【作者】 董哲林；

【导师】 陈国华；

【作者基本信息】 华中科技大学 ， 动力机械及工程， 2013， 博士

【摘要】 发动机现代分析技术是发展高效、低排放与高可靠性发动机的重要工具，其中，发动机工作过程数值分析和发动机传热与热负荷分析是最重要工具之一。由于发动机结构的复杂性以及工作过程的多变性，长期以来，国内外的研究工作都是分别进行发动机工作过程分析和结构分析，但由于发动机性能分析中涉及到的气体域温度场、压力场、速度场等与发动机结构分析中涉及到的固体域温度场、热应力场是一种相互影响的关系，只有建立完整及全面的发动机工作过程与发动机结构传热与热负荷的多场耦合模型，才能有效地考虑他们之间的相互影响和作用，设计出高性能和高可靠性的发动机。本文建立了一种基于有限元和CFD分析的内燃机工作过程与燃烧室传热三维多场耦合模型，其中工作过程计算中的流体域采用结构化六面体网格进行离散，燃烧室部件热传导分析中的固体域采用非结构化四面体网格进行离散，提出了两种应用于气—固耦合的网格生成策略，建立起了气—固瞬态传热联系。发展了燃烧室耦合部件传热有限元计算程序，改进了KIVA程序，并且建立了有限元计算程序与KIVA之间的接口程序。然后以此为基础，研究了燃气温度、对流换热系数的时空非均匀性分布对燃烧室壁面温度的影响，以及分析壁面温度非均匀性分布对缸内流动、燃油蒸发、排放产物生成的影响。结果显示：（1）燃烧室壁面附近燃气的温度、对流换热系数不均匀分布对燃烧室壁面（特别是活塞顶面）稳态温度场具有重要影响。（2）燃烧室壁面附近燃气的温度、对流换热系数不均匀分布对燃烧室壁面（特别是活塞顶面）瞬态温度场具有重要影响。但瞬态温度波对燃烧室部件的影响仅限于离燃气侧表面很近的区域。随着距离燃烧室壁面的深度的增加，瞬态温度波动变弱。当深度达到1.0mm时温度波动已经不明显，基本服从准静态温度分布。(3)燃烧室壁面附近燃气的温度、对流换热系数不均匀分布对燃烧室壁面热流量计算结果具有重要影响。燃烧室的各个表面的热流量在排吹阶段有较大差异。在排吹阶段，缸盖燃气侧表面出现了明显的温度波动，而此期间其它燃烧室表面则不存在明显的温度波动。此外，在燃烧室同一表面的不同区域热流量差异也较大。(4)燃烧室壁面温度不均匀性对缸内流动的影响非常微弱，分别采用均匀温度边界条件与非均匀温度边界条件得到的计算结果看不出明显差异。燃烧室壁面温度不均匀性对燃油蒸发的影响主要存在于燃油蒸发的早期，在接近压缩冲程末期时，燃烧室壁面温度不均匀性对燃油蒸发的影响非常弱。燃烧室壁面温度不均匀性对缸内排放物NOx、 SOOT的生成有较大影响，壁面温度不均匀性对NOx的分布有一定的影响。更多还原

【Abstract】 The modern engine analysis is an important tool that helps design an engine withhigh efficient, low emissions and high reliability, in which the engine working processsimulation and engine heat transfer analysis is one of the most important tools. Due to thecomplexity of the structure and the variability of the working process of the engine, for along time, the related research work at home and abroad are respectively analyzing theworking process and structure strength of the engine. However, due to the temperaturefield of the gas domain related to engine performance analysis, pressure, velocity, etc. withthe engine structure analysis involves solid domain temperature field and thermal stressfield is a mutual influence relationship, as a result, only establishing a complete andcomprehensive multifield coupled model which coupling the engine working process withthe engine heat transfer and thermal load can effectively take account of their mutualinfluence and help design a high-performance and high reliability engine.In this thesis, a3-D model for multifield coupling engine work process andcombustion chamber heat transfer was built based on the FEM and CFD. The fluid domainwas discretized by a block structured hexahedron grid, whose corresponding interfacemesh is quadrilateral, and the solid (FEM) domain was discretized by an unstructuredtetrahedral grid, whose corresponding interface mesh is triangle. Two special treatmentsfor the grid generation were designed and utilized. In order to implement the coupled heattransfer model, a FEM program was developed, the KIVA3V code was improved, and aKIVA-FEM interface program was built. Then on this basis, the gas-solid coupled modelwas utilized to simulate the3-D work process and combustion chamber heat transfer of agasoline engine. The result shows：(1)The temporal and spatial non-uniformity of thermalboundary conditions has an important influence on the steady temperature field of thechamber components, especially near the piston crown.(2)The temporal and spatialnon-uniformity of thermal boundary conditions has an important influence on the transienttemperature field of the chamber components, especially near the piston crown. However,the transient temperature wave of the combustion chamber components is limited in thearea very close to the surface of the gas-side. With the distance increased from thecombustion chamber wall, the transient temperature fluctuations weakened. When thedepth reached1.0mm, the temperature fluctuation is not obvious, according to quasi-statictemperature distribution。(3)The temporal and spatial non-uniformity of thermal boundary conditions has an important influence on the heat flux of the of the chamber components,especially during the blow-down period. During this period, a significant temperaturefluctuation appears near the gas-side surface of the cylinder head, but there are nosignificant temperature fluctuations near the other surfaces of combustion chambers.Furthermore, the heat flux is very different among the different regions of the samesurface of the combustion chamber.(4) The temporal and spatial non-uniformity ofchamber wall temperature has a weak influence on the in-cylinder flow. The calculationresults are no obvious difference when adopting uniform temperature boundary conditionsand non-uniform temperature boundary conditions respectively. The temporal and spatialnon-uniformity of chamber wall temperature influence the fuel evaporation in the earlyperiod of the fuel evaporative process. However, when close to the later period of thecompression stroke, this influence is weak. The spatial non-uniformity of chamber walltemperature obviously influence the emissions of the NOx and SOOT, and it alsoinfluence on the distribution of NOx.更多还原