Blending of hydrocarbon fuels with hydrogen is a practically feasible way to rapidly integrate a carbon neutral energy vector in the transport sector and to effectively reduce harmful particulate matter emissions. This work investigates the effects of hydrogen (H₂) addition on soot formation in n-heptane in low strain rate counterflow diffusion flames with different oxygen mole fractions (X_O2=0.3 ∼ 0.45). Flame temperature, soot volume fraction (f_v), monocyclic (MAHs), and polycyclic aromatic hydrocarbons (PAHs) are measured by using OH-2C-PLIF/thermocouple, LII/LE, and PAH-LIF methods, respectively. Measurements of n-heptane flames with addition of helium (He), as an inert gas with a specific heat capacity similar to that of H_2, are also carried out and compared. Numerical simulations are then performed using a soot discrete sectional model coupled with detailed gas-phase kinetics to interpret the data obtained. Temperature and soot volume fraction profiles are better predicted by 2D simulations, which account for the non-negligible impact of radial diffusion and buoyancy under low strain rate conditions. Then, it is shown that both the f_v and PAH yields almost linearly decrease by increasing H₂ or helium (He) addition. The reduction of PAHs and soot is larger in n-heptane/H₂ flames due to H₂ chemical effects, absent in the n-heptane/He flames, hampering the formation of peri‑condensed structures. The effect of O₂ concentration in the oxidizer stream is also studied. Experimental and simulation results show that PAHs and soot increase with X_O2 for all flames. Finally, the effects of H₂/He addition varying X_O2 on soot formation are investigated. With the increase of X_O2, the difference in the peak flame temperatures of n-heptane/H₂ and n-heptane/He flames decreases. Consequently, compared to the neat n-heptane flame, the reduction of peak f_v becomes more and more pronounced in the case of hydrogen addition rather than the helium addition since the H₂ soot inhibiting chemical effect prevails over the H₂ temperature effect which instead promotes soot formation.

将碳氢化合物燃料与氢混合是一种切实可行的方法，可以在交通部门快速整合碳中和能源载体，并有效减少有害颗粒物排放。这项工作研究了在具有不同氧摩尔分数（X _O2 =0.3 ∼ 0.45）的低应变率逆流扩散火焰_{中，添加氢 (H 2 ) 对}正庚烷中烟灰形成的影响。火焰温度、烟灰体积分数 ( f _v )、单环 (MAHs) 和多环芳烃 (PAHs) 分别使用 OH-2C-PLIF/热电偶、LII/LE 和 PAH-LIF 方法测量。n的测量_{-添加氦 (He) 的庚烷火焰，作为惰性气体，比热容与 H 2}相似，也进行了比较。然后使用烟灰离散截面模型结合详细的气相动力学进行数值模拟，以解释获得的数据。二维模拟可以更好地预测温度和烟灰体积分数分布，这说明了低应变率条件下径向扩散和浮力的不可忽略的影响。然后，表明通过增加 H _{2或氦 (He) 添加量，} f _v和 PAH 产量几乎呈线性下降。由于 H _{2的存在，}正庚烷/H ₂火焰中 PAHs 和烟灰的减少量更大化学效应，在正庚烷/He 火焰中不存在，阻碍了围凝聚结构的形成。还研究了氧化剂流中O ₂浓度的影响。实验和模拟结果表明，对于所有火焰，多环芳烃和烟尘随着 X _{O2的增加而增加。}最后，研究了H ₂ /He 添加量变化的 X _O2对烟灰形成的影响。_{随着X O2}的增加，正庚烷/H ₂和正庚烷/He火焰的峰值火焰温度之差减小。因此，与纯正庚烷火焰相比，峰值f _v的减少在添加氢气而不是添加氦气的情况下变得越来越明显，因为 H ₂烟灰抑制化学效应胜过 H 2 温度效应，而 H ₂温度效应反而促进烟灰形成。