Experimental study on the effect of speed and port-injected fuel blend ratio on a reactivity-control compression ignition (RCCI) engine performance

In the present study, an experimental investigation on a port-injected gasoline-ethanol blended RCCI engine was carried out. The results showed a maximum cylinder pressure, and HRR as 91 bar, and 64 J/CA respectively at 3000 rpm for the G25E75-RCCI engine operation, and a minimum of 58 bar and 12 J/CA at 2600 rpm for baseline fuel (D100G0E0). The engine showed a minimum emission of NOx and CO2 for G25E75- RCCI. Unburned hydrocarbon and carbon monoxide, which are critical issues in RCCI combustion, were reduced at intermediate speeds in G50E50-RCCI combustion which can be considered as a good finding in the study. The brake power in RCCI mode slightly increased over the diesel case at higher speeds while the brake torque was seen to be consistently higher across the entire speed range, 2000-3000 rpm with a maximum at 2400 rpm for a G50E50-RCCI engine. The brake thermal efficiency with RCCI was observed to be on par or higher over conventional diesel at higher speeds. The fuel blend of G25E75 showed higher efficiency at higher speed while G50E50 yielded better thermal efficiency at lower speeds. RCCI operation as such resulted in better performance at higher speeds while the best overall emission performance was noticed at intermediate speeds. In this regard, further work is called for to identify the optimal operating conditions by varying further the port-injected fuel blend ratio along with other variables tested in this study.