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Mercuryjie2008

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旋流干燥器内部的流场非常复杂，使得旋流干燥器的研究存在很大的困难。气体以切向进入干燥体，这有助于强化气固两相的传递过程，同时切向流动加剧了固相颗粒间相互的摩擦与碰撞，也增大了颗粒与气流的接触面积，加快了颗粒的干燥。由于旋流板的作用，进一步使气固湍动作用加剧，使得不同粗细的颗粒得以均匀的干燥。目前，对于旋流干燥器的理论与实验研究均非常少见，本文将借助计算机模拟技术和实验对其进行初步的探讨。
本文主要采用计算流体动力学CFD方法对旋流干燥器中气固两相流速度场进行了CFD模拟分析，研究了单相流场、气固两相流场、颗粒的体积分率、颗粒运动轨迹、压力损失。
首先，本文采用三种模拟湍流的常见模型－－标准模型、RNG 模型、Reynolds应力模型(RSM模型)对旋流干燥器相流场进行模拟，经比较得出RSM模型更适合于模拟旋流干燥器内的流场。然后，采用RSM模型对气固两相进行耦合计算。通过对气相流场的模拟得出了旋流干燥器内速度场轴向、径向、切向三维分速度的分布特征。三者以切向速度为主，其值远大于其它两个方向的速度。并进一步分析压力的分布规律以及和进口气速的关系。
其次，对气固两相流动进行模拟，气相采用欧拉坐标系下的RSM模型，颗粒相分别采用两种模型－欧拉坐标系下的混合模型和拉格朗日坐标系下的随机轨道模型进行模拟，同时考虑相互的耦合作用。结果：① 混合模型模拟给出了固体颗粒在干燥器内的分布情况，结果表明固体颗粒的体积分率随着径向的增大而增大，在干燥器壁含量最高。② 随机轨道模型模拟给出了颗粒的运动轨迹，表明颗粒在干燥器内的运动具有很大的随机性。
最后，为了更好的了解旋流干燥器的流动特性，本文对旋流干燥器内停留时间的分布进行了实验测定。

通过把部分实验数据与模拟结果进行对比，发现数值模拟的结果和实验数据较为吻合，从而验证了所建模型的正确性，对今后的设计以及理论研究工作具有一定的参考意义。

[ Last edited by Mercuryjie2008 on 2011-3-20 at 07:43 ]

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1楼 2011-03-19 15:46:26

已阅回复此楼关注TA 给TA发消息送TA红花 TA的回帖

dictall

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Mercuryjie2008(金币+100, 翻译EPI+1): 非常感谢啊 2011-03-21 19:22:11

Flow field inside of cyclone dryer is very complicated, thus making the research extremely difficult. The gas tangentially flows into the drying body, which helps strengthen the transmission of gas-solid process, enhance the collision or friction between solid particles, increase the contact area between particles and air flow, and speed up the air drying process. Due to the cyclone board, gas-solid turbulent action becomes further intensified, which makes different scales of the particles dried homogeneously. At present, either theoretical or experimental studies about cyclone dryer are rare. Our paper is a preliminary research on this respect with the help of computer simulation and some experiments.
In this paper, we mainly take the computational fluid dynamics CFD methods to simulate the flow velocity field of gas-solid inside the dry body, and analyze the single-phase flow field, gas-solid flow field, particle volume fraction, particle motion track, the pressure loss.
Firstly, we assume three common turbulence simulation model - the standard model, RNG model, and Reynolds stress model (RSM model) to simulate fluid flow field, and find RSM model is more suitable by comparison, so we adopt the RSM model for gas-solid coupling calculation. By gas flow field simulation, we obtain axial, radial, tangential 3D velocity field distribution, finding tangential velocity is much larger than the others. Further analysis focus on principle of pressure distribution and its relationship with gas incoming speed.
Secondly, simulation on gas-solid flow is made. Euler coordinate RSM model is used for gas simulation, and two models are used for particles simulation - Euler coordinate hybrid model and Lagrange coordinate stochastic model. The mutual coupling is also taking into account during the computing process. Conclusions: ① The hybrid model simulation shows the solid particles distribution in the dryer, namely the volume fraction of solid particles increases along with the radial direction, and reach the highest on the wall. ② stochastic model shows the particle trajectories, indicating that the movement of particles in the dryer is randomness.
Finally, in order to get a better understanding of the dynamic characteristics of cyclone dryer, we detect the particles’ residence time in the dryer.
By comparing some experimental data and simulation results, we find they agree well, which proves the correctness of our simulation. And we believe our work has a certain reference value for further design or theoretical research.

正好我也是做模拟的，刚好看到了，顺便翻译一下。

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