Abstract Non-premixed laminar or turbulent flames can undergo extinction when scalar dissipation rates exceed a critical value. When local extinction occurs, negative edge flames that act to expand the region of extinction are initially present. Steady negative edge flames have been previously studied in a combustor designed to support the negative propagation velocity of the flame edge, but unsteady negative edge flames have not received significant attention. The current study uses numerical simulations in a simple flowfield to produce unsteady negative edge flames which oscillate in response to imposed strain rate fluctuations in order to understand the dynamic response of extinction edge propagation. An energy balance through the edge shows that the unsteady behavior can be well described by a simple extension of the energy balance from steady flames. Furthermore, the edge velocity was calculated, and a physical interpretation of the extinction velocity was derived using the energy budget. The time scale of the imposed strain rate fluctuations was varied to show a limited response time for the extinction edge flame dynamics.

中文翻译：

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周期性流动中非定常负边缘火焰的能量分析

摘要 当标量耗散率超过临界值时，非预混层流或湍流火焰可能会消失。当局部消光发生时，最初会出现用于扩大消光区域的负边缘火焰。稳定负边缘火焰先前已经在设计用于支持火焰边缘的负传播速度的燃烧器中进行了研究，但不稳定负边缘火焰并未受到显着关注。目前的研究在简单的流场中使用数值模拟来产生不稳定的负边缘火焰，这些火焰响应于施加的应变率波动而振荡，以了解消光边缘传播的动态响应。通过边缘的能量平衡表明不稳定行为可以通过稳定火焰的能量平衡的简单扩展来很好地描述。此外，计算边缘速度，并使用能量预算推导出消光速度的物理解释。施加应变率波动的时间尺度是变化的，以显示消光边缘火焰动力学的有限响应时间。