In order to study the potential improvement of intake port water injection (w PWI) technology on the thermal efficiency of gasoline engines

a research single cylinder gasoline engine was used to compare and study the effects of w PWI on the engine combustion performance under different spray ratios

load conditions

and compression ratios (CRs) through experimental means. The results show that the w PWI technology can effectively reduce the knock tendency of the engine. With the increasing of water injection ratio

the CA50 is gradually advanced

the ignition delay period and combustion duration are increased

and the heat transfer loss is gradually increased. Comparing with the result of no port water injection (w/o PWI)

although the introduction of water injection leads to the increase in unburned loss

it is conducive to the substantial reduction of exhaust energy loss. The final economic performances of engine show that the thermal efficiency increases firstly and then decreases with the increasing of proportion of water injection

and the fuel consumption rate is opposite to that of the thermal efficiency. At this time

the best gross indicating thermal efficiency (GITE) is 43.1%

which is 2.5% percentage points higher than that of w/o PWI; The best gross indicated specific fuel consumption (GISFC) is 197.9 g/(kW·h)

which is 11.8 g/(kW·h) lower than that of w/o PWI. The application of water injection technology at high load will achieve more significant improvement in thermal efficiency and fuel consumption. At the same time

the introduction of the water injection technology makes it possible to apply the high compression ratio (CR) on the engine.