Disparities in the constituents among biogases pose various control challenges during combustion, thus complicating its operability. Improving biogas by eliminating carbon dioxide (CO2) remains difficult, and high CO2 concentration is known to affect combustion. Still, the effect on Biogas/Diesel dual-fuel reactivity-controlled compression ignition (RCCI) combustion is not well explored. The influence of high diluent (CO2) proportions (25 – 45%) and Biogas fraction (40 – 70%) on Biogas/Diesel dual-fuel RCCI combustion was evaluated experimentally, at full load and 1600 rpm. The results show distinct temperature trends across the combustion regimes for all the CO2 ratios and Biogas fractions. The radiation absorption effect of high CO2 reduces the cylinder temperature and delays the expansion to a 10 – 20o crank angle after the top dead centre (CA ATDC). The temperature and pressure decrease with the increase in CO2 ratios and Biogas fractions, unlike heat released rate. Burning Diesel and 45% CO2 indicate the fastest combustion, with combustion phasing (CA50) at 6.353 ms ATDC while 25 and 35% CO2 were slowed by 0.258 and 0.578 ms, respectively. Inferentially, 35% CO2 at a fraction of 50% could form the best reactivity.
Keywords: RCCI combustion; high CO2 content; biogas