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首页> 外文期刊>Combustion and Flame >Homogeneous combustion of fuel-lean syngas mixtures over platinum at elevated pressures and preheats
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Homogeneous combustion of fuel-lean syngas mixtures over platinum at elevated pressures and preheats

机译：在升高的压力和预热下，贫燃料合成气混合物在铂上均质燃烧

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摘要

The gaseous oxidation of H_2/CO/CO_2/O_2/N_2 mixtures was investigated experimentally and numerically in a platinum-coated channel at fuel-lean stoichiometries (equivalence ratios φ ≤ 0.30), H_2:CO molar ratios 0.47-4.54, pressures 2-14 bar, and reactant preheats up to 736 K. Two-dimensional laser induced fluorescence of the OH radical monitored the homogeneous (gaseous) combustion, while 1-D Raman spectros-copy assessed the heterogeneous (catalytic) conversion of H_2 and CO. Numerical simulations, which were carried out with a 2-D elliptic code and detailed hetero-/homogeneous reaction schemes, reproduced the measured onset of homogeneous ignition, the ensuing flame shapes, and the mass-transport-limited catalytic conversion of H_2 and CO. Additional simulations in practical tubular channels with 1 mm diameter have shown that gaseous oxidation was suppressed at atmospheric pressure due to the intrinsic slow gas-phase ignition kinetics in conjunction with the competition from the catalytic pathway for H_2 and CO consumption. At pressures p > 4 bar, homogeneous combustion was largely controlled by flame propagation characteristics due to the near-wall confinement of the established flames. The decrease in laminar mass burning rates at p > 4 bar led to a push of the gaseous combustion zone close to the channel wall, to leakage of H_2 and CO through the flame and, finally, to subsequent catalytic conversion of the leaked fuel components. Radical heterogeneous reactions promoted mildly the onset of homogeneous ignition at p 3 ≥ 2 bar due to the net desorptive flux of OH over the gaseous induction zone. The catalytically produced H_2O had a strong kinetic impact on homogeneous combustion by inhibiting the gaseous oxidation of both H_2 and CO at high H_2:CO ratios and by promoting CO gaseous oxidation at low H_2:CO ratios. The catalytically produced CO_2 always inhibited kinetically the gaseous combustion of H_2 and CO, although its effect was much weaker compared to that of H_2O.
机译：在贫油化学计量比（φ≤0.30），H_2：CO摩尔比为0.47-4.54，压力为2-的情况下，在镀铂通道中对H_2 / CO / CO_2 / O_2 / N_2混合物的气态氧化进行了实验和数值研究。 14 bar，反应物预热到736K。二维激光诱导的OH自由基荧光监测了均相（气态）燃烧，而一维拉曼光谱仪评估了H_2和CO的异质（催化）转化。使用2-D椭圆代码和详细的异质/均质反应方案进行的模拟模拟，再现了所测量的均质着火开始，随之而来的火焰形状以及H_2和CO的质量极限运输催化转化。在直径为1 mm的实际管状通道中进行的模拟表明，由于固有的缓慢气相点火动力学以及来自催化剂的竞争，在大气压下抑制了气态氧化H_2和CO消耗的生物途径。在压力p> 4 bar时，由于已建立火焰的近壁限制，均匀燃烧在很大程度上受火焰传播特性控制。在p> 4 bar时，层流质量燃烧速率的降低导致气态燃烧区靠近通道壁的推动，导致H_2和CO通过火焰泄漏，最后导致泄漏燃料成分的后续催化转化。自由基异质反应在p 3≥2 bar时由于在气态感应区上OH的净净吸附通量而促进了均匀点火的开始。催化生成的H_2O通过抑制高H_2：CO比率下的H_2和CO的气态氧化并通过促进低H_2：CO比率下的CO气态氧化而对均质燃烧产生强烈的动力学影响。催化生成的CO_2始终在动力学上抑制H_2和CO的气体燃烧，尽管与H_2O相比，其作用要弱得多。

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