• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >*Mixing and dispersion of particle ropes in lean phase pneumatic conveying
【24h】

*Mixing and dispersion of particle ropes in lean phase pneumatic conveying

机译：*稀相气动输送中颗粒绳的混合和分散

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The objective of the present study was to investigate mixing mechanisms in lean phase pneumatic conveying, with the emphasis on techniques for dispersing of severe particle stratification caused by flow through a 90 degree elbow. The study consisted of a combined numerical and experimental study of the rope dispersion characteristics of various mixing devices which were installed immediately downstream of elbow. The laboratory experiments were conducted in a 0.154 m. I.D. vertical test section. Pulverized coal particles with a mean diameter of 59 micron were used as a test material. The numerical simulations were carried out using the CFX-4.2 code developed by AEA Technology. Local particle velocities and concentrations were measured using a reflective type fiber optic probe. Comparisons with the fiber optic probe measurements for time average particle concentration and velocities revealed that the CFD code accurately predicted most of the important flow behavior occurring in the particulate phase in the presence of the mixing devices.;The effect of secondary velocities on the rope dispersion characteristics was investigated by using a flow straightener installed after the elbow. Both numerical and experimental results revealed that the rope dispersion rate in axial and radial directions was significantly reduced in the absence of secondary velocities.;The effectiveness of several different types of flow mixers were investigated. These included, nozzles, air jet injection, swirl vanes, orifice plates, and deflector blocks. Although all mixing techniques were able to disperse the particle rope within nine pipe diameters from the bend exit plane, nozzles with beta ratios (beta) of 0.5 and 0.67, an orifice plate with a beta ratio (beta) of 0.7, and air jet injection from the inner wall caused the most more rapid rope dispersion. However, both the nozzles and orifice plate caused excessive pressure drop and the air jet injection technique increases the flow rate of conveying fluid carried by the pipe.;In addition to the time average particle concentration and velocity measurements, a detailed study was performed on the limits of the cross-correlation technique along with the window overlapped processing technique to measure instantaneous particle velocities using a fiber optic probe. It is shown that the cross-correlation technique is able to measure particle velocity fluctuations up to 75 Hz. More importantly, the window overlapping does not increase the velocity sampling frequency as claimed in the literature. However, this processing technique reduces the error in estimating rms particle velocities when the probe sampling frequency is approximately four times less than the highest frequency occurring in the flow.
机译：本研究的目的是研究稀相气力输送中的混合机理，重点是分散由于流过90度弯头而引起的严重颗粒分层的技术。该研究包括对直接安装在弯头下游的各种混合装置的绳索分散特性进行数值和实验的组合研究。实验室实验在0.154 m内进行。 ID。垂直测试部分。将平均直径为59微米的粉煤颗粒用作测试材料。使用AEA Technology开发的CFX-4.2代码进行了数值模拟。使用反射型光纤探针测量局部颗粒速度和浓度。与光纤探头的时间平均颗粒浓度和速度测量结果的比较表明，CFD代码准确地预测了存在混合装置时颗粒相中发生的大多数重要流动行为。次级速度对绳索分散的影响通过使用安装在肘部之后的整流器来研究其特性。数值和实验结果均表明，在不存在次级速度的情况下，绳索在轴向和径向上的分散速率显着降低。;研究了几种不同类型的混流器的有效性。这些包括喷嘴，空气喷射注入，旋流叶片，孔板和导流板。尽管所有混合技术都能够将颗粒绳分散在从弯管出口平面起的九个管道直径内，但β比率（β）为0.5和0.67的喷嘴，β比率（β）为0.7的孔板和空气喷射注入从内壁引起的绳索扩散最迅速。但是，喷嘴和孔板都造成过大的压降，并且空气喷射注入技术增加了管道输送的输送流体的流量。除了时间平均颗粒浓度和速度测量外，还对管道进行了详细研究。互相关技术的局限性以及与窗口重叠处理技术一起使用光纤探头测量瞬时粒子速度的技术。结果表明，互相关技术能够测量高达75 Hz的粒子速度波动。更重要的是，窗口重叠不会增加文献中所要求的速度采样频率。但是，当探针采样频率比流中出现的最高频率小大约四倍时，这种处理技术会减小估计均方根粒子速度的误差。

著录项

  • 作者

    Bilirgen, Harun.;

  • 作者单位

    Lehigh University.;

  • 授予单位 Lehigh University.;
  • 学科 Mechanical engineering.;Chemical engineering.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 310 p.
  • 总页数 310
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号