Hydrogen and n-butanol are superior alternative fuels for SI engines, which show high potential in improving the combustion and emission characteristics of internal combustion engines. However, both still have disadvantages when applied individually. N-butanol fuel has poor evaporative atomization properties and high latent heat of vaporization. Burning n-butanol fuel alone can lead to incomplete combustion and lower temperature in the cylinder. Hydrogen is not easily stored and transported, and the engine is prone to backfire or detonation only using hydrogen. Therefore, this paper investigates the effects of hydrogen direct injection strategies on the combustion and emission characteristics of n-butanol/hydrogen dual-fuel engines based on n-butanol port injection/split hydrogen direct injection mode and the synergistic optimization of their characteristics. The energy of hydrogen is 20% of the total energy of the fuel in the cylinder. The experimental results show that a balance between dynamics and emission characteristics can be found using split hydrogen direct injection. Compared with the second hydrogen injection proportion (IP2) = 0, the split hydrogen direct injection can promote the formation of a stable flame kernel, shorten the flame development period and rapid combustion period, and reduce the cyclic variation. When the IP2 is 25%, 50% and 75%, the engine torque increases by 0.14%, 1.50% and 3.00% and the maximum in-cylinder pressure increases by 1.9%, 2.3% and 0.6% respectively. Compared with IP2 = 100%, HC emissions are reduced by 7.8%, 15.4% and 24.7% and NOx emissions are reduced by 16.4%, 13.8% and 7.9% respectively, when the IP2 is 25%, 50% and 75%. As second hydrogen injection timing (IT2) is advanced, CA0-10 and CA10-90 show a decreasing and then increasing trend. The maximum in-cylinder pressure rises and falls, and the engine torque gradually decreases. The CO emissions show a trend of decreasing and remaining constant. However, the trends of HC emissions and NOx emissions with IT2 are not consistent at different IP2. Considering the engine's dynamics and emission characteristics, the first hydrogen injection proportion (IP1) = 25% plus first hydrogen injection timing (IT1) = 240°CA BTDC combined with IP2 = 75% plus IT2 = 105°CA BTDC is the superior split hydrogen direct injection strategy.

氢气和正丁醇是 SI 发动机的优质替代燃料，在改善内燃机燃烧和排放特性方面显示出巨大潜力。然而，单独应用时，两者仍然存在缺点。正丁醇燃料的汽化雾化性能差，汽化潜热高。单独燃烧正丁醇燃料会导致燃烧不完全和气缸内温度降低。氢气不易储存和运输，仅使用氢气发动机容易发生逆火或爆震。所以，基于正丁醇进气道喷射/分流氢气直喷模式，研究了氢气直喷策略对正丁醇/氢气双燃料发动机燃烧和排放特性的影响及其特性的协同优化。氢气的能量是气缸内燃料总能量的 20%。实验结果表明，使用分流氢气直接注入可以找到动力学和排放特性之间的平衡。与二次注氢比例（IP2）=0相比，分流直喷氢能促进稳定火焰核的形成，缩短火焰发展期和快速燃烧期，减少循环变化。IP2为25%、50%和75%时，发动机扭矩分别增加0.14%、1.50%和3。00%和最大缸内压力分别增加1.9%、2.3%和0.6%。与IP2=100%相比，当IP2为25%、50%和75%时，HC排放量减少7.8%、15.4%和24.7%，NOx排放量分别减少16.4%、13.8%和7.9%。随着第二次注氢时机（IT2）的提前，CA0-10和CA10-90呈现先下降后上升的趋势。最大缸内压力上升和下降，发动机扭矩逐渐下降。CO 排放量呈下降趋势并保持不变。但是，在不同的 IP2 下，HC 排放量和 NOx 排放量与 IT2 的趋势并不一致。考虑到发动机的动力和排放特性，