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Maps of flame dynamics for premixed lean hydrogen-air combustion in a heated microchannel

机译：在加热的微通道中预混合贫氢空气燃烧的火焰动力学图

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摘要

In the present work, flame dynamics are extracted for combustion of premixed lean hydrogen-air in a heated microchannel using numerical simulation. In this simulation, Navier-Stokes equations along with energy and species conservation equations are considered by formulation of low Mach number and with consideration of detail chemical kinetics. Regarding different conditions, three dynamics are observed in the microchannel which are periodic repetitive ignition-extinction, steady symmetric flame, and steady asymmetric flame. The effects of different parameters such as inlet velocity, equivalence ratio, and channel width are investigated on the flame dynamics. The periodic repetitive ignition-extinction dynamics is observed at low velocities close to the lower flammability limit. Upon increasing the inlet velocity and creating a balance between the reaction time and fluid residence time in the channel, a steady symmetric flame is shown in the channel. In this situation, the maximum temperature and mass fraction of species are located on the symmetry line of the channel. Then by increasing the inlet velocity in a specific channel, the flame moves toward downstream at the symmetry line of the channel and it will be stretch near the walls. Hence, the surface of the flame front is susceptible to instability and becomes unstable due to the flow perturbations. The maps of flame dynamics in the small scales are presented for the hydrogen-air mixture based on three parameters, inlet velocity, and equivalence ratio and channel width in the microchannel. The obtained results show that by increasing the equivalence ratio, channel width, and inlet velocity, the steady symmetric dynamics is eliminated, replaced by a steady asymmetric dynamics.
机译：在目前的工作中，使用数值模拟提取火焰动力学以在加热的微通道中燃烧预混合的贫氢空气。在此模拟中，通过制定低马赫数并考虑详细的化学动力学来考虑Navier-Stokes方程以及能量和物种守恒方程。对于不同的条件，在微通道中观察到三种动力学，分别是周期性的重复着火熄灭，稳定的对称火焰和稳定的不对称火焰。研究了不同参数（例如入口速度，当量比和通道宽度）对火焰动力学的影响。在接近可燃性下限的低速下观察到周期性的重复性熄灭动力学。在增加入口速度并在反应时间和流体在通道中的停留时间之间建立平衡之后，在通道中显示出稳定的对称火焰。在这种情况下，物质的最高温度和质量分数位于通道的对称线上。然后，通过增加特定通道中的入口速度，火焰在通道的对称线处向下游移动，并在壁附近伸展。因此，火焰前缘的表面易于不稳定，并且由于流动扰动而变得不稳定。基于三个参数，进气速度，当量比和微通道中的通道宽度，给出了氢-空气混合物的小尺度火焰动力学图。所得结果表明，通过增加当量比，通道宽度和入口速度，消除了稳态对称动力学，而由稳态非对称动力学代替。

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