Influence of Intake Air Humidification on Emission of a Port Fuel Injected SI

As a sound solution for decreasing the in-cylinder and exhaust temperature, prevention of the
engine knock and reduced NOx emissions, water injection on various engine types has stimulated
significant interest in recent years further to enhance fuel efficiency and comply with more stringent
emission regulations. Even though water injection mechanisms with various objectives are different,
there are also varied advantages on engine performance and emissions. In this study, experimental
analysis was performed to examine the effect of humidified air induction on a single cylinder, four
stroke, air-cooled, 350cc Royal Enfield Bullet spark ignition engine exhaust emissions, with
modifications made to assist port fuel injection. Tests have been performed on test engine fuelled with
gasoline over a range of engine loads and at rated speed for 75% and 95% relative humidity with
water injection. The outcomes of the experimental analysis reveal that increasing the intake air
humidity from 75% to 95% decreased the exhaust emissions of NOx, CO, HC and CO2 at 95% rated
load of the engine without much or less impact on the thermal brake efficiency.