅度的提高.     

三维绕障井双面法井眼轨道优化设计研究

大庆油田老区井网密度不断加大,在进行定向井和水平井的轨道设计时,因地面环境和邻井的限制需要采用三维绕障轨道设计。本文通过二维轨道与老井轨迹的水平投影图和垂直投影图进行绕障分析与轨道优化设计,结合水平投影图和垂直投影图绕障设计,给出整体三维井眼轨道优化设计。利用该方法对井网密集区的57口三维绕障井进行了绕障优化设计与施工,优化后的三维绕障轨道造斜率、摩阻及扭矩满足现场施工要求,达到了较好地防碰绕障效果,该三维绕障设计方法为今后大庆油田三维绕障水平井的设计及钻井施工提供了借鉴。     

Experimental and computational fluid dynamic (CFD) studies on mixing characteristics of a modified helical ribbon impeller

Experimental and computational fluid dynamic (CFD) modeling studies have been performed on mixing characteristics of a new modified helical ribbon impeller in a viscous medium. A novel arrangement for the multiple reference frame (MRF) technique was proposed and the modeling results were compared with those of conventional MRF selecting method. Calculations were performed to study the effects of several parameters: axial flow number, axial circulation time, impeller clearance, and power consumption. The higher performance of the modified impeller has been proven in terms of axial flow number and axial circulation time. The results showed that significant improvement in mixing performance can be obtained at a higher impeller clearance with the modified impeller employed. In addition, the power consumption by the new impeller has been compared with that of the classic one. The CFD-predicted flow patterns generated by the impellers were used to explain the higher performance of the modified impeller. In addition, the results reveal that the CFD-predicted particle volume fractions at various axial distances from the tank bottom are reasonably in agreement with the experimental observations.     

Coupling simulation of fluid structure interaction in the stirred vessel with a pitched blade turbine

The interaction between fluid and a down-pumping pitched blade turbine fixed with a flexible shaft in the stirred vessel,as a typical fluid structure interaction phenomenon,was simulated by coupling the Computational Fluid Dynamics and Computational Structural Dynamics.Based on the verification of the simulated impeller torque and dimensionless shaft bending moment with experimental result,the dimensionless shaft bending moment and various loads acting on impeller (including lateral force,axial force and bending moment) were discussed in detail.By separating and extracting the fluid and structural components from those loads,the results show that the shaft bending moment mainly results from the lateral force on impeller although the axial force on impeller is much larger.The impeller mass imbalance increases the shaft bending moment and the lateral force on impeller,but has little influence on the axial force and bending moment acting on impeller.The dominant frequencies of impeller forces are macro-frequency,speed frequency and blade passing frequency,and are associated with the impeller mass imbalance.     

分段式多级叶片离心泵轴向力的计算

介绍了国内外常用的多级离心泵轴向力计算公式 ,分别用这些公式计算了TP 4 1 1 3 P5 1 2型泵的轴向力。通过轴向力在线监测装置对此泵的轴向力进行了在线监测 ,并将计算结果与实测结果进行了比较 ,确定了比较准确的轴向力计算公式 ,从而为多级离心泵的设计提供了一定的理论依据。     

Heat transfer similarities between impinging jets and axial-flow impellers

Similarities in the flow and heat transfer characteristics between simulation results of a round impinging jet and experimental data obtained on an agitated vessel with an axial flow impeller are presented in this paper. The electrodiffusion method was used in measuring the local heat transfer coefficients on a flat bottom of an agitated vessel. A small axial impeller has been built to provide a clearly defined flow imitating a submerged confined jet impinging the vessel bottom. Our simulation and experimental results show that the flow pattern in the impinging jet region below the axial flow impeller can be compared to the stagnation region of a round impinging jet with a corresponding tangential velocity component. CFD simulations of an impinging jet showed also the importance of different boundary conditions on small electrodes used with the electrodiffusion method and give an approximation of necessary correction factor.     

