【作者】 易林；

【导师】 王灿星；

【作者基本信息】 浙江大学 ， 流体力学， 2005， 硕士

【摘要】 螺旋型旋风分离器是一种新型结构的旋风分离器,这种旋风分离器的最主要特点是其筒体内拥有一定圈数的螺旋型通道,从而能够形成有利于颗粒分离的气体流场。实验已经证实,这种结构的旋风分离器具有体积小、效率高、压力损失小的优点。 本文首先计算了二维情况下螺旋通道内的两相流动,得到了螺旋通道内的速度和压力分布以及颗粒的运动轨迹。二维计算的目的是为了对螺旋型旋风分离器内的流场结构和颗粒分离有一个初始的了解,并可以积累实体建模、网格生成等方面的经验,为三维数值模拟做准备。 由于种种原因,本文没有能够进行实验研究。为了验证数值计算方法的准确性,本文分别对普通旋风分离器内的气体流场和颗粒分离性能进行了数值模拟,并和其他研究者的实验结果进行了对比。这种验证工作也可以获得计算格式选取等方面的经验,为之后的螺旋型旋风分离器的三维数值模拟提供依据。这些验证工作单独成为一章,成为本文不可缺少的一部分。 这些准备工作结束后,可以根据得到的结论建立一套适合于螺旋型旋风分离器三维数值模拟的方法,且由于前期验证工作的存在,得到的结果是值得相信的。气体流场的计算结果表明,螺旋通道内的流场是比较稳定的类似自由涡的流场,简体中心区域的流场是包含强旋和回流的复杂流场。颗粒运动轨迹的计算表明了颗粒的入口速度和位置对颗粒捕集有明显的影响。本文对不同工况和不同结构参数的螺旋型旋风分离器进行了三维两相流的数值模拟,探讨了不同气体流量和各种结构参数对分离器分离性能和压力损失的影响。发现随气体流量的增加颗粒分离效率显著变高,但随之而来会使分离器的压力损失急剧上升;同时发现对分离效率影响较大的是旋转圈数N和阿基米德螺线常数k,而各个结构参数对压力损失均有较大影响。 在三维数值模拟结果的基础上,结合理论分析,本文得到了螺旋型旋风分离器的分级效率和压力损失系数的半经验计算公式。这些公式成为螺旋型旋风分离器优化设计模型的重要组成部分——在本文的最后一章里,作者从数学规划的角更多还原

【Abstract】 The spiral cyclone is a new type of cyclone. Its main character is that there is a continuous spiral channel with some turns inside the cyclone body, so a reasonable gas flow field can be formed which is advantageous for particle separation. Experimental studies have demonstrated that spiral cyclones have significant advantages of higher collection efficiency, lower pressure drop and smaller geometry dimension than conventional cyclones.In the first part of this paper, the two-dimension gas-flow field in the spiral channel is simulated numerically. The gas flow field is obtained by solving the N-S equations along with turbulence model; and particle trajectories are obtained by solving their momentum equations. The purpose of this simulation is to get the first impression of flow field features in a spiral cyclone, and to get the experiences of geometry construction and grid generation.For some reasons, experimental study has not been carried out in this paper. To validate the effectiveness of numerical method, the simulations of the gas flow and particle separation in conventional cyclones are performed. Comparisons between the numerical results and experimental data have been made and it is shown that there are reasonable agreements. This investigation can also provide the experiences about numerical schemes selecting, which is helpful for the next three-dimension simulation of the performance of spiral cyclones. These work of validation are specified as an individual chapter, which becomes to be an indispensable part of this paper.After these above preparations, a numerical solution strategy for the simulation of three dimensional gas-particle flow in the spiral cyclone can be constructed. For the existence of validations described above, results from these numerical simulations can be considered to be reliable. In this paper, we have calculated the two-phase flow in many spiral cyclones with different operating condition and various geometrical dimensions, and the effects of them on the spiral cyclone performance are discussed.Based on theory analysis and on the above numerical results, we construct the semi-empirical function expressions of particle collection efficiency and pressure drop coefficient. These expressions play an important role in the model of optimum design of configuration size of spiral cyclones—in the last part of this paper, we have discussed the method of constructing the optimum model from the view of mathematical programming, and the content includes: the establishment of objective function, the choosing of design variables and the specification of restriction conditions.更多还原