【作者】 刘志恩；

【导师】 陈国华； 蒋炎坤；

【作者基本信息】 华中科技大学 ， 动力机械及工程， 2007， 博士

【摘要】 本文发展了一种内燃机燃烧室多个零部件间耦合传热的三维数值分析模型,该模型考虑了活塞组-气缸套耦合系统的周期性瞬态传热过程,以及活塞组-气缸套/气缸体-气缸垫-气缸盖-进排气门耦合系统的周期性瞬态传热过程。并开发了内燃机燃烧室多体耦合系统瞬态传热数值模拟软件,为内燃机的整机系统传热,热平衡及热负荷研究提供了一个重要的分析工具。在燃烧室多体耦合系统三维瞬态传热模型的建立过程中,完成了数学公式的推导、物理模型的分析、有限元模型的建立、计算程序的开发、模拟结果的研究和模型的验证六个方面的内容。1)建立了活塞组-气缸套三维耦合系统瞬态传热模型。通过将润滑油膜假设成一维热阻,使用完全耦合的分析方法,建立了该运动零部件间相互传热的有限元模型。在该模型中,考虑了活塞环组摩擦热的影响。采用三维流体动压润滑分析程序计算了沿活塞环周向瞬时变化的油膜厚度和摩擦热,实现了对该耦合传热过程更加精确的模拟。通过对活塞环组、活塞、气缸套、气缸体分别进行有限元网格离散,来反映不同材料属性对温度分布的影响。计算的结果还获得了活塞环、活塞的瞬时温度波。2)在活塞组-气缸套三维耦合系统瞬态传热模型的基础上,建立了燃烧室多体耦合系统的瞬态传热模型。该模型包含了活塞组、气缸套/气缸体、气缸垫、气缸盖、进排气门等燃烧室主要零部件,通过使用两种不同的耦合传热模型:运动零部件间的油膜导热模型和静止零部件间的固体接触导热模型,以及完全耦合的有限元分析方法,建立了这些零部件间的相互传热关系。计算获得了传统研究方法无法获得的进排气门的瞬时温度分布,揭示了气门与气门座接触传热的过程,同时也对传统研究中研究较少的气缸垫的传热作用进行了分析。3)开发了内燃机燃烧室多体耦合系统瞬态传热数值分析软件。通过建立一套规范的数据标准格式,实现了前后处理程序的无缝连接,使得该数值分析程序成为一个完整的软件系统。并采用单链表和双链表相结合的稀疏矩阵数据结构完成了该耦合系统总体刚度矩阵的存储,采用一定的选主元策略完成了对该稀疏矩阵的高斯求解。在保证计算精度的情况下,上述方法极大地减少了程序的运算时间和内存占用量。4)应用所开发的软件,完成了对设计中的LJ377MV发动机活塞组-气缸套耦合系统,以及燃烧室多体耦合系统,即活塞组-气缸套/气缸体-气缸垫-气缸盖-进排气门耦合系统瞬态传热的研究,为LJ377MV发动机的改进和优化设计提供了依据。5)采用两种方法来验证多体耦合系统传热模型及所开发程序。一是通过使用商业有限元软件对简单耦合传热模型的对照比较来验证,二是通过CUB100汽油机的温度测试试验,使用模拟结果和测试结果相比较的方法验证了本文所建立的三维耦合传热模型及所开发程序的正确性。内燃机燃烧室是复杂的耦合体,其传热过程与多个物理场相互作用,如与缸内燃气的流动与燃烧过程,循环冷却水的流动过程等。采用完全耦合方法对内燃机整个燃烧室、多个物理场进行耦合模拟将是内燃机传热研究发展的必然趋势。本文所发展的内燃机燃烧室多体耦合系统三维瞬态传热的数值分析模型,是内燃机传热全仿真模拟研究中的重要组成部分。更多还原

【Abstract】 A 3-D numerical analysis model of transient heat transfer among the multi-components coupling system in combustion chamber of internal combustion engine has been developed successfully in the paper. The model includes cyclic transient heat transfer of the 3-D moving piston assembly-liner coupling system and the piston-liner-gasket-head-valves coupling system. And the simulation software of transient heat transfer model of the multi-components coupling system has been also developed successfully. The model and the software will be important analysis tools to study the whole engine heat transfer, heat balance and heat loads in internal combustion engine.During the development of the multi-components coupling system transient heat transfer model ,some work has been finished as follows : the deduction of the mathematical formula; the analysis of the physics model; the establishment of the FEA model; the development of the computational program; the evaluation of the result; the verification and application of the model, etc.1) Developed the transient heat transfer model of the coupling 3-D moving piston assembly-liner system. With hypothesizing the lubricant film as 1-D thermal resistances and applying the direct coupled-field analysis method, the heat transfer relation among the moving components is established. In the model, the effect of friction heat generated on the piston ring/liner interfaces is also taken into account. A 3-D hydrodynamic mixed lubrication model has been employed to calculate the lubricant film thickness and the friction heat which varies with crank angle and circumferential direction. To reflect the influence of the different material property on the temperature distributions, the piston ring assembly, the piston, the liner and the cylinder body are meshed respectively in the model. The transient temperature waves on the surface of the piston rings are also obtained.2) Based on the model of 3-D moving piston assembly-liner coupling system, the transient heat transfer model of multi-components coupling system of the internal combustion chamber is also developed. The model includes almost all components in combustion chamber, such as piston assembly, cylinder liners, cylinder head gaskets, cylinder heads, intake valves and exhaust valves, etc. With two different coupling heat transfer modes-----one is the lubricant film conduction between two moving components, another is the contact conduction between two immovable solid components------and the direct coupled-field analysis method, the heat transfer relation among the components is established. The result dedicates the transient heat transfer process between the valve head and valve seat. The effect of cylinder head gaskets on heat transfer among the components is also studied.3) Developed the numerical simulation computational software of the multi- components coupling system transient heat transfer model. By establishing the standard data format, the preprocessor and the post-processor of the main computational program have been connected smoothly. The data structure of spare matrix is applied to save the whole temperature stiffness matrix of the coupling system model to reduce the time of calculation and the quantity of used memory.4) Applied the developed software to study the transient heat transfer process of the 3-D moving piston assembly-liner coupling system and the piston-liner/cylinder- gasket-head-valves coupling system for LJ377MV gasoline engine. The results provide a basis of the improvement and optimum design for the engine.5) Adopted two kinds of methods to verify the heat transfer model and the software of the multi-components coupling system. one is comparison between the developed software and the commercial FEA software on a simple coupling heat transfer example. Another is comparison and contrast between the simulation result and the experimental result on the CUB100 gasoline engine.The heat transfer of internal combustion engine is very complex, whose heat transfer process couples with many physics fields. So, the discrete theories, the developed software and the model in the paper are the most important parts in the heat transfer of the complete model simulation research and the bases of the virtual design for the internal combustion engine.更多还原