Laminar Burning Velocities of Diluted Stoichiometric Hydrogen/Air Mixtures
Laminar Burning Velocities of Diluted Stoichiometric Hydrogen/Air Mixtures
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DOI：
10.4271/2023-01-0331
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发表时间：
2023-04
期刊：
影响因子：
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通讯作者：
Ahmed Barain;Grace Trombley;B. Duva;E. Toulson
中科院分区：
文献类型：
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作者：
Ahmed Barain;Grace Trombley;B. Duva;E. Toulson
自实施以来，废气再循环已被证明是一种通过降低燃烧温度来控制NOx排放的可靠技术。无论是在内燃机还是在顺序分级燃气涡轮机燃烧室中，废气再循环的稀释都会影响火焰反应性和稳定性，这与热释放速率和发动机功率有关。另一种控制排放的方法是使用氢作为无碳替代燃料，这被认为是能源脱碳之旅的里程碑。然而，氢的高反应性是它的障碍之一，了解这种影响层流燃烧速度是很重要的。火焰传播和燃烧速度控制着混合气的反应性和可燃性，并与回火和爆震等异常燃烧现象有关。因此，了解废气添加对氢/空气混合物层流燃烧速度的影响对于发动机设计是必要的。本文采用定容燃烧室，在1bar和423 K条件下，测量了化学计量比的氢/空气混合气在燃烧产物稀释下的层流燃烧速度。使用实际燃烧产物（35%H2O +65%N2，按摩尔计）以0- 50%的比率稀释。计算所有混合物的燃烧气体Markstein长度。所有混合物的层流燃烧速度的实验结果进行了比较与动力学模型的结果。这些测量表明，反应性和层流燃烧速度与稀释的单调减少。在较高稀释度下燃烧速率的降低反映在容器内的压力梯度上。Markstein长度值随稀释而减小，这意味着火焰不稳定性随稀释而增加。
Since its implementation, exhaust gas recirculation has proven to be a reliable technique to control NOx emissions by lowering combustion temperature. Dilution with exhaust gas recirculation, whether in internal combustion engines or sequential-staged gas turbine combustors, affects flame reactivity and stability, which are related to the heat release rate and engine power. Another way to control emissions is to use hydrogen as a carbon-free alternative fuel, which is considered a milestone in the energy-decarbonization journey. However, the high reactivity of hydrogen is one of its hurdles and understanding this effect on laminar burning velocity is important. Flame propagation and burning velocity control the mixture reactivity and exothermicity and are related to abnormal combustion phenomena, such as flashback and knock. Therefore, understanding the effect of exhaust gas addition on the laminar burning velocity of hydrogen/air mixtures is imperative for engine design. In this work, a constant volume combustion chamber was used to observe the laminar burning velocity of stoichiometric hydrogen/air mixtures diluted with combustion products at 1 bar and 423K. Actual combustion products (35 % H2O + 65 % N2, by mole) were used for dilution at rates of 0-50%. The burned gas Markstein length was calculated for all mixtures. Experimental results of the laminar burning velocities for all mixtures were compared with kinetic modeling results. These measurements showed the monotonic reduction of reactivity and the laminar burning velocity with dilution. The reduced burning rates at higher dilution were reflected on the pressure gradient inside the vessel. Markstein length values decreased with dilution, meaning that flame instabilities increased with dilution.