可控宽压力强湍流下点火及火焰传播机理研究

The ignition and flame propagation of premixed mixture in confined space are common key processes in engines, which are essential for reliable engine operations and therefore are highly relevant for the investigation of subtle turbulence-chemistry interaction in engine combustion. Currently due to experimental constraints, most fundamental studies on the ignition process in confined space have been limited to a narrow pressure range of 1-10 atm and low turbulence intensity (Ret<14000)m, which are not representative of engine operating condition. In the proposed research, a systematic study of the ignition and flame propagation of hydrogen, methane and aviation surrogate fuel will be performed over the pressure range of 0.3-30atm in turbulent flows with Ret up to 35000. The breakthrough in experimental techniques enables the study of the whole ignition process at high pressures in highly turbulent flows. The study will unravel the mysteries of the turbulence promotion/suppression mechanism for ignition and the reactive scalar small-scale mxing mechanism, which are both affected by chemical kinetics, turbulence and differential diffusion. Through the study, a universal scaling law for turbulent flame speed over a wide range of pressures will be formed and a theory will be developed for laminar flame to turbulent flame transition resulting from propagation acceleration due to flame instability. Moreover predictive PDF simulations with uncertainty quantification will be developed for the numerical investigation of the physio-chemical processes in the ignition and flame propagation process. In addition, an engineering model based on turbulence-chemistry interaction will be developed for the prediction of the probability of successful ignition events. The proposed research will dramatically improve the understanding of turbulent combustion at engine operating conditions and form the basis for ignition control technology.

受限空间内可燃预混气点火及火焰传播是发动机可靠运行关键共性问题，是重大专项中“受限空间内复杂湍流和燃烧的相互作用”的关键科学问题。已有湍流下的基础研究集中于1-10atm大气压，弱湍流(Ret<14000)，不能覆盖发动机宽压力强湍流工况。本项目结合实验、理论和数值模拟对压力（0.3-30atm）可控/强湍流（Ret达35000）条件下氢气、甲烷和航空替代燃料的点火和火焰传播开展系统研究。项目成功实施可：突破现有实验技术实现高压强湍流下火焰发展全过程研究；揭示湍流对点火抑制/促进机理，化学反应、湍流和组分差异扩散协同控制的标量小尺度混合机制；建立火焰面不稳定加速火焰传播而导致层流燃烧转捩为湍流燃烧的理论，湍流火焰传播速度统一标度律理论；形成高精度PDF数值模拟及其不确定性分析方法和点火成功概率预测模型。创新性研究成果将完善发动机工况下的湍流燃烧理论，为我国发动机可控点火技术的发展提供支撑。

该项目针对重大研究计划的核心科学问题“受限空间内复杂湍流和燃烧的相互作用”，开展宽压力范围、强湍流下点火及火焰传播机理研究。在湍流化学反应耦合机制及其对点火和火焰传播的影响、湍流燃烧建模、高精度数值模拟及不确定分析等基础问题进行了深入研究。研究实现了适用于发动机工况的点火及火焰传播特性的实验研究，发现由火焰面不稳定性引起的火焰多级加速现象并揭示了其机制；研究了湍流对火核生成和传播的影响机制和湍流火焰传播速度标度率；发展了火焰传播速度的新的外推不确定性准则；揭示了发动机燃料着火负温度系数区转折点的控制机制，实现了详细化学反应动力学在数值模拟中的高效运用；揭示了湍流预混燃烧中湍流和火焰协同控制的反应标量混合机制，发展一个新的反应标量小尺度混合速率模型，提升了PDF模拟的适用性和准确性；发展了数值模拟的不确定性分析理论和方法，提出了运用低维子空间实现了动力学不确定性在模拟中的传递，用于揭示点火和火焰传播中的主导物理化学过程及模型参数；研究同时发展了基于湍流-化学反应耦合机制的低维发动机火核生成概率预测模型，为发动机可靠点火优化提供理论和预测工具的支撑。该项目已发表29篇SCI学术论文（其中Combustion and Flame 和 Proceedings of the Combustion Institute 16篇），EI论文8篇；授权国家发明专利3项；参加国际学术会议并作报告20余人次,其中邀请报告1次，国内燃烧学大会报告1次；培养博士后3人，毕业博士3人、硕士2人，在读博士6人。