Takahashi Fumiaki, Katta Viswanath R, Linteris Gregory T, Babushok Valeri I
Case Western Reserve University, Cleveland, OH 44106, USA.
Innovative Scientific Solutions, Inc., Dayton, OH 45440, USA.
Proc Combust Inst. 2019;37. doi: 10.1016/j.proci.2018.06.140.
The effects of phosphorus-containing compounds (PCCs) on the extinguishment and structure of methane-air coflow diffusion flames, in the cup-burner configuration, is studied computationally. Dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), or phosphoric acid is added to either the air or fuel flow. Time-dependent axisymmetric computation is performed with full gas-phase chemistry and transport to reveal the flame structure and inhibition process. A detailed chemical-kinetics model (77 species and 886 reactions) is constructed by combining the methane-oxygen combustion and phosphorus inhibition chemistry. A simple model for radiation from CH, CO, CO, HO, and soot based on the optically thin-media assumption is incorporated into the energy equation. The inhibitor effectiveness is calculated as the minimum extinguishing concentrations (MECs) of CO (added to the oxidizer) as a function of the PCC loading (added to the oxidizer or fuel stream). The calculated MEC of CO without an inhibitor is in good agreement with the measured value. For moderate DMMP loading to the air (<1 %), the measured value becomes significantly smaller, presumably due to particle formation in the experiment. An inhibitor in the oxidizer flow is an order of magnitude more effective compared to that in the fuel flow in gas-phase inhibition of co-flow diffusion flames. The three PCCs studied behave similarly with regard to flame inhibition, lowering radical concentrations and the heat-release rate at the flame-stabilizing peak reactivity spot (i.e., reaction kernel) in the base, promoting flame blow-off. The three compounds behave differently, however, with regard to the trailing flame. While all three raise the maximum temperature in the trailing flame, DMMP and TMP, which contain three methyl groups, result in higher maximum flame temperature and combustion enhancement there, with a unique two-zone flame structure, whereas phosphoric acid does not.
采用计算方法研究了含磷化合物（PCCs）对杯式燃烧器结构中甲烷 - 空气同轴流扩散火焰熄灭及结构的影响。将甲基膦酸二甲酯（DMMP）、磷酸三甲酯（TMP）或磷酸添加到空气流或燃料流中。利用完整的气相化学和传输过程进行了随时间变化的轴对称计算，以揭示火焰结构和抑制过程。通过结合甲烷 - 氧气燃烧和磷抑制化学构建了一个详细的化学动力学模型（77种物质和886个反应）。基于光学薄介质假设的CH、CO、CO、HO和烟灰辐射的简单模型被纳入能量方程。抑制剂效率计算为CO（添加到氧化剂中）的最低灭火浓度（MECs），它是PCC负载量（添加到氧化剂或燃料流中）的函数。计算得到的无抑制剂时CO的MEC与测量值吻合良好。对于向空气中适度添加DMMP（<1%），测量值显著变小，可能是由于实验中形成了颗粒。在抑制同轴流扩散火焰的气相过程中，氧化剂流中的抑制剂比燃料流中的抑制剂有效一个数量级。所研究的三种PCCs在抑制火焰方面表现相似，可降低自由基浓度以及火焰稳定峰值反应性位置（即反应核）处的热释放率，促进火焰吹熄。然而，这三种化合物在尾焰方面表现不同。虽然这三种化合物都提高了尾焰中的最高温度，但含有三个甲基的DMMP和TMP会导致更高的最高火焰温度并增强那里的燃烧，形成独特的两区火焰结构，而磷酸则不会。
