随着国家对环保要求的不断提高，大型工业裂解炉的NOx减排已经成为国内石化行业的重要目标，其中最直接有效的方法是改进和优化炉膛内的燃烧过程。MILD燃烧是低氧稀释条件下的一种无焰燃烧模式，相比传统燃烧更加均匀高效，并且可以有效减少NOx排放达50%以上，被誉为21世纪最具潜力的新型燃烧方式之一。然而MILD燃烧的特征与传统燃烧差别很大，燃烧过程的发生和演变机制尚未被完全理解，因此限制了其工业应用。本项目拟采用计算流体力学方法，重点研究MILD燃烧的湍流-化学反应相互作用，对MILD燃烧特性和NOx减排机制进行阐释，从而建立能够准确模拟MILD燃烧的计算流体力学模型。在此基础上对工业裂解炉进行数值模拟，重点探究裂解炉内实现MILD燃烧的主要影响因素和操作范围，并且建立各操作变量与NOx排放和炉膛热效率的关系，力图为工业裂解炉实现高能效、低排放的新型燃烧工艺提供理论和实践指导。

With the rising demand for environmental protection, NOx reduction in large scale steam cracking furnaces has become the most important goal of the development of the domestic petrochemical industry. A direct way of NOx reduction is to improve the combustion process in the furnace. MILD combustion is a type of flameless combustion mode under low oxygen concentration condition. It has the advantages of more uniform temperature, higher thermal efficiency and more than 50% NOx reduction over traditional combustion mode and is therefore considered as the most promising combustion technology in the 21st century. However, industrial applications of the MILD combustion are still quite limited due to the big difference between MILD and the traditional combustion mode. The origin and evolution of MILD combustion is still far from well understood. This project investigates the turbulence-reaction interaction of MILD combustion by means of computational fluid dynamics (CFD) simulations to provide better understanding of the MILD combustion characteristics as well as its NOx reduction mechanism. A CFD-based model which can accurately describe the important characteristics of MILD combustion will be established and used for numerical simulations of MILD combustion in large scale industrial steam cracking furnaces to investigate the key factors and operating range to realizing MILD combustion in such furnace. Moreover, the effects of different operating variables on NOx reduction and furnace thermal efficiency will also be studied to provide theoretical and practical guidance for combustion process improvement, which allows to increase thermal efficiency and reduce NOx emission in steam cracking furnaces.