The influence of the pilot injection on the main injected diesel fuel combustion under a split injection at low temperature was studied using a visualized constant volume combustion chamber and a high speed digital camera. The experimental study on single injection combustion process showed that both of its ignition delay and combustion duration decreased

while the flame lift-off length and liquid length increased with the increase of the injection pressure. A comparison was made of the combustion processes of single injection and the main injection of a split injection with the same injection pressure and pulse width. The results show that the initial ignition position of the main injection is closer to the nozzle than that of the single injection

and the ignition delay of the main injection is greatly shortened because of the pilot injection

but the influence of the pilot injection ratio on the ignition delay of the main injection is small. Meanwhile

the combustion duration of the main injection is longer and increases with the increase of the pilot injection ratio. The flame lift-off length of the main injection is smaller than that of the single injection

and slightly increases with the increase of the pilot spray ratio. Furthermore

the liquid length of the main injection is shorter than that of the single injection during combustion

and decreases with the increase of the pilot injection ratio.