A Study of Natural Gas Mixing Percentage on Combustion and Emission Characteristics of a CNG/Diesel Dual-Fuel Engine

摘要

A compression ignition engine was modified into a dual-fuel engine that allows small pilot injection of diesel fuel followed by combustion of compressed natural gas as a primary fuel with a pressurized common rail direct injection system. The modified engine sprayed a small amount of pilot diesel fuel as an ignition source, while CNG was injected through the intake manifold under different operating conditions. During the dual fuel operating mode, the effects of different amounts of natural gas mixing percentages were varied with a maximum CNG substitution of 90%. The effects of different CNG mixing contents (CNG 65%, CNG 80%, and CNG 90%) on dual-fuel performance and emission were carried and compared with a base engine at increasing engine speed of 1000-3500 rpm. The in-cylinder pressure, combustion duration, heat release rate and ignition delay were analyzed and compared to both engines.