非稳态条件下柴油机喷雾系统空化效应的产生机理及对喷雾特性的影响研究

项目名称： 非稳态条件下柴油机喷雾系统空化效应的产生机理及对喷雾特性的影响研究

项目编号： No.50876072

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 杜青

作者单位： 天津大学

项目金额： 36万元

中文摘要： 空化效应对柴油机喷嘴内部流动状态及雾化特征具有显著影响，已成为柴油机喷雾破碎雾化研究中的关键问题。目前对空化现象在喷嘴内非稳态条件下的产生机理及特征，以及对喷雾雾化特征的影响规律还不清楚。本项目拟以此作为研究对象，设计基于流体动力学相似原理的可视化多喷孔喷嘴实验系统，研究喷嘴内不同模式空化效应的产生、发展、溃灭和振荡特征、各种结构参数和射流参数对空化效应的影响规律，以及喷嘴内部空化效应与湍流效应的耦合关系。通过对喷嘴出口截面处流体的流量和动量测量，研究非稳态条件下空化效应对喷嘴出口截面处流通特性的影响，进而获得空化效应对非稳态条件下喷雾破碎宏观特征的影响。在此基础上，探讨非稳态条件下，喷嘴内部的空化效应和湍流运动对于现有柴油机喷雾预报模型，特别是基于空气动力干扰理论的预报模型的有效修正方法，并提出主动利用空化效应以提高柴油机高压喷雾的雾化质量在喷嘴结构上所应采取的技术方案。

中文关键词： 空化;非稳态;湍流;流通特性;雾化特性

英文摘要： The fuel cavitation in the nozzles is one of the key issues for diesel engines because it has significant influence on the fuel injection and spray characteristics. However, the mechanism of cavitation and its effect on the consequent spray processes are still not fully understood. In this study, based on the similarity theory, an experimental setup with enlarged transparent nozzles for the flow visualization is developed. Different cavitation patterns including inception, growth, oscillation, translation and collapse are observed. The impacts of nozzle structures and fuel injection characteristics on the cavitation are investigated. The coupled turbulence and cavitation effects are discussed. Through the cavitation visualization and the measurements of volume flow rate and momentum at the nozzle exits, the relationship between the cavitation in nozzles and the flow characteristics at nozzle exits is analyzed to further understand the cavitation effects on the macroscopic jet breakup mechanisms. The experimental results can be used to develop more accurate spay models for diesel engines, and provide performance optimization strategies to utilize the cavitation effect.

英文关键词： Cavitation;Unsteady state;Turbulence;Flow property;Atomization