An Experimental-Numerical Investigation of Unsteady Partially Premixed Flames

本文研究了非定常部分预混火焰的结构和动力学，包括与三重火焰相关的升空和稳定机制，以及拉伸和曲率对火焰结构和稳定性的影响。实验工作使用了成熟的非侵入性光学诊断方法，如激光多普勒测速、粒子图像测速、高速摄像、C2*自由基成像和全息干涉计量学。火焰的数值模拟采用了高阶时间精度的多维算法，其中包含了氢、甲烷和正庚烷等燃料氧化的详细化学动力学模型。在逆流燃烧器中研究了流体动力拉伸对火焰的影响，在缝隙燃烧器中研究了曲率对拉伸的贡献。研究了由浮力或剪切引起的三重火焰中的不稳定性；模拟表明，这些不稳定是流量的函数。在计算上，基于改进的混合分数的守恒标量方法被用来表征状态关系。

This is study of the structure and dynamics of unsteady, partially premixed flames including liftoff and stabilization mechanisms associated with triple flames and the effects of stretch and curvature on flame structure and stability. The experimental effort uses established nonintrusive optical diagnostics such as laser Doppler velocimetry, particle image velocimetry, high-speed videography, C2* radical imaging, and holographic interferometry. Numerical simulations of the flames employ higher-order time-accurate multidimensional algorithms incorporating detailed chemical kinetics models for oxidation of such fuels as hydrogen, methane, and n-heptane. Hydrodynamic stretch effects on flames are studied in a counterflow burner, while the contribution of curvature to stretch is investigated in a slot burner. Instabilities in triple flames induced by buoyancy or shear are investigated; simulations suggest that these occur as functions of flow rate. Computationally, a conserved scalar approach based on a modified mixture fraction is used to characterize state relationships.