稀释剂和氧浓度对甲烷非预混MILD富氧燃烧影响的模拟研究  

Numerical Investigation on Impacts of Diluent and Oxygen Concentration on Non-premixed MILD Oxy-Combustion of Methane

作　　者：司济沧 舒子云 王国昌 王勃 米建春[1] SI Jicang;SHU Ziyun;WANG Guochang;WANG Bo;MI Jianchun(College of Engineering,Peking University,Haidian District,Beijing 100871,China;China Ship Development and Design Center,Wuhan 430072,Hubei Province,China;Beijing Municipal office for Science and Technology Awards,Haidian District,Beijing 100444,China)

机构地区：[1]北京大学工学院,北京市海淀区100871 [2]中国舰船研究设计中心,湖北省武汉市430072 [3]北京市科学技术奖励工作办公室,北京市海淀区100444

出　　处：《中国电机工程学报》2021年第11期3692-3701,共10页Proceedings of the CSEE

基　　金：国家自然科学基金项目(51776003)。

摘　　要：通过数值模拟方法研究了不同氧化剂(O_(2)/N_(2)、O_(2)/CO_(2)和O_(2)/H_(2)O)和燃烧器出口氧浓度(21%~30%)对15kW实验炉内甲烷非预混中度与极度低氧稀释(moderate or intense lowoxygen dilution,MILD)富氧燃烧的流场、燃烧场及湍流–化学相互作用的影响。研究结果表明,不同稀释剂下炉内流动和烟气卷吸情况几乎相同,但在炉内反应方面存在较大差异。各稀释剂下炉内燃烧温度和CO、OH浓度的高低顺序为:N_(2)>CO_(2)>H_(2)O。而且,N_(2)稀释时炉内存在集中的高温区(>1800K),且温度和组分浓度随氧浓度增大而快速升高。而CO_(2)或H_(2)O稀释时炉内温度、组分分布均匀,且对氧浓度变化不敏感。另外,相比CO_(2)或H_(2)O稀释,N_(2)稀释下反应区内的层流火焰速度和Damköhler数(Da)更大,且随氧浓度的升高而急剧增加,30%氧浓度下已经进入传统薄反应区燃烧模式。而CO_(2)或H_(2)O的稀释可以显著降低层流火焰速度,增长化学反应时间,减小Da数,在高氧浓度下依旧保持在分布式反应区,即MILD燃烧区。因此,相比N_(2)稀释,CO_(2)或H_(2)O稀释下更有利于建立MILD富氧燃烧。The present work numerically investigated the effects of oxidizing atmosphere(O_(2)/N_(2), O_(2)/CO_(2) and O_(2)/H_(2)O)and oxygen concentration on the non-premixed MILD oxy-combustion of methane in a 15 kW combustion furnace.Specifically, the flow field, reaction field, as well as the turbulence-chemical interaction were studied. Results show that under different diluents, the flow structure and flue gas entrainment are similar, but combustion reactions vary greatly.The combustion temperature T and CO and OH concentrations under different diluents are in the following order: N_(2)>CO_(2)>H_(2)O.Moreover, when N_(2) is used as the diluent, there exists a concentrated high temperature region(>1800 K) in the furnace,and the temperature and species concentrations rise quickly as oxygen level increases. Conversely, the distributions of temperature and species are more uniform and not sensitive to the variance of oxygen level under CO_(2) or H_(2)O dilution. Furthermore,comparing to CO_(2) or H_(2) O dilution, the laminar flame speed and Damköhler number(Da) in the reaction zone is much larger under N_(2) dilution, and they will rise abruptly as the oxygen level increases. At 30% oxygen level, the in-furnace combustion is in the traditional thin reaction zone mode. Relatively, CO_(2) or H_(2)O dilution can significantly reduce the laminar flame speed,and increase the chemical reaction time, thus lower Da, and keep the distributed reaction mode, i.e., MILD combustion mode. Therefore, comparing to N_(2), it is more favorable to establish MILD oxy-combustion under CO_(2) and H_(2)O dilutions.

关 键 词：中度与极度低氧稀释富氧燃烧 非预混 稀释剂 氧浓度 湍流–化学相互作用 

分 类 号：TK16[动力工程及工程热物理—热能工程]