For a direct-injection gasoline engine equipped with a centrally located high-pressure fuel injector

the experimental study was conducted on the effect of the airway water injection on the combustion and emissions performance of spark-ignition gasoline engines. By adjusting the water injection quantity and ignition timing

the study investigated the differences in combustion characteristics and emissions under different water-to-fuel ratios (W/F). The results indicate that under constant ignition timing

the combustion phase delays significantly and the average effective pressure decreases with the increasing of W/F. Advancing the ignition timing can advance the combustion phase

suppress the tendency of knocking combustion

and further increase the engine load. Under different load conditions

the influence of W/F on the combustion process varies. At medium to high loads

an increase in W/F can shift the overall combustion process forward

significantly improving the combustion stability and reducing the fuel consumption. For instance

comparing W/F = 0.3 with W/F = 0

the fuel consumption can be reduced to be approximately 10%. However

at low loads

the excessively high W/F can deteriorate the combustion stability and increase the fuel consumption. Simultaneously

as W/F increases

the combustion temperature decreases

leading to a decrease in NOx emissions. However

the combustion efficiency decreases

and hydrocarbon emissions worsen.