【作者】 董理；

【导师】 季振林；

【作者基本信息】 哈尔滨工程大学 ， 动力机械及工程， 2008， 硕士

【摘要】 汽车尾气净化是控制发动机排放的重要手段之一。为达到欧Ⅳ排放法规的要求,通常将催化转换器安装在发动机排气歧管的出口位置,也就是开发并使用了紧耦合式排气歧管。与传统布置方式相比,这种布置可以使催化剂快速起燃,充分发挥某些配方催化剂的效能,因而被执行欧Ⅳ排放标准的车辆广泛采用。本文建立了紧耦合式排气歧管及排气系统的三维模型,运用有限元法及大型商用软件ANSYS对其振动问题进行了分析。首先,将紧耦合式排气歧管作为单独零件进行研究,分析其固有振动特性。针对排气歧管燃气加热作用比较明显的特点,运用间接法计算了热应力在排气歧管上的分布情况及其对排气歧管模态的影响。其次,以安装有紧耦合式排气歧管的排气系统作为研究对象分析整个排气系统的振动情况,得到整个排气系统的振型及在单位位移作用下的响应。本文还针对气流在排气系统上所激发的振动进行了特别研究,主要研究对象为紧耦合式排气歧管及排气系统中振动比较大的管段。最后,对排气系统振动分析中所发现的问题,通过重新设计悬挂点、调整隔振器刚度及安装动力吸振器等方法对其进行了优化设计。更多还原

【Abstract】 The exhaust purification of the vehicle is one of the important measures to control engine exhaust discharging. In order to meet the requirements of Euro IV emission standard, the catalytic converter is installed at the exit of exchaust manifold usually, that means the tight coupled manifolds are developed and used. Compared with the traditional arrangement, this structure could make the catalyst combust rapidly and full use of the catalyst efficiency, which is used widely in the Euro IV emission standard vehicle.This paper has established the three-dimensional models of tight coupled manifold and exhaust system, and the Finite Element Method and software ANSYS are employed to analyze their vibration problems. Firstly, the tight coupled manifold is investigated as a single part to analyze its natural vibration characteristics. In view of the characteristics of heated manifold by exhaust gas, the indirect method is used to calculate the thermal stress of exhaust manifold and the influence on the modes of the manifold. Secondly, the vibration situation of the whole exhaust system with the tight coupled manifold as the research object is analyzed, and the entire exchaust system vibration modes and the response are obtained under unit displacement. The vibration excited by exhaust gas is investigated also, which includes mainly the tight coupled manifold and the part of exhaust system with strong vibration. At last, regarding the problems discovered from vibration analysis of exhaust system, the optimum designs are conducted by redesigning the hanging of exchaust system, adjusting vibration isolator stiffness and installing dynamic vibration absorber.更多还原