The catalytic and gas-phase combustion of fuel-lean H₂–O₂–N₂ premixtures was investigated in a channel coated with platinum at pressures 1.0–3.5 bar, a range encompassing microreactors in portable power generation systems and passive hydrogen recombiners in nuclear power plants. One-dimensional Raman spectroscopy assessed the progress of catalytic hydrogen combustion, while planar laser-induced fluorescence (LIF) of the hydroxyl radical monitored gaseous combustion. Simulations were performed using a 2-D code with detailed catalytic and gas-phase reaction mechanisms and realistic transport. Both LIF measurements and simulations revealed that homogeneous combustion was vigorously sustained below ∼2.5 bar, while it was effectively suppressed at higher pressures. This was due to the intricate pressure dependency of the hydrogen gaseous ignition chemistry and the competition between catalytic and gaseous chemical reactions for hydrogen consumption. Parametric simulations determined the smallest critical channel heights allowing for appreciable gaseous combustion and their dependency on pressure, wall temperature, and inlet velocity. It was shown that for the narrower channels of catalytic microreactors homogeneous combustion was relevant only for wall temperatures above 1300 K, whereas for the wider hydrogen recombiner channels it could be relevant for wall temperatures down to 1100 K. Furthermore, at 1100 K the critical channel heights were nonmonotonic functions of pressure, reaching their peaks at 2.0–2.5 bar.

中文翻译：

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气态化学计量比和1.0-3.5 bar压力下，气态化学对H ₂ -O ₂ -N ₂燃烧对铂的影响

贫燃料H ₂ -O ₂ -N ₂的催化燃烧和气相燃烧在压力为1.0-3.5 bar的涂有铂的通道中研究了预混合物，该范围涵盖便携式发电系统中的微反应器和核电站中的无源氢重组器。一维拉曼光谱评估了催化氢燃烧的进展，而羟基自由基的平面激光诱导荧光（LIF）则监测了气态燃烧。使用具有详细催化和气相反应机理以及实际传输的二维代码进行了模拟。LIF测量和模拟均表明，均匀燃烧在〜2.5 bar以下有力维持，而在较高压力下则得到有效抑制。这归因于氢气气态点火化学的复杂压力依赖性以及催化和气态化学反应之间对氢消耗的竞争。参数模拟确定了最小的临界通道高度，可允许明显的气体燃烧以及它们对压力，壁温和入口速度的依赖性。结果表明，对于催化微反应器的较窄通道，均质燃烧仅与壁温高于1300 K有关，而对于较宽的氢重组通道，则与壁温低至1100 K有关。此外，在1100 K时，临界通道高度是压力的非单调函数，在2.0–2.5 bar时达到峰值。参数模拟确定了最小的临界通道高度，可允许明显的气体燃烧以及它们对压力，壁温和入口速度的依赖性。结果表明，对于催化微反应器的较窄通道，均质燃烧仅与壁温高于1300 K有关，而对于较宽的氢重组通道，则与壁温低至1100 K有关。此外，在1100 K时，临界通道高度是压力的非单调函数，在2.0–2.5 bar时达到峰值。参数模拟确定了最小的临界通道高度，可允许明显的气体燃烧以及它们对压力，壁温和入口速度的依赖性。结果表明，对于催化微反应器的较窄通道，均质燃烧仅与壁温高于1300 K有关，而对于较宽的氢重组通道，则与壁温低至1100 K有关。此外，在1100 K时，临界通道高度是压力的非单调函数，在2.0–2.5 bar时达到峰值。