Two key flame macrostructures in swirling flows have been observed in experiments of oxy-combustion (as well as air-combustion); as the equivalence ratio is raised, the flame moves from being stabilized on just the inner shear layer (Flame III) to getting stabilized on both the inner and outer shear layers (Flame IV). We report results of an LES investigation of two different inlet oxy-fuel mixtures, in a turbulent swirling flow at $\text{Re}=20,000,$ that capture these two macrostructures. Previous work on the effects of heat loss have mostly focused on its impact on macro-scale observations. In this paper, we examine how heat loss impacts the flame microstructures as well for these two macrostructures. For both flames, the flamelet structure, as represented by a scatter plot of the normalized fuel concentration against the normalized temperature, depends on whether the combustor walls are adiabatic or non-adiabatic. For the adiabatic case, the flamelets of both macrostructures behave like strained flames. When wall heat transfer is included, Flame III microstructure is more bimodal. Since this flame extends farther downstream and part of it propagates along the walls, heat transfer has a greater impact on it’s microstructure. These results show that heat loss impacts not just the macro properties of the flame such as its shape or interactions with the wall, but also fundamentally changes its internal structure. Scatter plots of the turbulent flames are constructed and compared to different 1D laminar flame profiles (e.g., strained or with heat loss), and comparisons suggest the important role of the wall thermal boundary conditions in the accurate simulations of combustion dynamics and interpretations of experimental data, including data reduction and scaling.

在氧气燃烧（以及空气燃烧）实验中，已经观察到旋流中有两个关键的火焰宏观结构。随着当量比的提高，火焰从仅在内部剪切层上稳定（火焰III）移动到在内部和外部剪切层上稳定（火焰IV）。我们报告了在两种湍流中的两种不同入口含氧燃料混合物的LES研究结果。$\text{关于}=20，000，$捕获了这两个宏观结构。以前关于热损失影响的研究主要集中在其对宏观观测的影响上。在本文中，我们研究了热量损失如何影响火焰微观结构以及这两个宏观结构。对于两种火焰，小火焰结构（由归一化燃料浓度相对于归一化温度的散点图表示）取决于燃烧室壁是绝热的还是非绝热的。对于绝热情况，两个宏观结构的小火焰都表现为应变火焰。当包括壁面传热时，Flame III的微观结构更加双峰。由于该火焰向下游延伸得更远，并且一部分火焰沿着壁传播，因此热传递对其火焰的微观结构影响更大。这些结果表明，热损失不仅影响火焰的宏观特性，例如其形状或与壁的相互作用，而且从根本上改变了其内部结构。构造了湍流火焰的散点图，并将其与不同的一维层流火焰轮廓（例如，应变或有热损失）进行了比较，比较结果表明壁热边界条件在燃烧动力学的精确模拟和实验数据的解释中起着重要作用。 ，包括数据缩减和缩放。