撞击流对喷雾燃烧过程的强化机理研究

The scientific concept of impinging streams (IS) was proposed to intensify the interphase heat and mass transfer process in gas-particle two-phase systems. The IS devices have a broad application in some industrial processes, such as coal gasification, combustion, drying, extraction, etc. IS can enhance the combustion process. Nevertheless, the physical and chemical processes in an IS are extremely complex and fast, in which the enhanced mechanism is not clear. This project will study on the enhanced mechanism of spray combustion process by IS. The spray combustion in IS is used as the research object in this project. The later development model after collision between droplets will be proposed, and then the integrated mathematical model for the spray combustion process based on the DSMC method will be established for the first time. Based on combination of the experimental study, theoretical analysis and numerical simulation, the interactions of spray combustion process and the law of droplet vaporization, the law of droplet motion, collision and later development, the gas phase flow field, the gas component distribution, and so on, will be analyzed. The main influencing factors and the optimum operating parameters of spray combustion in IS will be obtained to reveal the enhanced mechanism of spray combustion process by IS. The challenges in this project are on the searching of the main influencing factors of spray combustion process in IS and the establishment of later development model after collision between droplets. The theoretical basis will be established for the engineering applications of IS in spray combustion field by the successful implement of the present project.

撞击流是针对强化气固相间热质传递过程而提出的，现已广泛应用于煤气化、燃烧、干燥、萃取等工业过程中。撞击流能够有效强化燃烧过程，但由于撞击流内物理化学过程非常复杂且迅速，其中所包含的强化机理还不清楚。本课题将针对撞击流对喷雾燃烧过程的强化理展开研究。 本课题拟以喷雾撞击流燃烧为研究对象，构建雾滴碰撞后续发展模型，首次建立基于直接模拟蒙特卡洛(DSMC)方法的喷雾撞击流燃烧综合模型。以实验研究、理论分析与数值模拟为手段，对撞击流内喷雾燃烧过程与雾滴蒸发规律、雾滴运动，碰撞及后续发展规律、以及气相流场及组分分布规律等的相互作用进行分析研究，掌握喷雾撞击流燃烧过程的关键影响因素和最佳操作参数，揭示撞击流对喷雾燃烧过程的强化机理。本课题的难点在于撞击流强化喷雾燃烧过程的关键影响因素的寻求，以及雾滴碰撞后续发展模型的构建等。 本课题的成功实施，将为撞击流在喷雾燃烧领域的有效应用奠定更坚实的理论基础。

本课题针对撞击流对喷雾燃烧过程的强化理展开研究。. 首先，采用数值模拟、理论分析和实验方法对撞击流内液滴运动、碰撞与后续发展规律，以及液滴碰撞后续发展的关键影响因素进行分析研究。利用所建立的理论模型，研究了同轴对置气液两相撞击流中液滴碰撞后液滴融合聚并或二次雾化的影响因素。模拟结果表明：进口液滴粒径越小、黏度越大，液滴发生碰撞后聚合的概率越大；进口液滴速度越大，液滴碰撞后二次雾化的概率越大；在相同条件下，液滴发生斜碰时二次雾化的概率比发生正碰时要大。为了进一步探索撞击流内液滴碰撞后续发展行为，设计搭建了由激光点光源和高速数码摄像机构成的高速数码摄像系统，及气液两相撞击流实验平台。利用高速数码摄像系统，分析了各种参数对撞击流中液滴碰撞结果的影响规律。实验结果表明：两个液滴相向运动相互碰撞后，发生拉伸断裂的条件是：We≥6.29B-4，0.38＜B＜1；发生反射分离的条件是：We＞18.67[2(1.08-B)5/2-1]-1，0＜B＜0.28；进口液滴粘度越小、表面张力越大、欧森数越小，液滴碰撞后越容易破碎。. 其次，为了揭示撞击流对喷雾燃烧过程的强化机理，建立了喷雾撞击燃烧综合理论模型，并搭建了喷雾撞击燃烧实验平台。通过对撞击流内喷雾燃烧过程气相流场、组分分布、温度分布规律等进行分析研究，掌握喷雾撞击燃烧过程的关键影响因素和最佳操作参数，揭示撞击流对喷雾燃烧过程的强化机理。研究结果表明：撞击流对喷雾燃烧有很好的稳燃作用；撞击流对喷雾燃烧的强化主要是由于撞击区的高度湍动，以及该区域液滴的振荡汇集作用。本课题的成功实施，将为撞击流在喷雾燃烧领域的有效应用奠定更坚实的理论基础。. 项目资助发表期刊和会议论文共6篇，申请燃烧方面发明专利1项，培养硕士研究生3名，其中1名已经取得硕士学位，2名在读。