A Quasi-Dimensional Engine Model Using Fractal Geometry

分形几何是粗糙表面几何的一种数学处理方法，最近被用于描述一般的湍流火焰。作者认为，该方法可能为四冲程均质装药火花点火（SI）活塞发动机的建模应用提供一种机制突破。与以往准维发动机代码中使用的燃烧速率模型不同，本文提出的湍流燃烧速率模型不需要对可调建模常数进行实验校准。模型预测对各种建模参数的敏感性，如分形维数和大涡流的规模，将被研究。模型预测将根据现有的实验数据进行检验。基于分形的湍流扩散模型的可用性将使设计人员能够用一个比现有模型更简单、更通用的模型来预测燃烧现象。目前对猜测和实验检查的需求将在很大程度上消除，计算机性能可以用于发动机燃烧的其他方面（例如几何方面），这些方面目前无法用现有的笨拙的湍流模型来管理。

Fractal geometry is a mathematical treatment of the geometry of rough surfaces that has been applied recently to describe a generic turbulent flame. The proposers believe this method may provide a mechanism for a modeling breakthrough for the 4-stroke homogeneous charge spark-ignition (SI) piston engine application. Unlike the burning rate models used in previous quasi-dimensional engine codes, the proposed model for the turbulent burning rate will not require experimental calibration of adjustable modeling constants. The sensitivity of the model predictions to various modeling parameters, such as the fractal dimension and the scale of the large eddies, will be investigated. The model predictions will be tested against available experimental data. The availability of a fractal based turbulent diffusion model would enable designers to predict combustion phenomena with a model both simpler and more generic than the current ones. The current need for guessing and experimental checking would be largely eliminated, and computer performance could be dedicated to other aspects of engine combustion (e.g. geometrical aspects) not currently manageable with the existing unwieldy turbulence models.