An Experimental Study of the Combustion, Performance and Emission Characteristics of a CI Engine under Diesel-1-Butanol/CNG Dual Fuel Operation Mode

In order to comply with the stringent emission regulations, many researchers have been focusing on diesel-compressed natural gas (CNG) dual fuel operation in compression ignition (CI) engines. The diesel-CNG dual fuel operation mode has the potential to reduce both the soot and NO_x emissions; however, the thermal efficiency is generally lower than that of the pure diesel operation, especially under the low and medium load conditions. The current experimental work investigates the potential of using diesel-1-butanol blends as the pilot fuel to improve the engine performance and emissions. Fuel blends of B0 (pure diesel), B10 (90% diesel and 10% 1-butanol by volume) and B20 (80% diesel and 20% 1-butanol) with 70% CNG substitution were compared based on an equivalent input energy at an engine speed of 1200 RPM. The results indicated that the diesel-1-butanol pilot fuel can lead to a more homogeneous mixture due to the longer ignition delay. Using certain multiple injection strategies under medium load (a diesel equivalent load of 20 mg/cycle), the diesel-1-butanol-CNG combustion mode can significantly improve the indicated thermal efficiency (ITE). B10 showed low unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions; while B20 presented low NO_x and soot emissions. The results also indicated that B20 case has the potential to obtain high ITE and low NO_x and soot emissions simultaneously under low and medium load conditions.