搅拌生物反应器的循环时间分布和混合结构模型

利用磁粒子流动跟踪法对搅拌生物反应器的循环时间分布进行测定,并将Rushton径向流桨和两种新型轴向流桨在不同介质粘度和转速下的循环时间分布进行比较和性能评价。建立了单桨搅拌生物反应器的混合结构模型,对循环时间分布数据进行拟合,求得模型参数,进而讨论了不同实验条件下模型参数的变化。结果表明,对于非牛顿、高粘度发酵过程,轴向流桨比Rushton桨具有更好的混合特性。     

Numerical determination of the three-dimensional velocity distribution in a baffled pitched blade impeller stirred vessel

The objective of the work presented here was the development of a method of modeling the effect of an impeller on the velocity distribution in a stirred vessel. The developed model makes it possible to numerically investigate the flow field almost independently of any experimental data. The starting point was a force balance around an impeller blade, which took into consideration the lift and drag forces. The obtained volume forces were circumferentially averaged in the impeller region. The calculations were carried out time-averaged for the case of a pitched blade impeller. The results were compared with experimental data which were obtained by laser Doppler anemometry. The comparison of the axial velocity components shows a good agreement between numerical and experimental data. Furthermore some characteristic integral values were calculated, which demonstrate the efficiency of the impeller.     

Gas-Liquid Mixing in a Grid-Disc Impeller Stirred Tank

To enhance the gas-liquid mixing performance in stirred tanks, the grid-disc impeller was designed by replacing the solid disc of the standard Rushton impeller with a grid disc. Gas-liquid hydrodynamics of the new impeller was studied by employing the Eulerian-Eulerian two-phase model coupled with the dispersed k-ε turbulence model. Rotation of the impeller was simulated with the multiple reference frame method. Flow field, gas holdup, and power consumption were investigated and compared with the standard Rushton impeller. The numerical method was validated by comparing the gas holdup with literature. The grid-disc impeller performed better than the Rushton impeller in terms of gas dispersion performance, axial pumping capacity, and energy requirement, indicating its potential for gas-liquid mixing applications.     

Continuous blending of cohesive granular material

Results are presented from discrete element method (DEM) computer simulations of cohesive particles in a periodic slice of a continuous blender. The influence of inter-particle cohesion at various impeller speeds and fill levels is reported. Although increasing cohesion does not significantly change axial flow rates, mixing rates in the transverse plane and axial direction are affected. Mixing is generally enhanced for slightly cohesive materials, but decreases for larger cohesion, similar to trends observed in tumbling batch mixers. Changes in fill level are also shown to affect axial transport rates and mixing. These results suggest that the controllable operating parameters, such as feed rate and impeller speed, may be adjusted for cohesive powder formulations to obtain optimal mixing performance.     

Flow characteristics in a column agitated by blade impellers

Flow characteristics, axial dispersion coefficients in the continuous phase, and holdup of the dispersed phase were studied in a 4.66 cm inside diameter and 100 cm height column agitated by blade impellers. Flow characteristics were analyzed by residence time distribution using impulse input of a tracer. The best reasonable values of Peclet number and holding time were able to obtain by using the response surface method. The axial dispersion coefficients in the single phase flow, and in the two-phase countercurrent flow have been correlated within a confidence level of ±10% when impeller diameter, impeller speed and compartment height, were used as variables. The holdup of the dispersed phase was also correlated in terms of impeller diameter and the operating variables.     

浮动式叶轮结构旋涡泵不稳定运行的问题解决

介绍一般旋涡泵的原理、结构特点,旋涡泵浮动式叶轮与流道环端面存在相摩擦现象,叶轮损坏影响了泵的性能。分析了叶轮受力情况,在平衡轴向力和保证叶轮与流道环轴向间隙前提下,对叶轮进行定位,延长叶轮的使用周期,降低维修成本,提高一般旋涡泵运行可靠性。