Considering the fuel pressure building process inside the nozzle sac

a model suitable for the liquid penetration at the initial stage of fuel injection was derived. Then

in the high-temperature and high-pressure environment near the top dead center of a diesel engine built in a constant volume combustion vessel

the effects of the injection pressure

ambient temperature and density on the development process of evaporating spray liquid penetration were tested by using diffused back-illumination method

and compared with the simulation calculation. Results show that at the initial stage of fuel injection

the liquid penetration does not change linearly with the time of t as predicted by Hiroyasu model

but first presents an acceleration process that varies with the time of t1.5 and then changes with the time of t0.75 and t0.5

respectively

due to the spray breakage and fuel pressure built up in the nozzle sac.