【作者】 张文彬；

【导师】 谭建荣； 刘振宇；

【作者基本信息】 浙江大学 ， 机械设计及理论， 2007， 硕士

【摘要】 近年来，数字样机技术已经成为产品开发的一种主要方法，它以计算机仿真模型为基础，为相关产品建立合适的数字化模型。本文通过研究内燃机场景中，液体燃料从喷油到雾化到燃烧的一系列物理过程，结合了计算机图形学领域对不规则物体真实感模型的相关研究，分别为以上物理过程建立起相关的数学模型。粒子系统以及细胞自动机模型是描述不规则物体的有效手段，本文将粒子系统以及细胞自动机应用到那内燃机场景中，并在WD615内燃机的数字样机环境中实现了喷油、雾化以及燃烧的可视化效果。第一章概述了当前数字样机技术的发展趋向，提出了在数字样机中建立可视化模型的现实意义。同时对计算机图形学中对不规则物体的描述方法进行了研究，比较了通过研究物质运动规律建立数据模型和通过预运算建立伪随机效果的区别，并以粒子系统和细胞自动机为例概述了通过建立数据模型对不规则物体进行描述的建模方法。最后给出了全文的研究方向以及结构组织。第二章描述了内燃机的喷油效果，并对喷油过程的物理模型进行数学建模。通过应用粒子系统对油雾粒子的物理运动模型进行描述，定义了粒子系统中粒子的特征属性以及运动规律，同时结合喷油装置的参数定义场景的喷油周期以及每次的喷油量。同时阐述了在场景实现中使用的的基于广告板技术的纹理映射方法。第三章描述燃料粒子在点燃以前受热蒸发并且与空气混合的雾化效果。通过建立场景中随机产生的扰动效果与雾化现象之间的关系，定义了液体燃料蒸气及其相邻粒子之间的相互作用规律。利用细胞自动机建立了与场景对应的细胞空间，同时基于粒子相互作用的机制建立细胞自动机的演化规律，并对雾化过程的扩散趋向性的可视化实现了控制。最后阐述了如何通过应用元球的思想实现了粒子密度的可视化连续分布。第四章根据内燃机气缸中的燃烧过程的物理模型，描述了火焰传播的方式以及气缸中燃烧模型的分类。基于气缸内粒子数量守恒同时体积不断变化的特点，提出了变体积的细胞自动机模型。变体积的细胞自动机模型根据体积的变化需要，进行细胞空间的重新划分，并且在细胞空间重新划分以后对新老细胞进行状态的转移。最后根据火焰传播模型建立该细胞自动机的转换规则，实现了燃烧效果的可视化模型。第五章实现了将内燃机喷油、雾化以及燃烧现象的相关数据模型以及可视化效果集成到WD615数字样机环境中。将通过OpenGL函数实现的喷油、雾化以及燃烧等不规则的视觉效果嵌入到基于WTK(WorldToolKit)开发的数字样机场景中去，为该场景提供了可视化的研究模型。第六章中对全文研究内容进行了总结并对今后的技术发展方向进行展望。更多还原

【Abstract】 Lately, the technology of virtual prototype has become a main method to develop products. It is a digitalized model based on computer simulation model. This paper has studied a series of burning physical processes and used mathematical models to simulate the scenes, from fuel injection to fog effect in engine scenario, leveraging the relevant researches of irregular objects realistic image in the field of computer graphics. Besides, particle system and cellular automaton are effective methods to describe irregular objects and both of them are implemented in the simulation models to realize irregular objects visualized effects in WD516 engine scenario.The chapter 1 summarizes the development trend of the virtual prototype technology, pointing out the significance of constructing a visualize model in virtual prototype scenario. It compares the computer graphic method to describe irregular objects the mathematical model based on rules of object movement and stochastic effect based on pre-calculation. A mathematical model of irregular objects for particle system and cellular automaton is given as an example. At the end of this chapter, the research direction and structure of the whole paper is laid out.The chapter 2 mainly describes the physics characteristics of fuel injection in the engine scenario. Particle system, oil fog physical movement model, the corresponding particle characteristics and rules of movement and the index for fuel injection equipment are used to define the fuel injecting cycle and volume. A method of texture mapping, which is broadly used in advertisement board technology, is also introduced here.The chapter 3 focuses on the fog effect of evaporation of fuel particles and mixture with air before ignition. The interaction rules between liquid fuel steam and its particle "neighbors" are constructed by studying the relation between the stochastical perturbation effect and foggy effect. According to the cellular automaton and its corresponding space and interactions among particles, the diffusion of foggy process has been controlled. Lastly, it is described that how to use metaball to visualize continuous distribution of particle density.The chapter 4 concentrates on the research on burning model in engine gas cylinder, including the transmission of flames and the categorization of burning models. Due to the truth that the number of particles stays the same within cylinder while the volume is changing all the time, it is necessary to re-divide space for cellular and take into consideration the change of condition from mother cells to new cells. That’s the underlying rationale of a volume-changing cellular automaton. Finally, I visualize the burning effect via flame transmission model and cellular automaton generating rules. The chapter 5 integrate the relative data module and visual effect into the vitual prototype environment of WD615. The fuel injection effect, fog effect and burning effect is realized via OpenGL functions. And they’re embeded into the vitual prototype environment to provide a visualization research module of the scenario.At last, the chapter 6 makes a summary of the whole thesis, and looks forward to the future development of the corresponding technique.更多还原