Parametric investigations to establish the potential of methanol based RCCI engine and comparison with the conventional dual fuel mode

This experimental study explores the potential of Methanol- Diesel Reactivity Controlled Compression Ignition (RCCI) in achieving low emissions and high thermal efficiency and compares this with the conventional dual fuel mode. A single cylinder light duty common rail water-cooled diesel engine was run at a constant speed of 1500 rpm and IMEP of 5 bar (50% of rated load) with methanol being port injected. In the conventional dual fuel mode, diesel was directly injected as a single pulse and its injection timing was adjusted for maximum efficiency. The RCCI mode of combustion could only be supported with one early injection pulse followed by another late injection pulse of diesel. The methanol to diesel energy share (MDES) could be enhanced to 56% in the RCCI mode with proper setting of the injection parameters from 45% in the dual fuel mode. A higher quantity in the second diesel pulse that occurred close to TDC led to higher thermal efficiency and good combustion stability. The NO level was significantly lower in the RCCI mode by about 95% and soot emission was reduced by about 78% while the thermal efficiency was increased from 36% to 38% as compared to the dual fuel mode at a fixed MDES. Beyond an MDES of 45% heating of the intake air to about 85 degrees C was needed to enhance the thermal efficiency to about 42% without affecting NO emissions. Higher MDES values always reduced the soot and NO levels and but enhanced the HC and CO emissions which could be controlled by increasing the temperature of the intake air. On the whole, thermal efficiency higher than the conventional dual fuel mode along with considerably lower NO emissions and comparable soot, HC and CO emissions and enhanced methanol share can be achieved in the Methanol RCCI mode when twin pulse injection of diesel.