低速轴流压气机单转子旋转失速三维数值模拟和实验比较

本文通过求解三维不可压N-S方程,对三级低速轴流压气机第一级的孤立转子进行数值模拟,在出口加上节流阀进行了非定常计算,得到了失速先兆的特性,并且与压气机失速实验进行了比较。结果表明,计算与实验的特性线符合较好,单转子三维计算与压气机三级实验中第一级转子在失速先兆和失速团的特性一致。并且数值失速过程中动叶通道内部动态压力的变化与实验结果也很接近。     

用SPIV技术测量压气机转子尖区复杂流动

本文将数字式SPIV技术应用到低速大尺寸压气机实验台上,并在设计状态和近失速状态下,对转子槽道内叶尖区域多个截面内的三维瞬态速度场进行了成功测量。测量结果表明SPIV透过机匣视窗及即可直接测量旋涡和二次流的瞬态结构,而且能够解决多级压气机内部流场的测量.在压气机SPIV测量中,激光反光的控制和示踪粒子的均匀稳定散播是决定成败的关键因素。     

进口附面层厚度对弯叶片扩压叶栅损失的影响

本文通过人工加厚叶栅进口附面层厚度，考察了叶搬进口附面层厚度对弯叶片扩压叶栅损失的影响．实验结果表明，进口附面层厚度增加时，叶栅两端区二次流增强，叶栅损失增大．采用正弯曲叶片在参考进口附面层状态和人工加厚附面层时均未得到叶栅损失的降低，而反弯曲叶栅损失的降低出现在参考进口附面层状态下．     

离心压气机叶轮内部流动的数值研究:分流叶片的作用

本文对一台单级压比为4/1的离心压气机叶轮内部流动,进行了数值模拟的研究。计算方法基于Jameson格式,湍流模型选择Baldwin-Lomax模型。计算结果为分析叶轮流道内二次流的形成与发展,提供了详细的流动结构。通过对不同通流截面速度分布的比较,发现分流叶片可以延缓横向二次流的发展,降低叶片吸力面扩压程度,减小叶轮出口尾迹的强度与范围,对提高叶轮效率起到决定性的作用。     

一台低速压气机的失速前扰动分析

本文应用小波的方法对一台三级、低速、轴流压气机的动态实验数据进行了分析。所分析的数据点的范围从压气机发生旋转失速前1000转开始,分析结果表明:失速前扰动的出现是间歇性的,即扰动出现、发展、消失、再出现、再发展、再消失。将所有沿圆周方向布置的传感器信号一起分析,失速前扰动形成的团沿圆周方向旋转。而且,越接近失速点,失速前扰动团沿圆周方向传播的距离相对越长。同时,表明结构的不均匀产生在第七传感器和第一传感器之间。     

Twin Bifurcation Phenomena and Isolas of Multiple-Steady-States Transition in Nonideal Chemical Reaction-Diffusion Systems

The present paper narrates the influence of nonideality of externally controlled components on multiple-steady-state transitions studied by using the regular solution model. Under certain conditions the splitting of the original cusp causes "twin" bifurcation points accompanied by isolas which could shrink to an elliptic singular point or a cusp, or even collapse to a hyperbolic singular point in the different cases.     

Twin column chromatography for industrial-scale decontamination processes

A frontal chromatographic unit was devised consisting of a column-detector-column array. The unit is either equipped with identical columns (identical twins) or with columns of varying length (fraternal twins). Due to the finite nature of the columns, a prerun is formed at the column walls following the same regularities as the main stream. These regularities are used for the identification of the process termination below the detection limits of the monitor. For the implementation, a clear preference is given to the employment of fraternal twins, as the feed assay can be integrated into the separation process.     

Extended finite element method for viscous flow inside complex three‐dimensional geometries with moving internal boundaries

A three‐dimensional extended finite element method is presented to simulate Stokes flow in complex geometries with internal moving parts. Instead of re‐meshing the flow domain, the kinematics of the internal objects are imposed on the conservation equations using a constraint, implemented with a Lagrangian multiplier. To capture discontinuities of field variables, such as pressure and velocity, on the intersected elements, XFEM is used. To validate our method, it is first applied to a relatively simple problem, that is, the flow around a cylinder in a channel. The results are verified by comparing with a boundary‐fitted solution. After validation of the model and its implementation, the three‐dimensional flow in a twin‐screw extruder is simulated and the results are compared with experimental data from literature. XFEM shows very good accuracy for complex geometries with internal moving parts and narrow gap regions where the shear rate is orders of magnitude higher than in other regions. Copyright © 2011 John Wiley & Sons, Ltd.     

静压气体轴承支撑的线性压缩机低频输出特性研究

气体轴承是线性压缩机的一种新型支撑方式,可消除活塞与气缸之间的磨损,提高压缩机的寿命。为了清晰了解气体轴承在低频下的特性,对气体轴承支撑的Redlich线性压缩机输出能力进行了模拟。气体轴承在低频下的稳定性以及压缩机的输出能力特性研究,可进一步拓展气体轴承在线性压缩机和斯特林制冷中的应用。     

主动式冷却系统微型化发展现状

常规的制冷系统在一些特殊场合下不能用作消除热害的理想解决方案.得益于微系统工艺和微尺度传热传质理论的不断完善,以蒸气压缩系统、吸收式系统和热电系统为代表的主动冷却系统在微型化和轻量化方面取得显著进展.文中基于国内外最新文献分别介绍了这三种主动冷却系统的优、缺点及发展现状,通过实例对比说明蒸气压缩系统具有较大发展潜力,就...