基于熵产理论的旋风分离器气固分离性能研究

Since the cyclone separators for the natural gas purification have the disadvantages of high energy consumpsion, narrow highly effective separation scope and lacking of theoretical guidance for scale-up engineering design, the second law of thermodynamics is applied to investigate the mechanism of the energy consumption and the characteristic of the energy consumption efficiency. Thus, it offers new solusions for the research and development of cyclone separators. The characteristic of the minimium separation work versus the seperation efficiency during gas-soild two-phase separation process will be studied by the entropy generation rate model of irreversible processes thermodynamics and the mass transfer theory. The influence of operating pressure and the engineering scale-up parameters on the distribution of entropy generation due to turbulent dissipation, heat transfer and fluid viscosity will be investigated. Therefore, the pressure drop model of cyclone separators will be established on the basis of entropy generation theory and the experiments. In order to reveal the relationship among the driving force potential energy function of the separation field, particle migration features and total separation efficiency in each local region, the gas-solid two-phase flow simulation and experiments involving the local region separation efficiency will be carried out.According to the particle properties and the requriment of the separation accuracy, the optimization method of the cyclone separation vane with the objective function of the minimum entropy generation will be consequently constructed and the active control of separation for gas-solid two-phase flow will be achieved. Hence, the combination design method of the vane cyclone separator is established, which is suitable for the conditions of high operating pressure, broad highly efficiency separation scope and large capacity.

针对天然气净化用旋风分离器存在能耗高、高效分离工作范围窄和缺乏工程放大理论依据等问题，应用热力学第二定律系统研究其内能耗产生机制和用能效率特性，为旋风型分离器的研发提供新思路。利用不可逆过程热力学熵产率方程和传质理论，探讨气固两相分离过程的最小分离功随分离效率的变化特性。研究操作压力和工程放大比例对旋风分离器内湍流熵产、温差传热熵产和粘性熵产分布特性的影响规律，建立基于熵产机理和实验测定数据结合的旋风分离器压降计算模型。采用气固两相流动模拟和局部区域分离性能实验测定方法，揭示旋风分离器内各局部区域分离场势能函数、颗粒运移特性以及总分离性能间的影响机制。在以上研究基础上，依据颗粒物性和分离精度要求，构建以分离过程熵产最小为目标函数的旋风型分离叶栅优化方法，实现气固两相分离流场的主动控制，进而建立满足低能耗、高效分离范围宽和大处理量工况要求的多级旋风型叶栅间匹配设计方法。

针对天然气净化用旋风分离器存在能耗高、高效分离工作范围窄和缺乏工程放大理论依据等问题，结合热力学第一定律和热力学第二定律建立流动过程熵产与㶲损及压降间的关系，建立了壁面熵产计算模型，形成了基于熵产计算的定量分析方法。将熵产分析方法应用于研究旋风分离器内的能耗，得到壁面熵产和湍流熵产占总熵产的比例分别大于56%和38%，是影响旋风分离器能耗的主要因素。在不同结构尺寸、操作参数下，采用熵产分析方法研究旋风分离器能耗，并对比多个压降模型计算值和实验测量值。结果表明熵产计算方法能够比较准确地预测旋风分离器的能耗。找出能耗分布的核心部位，通过对核心部位进行结构改进，得到几种新型结构旋风分离器。此外还研究旋风了分离器升气管直径比、入口截面比以及几何放大等因素对切向入口旋风分离器内熵产分布特性的影响规律。通过局部加料方式研究旋风分离器内各区域的分离能力，结果表明在分离空间内，局部分离能力随径向位置的增大而提高，并且在 时，分离能力提高较快；随着轴向位置向下移动，局部分离能力提高，且在筒体部分提高的速度较快。进行了旋风型分离叶栅内部流场数值模拟计算，波形板除雾器的屈角、折弯次数、流道宽度以及分离气速等结构参数和操作参数是影响其性能的最主要因素，建立了分离性能多元回归模型，得到最佳参数为新式旋风型分离叶栅优化设计提供参考，进而建立满足低能耗、高效分离范围宽和大处理量工况要求的多级旋风型叶栅间匹配设计方法。