【作者】 黄迎；

【导师】 宁智；

【作者基本信息】 北京交通大学 ， 工程热物理， 2010， 硕士

【摘要】 柴油机微粒排放问题及其相关研究已受到国内外高度重视,然而,人们对柴油机微粒在排气过程中的再悬浮规律及其影响因素的了解却非常有限。微粒再悬浮作为柴油机微粒净化捕集及微粒采样等过程中的一个重要现象,研究其影响因素、作用规律并总结出再悬浮的控制方法,就显得尤为重要。本文首先从接触半径和材料性质两方面入手,对现有接触模型进行分析及选择,确定将DMT模型作为微粒团再悬浮模型的基础。在DMT模型的基础上,分析现有微粒再悬浮模型,选择微粒瞬时力矩平衡模型作为初始模型,并针对球形微粒团的受力特性,建立了球形微粒团再悬浮静态模型。在球形微粒团再悬浮静态模型的基础上,结合椭球形微粒团所具有的形态特征及物理特性,建立了椭球形微粒团再悬浮静态模型；其中,通过曳力系数推导了椭球形微粒团所受曳力的表达式,弥补了球形微粒团再悬浮静态模型的不足。利用建立的球形微粒团再悬浮静态模型和椭球形微粒团再悬浮静态模型,对球形、椭球形微粒团所受重力、粘附力、碰撞力、曳力以及浮力进行了分析,重点研究了微粒团形态变化对其受力的影响及其变化规律。对球形、椭球形微粒团所受重力力矩、粘附力矩、碰撞力矩和曳力力矩进行了分析,重点研究了微粒团形态变化对力矩的影响、力矩变化规律以及各力矩作用的主次关系。对球形、椭球形微粒团各力矩的综合作用进行了研究,分析了粘附角、管径和平均气流速度对微粒团再悬浮的影响,重点分析了平衡状态下的微粒团形态与力矩间的关系以及力矩变化能够引发的微粒团运动状态的改变。通过论文的工作,得到了不同形态微粒团所受力和力矩的影响因素、所受力和力矩的变化规律以及微粒团形态变化带来的影响,给出了微粒再悬浮的影响规律,并提出了微粒再悬浮的控制方法。研究成果可以为不同形态柴油机沉降微粒在排气净化和微粒采样中再悬浮规律的研究提供一定的理论依据和研究基础。更多还原

【Abstract】 High attention is paid to the research on the problem of diesel particles emission at home and abroad, but diesel particle reentraiment in exhaust pipe and the influence factors what we know are very limited. As one of the important phenomena in controlling of the diesel engine’s particles and paticle sampled, analysing particle reentrainment’s influence factors, regulary and summarising the way of controllong particle reentrainment become very meanful.According to contact radius and werkstoffart, analysing and choosing contact models, the DMT model was chosed as the foundation of aggregate reentrainment model. On that base, analsing reentrainment mechanism models, present the model to clarify the reentrainment mechanism of spherical aggregates. Then, present the model to clarify the reentrainment mechanism of ellipsoidal aggregates, basing on the model of spherical aggregates and configuration of ellipsoidal aggregates. Especially, derive the expression of drag force to consummate the model.The reentrainment of spherical and ellipsoidal deposited aggreagets in turbulent aerosol flow has been studied theoretically. The forces, i.e., gravitational force, adhesive force, collision force, aerodynamic drag force and lift force, especially the forces change with aggregate figuration are studied. The moment of forces, i.e., gravity, particle adhesion, aerosol collision and aerodynamic drag, especially the moment of forces change with aggregate figuration are studied. Then, analsing the adhesion angle, the tube diameter and the average flow velocity acting on aggregates, the relationship between the moment of forces and the figuration of aggregate, and the way of motion status changing with the moment of forces.In this paper, analyse the forces and the moment of forces changing regularity, the way of controlling particle reentrainment. Theoretical basis and research foundation of diesel particle reentrainment regularity in turbulent pipe exhaust system are supplied by the research results.更多还原