By using the wet conditions generated by changing the air change density （7.5 kg/m3 to 15.0 kg/m3）and injection hole diameter(0.11 mm to 0.22 mm) in a constant volume combustion chamber test device

a high-speed camera was used to study the effect of different wet wall conditions on the spray wall impingement combustion process. The ignition delay of spray combustion increases with the decrease of the air charge density and increases with the rise of wall humidity

but it is more significantly affected by the air charge density. For the given high fuel injection pressure and air intake density

spray atomization with different injection hole diameters is very good. The spray ignition is mainly influenced by the time of chemical preparation

and the fluctuation of ignition delay is not large. With the increase of humidity on the wall

the time for the spray burning to outer the high temperature ignition phase will be much later. Resulting in a serious post combustion and increased combustion duration

which leads to a sharp increase in soot emissions.