科氏力作用下旋风分离器内颗粒运动规律的研究

发布时间：2018-11-18 20:46

【摘要】：旋风分离器作为一种结构简单、方便快捷、高效可靠的气固分离设备,被广泛地应用于化工、石油、能源、环保、矿业等诸多领域。目前,在能源短缺和环境恶化的大背景下,工业生产中对旋风分离器的设计和应用提出了更加严格的要求。但由于旋风分离器内部为科氏力作用下各向异性的三维强旋流流场,颗粒在其中的运动极其复杂。因此,深入研究旋风分离器内部流场结构以及颗粒的运动规律,对旋风分离器的结构优化和性能提升有着重要的意义。本文采用实验和数值模拟相结合的方法,对直切式旋风分离器内的流场和固相颗粒运动规律进行了深入的研究,具体内容如下:(1)通过实验测量了不同流量下旋风分离器的进出口压力差和颗粒的分离效率。(2)采用不同的湍流模型计算了旋风分离器的进出口压差,并与实验数据对比。结果表明雷诺应力模型(RSM),对流项的QUICK格式和压力梯度项的PRESTO压力插补格式更适合用于旋风分离器的流场模拟。通过对气相流场的分析可知,切向速度和轴向速度在颗粒的分离中起主导作用;旋风分离器内的流动伴随着能量的损失,其表现为压力的损失;旋风分离器外圈向下的流体和内圈向上的流体中夹杂着二次流动,它们的存在会改变流场结构,从而影响颗粒的分离。(3)在气相流场的基础上,利用离散相模型(DPM)对旋风分离器的气固两相流场进行了数值模拟,其中湍流扩散采用基于随机轨道模型的随机游走模型(DRW)。通过对比实验、理论和数值计算的分级效率可知,三者吻合较好,说明离散相模型和随机游走模型在气固两相流场的模拟上能够保证结果的准确性。(4)通过研究颗粒运动轨迹与粒径、入口位置的关系可知,细微颗粒由于受空气粘带的作用较大,因此受短路流的影响较大;小颗粒受纵向涡流的影响较大,因此呈现出在内外旋流间交替运动的情况;大颗粒则主要受锥体段底部偏心环流的影响。此外,细微颗粒从入口中下部靠外侧的区域进入时分离效率最高;小颗粒从入口中下部进入时分离效率最高;大颗粒从入口上部和外侧区域进入时分离效率最高。(5)针对颗粒运动规律的研究结果,将旋风分离器的进气管改为缩口式结构。通过模拟研究发现,当缩口角为20°时,既能有效地提升旋风分离器的分离效率,又不会使分离器的压降升高太大而造成过多的能量损耗。
[Abstract]:As a simple, convenient, efficient and reliable gas-solid separation equipment, cyclone separator has been widely used in many fields such as chemical industry, petroleum, energy, environmental protection, mining and so on. At present, under the background of energy shortage and environmental deterioration, the design and application of cyclone separator in industrial production is more stringent. However, the motion of particles in the cyclone separator is extremely complex because of the anisotropic three-dimensional strong swirl flow field under the action of Coriolis force. Therefore, it is of great significance to study the flow field structure and the movement of particles in the cyclone separator to optimize the structure and enhance the performance of the cyclone separator. In this paper, the flow field and the motion of solid particles in a tangential cyclone separator are studied by means of both experimental and numerical simulation. The main contents are as follows: (1) the inlet and outlet pressure difference and particle separation efficiency of cyclone separator under different flow rates are measured experimentally. (2) the inlet and outlet pressure difference of cyclone separator is calculated by using different turbulence models. And compared with the experimental data. The results show that the QUICK scheme of the Reynolds stress model (RSM), convection term and the PRESTO pressure interpolation scheme of the pressure gradient term are more suitable for the flow field simulation of the cyclone separator. Through the analysis of gas phase flow field, it can be seen that tangential velocity and axial velocity play a leading role in the separation of particles, and the flow in the cyclone separator is accompanied by the loss of energy, which is the loss of pressure. There are secondary flows in the downward fluid in the outer circle of the cyclone separator and in the upward fluid in the inner circle. Their existence will change the flow field structure and thus affect the separation of particles. (3) on the basis of the gas phase flow field, Numerical simulation of gas-solid two-phase flow field in cyclone separator was carried out by using discrete phase model (DPM), in which the stochastic walk model based on stochastic orbital model (DRW).) was used for turbulent diffusion. Through the comparison experiment, the classification efficiency of theoretical and numerical calculation shows that the three are in good agreement with each other. The results show that the discrete phase model and the random walk model can guarantee the accuracy of the results in the simulation of gas-solid two-phase flow field. (4) by studying the relationship between particle trajectory, particle size and inlet position, we can see that, The fine particles are greatly affected by short-circuit flow because of the effect of the air adhesion zone. The small particles are greatly affected by the longitudinal eddy current, so they appear to move alternately between the inner and outer swirls, while the large particles are mainly affected by the eccentric circulation at the bottom of the cone segment. In addition, the separation efficiency of fine particles is the highest when entering from the region near the outside of the middle and lower part of the entrance, and the separation efficiency of the small particles is the highest when entering from the middle and the lower part of the entrance. The separation efficiency of large particles is the highest when entering from the upper and outer regions of the inlet. (5) according to the results of the study on the law of particle movement, the intake pipe of the cyclone separator is changed into a reentrant structure. The simulation results show that when the angle is 20 掳, the separation efficiency of the cyclone separator can be improved effectively, and the pressure drop of the separator will not be increased too much, resulting in too much energy loss.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.8

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