GOALI: Experimental and Computational Study of Bluff-body Flame Stabilization with Nonhomogeneous Upstream Mixing

项目编号：CTS- 0553504项目负责人：Cetegen， Baki m .机构：University of connecticut项目名称：目标：上游非均匀混合崖体火焰稳定的实验与计算研究在许多实际的燃烧装置中，包括飞机增压器，火焰保持发生在高速湍流中，通过位于喷油器下游的崖体。在火焰稳定区域，混合成分预计会发生显著的时空变化。目前已有大量的实验研究，对钝体或旋流锚定的完全预混或非预混火焰进行了实验研究，并对火焰在混合成分梯度中的传播进行了单独的研究。然而，尽管它们与飞机推进系统中的火焰保持有关，但在成分梯度和再循环热产物区域的火焰稳定性还没有全面的研究。本项目的智力优势在于对高速流动中崖体稳定部分预混火焰进行了详细的实验研究，并对火焰动力学和稳定性进行了补充计算。这项工作的目标是提高对循环、部分预混流中火焰传播的基本理解，评估模型的准确性，并检验用于预测火焰稳定性的降阶模型。本研究的结果直接适用于目前使用钝体稳定化的飞机增强器，但也将广泛适用于氢基合成气燃料的新型燃烧室设计，这些燃烧室可能需要增强钝体稳定化以实现燃料的灵活运行。详细的激光诊断技术将应用于深入了解导致高速火焰吹灭的局部条件，以及混合物不均匀性对火焰吹灭的开始和吹灭前火焰结构的影响。实验将在平面二维结构中进行，测量技术将包括速度成像、激光诱导荧光火焰结构成像和混合物成分的上游剖面。全面的文件和边界条件的控制将强调与数值模拟的兼容性。实验研究的几何形状的计算建模将由我们在联合技术研究中心（UTRC）的GOALI合作伙伴进行。在实验研究的相同情况下，完成崖体火焰保持的非定常数值模拟。目标是评估这些模拟在分层流动中捕捉火焰传播的能力，并开发部分预混火焰稳定的数值方法的扩展。本研究的更广泛的科学影响将是更好地理解火焰在部分预混流中的传播。这对工业设备的设计有直接影响，如飞机发动机的增强器，但也扩展了对湍流中基本火焰行为的理解，可以广泛适用于改进新燃料的燃烧室设计。该项目将有助于培养两名研究生。通过直接与UTRC合作，这些学生将获得该领域的经验，并将为美国在先进推进系统设计领域的竞争力做出贡献。该项目由燃烧和等离子体系统计划和学术联络资助机会（GOALI）计划共同资助。

Award AbstractProposal Number: CTS- 0553504 Principal Investigator: Cetegen, Baki M.Institution: University of ConnecticutProposal Title: GOALI: Experimental and Computational Study of Bluff-Body Flame Stabilization with Nonhomogeneous Upstream MixingIn many practical combustion devices, including aircraft augmentors, flame holding occurs in a high speed turbulent vitiated flow via bluff-bodies placed just downstream of fuel injectors. Significant spatial and temporal variations in mixture composition are expected in the flame stabilization region. There have been numerous experimental studies on fully premixed or nonpremixed flames anchored either by bluff bodies or swirling flow, and separate studies of flame propagation in mixture composition gradients. However, there have been no comprehensive investigations of flame stability in regions with both composition gradients and recirculating hot products, despite their relevance to flame holding in aircraft propulsion systems. The intellectual merits of this project involve a detailed experimental investigation of bluff-body stabilized partially-premixed flames in high velocity flows and a complementary computational effort on flame dynamics and stability. The goal of this work is to improve fundamental understanding of flame propagation in recirculating, partial-premixed flows, to assess model accuracy and to examine reduced order models for predicting flame stabilization. The results of this study are directly applicable to aircraft augmentors, which currently use bluff-body stabilization, but will also be broadly applicable to new combustor designs for hydrogen based syngas fuels, which may require enhanced bluff-body stabilization for fuel flexible operation. Detailed laser diagnostic techniques will be applied to develop an in-depth understanding of local conditions leading to flame blow-off at high velocities, and effects of mixture non-uniformities on the onset of flame blow-off and on flame structure prior to blow-off. The experiments will be performed in a planar two dimensional configuration, and the measurement techniques will include velocity imaging, flame structure imaging through laser-induced fluorescence, and upstream profiling of mixture composition. Thorough documentation and control of boundary conditions will be emphasized for compatibility with numerical simulations. Computational modeling of the geometries studied experimentally will be carried out by our GOALI partner at the United Technologies Research Center (UTRC). Unsteady numerical simulations of bluff-body flame holding will be completed for the same cases studied experimentally. The goal will be to assess the capabilities of these simulations to capture flame propagation in stratified flows and to develop extensions of the numerical approach to partially-premixed flame stabilization. The broader scientific impact of this research will be a better fundamental understanding of flame propagation in partially-premixed flows with recirculation. This has direct impact on the design of industrial devices such as augmentors for aircraft engines, but also expands understanding of basic flame behavior in turbulent flows that could be broadly applicable to improved combustor design for new fuels. The project will facilitate training of two graduate students. By working directly with UTRC, these students will gain experience in this field and they will contribute to the U.S. competitiveness in the area of advanced propulsion system design.This project is co-funded by the Combustion and Plasma Systems Program and the Grant Opportunities for Academic Liaison with Industry (GOALI) Program.