Molecular Transport and Kinetics in Hydrogen-Fueled Cellular and Non-Cellular Flames

1134268 PitzH原子通过链分支步骤H + O2 OH + O在氢（H2）和烃（HC）燃烧化学动力学中起主导作用，其速率强烈地决定火焰速度和总燃料/空气反应速率。 氢原子输运的准确预测对于给出H2、HC燃料以及生物燃料的燃烧的准确火焰性质是必不可少的。 然而，氢原子输运的预测仍然存在很大的不确定性。 更精确的氢原子传输模型已经提出，但很少实施，并没有得到验证的火焰结构测量。在实际燃烧条件下，火焰中氢原子的定量测量很少。氢原子传输在拉伸和弯曲的火焰中特别重要，其中氢原子（和其他轻气体如H2）的优先扩散非常强，并且极大地影响火焰温度、熄灭极限和蜂窝状火焰形成的开始。高度弯曲和拉伸的火焰细胞可以生存超过正常的一维消光极限和H原子的快速扩散是必不可少的火焰生存。管状燃烧器产生高度弯曲和拉伸的火焰，是研究氢原子传输的理想选择，这将导致先进和有效的分子传输模型。预混和非预混火焰可以在均匀拉伸和曲率下进行研究，其中整体拉伸和曲率可以独立变化。在高拉伸和曲率下，氢原子的优先扩散将是最强的，并且可以在范德比尔特的具有氢原子LIF的光学可达燃烧器中测量氢原子分布。拉伸的细胞火焰可以研究与高的局部曲率，提高氢原子的优先扩散。在极端条件下形成的管状燃烧器的火焰细胞可以测量氢原子LIF和拉曼散射和数据进行比较，详细的三维计算流体力学模型与先进的氢原子分子运输。智力优势：在这个建议中，我们将验证先进的氢原子（和小，重量轻的分子）在氢燃料管状火焰传输模型。氢原子分布将在氢燃料的非预混和预混管状火焰中测量，以验证先进的分子输运代码。氢原子的定量双光子LIF测量将使用拉曼位移ArF激光器。将从Hencken燃烧器中的H原子LIF测量值校正H原子LIF淬灭，所述Hencken燃烧器中的H原子LIF测量值与管状燃烧器中的火焰浴气体的拉曼测量值相关。 OH浓度将使用经拉曼散射猝灭校正的OH LIF信号来确定。H/OH自由基的比例（发现是非常敏感的H原子运输）将实验和模型之间进行比较，以验证先进的分子运输代码。中国厦门大学的王培勇博士将在1D和3D模拟中实现精确的氢原子分子输运模型。细胞和非细胞管状火焰将进行研究，以验证准确的氢原子运输在各种环境中。最终的成果将是一个先进的验证分子输运代码，可用于各种燃烧设备（燃气轮机，锅炉，发动机）燃烧H2，HC和生物燃料，以提高可靠性，安全性和效率。更广泛的影响：研究生和本科生，包括代表性不足的少数民族将接触到最新的计算机模拟和激光诊断设施。工程师将指导当地高中学生进行工程设计项目和研究。厦门大学和范德比尔特大学的学生将进行交流，以获得实验和计算燃烧方面的全球研究经验，并促进亚洲-美国的互动。 根据范德比尔特大学教师研究经验项目，当地纳什维尔高中教师将在夏季参与激光诊断和燃烧研究。

1134268PitzH-atoms play a dominate role in hydrogen (H2) and hydrocarbon (HC) combustion chemical kinetics through the chain branching step H + O2 OH + O whose rate strongly dictates flame speeds and overall fuel/air reaction rates. Accurate prediction of H-atom transport is essential to give accurate flame properties for combustion of H2, HC fuels as well as bio-fuels. However, great uncertainties in the prediction of H-atom transport remain. More accurate H-atom transport models have been proposed but are seldom implemented and have not been validated by flame structure measurements. There are few quantitative H-atom measurements in flames under realistic combustion conditions. H-atom transport is particularly important in stretched and curved flames where preferential diffusion of the H atoms (and other light gases such as H2) is very strong and greatly affects flame temperature, extinction limits and the on-set of cellular flame formation. Highly curved and stretched flame cells can survive beyond normal 1D extinction limits and fast diffusion of H-atoms is essential to the flame survival. The tubular burner creates a highly curved and stretched flame that is ideal for the study of H-atom transport that will lead to advanced and validated molecular transport models. Premixed and non-premixed flames can be studied under uniform stretch and curvature where the overall stretch and curvature can be varied independently. At high stretch and curvature, preferential diffusion of H-atoms will be the strongest and the H-atom distributions can be measured in Vanderbilt's optically accessible burner with H-atom LIF. Stretched cellular flames can be studied with high local curvature that enhances H-atom preferential diffusion. The flame cells formed at extreme conditions in the tubular burner can be measured with H-atom LIF and Raman scattering and the data compared to detailed 3D CFD models with advanced H-atom molecular transport. Intellectual Merit: In this proposal, we will validate advanced H-atom (and small, light-weight molecule) transport models in H2-fueled tubular flames. H-atom profiles will be measured in hydrogen-fueled non-premixed and premixed tubular flames to validate advanced molecular transport codes. Quantitative 2-photon LIF measurements of H-atoms will be developed using a Raman-shifted ArF laser. The H-atom LIF quenching will be corrected from H-atom LIF measurements in a Hencken burner that are correlated to Raman measurements of flame bath gases in the tubular burner. OH concentrations will be determined with OH LIF signals that are quenching corrected with Raman scattering. The H/OH radical ratio (found to be very sensitive to H atom transport) will be compared between experiment and model to validate the advanced molecular transport code. Accurate H-atom molecular transport models will be implemented into 1D and 3D simulations by Dr. Peiyong Wang at Xiamen University in China. Cellular and non-cellular tubular flames will be studied to validate accurate H-atom transport in a variety of environments. The ultimate outcome will be an advanced validated molecular transport code that can be used in a wide variety of combustion devices (gas turbines, boilers, engines) burning H2, HC and bio-fuels to improve reliability, safety and efficiency.Broader Impacts: Graduate and undergraduate students including underrepresented minorities will be exposed to the latest computer simulation and laser diagnostic facilities. Engineers will mentor local high school students in engineering design projects and research. Students from Xiamen University and Vanderbilt University will be exchanged to gain global research experiences in experimental and computational combustion and promote Asian-US interactions. Local Nashville high school teachers will be involved in laser diagnostic and combustion research in the summer under the Research Experience for Teachers Program at Vanderbilt University.