• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Development of an Integrated CFD Approach for Internal Nozzle Flows and Sprays.
【24h】

Development of an Integrated CFD Approach for Internal Nozzle Flows and Sprays.

机译：开发用于内部喷嘴流和喷雾的集成CFD方法。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

In modern automotive internal combustion engines the atomization and spraying processes of liquid fuel is an important mechanism by which the fuel is mixed effectively with the combustion chamber gas. The homogeneity of the fuel-air mixture charge and the timing to achieve it affect the characteristics of the subsequent combustion in a number of ways. Experimentalists have found that the atomization process is influenced by the fuel delivery system, specifically, the operating conditions of fuel injection and the internal geometry of the injector nozzles. Therefore, modeling researchers must develop spray models that properly take into account these effects from the injectors.;A Computational Fluid Dynamics (CFD) model is developed to simulate internal injector nozzle flows and the external-nozzle atomization and sprays in an integrated way. In light of the continuous nature of the flow within and near the nozzle, an Eulerian flow solver is developed and applied in these regions. This flow solver models compressible two-phase flows with general conservation laws of fluid dynamics. Differences in the thermodynamic states of liquid and gas phases are properly modeled with an Equation of State (EOS). The chosen numerical methods are sufficiently robust to handle pressure and density gradients up to 1000:1 and are able to cover the typical operating ranges of modern diesel and gasoline injection systems.;A phase equilibrium model is developed based on the fundamental thermodynamic laws. It is implemented into the Eulerian flow solver to predict phase change in the flows---in particular, the cavitation of liquid fuel within the fuel injector nozzle and how it influences the external flows. A number of test problems are simulated to verify the numerical methods and validate the proposed models. These include two-phase shock tube problems, a shock-interface interaction problem, a converging-diverging nozzle flow problem, and most importantly, high-pressure fuel injection problems.;The Eulerian flow solver requires the CFD mesh size to be smaller than the characteristic phase interface length scale in order to apply the continuum fluid assumption. This requirement is challenged beyond a certain distance from the nozzle where the spray is dispersed. Here the mesh size affordable by engineering calculation is too coarse for the Eulerian solver to be applied. At this stage, the Eulerian liquid phase can be transitioned into Lagrangian discrete particles to model the dispersed spray droplets. The modeling of the sub-grid droplet size at this transition stage is based on local balances between turbulent kinetic energy and surface energy.;The Eulerian flow solver coupled with the phase equilibrium model and the Eulerian-Lagrangian transition model provides an engineering CFD approach to study the effects of injector nozzle flows on the atomization and sprays.
机译：在现代汽车内燃机中，液体燃料的雾化和喷雾过程是一种重要的机制，通过这种机制燃料可以有效地与燃烧室气体混合。燃料-空气混合物充气的均匀性及其实现的时机以多种方式影响后续燃烧的特性。实验人员发现，雾化过程受燃油输送系统的影响，特别是受燃油喷射的运行条件和喷嘴内部几何形状的影响。因此，建模研究人员必须开发喷雾模型，以适当考虑喷射器的这些影响。开发了计算流体动力学（CFD）模型，以集成方式模拟内部喷射器的喷嘴流动以及外部喷嘴的雾化和喷射。鉴于喷嘴内和喷嘴附近流体的连续性，开发了一种欧拉流量求解器并将其应用于这些区域。该流动求解器利用流体动力学的一般守恒定律对可压缩的两相流进行建模。液相和气相热力学状态的差异可以通过状态方程（EOS）进行适当建模。选择的数值方法具有足够的鲁棒性，可以处理高达1000：1的压力和密度梯度，并且能够涵盖现代柴油和汽油喷射系统的典型工作范围。;基于基本的热力学定律，建立了相平衡模型。它被实施到欧拉流求解器中，以预测流中的相变-尤其是燃料喷嘴内液体燃料的空化作用以及它如何影响外部流。模拟了许多测试问题，以验证数值方法并验证所提出的模型。这些问题包括两相激波管问题，激波-界面相互作用问题，会聚-发散喷嘴流量问题，最重要的是高压燃料喷射问题。欧拉流量求解器要求CFD网格尺寸小于特征相界面长度尺度，以便应用连续流体假设。在离喷雾分散的喷嘴一定距离之外，对这一要求提出了挑战。在这里，工程计算负担得起的网格尺寸对于使用Eulerian求解器来说太粗糙了。在这一阶段，欧拉液相可以转变为拉格朗日离散颗粒，以模拟分散的喷雾液滴。在此过渡阶段，对子网格液滴尺寸的建模是基于湍动能和表面能之间的局部平衡。欧拉流动求解器与相平衡模型和欧拉-拉格朗日过渡模型相结合，提供了一种工程CFD方法研究喷油嘴流量对雾化和喷雾的影响。

著录项

  • 作者

    Wang, Yue.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 136 p.
  • 总页数 136
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号