热流掺混下液滴-火焰耦合机理及两相火焰面建模研究

液滴-火焰耦合作用是影响燃烧室燃烧特性和排放的关键基础理化过程。然而，有关其中液滴与火焰多模式耦合作用的认识和研究尚显不足，且现有数理模型也缺乏针对性和对单液滴及滴群中不同燃烧模式的动态描述，不利于对两相耦合机理的探究。本项目针对燃烧室内热流掺混环境特点，拟以煤油液滴燃烧的试验和数值分析出发，阐明该环境下主导单液滴燃烧的气/液参数，以此提出和发展针对性的考虑液滴燃烧蒸发多模态和多场域火焰耦合作用的两相火焰面模型，同时在直接数值模拟检验该新燃烧模型基础上，结合大涡模拟对航空发动机模型燃烧室进行计算，采用燃烧区域识别方法、瞬态液滴响应分析，以及建立对照组解算数据，和区域火焰结构与液相参数间的关系图谱，研究液滴燃烧蒸发属性与预混/扩散反应区间的关联影响规律，揭示燃烧室液滴-火焰复杂耦合机理。本研究可加深认识和理解燃烧室中两相燃烧基本规律，为设计清洁高效燃烧室提供理论依据和模型方法。

Droplet-flame coupling is the fundamental physico-chemical process that plays a vital role in affecting the combustion performance and emission characteristics of liquid-fueled engines. However, the study on the mechanism underlying the multimode gas/liquid interactions in engines, which remains not well understood, is insufficient, and is compounded by the fact that the pertinent models for spray combustion are lacking with the present models deficient in capturing the local combustion mode dynamically within the single droplet and droplet clouds. Given the prevailing vitiated air-flow condition encountered in the practical engine combustors, the present study first investigates experimentally and numerically the dynamics of kerosene single droplet combustion under the hot and multiple species environment, aiming at the identification of the key gas/liquid parameters at this condition that are relevant to the characterization of the droplet combustion behavior, based on which a two-phase flamelet model is proposed and developed to consider the coupling among the multimode droplet evaporation and the multiple combustion regimes. Validated and optimized by the direct-numerical simulation, this new combustion model is then implemented in a large-eddy simulation of turbulent spray combustion in a subscale jet engine combustor with kerosene fuel. Utilizing the combustion regime and droplet trajectory analysis, and establishing a comparative computation with conventional combustion model, as well as constructing a local flame state diagram as a function of liquid-phase parameters, the evaporating/burning droplets and their interactions with the flame dynamics at the premixed/nonpremixed combustion regimes are studied, shedding light on the droplet-flame coupling mechanism within the engine combustor. This work can improve our understanding of the complex two-phase combustion behavior in engines, and provide the necessary theory and model for the design of more clean and efficient combustors.