Flame-Vortex Interaction Studies to Reduce Pollutants from Engines

这项工作的目的是了解火焰拉伸和火焰曲率如何影响预混火焰的性质。层流涡旋将在现有的测试装置中产生，并将与层流预混火焰相互作用。旋涡条件首先将被选择来代表湍流中的单个涡流，以显示应变和火焰曲率如何影响局部燃烧速度、未燃烧CO污染物的产生、火焰熄灭以及偏离温度和OH浓度的“层流火焰”剖面。其次，选取旋涡条件来表示内燃机活塞产生的旋涡，并将旋涡与中心点燃的火焰核相互作用，以了解核在真实应变场中的生长情况。第三，测量结果将用于评估和改进最近的层流火焰-涡相互作用的完整Navier-Stokes CFD模拟，该模拟构成了未来模型的“基石”，并可以为现有统计模型提供有用的子模型。操作诊断包括瑞利散射的温度图像和剖面，OH和NO荧光成像，以及PIV成像的二维应变场。本研究将为紊流预混火焰结构领域的许多其他研究工作提供有用的信息。特别是，它应该用于开发更好的火焰-涡相互作用的模拟，从而更好地理解和模拟影响诸如内燃机中一氧化碳和氮氧化物生产水平的关键过程，其中火焰-涡相互作用起着至关重要的作用。这反过来将导致设计策略的定义，以减少这些发动机产生的这些污染物的水平，这是一个重要的国家需要。

The goal of this work is to understand how flame stretch and flame curvature affect premixed flame properties. A laminar vortex will be created in an existing test apparatus and will be interacted with a laminar premixed flame. Vortex conditions first will be chosen to represent a single eddy in a turbulent flow to show how strain and flame curvature affect the local burning velocity, the creation of pockets of unburned CO pollutants, flame extinction, and deviations from the "laminar flamelet" profiles of temperature and OH concentration. Secondly, vortex conditions later will be chosen to represent the piston-generated vortex of an internal combustion engine and the vortex will be interacted with a centrally ignited flame kernel in order to understand kernel growth in a realistic strain field. Thirdly, the measurements will be used to assess and improve a recent full Navier-Stokes CFD simulation of the laminar flame-vortex interaction, which forms the "building block" of future models and can provide a useful submodel for existing statistical models. Operational diagnostics to be employed include Rayleigh scattering for temperature images and profiles, OH and NO fluorescence imaging, and PIV to image the two-dimensional strain field. This study should provide information useful to a number of other research efforts in the area of turbulent premixed flame structures. In particular, it should be of use in development of better simulations of flame-vortex interactions, leading to better understanding and modeling of critical processes affecting levels of production of carbon monoxide and oxides of nitrogen in devices such as internal combustion engines, in which flame-vortex interactions play a crucial role. This in turn will lead to definition of design strategies for reduction of levels of these pollutants produced by such engines, an important national need.