Experimental Study of Port Water Injection on GDI Engine Fuel Economics and Emissions.

This experimental study investigates the impact of water injection into intake ports on combustion and emissions in gasoline engines. It also examines particle size distribution at various water-to-fuel ratios and explores the combined effects of water injection and compression ratios in gasoline engines. The results indicate that water injection effectively mitigates engine knock, reduces peak firing pressures, and moderates heat release rates through charge cooling. Advancing ignition timing with water injection advances combustion, resulting in reduced specific fuel consumption, particularly under moderate load conditions. Water injection lowers NOx emissions by reducing combustion temperatures but increases unburned THC emissions due to inhibited oxidation reaction rates. Minor effects were observed on CO emissions. Furthermore, particle numbers were significantly reduced with water injection, particularly in the nucleation mode particles. The simultaneous application of a higher compression ratio and water injection yields substantial improvements in fuel consumption with minimal impact on NOx and THC emissions.