The aim of the study was to investigate the effect of ignition timing and hydrogen fraction on the performance and exhaust emissions of an engine. The engine was converted from port injection system to direct injection with enrichment hydrogen to natural gas at WOT condition and engine operation at 4000 rpm. The results showed that when hydrogen volume fraction was raised from 0 up to 50% at 20 bar injection pressure and at the ignition timing from 19 to 28 °CA BTDC, a good stratified effect was achieved. Also, performance results demonstrated that fuel conversion efficiency, power output, and torque were increased up to 3.7% and the brake thermal efficiency first rose and then fell with an increment of hydrogen enrichment to CNG. The peak cylinder pressure and temperature with the advance of ignition timing increased. In addition, the advance of the ignition timing caused NOx, HC, and CO emissions to decrease but with the increase in hydrogen fraction in the blend of fuel, HC, and CO dropped and NOx emission rose. This study concluded that the 30% blends of hydrogen and 21° BTDC ignition timing can optimize engine performance and emission without any engine modification.

中文翻译：

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点火时间和天然气混合物中的氢分数对 DI 发动机性能和废气排放的影响

该研究的目的是研究点火正时和氢含量对发动机性能和废气排放的影响。发动机从进气道喷射系统转换为在 WOT 条件下和发动机以 4000 rpm 运行的情况下直接喷射富集氢气到天然气。结果表明，当氢气体积分数在 20 bar 喷射压力和 19 至 28 °CA BTDC 时，氢气体积分数从 0 提高到 50%，实现了良好的分层效果。此外，性能结果表明，燃料转换效率、功率输出和扭矩提高了 3.7%，制动热效率随着向 CNG 加氢的增加而先升后降。随着点火正时的提前，峰值气缸压力和温度增加。此外，点火正时提前导致 NOx、HC 和 CO 排放量减少，但随着燃料混合物中氢含量的增加，HC 和 CO 降低，NOx 排放量增加。该研究得出的结论是，30% 的氢气混合物和 21° BTDC 点火正时可以优化发动机性能和排放，而无需对发动机进行任何改装。