【作者】 张小林；

【导师】 于学兵；

【作者基本信息】 大连理工大学 ， 车辆工程， 2008， 硕士

【摘要】 高压共轨是控制柴油机排放的一项新技术,国内还处于发展阶段,因此具有研究的实际意义。共轨式内燃机的流体动力特性是共轨式内燃机的重要特性,对内燃机的动力性和燃油经济性有重要影响,这种影响通过速度场、温度场与压力场表现出来。数值模拟是研究流体动力性的直观而有效的研究方法.本文利用流体动力学仿真软件FLUENT研究探讨高压共轨轨腔结构与内部流动特性的关系。本文详细分析了高压共轨轨腔模型的简化过程、影响因素以及目前该领域的研究现状。并介绍了FLUENT/GAMBIT软件的操作方法和理论基础,为后面的建模和数值分析奠定了基础。本文利用GAMBIT2.3软件建立了高压共轨轨腔各种方案的几何模型并划分六面体网格。在用FLUENT数值分析中,首先计算分析了三种极限截面形状轨腔的流动特性,比较出较优的轨腔截面形状。其次,对轨腔截面形状进一步计算分析,比较出最佳截面形状。最后,分别计算分析进气口压力、容积以及小倒角方案的流场特性,并分析其对轨腔内部流场特性的影响。结果表明:高压轨腔最大壁面夹角在80°～90°范围内,有较好的流场特性,并且在本模型中最大壁面夹角为的84°轨腔模型时,流场特性最佳。比较分析轨腔的各种模型方案,认为进口压力只能改变各位置的速度大小而不影响流场特性;较大的轨腔容积的保压性能提高并且压力损失小;小倒角是有利的,但最大倒角必须使最大壁面夹角在80°～90°范围内。更多还原

【Abstract】 High Pressure Common Rail is a new technology for controlling diesel engine emission and still is in development stage in China, so it has the practical significance of studying. Fluid dynamic characteristics of the Common Rail is an important characteristic of the internal combustion engine and has an important effect to the internal combustion engine power performance and fuel economy, which is shown by velocity, temperature and pressure field. Numerical simulation is an intuitive and effective method of researching fluid dynamics. This article uses CFD simulation software FLUENT to study relationship between the cavity of the High-Pressure common rail and the characteristics of flowing.In this paper, the simplify process of the cavity model, the impact of factors and the current researching status of the High-Pressure common-rail is analyzed. And then the operating methods and the basic theories of FLUENT/GAMBIT software is introduced, which is the foundation of modeling and numerical analysis.In this article, GAMBIT2.3 is used to establish various schemes of the cavity High-Pressure common rail and mesh the hexahedral gridding. Firstly, the characteristics of flowing about the three limit cross-section shapes of the cavity is analyzed in numerical analysis of FLUENT and compared to optimum cross-section shape of the common rail cavity. Secondly, the cross-section shape of the cavity is also analyzed and compared to the best cross-section shape of the cavity. Lastly, the fluid characteristics of the schemes of the inlet pressure, volume and small chamfering are respectively analyzed as well as its influence about the fluid characteristics.The results show that, when the largest wall angle of the High-Pressure is within 80 to 90 degree, there is a better fluid characteristic. When the largest wall angle of the model is 84 degree, it has the fluid characteristic of the best. By comparative and analysis of the various scheme, it concludes that the inlet pressure scheme can only change the value without affecting the flow characteristics; Larger volume scheme of common rail can improve pressure-retaining capacity and has a small pressure loss; The small chamfering is beneficial, but the biggest chamfer value must ensure the largest wall angle is within 80 to 90 degree.更多还原