A well-resolved database of a small-scale heptane pool fire is analyzed to assess the assumptions of flamelet models in fire simulations. The pool fire database features well-resolved turbulence fields, finite-rate chemistry for heptane using a 33-species skeletal mechanism, and a coupled Monte Carlo ray-tracing radiation solver with a line-by-line spectral model. A budget analysis of the flamelet equation is performed by transforming temperature and species to the mixture fraction space and extracting instantaneous flamelet solutions along flame-aligned directions. Five flame-aligned budget terms and one unsteady term are identified through transformation of the temperature equation. Three conditions are examined, including an adiabatic case, a case involving only gas radiation, and a case involving both gas and soot radiation. The budget analysis shows that preferential diffusion is non-negligible near the base of the pool. Radiation is found to be appreciable in the transition region of the fire, resulting in a reduction of flame temperature by as much as 270 K due to radiative heat losses. The curvature of the flame surface is found to have a minor impact on the temperature dynamics near the flame front. The extracted flame structures deviate from those predicted from a steady-state adiabatic laminar flamelet model, particularly in the profiles of CO, ${\mathrm{CO}}_2,$ and OH. A time scale analysis is performed, indicating that steady state assumptions for chemical species are reasonable for this flame, although radiation is much slower compared to chemistry and requires consideration to correctly capture the temperature evolution. The source terms from radiative absorption and emission show pronounced non-proportionality between the two, where absorption can exceed emission, thereby serving as a heating source for the fuel and oxidizer streams. The controlling factors for radiative absorption are analyzed, based on which a non-local model is proposed to approximate absorption in pool fires. A priori assessment of this model shows good agreement with the pool fire database, demonstrating the feasibility of enhancing the flamelet formulation to account for radiative emission and absorption effects.

分析了一个很好解析的小规模庚烷池火灾数据库，以评估火灾模拟中小火焰模型的假设。池火数据库具有良好的解析湍流场，使用33种骨骼机制的庚烷有限速率化学以及耦合的逐行光谱模型的蒙特卡洛射线追踪辐射求解器。通过将温度和物质转换为混合物馏分空间并沿火焰对齐方向提取瞬时小火焰溶液，可以对小火焰方程进行预算分析。通过转换温度方程式，可以确定五个与火焰对齐的预算项和一个非稳态项。检查了三个条件，包括绝热情况，仅涉及气体辐射的情况以及涉及气体和烟尘辐射的情况。预算分析表明，优先扩散在池底附近是不可忽略的。在火的过渡区域发现有明显的辐射，由于辐射热损失，火焰温度降低了多达270K。发现火焰表面的曲率对靠近火焰前沿的温度动态影响很小。提取的火焰结构与稳态绝热层流小火焰模型预测的结构不同，特别是在CO的分布中，发现火焰表面的曲率对靠近火焰前沿的温度动态影响很小。提取的火焰结构与稳态绝热层流小火焰模型预测的结构不同，特别是在CO的分布中，发现火焰表面的曲率对靠近火焰前沿的温度动态影响很小。提取的火焰结构与稳态绝热层流小火焰模型预测的结构不同，特别是在CO的分布中，${\mathrm{一氧化碳}}_2，$和OH。进行了时间标度分析，表明对于该火焰而言，化学物质的稳态假设是合理的，尽管辐射比化学物质要慢得多，并且需要考虑正确地捕获温度的变化。辐射吸收和发射的源项在两者之间显示出明显的不成比例性，其中吸收可能超过发射，从而成为燃料和氧化剂流的加热源。分析了辐射吸收的控制因素，在此基础上，提出了一种非局部模型来近似池火的吸收。先验 对模型的评估表明，该模型与池火数据库具有很好的一致性，证明了增强小火焰公式以解决辐射发射和吸收效应的可行性。