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为探讨反应物预热温度和稀释率对稀释燃烧机理的影响,该文以氮气稀释的甲烷–空气对冲扩散火焰为研究对象,采用氢氧基平面激光诱导荧光法(hydroxy radical planar laser induced fluorescence,OH-PLIF)进行实验研究。以OH基反应区厚度表征火焰厚度,实验结果表明,在反应物预热温度较低情况下,当预热温度一定时火焰厚度随反应物稀释率增大(或者浓度减小)而减小,当反应物稀释率一定时火焰厚度随预热温度升高而增大。但进一步分析表明,在反应物预热温度足够高时,火焰厚度将随反应物稀释率增加而增大。根据预热对化学反应速度的增大与稀释对化学反应速度的减小的共同作用,从火焰厚度随反应物预热温度与稀释率的变化情况可推断,在低预热温度稀释燃烧过程中,预热温度是影响火焰结构的主要因素;在预热温度足够高的稀释燃烧过程中,稀释率是火焰结构的主要影响因素,此时由于稀释引起化学反应速度大大降低,因此火焰厚度或体积显著增大。
In order to investigate the effect of reactant preheating temperature and dilution rate on the mechanism of dilution combustion, a new methane-air heaped diffusion flame diluted with nitrogen was used as the research object. Hydroxy radical planar laser induced fluorescence OH-PLIF) for experimental study. The flame thickness was characterized by the thickness of the OH-based reaction zone. The experimental results show that the flame thickness decreases with the increase of reactant dilution rate (or the concentration decreases) when the preheating temperature is low, The flame thickness increases with the preheating temperature when the reactant dilution rate is constant. However, further analysis showed that the flame thickness will increase with the increase of reactant dilution rate when the reactant preheating temperature is high enough. According to the synergistic effect of preheating on chemical reaction rate and dilution on the decrease of chemical reaction rate, it can be inferred from the variation of flame thickness with the preheating temperature and dilution rate of reactants. In the course of low preheating temperature dilution combustion , The preheating temperature is the main factor that affects the flame structure. At the pre-heating temperature of the dilution combustion process, the dilution rate is the main factor of the flame structure. At this time, the chemical reaction speed is greatly reduced due to the dilution, so the flame thickness or volume Significantly increased.