In this work, we propose a physics-based scaling theory for the evolution of small-scale turbulence eddies in the unburnt mixture when they travel across the preheat zone of a premixed flame. This scaling theory is developed to explicitly account for the effects of viscous diffusion on the length and velocity scales of turbulence eddies that are smaller than the inner reaction zone thickness of a premixed flame. This scaling suggests that both the length and velocity scales of the turbulence eddies are significantly altered as they pass through the preheat zone. The applicability of the scaling is assessed using a series of detailed numerical simulations of flame-vortex interactions with finite-rate chemistry and detailed molecular transport. The scaling estimates of eddy evolution are compared to simulation predictions with reasonable agreement. The proposed scaling is then applied to estimate the required length and velocity scales of turbulence eddies in the unburnt mixture of a turbulent premixed flame to potentially create significant perturbation of the reaction zone by local mixing after passing through the preheat zone. These requirements are translated into a minimum estimated Karlovitz number (Ka) of approximately in the unburnt mixture of a turbulent premixed flame to potentially achieve distributed combustion. This estimated minimum Ka is significantly higher than the classical scaling estimate () for turbulent premixed flames, which supports the observations in recent experimental and Direct Numerical Simulation studies. The proposed scaling analysis implies that it is unlikely that turbulence eddies on the unburnt side of realistic turbulent premixed flames can be simultaneously sufficiently small and sufficiently strong to significantly alter the structure of the inner reaction zone.

中文翻译：

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跨预混火焰的小尺度湍流涡流演变对分布燃烧的影响的比例分析

在这项工作中，我们提出了一种基于物理学的标度理论，用于未燃烧混合物中的小尺度湍流涡流穿过预混火焰的预热区时的演变。该比例理论的开发是为了明确说明粘性扩散对小于预混火焰内部反应区厚度的湍流涡的长度和速度尺度的影响。这种尺度表明湍流涡流的长度和速度尺度在它们通过预热区时都发生了显着变化。使用有限速率化学和详细分子传输的火焰-涡流相互作用的一系列详细数值模拟来评估缩放的适用性。将涡流演化的标度估计与具有合理一致性的模拟预测进行比较。然后应用建议的标度来估计湍流预混火焰的未燃烧混合物中湍流涡流所需的长度和速度标度，以通过预热区后的局部混合可能对反应区产生显着扰动。这些要求被转化为大约在湍流预混火焰的未燃烧混合物中的最小估计卡洛维茨数 (Ka)，以潜在地实现分布式燃烧。这个估计的最小 Ka 显着高于湍流预混火焰的经典标度估计 ()，这支持了最近的实验和直接数值模拟研究中的观察结果。