Theoretical Investigation and Its validation of Unsteady State Combustion Phenomena in Limited Non-Uniform Space

本研究是为了建立对喷雾扩散燃烧的认识和推广，喷雾扩散燃烧是各种燃烧系统中常用的燃烧方式。研究了两个主要主题：(1)燃烧相似度，(2)喷雾火焰的夹带空气。在这里，燃烧相似是指在不同大小的燃烧系统中流动模式和火焰分布发展相似。在分析扩散燃烧控制方程的基础上，从理论上探讨了不同尺寸喷雾内燃机燃烧相似的可能性。由于这一理论背景，热释放率和热效率可以通过比例模型实验来预测。在分析NO生成和燃烧室壁温的基础上，建立了一种预测排放和热负荷的算法。然后进行了一项实验，将基于比例模型实验的预测结果与大型发动机的结果进行比较。结果与理论预测吻合较好。燃烧的三维计算机模拟也支持了比例模型实验。其次，对燃油喷射燃烧中夹带气流变化进行了理论推导和实验验证。该理论预测了不同旋涡速度、喷嘴孔数、喷嘴直径、发动机转速、喷射速度和燃料密度下空气夹带量的变化。为了比较不同尺寸发动机的理论预测和实验结果，进行了实验。结果与浅盘活塞发动机的理论预测结果一致。该研究提供了对喷雾扩散燃烧的理解和适用于燃烧系统设计和开发的理论。

This study was conducted for the establishment of understanding and generalizing spray diffusion combustion, which is commonly used in variety of combustion systems. Study was made for the two major topics : (1) combustion similarity, and (2) air-entrainments in spray flames. Here combustion similarity means that flow pattern and flame distribution develop similarly in differently sized combustion systems.The possibility of combustion similarity in differently sized spray combustion engines was theoretically investigated based on the analysis of governing equations of diffusion combustion. Because of this theoretical background, heat release rates and thermal efficiency can be predicted from scale model experiments. Based on an analysis of NO formation and the wall temperature of the combustion chamber, an algorithm to predict emissions and thermal loads were established. An experiment was then performed to compare predictions based on scale model experiments and results with large engines. The results showed good agreement with the theoretical predictions. Three dimensional computer simulation of combustion also supported the scale model experiments.Next theoretical formulation and its experimental validation for air entrainment changes in fuel spray combustion were performed. THe theory predicts air entrainment changes for a variety of swirl speeds, numbers of nozzle holes, nozzle diameters, engine speeds, injection speeds and fuel densities. Experiments were performed in order to compare theoretical predictions and experimental results in variety size of engines. All results showed good agreement with the theoretical predictions for shallow-dish piston engines.The study provides understanding of spray diffusion combustion and theories which are applicable for design and development of combustion systems.