合成气是洁净煤技术中煤气化的主要产物，在工业生产上具有重要的用途；但它是可燃气体，容易引发火灾和爆炸。管道就是其事故高发区域。但目前合成气预混火焰在管道内的传播机理尚不清晰，给相关安全防控技术的开发带来困难。本项目首先研究管道内合成气-空气预混火焰不稳定行为，特别是两种郁金香结构相互转化的条件及临界特征，并进一步考察郁金香结构继续变形和传播规律，拓展对火焰传播初期阶段及其特征现象的认识。同时，通过控制初始压力或氦气/氩气稀释的方法，改变火焰面厚度和体系路易斯数，定量研究水力学和热-扩散不稳定性对火焰形变及传播行为的耦合作用机理；并引入化学反应动力学这一重要影响因素，剖析火焰化学反应过程及其与火焰、火焰诱导流场和压力波运动的相互作用机制。最后，基于上述研究建立管道内合成气-空气预混火焰传播预测模型，揭示火焰传播不稳定性的动力学机制和临界判据。本项目研究成果可以为合成气安全利用提供科学指导。

Syngas is the main product of coal gasification as a clean technology. And it has extensive applications in industry. But as one kind of flammable gas, it is prone to cause fire and explosion. The duct is precisely the area where accident always occurs. However, the mechanism of flame propagation of syngas in the duct is still not clear, which brings great difficulty to the development of relevant safety technology. Accordingly, we intend to use syngas-air mixtures to investigate the propagation instability of flame in the duct, especially the transformation conditions and critical characteristics of two types of tulip structures. Then the following deformation and movement of tulip structures will be observed, which can extend the knowledge of multiple stages and features of early flame propagation. In the meantime, the coupling effects of hydrodynamic instability and diffusive-thermal instability on flame behavior will be scrutinized quantitatively with different flame thickness and global Lewis numbers by changing the initial pressure or adding helium/argon in the mixtures. Additionally, the chemical kinetics will also be emphasized. The important interaction between chemical reaction, flame, flame-induced flow and pressure wave will be explored. Based on above work, finally a prediction model of premixed syngas-air flame propagating in the duct will be established. And the dynamic mechanism and critical criterion of instability during flame propagation will be revealed and elucidated. This work can provide scientific details to promote the safe utilization of syngas.