Large Eddy Simulations are used to study the heat-release response to fuel inflow acoustic harmonic oscillations, in a coaxial jet flame where both reactants (O₂ and CH₄) are injected in a dense cryogenic state. The geometry is that of the academic test rig Mascotte, operated by ONERA (France), which high pressure operating conditions are relevant for the characterization of flame dynamics in Liquid Rocket Engines (LREs). The simulations, which are carried out with a real-gas fluid solver using a detailed kinetic scheme for CH₄ high-pressure oxycombustion, provide a thorough insight into the flame response for a wide range of forcing frequencies, spanning from approximately 1kHz to 20kHz. Local Flame Transfer Functions (FTF) are computed and analyzed: regions of preferential heat-release response are observed to be highly dependent on the forcing frequency. An analysis based on a flame sheet assumption is conducted to distinguish the main sources of heat release fluctuations: the primary contribution comes from the species diffusivity oscillations, while the density variations have a negligible effect. The second largest contributor is either the mixture fraction gradient or the flame surface area, depending on the forcing frequency. The FTFs are expected to be useful for thermoacoustic Low-Order Models or Helmholtz solvers, and the subsequent analysis has the potential to guide future development of analytical models for flame dynamics in LREs.

大涡模拟用于研究在两种反应物（O ₂和 CH ₄）都以致密低温状态注入的同轴喷射火焰中对燃料流入声谐波振荡的热释放响应。几何形状是由 ONERA（法国）运营的学术试验台 Mascotte 的几何形状，其高压操作条件与液体火箭发动机 (LRE) 中的火焰动力学特性相关。_{模拟使用真实气体流体求解器使用 CH 4}的详细动力学方案进行高压氧燃烧，提供了对从大约 1kHz 到 20kHz 的各种强制频率的火焰响应的全面洞察。计算和分析局部火焰传递函数 (FTF)：观察到优先放热响应区域高度依赖于强迫频率。进行基于火焰片假设的分析以区分热释放波动的主要来源：主要贡献来自物种扩散率振荡，而密度变化的影响可以忽略不计。第二大贡献者是混合分数梯度或火焰表面积，具体取决于强制频率。FTF 有望用于热声低阶模型或亥姆霍兹求解器，