The atomization characteristics of a plain orifice at subatmospheric pressure were studied by means of pulsed laser holography

and hologram images of cross-spray downstream fuel cloud field were analysed with computer image system.The results obtained show how the mean particle size and particle size space distribution vary with air velocity、ambient pressure and spray fuel pressure.The first

the air velocity is a primary factor that affacts the fuel atomization at either normal or subatmospheic pressure

the mean particle sizes monotonically increase as the air velocity decreases.The second

as the air density reduces with descending ambient pressure

aerodynamic force and turbulent fluctuation are reduced which force spray fuel sheet to breakup and drop size to fall to a critical value.As a result

the penetration is augmented

atomization is retarded

and mean drop diameter is increased

as well as fuel density space distrbution becomes non-umiform and the quality of atomization obviously deteriorates.Therefore

the ambient pressure is also important to atomization.The last

when the nozzle spary goes across the direction of air

at subatmospheric pressure spary penetration depth rises more rapidly than at atmospheric pressure as the fuel-injection pressure increases.