Computational exploration of single-fuel reactivity controlled compression ignition engine by integrating dimethyl ether/steam on-board reforming

A single-fuel dimethyl ether reactivity-controlled compression ignition engine system was established by integrating dimethyl ether/steam on-board reforming. For the dimethyl ether reforming reactivity-controlled compression ignition engine system, the product of dimethyl ether reforming (including the generated syngas and unreacted dimethyl ether) was provided through the intake port of the reactivity-controlled compression ignition engine, while the high-reactivity dimethyl ether was directly introduced into the cylinder to realize the reactivity stratification. In this study, computational investigations of dimethyl ether reforming and syngas/dimethyl ether reactivity-controlled compression ignition engine were respectively realized by the COMSOL software and the KIVA-3V code. The influences of the exhaust valve opening timing, the premix ratio, and the reformer number on the performance of the reformer and the reactivity-controlled compression ignition engine were studied. The results indicated that the earlier exhaust valve opening timing and the more reformer number are beneficial for the dimethyl ether reforming and energy recovery, and the effect of the premix ratio is relatively minor. For the test system, the highest exhaust energy that can be applied for the dimethyl ether reforming is around 25 %, and 8.8 % of the exhaust energy can be recovered into the fuel energy to realize the increase of the fuel energy. The highest conversion rate of dimethyl ether to syngas is 78 %, and the fuel energy is increased by 6.37 % after the reforming. With the introduction of the fuel reforming system, the improvement of the system thermal efficiency is between 0.52 % and 1.44 %. To realize the moderate, efficient, and clean combustion of the dimethyl ether on-board reforming reactivity-controlled compression ignition engine, the dimethyl ether conversion rate should be further improved at a lower exhaust temperature.