大颗粒鼓泡流化床颗粒压力脉动分析

发布时间：2018-03-16 17:09

本文选题：气固两相流动　切入点：颗粒压力脉动　出处：《东北电力大学》2015年硕士论文　论文类型：学位论文

【摘要】：近些年流化床技术在能源、化工等领域得到了十分广泛的应用，但是由于流化床内气固两相流动的复杂性和不确定性，使我们对气固流化床内流体的流动特性还不是完全认识。在流化床的设计和运行中颗粒压力的脉动是十分重要的参数，颗粒压力的特性是流化床内其它各种特性的总体反映，而应用试验方法研究流化床内的气固两相流动、传热传质以及在放大等方面还有很多不足，通过应用fluent数值模拟的方法辅助试验很好地解决了这些问题，也可以预测或检验实验的结果，对流化床的应用具有理论指导作用。本文应用欧拉-欧拉双流体模型模拟了D类粒子的流态化过程。通过测定双支腿流化床在相同布风板开孔率、不同的表观风速、不同床高以及观察高度时床内颗粒压力的脉动、颗粒浓度的变化以及双支腿流化床的翻床现象的产生，对所得的数据进行傅里叶变换、小波变换的分析，得出床内颗粒压力的脉动具有低频特性，颗粒浓度的变化具有宽频特性，且床内颗粒压力的脉动主要是由床内气泡的生成、合并、破裂及两侧床腿内颗粒相互交换造成的，，而双支腿流化床内翻床现象的产生主要是：在运行过程中两侧床内颗粒压力的不同使得床腿内的颗粒相互交换，进而导致两侧床内颗粒浓度的不同，这是一个正反馈过程，再不进行主动调节时，单侧床内颗粒浓度逐渐增大最后导致翻床。
[Abstract]:In recent years, fluidized bed technology has been widely used in the fields of energy and chemical industry, but because of the complexity and uncertainty of gas-solid two-phase flow in fluidized bed, The particle pressure fluctuation is a very important parameter in the design and operation of the fluidized bed, and the characteristics of the particle pressure is the overall reflection of the other characteristics in the fluidized bed. However, there are still many shortcomings in the study of gas-solid two-phase flow, heat and mass transfer and amplification in fluidized bed by using the experimental method. These problems are well solved by using the fluent numerical simulation method to assist the experiment. The experimental results can also be predicted or tested, which can be used to guide the application of fluidized bed. In this paper, Euler-Euler two-fluid model is used to simulate the fluidization process of D particles. Under different bed height and observed height, the fluctuation of particle pressure, the change of particle concentration, and the phenomenon of turning over bed in a fluidized bed with two legs are produced. The obtained data are analyzed by Fourier transform and wavelet transform. It is concluded that the pulsation of particle pressure in the bed has the characteristics of low frequency, the variation of particle concentration has the characteristic of wide frequency, and the pulsation of particle pressure in the bed is mainly caused by the formation, amalgamation and rupture of the bubbles in the bed, as well as the exchange of particles between the two sides of the bed leg. However, the phenomenon of double leg fluidized bed inversion is mainly caused by the different pressure of particles in both sides of the bed, which makes the particles exchange with each other, which leads to the difference of particle concentration in both sides of the bed, which is a positive feedback process. Without active adjustment, the particle concentration in the single bed increases gradually and finally results in the turning of the bed.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.13

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