燃油喷雾粒度分布测量及其信息熵分析.pdf

华中科技大学硕士学位论文 I 摘要喷雾雾化对提高内燃机的性能、改善其排放特性有着重要的意义,喷雾粒度分布是衡量喷雾雾化特性的一个重要指标,人们对其研究越来越重视。近年来,随着研究工作不断向纵深发展,人们在喷雾粒子特性及有关的理论计算等方面的研究工作,已经取得了新的突破,这必将对发动机性能的改进和提高产生深远的影响。本文首先综述了传统的和现代的燃油喷雾粒度分布的研究方法及其研究成果。在此基础上,作为不同燃油喷雾特性的基础研究,在本研究中使用单孔孔式喷嘴, 将室温下的轻柴油,以及柴油与汽油的混合油喷入静止的空气介质中。采用基于激光散射技术的激光粒度仪研究了不同燃油喷雾粒度的空间分布特性,探讨了喷射压力、喷嘴结构、燃油组份对喷雾场中不同轴向和径向位置处粒度分布的影响。研究结果表明,随着轴向距离的增加和距轴心线径向距离的增加, SMD 值随之减小;喷射压力的增加能显著降低喷雾粒度场的 SMD 值并显著增加小粒径液滴在整个粒子数中所占的份额;减小喷孔直径也能减小 SMD 值及改善粒度分布的均匀性。通过将汽油加入柴油中研究其对喷雾粒度分布的影响发现,添加低粘度的汽油可以显著减小喷雾的空间 SMD 值,改善其雾化特性。本文还采用高分辨率的数码相机对喷雾的宏观特性进行了观测,对比分析了在不同压力和不同喷孔孔径下的柴油喷雾形态,以及燃油物性对雾化宏观特性的影响。在对喷雾粒度分布开展试验测量的基础上,应用最大熵原理,对纯柴油与不同质量掺混比的柴油/ 汽油混合燃料的喷雾液滴粒度分布进行了预测分析,比较了不同燃料的雾化特性。对比理论计算结果与试验结果发现,粒度空间分布的变化趋势基本一致,理论计算的粒径分布范围较窄,粒径变化速度较快。关键词: 喷雾,粒度分布,激光粒度仪,信息熵华中科技大学硕士学位论文 II Abstract Sprays was widely used in lo ts of field during engineering, it has significan t aspect in bustion and emission characterist ics of bustion engine, drop size distribution is supposed to a important ta rget of spray atomization and obtain lots of interesting in the research of spray. This paper take a photo of spray under different pressure, structures of atomizers and fuel component to analysis the macrocosmic characteristic including atomi zation cone angle and rat ion. As the influence of high viscocity and surface tension of diesel, the sp ray was long and thin, we also found that as the pressure increase, cone angle and rat ion are also increased, the same influence as atomizer hole diameter decrease. When gasoline was add into diesel, cone angle increased, also with the ration. Laser Particle An alysis was used to measure the drop size of sprays in different axial and radial distance under different pressure, atomizer structure and fuel. The results shown that as the incr ease of axial and radial distance, the SMD decreased and the percent of small drop increased, highe r pressure and smaller hole diameter can clearly decrease SMD and improve the atomization of sprays. we also input gasolin