水蒸气对合成气层流火焰传播特性的影响

Effect of H_2O on Propagation of Laminar Syngas Flames

选用Davis-机理模拟研究初始温度400 K时,含有水蒸气的合成气/空气预混层流火焰传播特性.结合敏感性分析,从热力学效应、直接化学反应效应及化学三体反应效应方面详细分析水蒸气稀释作用.研究结果表明:当燃料中氢气的体积分数大于25%时,层流火焰传播速度、绝热火焰温度及重要自由基摩尔分数均随稀释剂比例的增加显著降低;在水蒸气整体稀释作用中,热力学效应起支配作用;随氢气体积分数的增加,当混合物当量比较小时,直接化学反应效应影响从促进作用发展为抑制作用;当稀释剂较少时,化学三体反应效应影响存在显著的抑制—促进—抑制作用的变化过程.

The laminar flame speeds of syngas/air mixtures with H2O dilution in the fuels were numerically studied at 400 K using Davis-Mech. Based on the calculated sensitivities of mass burning rate of mixtures with various H2O dilution ratios, the thermal, direct-reaction and third- body effects on the laminar flame speed of diluted mixtures were also carried out for an insightful understanding of the dilution effect of H2O. The results showed that when the volume fraction of H2 is larger than 25%, the laminar flame speed, adiabatic flame temperature and the mole fractions of the crucial radical of mixtures decrease significantly with the increase of dilution ration. The total dilution effect of H2 O was dominated by the thermal effect. When the equivalence ratio of mixture was small,the direct reaction effect caused by H2 O on the laminar flame speed was changed from promotion into inhibition with increasing volume fraction of H2. When the amount of H2 O was limited, the third-body effect on the laminar flame speed experiences a significant inhibition- promotion-inhibiting action.