某八缸柴油机缸盖热机械强度有限元耦合分析

发布时间：2018-04-18 07:23

本文选题：柴油机 + 气缸盖　；参考：《大连理工大学》2015年硕士论文

【摘要】：气缸盖是内燃机动力组装配中最为重要和复杂的部件之一,也是内燃机工作环境最恶劣的部件。在柴油机工作过程中,气缸盖火焰面需要承受缸内燃料燃烧产生的高温,同时,气缸盖还要承受巨大的缸内爆发压力。高温产生的热应力、缸内爆发压力、螺栓预紧力、气门座过盈力等同时作用在气缸盖上,使得气缸盖的工作环境十分复杂,大大增加了对气缸盖分析的难度。本文是对某八缸中速柴油机气缸盖进行有限元耦合分析,主要包括三个部分,第一部分是求解气缸盖温度场和热应力,首先,运用Pro/E软件建立柴油机气缸盖的三维实体模型,然后将模型导入有限元软件ANSYS workbench进行网格划分和热边界条件的设置,最后计算气缸盖的温度分布,把计算结果与实际测点温度进行对比,二者在误差范围内吻合。第二部分是对气缸盖进行热与机械强度的耦合分析,首先设置气缸盖的约束和力边界条件,计算机械应力对气缸盖的影响,然后把热与机械强度进行耦合计算,得到气缸盖的总的等效应力分布情况。最后把热应力云图、机械应力云图、总耦合应力云图进行对比和分析。第三部分我尝试对气缸盖结构做了一些改进,主要改变的区域是鼻梁区。计算结果表明气缸盖温度较高的位置主要是在气缸盖火力面两个排气道之间的鼻梁区域,同时排气道表面的温度整体较高。气缸盖耦合总等效应力较高的位置出现在进、排气门之间的两处鼻梁区,偏向于排气门一侧。把热应力分布图、机械应力分布图和耦合场应力分布图对比可以发现热应力对气缸盖整体受力分布的影响最大。耦合之后的应力并不是简单把热应力和机械应力相互叠加。由于该八缸柴油机处于研发设计阶段,本文的工作可以为气缸盖结构的设计和改进提供必要参考。
[Abstract]:Cylinder head is one of the most important and complex parts in the assembly of engine power group, and it is also the worst part in internal combustion engine working environment.In the working process of diesel engine, the flame surface of cylinder head has to bear the high temperature produced by the combustion of fuel in cylinder, and the cylinder head has to bear the huge burst pressure in cylinder at the same time.The thermal stress produced by high temperature, the burst pressure in the cylinder, the pretightening force of the bolt and the interference force of the valve seat act on the cylinder head at the same time, which makes the working environment of the cylinder head very complex, which greatly increases the difficulty of analyzing the cylinder head.In this paper, the finite element coupling analysis of the cylinder head of an eight-cylinder medium speed diesel engine is carried out, which mainly includes three parts. The first part is to solve the temperature field and thermal stress of the cylinder head. Firstly, the three-dimensional solid model of the cylinder head of the diesel engine is established by using Pro/E software.Then the model is imported into the finite element software ANSYS workbench to divide the mesh and set the thermal boundary conditions. Finally, the temperature distribution of the cylinder head is calculated, and the calculated results are compared with the actual measured point temperature. The results are in good agreement with each other in the error range.The second part is the coupling analysis of thermal and mechanical strength of cylinder head. Firstly, the constraint and force boundary conditions of cylinder head are set, the influence of mechanical stress on cylinder head is calculated, and the coupling calculation of heat and mechanical strength is carried out.The total equivalent stress distribution of the cylinder head is obtained.Finally, the thermal stress cloud, mechanical stress cloud and total coupled stress cloud are compared and analyzed.In the third part, I try to improve the cylinder head structure.The results show that the high temperature of cylinder head is mainly located in the nose beam area between two exhaust channels on the cylinder head fire surface, and the temperature of the exhaust duct surface is higher as a whole.The high position of the coupled total equivalent stress of cylinder head appears in the two areas of nose beam between the inlet and the exhaust valve, which is inclined to the side of the exhaust valve.By comparing the thermal stress distribution, mechanical stress distribution and coupled field stress distribution, it is found that the thermal stress has the greatest influence on the overall stress distribution of the cylinder head.The coupled stress is not simply a superposition of the thermal stress and the mechanical stress.Because the eight cylinder diesel engine is in the stage of R & D, the work in this paper can provide the necessary reference for the design and improvement of cylinder head structure.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK423

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