Understanding of Lean Premixed Combustors from Cinema-Imaging of Turbulent Eddy- Flame Interactions

这项研究旨在确定湍流涡流如何控制正在为新型燃气轮机和内燃机开发的稀薄预混燃烧室内发生的化学反应。独特的激光诊断技术正被用于放大和成像薄的、皱纹的化学反应层和邻近的湍流涡流，以确定涡流导致热量和各种气体物种扩散到反应层的速度。需要这些实验信息来指导开发新的计算机模型，这些模型现在可以模拟与湍流相关的高度不稳定的物理过程。其具体目标是拍摄高湍流预混火焰中的非定常速度场和气体浓度场的高速电影。这项工作提供了第一次测量一个重要的量，称为空气动力应变率，它出现在数值模型中。提取信息以确定这一数量和其他管理燃料消耗和一氧化氮污染物产生的化学速率的信息。获得超过1000帧/秒的高速电影是因为局部化学反应被涡流快速开启和关闭，这个不稳定的过程会导致未燃烧的燃料和一氧化碳逃逸。其学术价值在于评估Damkohler和Landau关于湍流反应流的经典理论，并确定如何对这些概念进行数值模拟。正在应用的新诊断方法提供了甲醛(CH2O)、羟基(OH)和其他燃烧中间体浓度的高速胶片，以及湍流涡流的同时大小和强度。通过技术出版物和专题介绍，通过培训学生和新科学家，以及通过国内和国际不同学科和不同机构之间的协同合作，这项工作产生了更广泛的影响。例如，实验数据被提供给在加州伯克利和德国斯图加特开发高级数值模型的研究人员。

0852910Driscoll This research seeks to establish how turbulent eddies control the chemical reactions that occur within lean premixed combustors that are being developed for new gas turbine engines and internal combustion engines. Unique laser diagnostics are being applied to zoom in and image the thin, wrinkled chemical reaction layers and the adjacent turbulent eddies, to determine the rates at which the eddies cause heat and various gas species to diffuse into the reaction layers. This experimental information is needed to guide the development of new computer models that now can simulate the highly unsteady physical processes that are associated with turbulence. The specific objectives are to take high-speed movies of the unsteady velocity field and the gas concentration fields in highly turbulent premixed flames. The work provides the first measurements of an important quantity called the aerodynamic strain rate which appears in numerical models. Information is extracted to determine this quantity and others that govern the chemical rates of consumption of fuel and the production of nitric oxide pollutants. High-speed movies taken at more than 1,000 frames/second are obtained because the local chemical reactions are rapidly turned on and off by the eddies, and this unsteady process can cause unburned fuel and carbon monoxide to escape. The intellectual merit is to assess classic theories of Damkohler and Landau for turbulent reacting flows and to determine how to numerically simulate these concepts. The new diagnostics being applied provide high-speed movies of the concentrations of formaldehyde (CH2O), hydroxyl (OH), and other combustion intermediates, as well as the simultaneous sizes and strengths of the turbulent eddies. Broader impacts of the work arise through technical publication and presentations, by the training of students and new scientists, and by synergetic collaborations between different disciplines and different institutions, both domestic and international. For example, the experimental data is being provided to researchers who are developing advanced numerical models in Berkeley CA and in Stuttgart Germany.