Spray Characteristics of Five-Hole V.C.O Nozzles of a Diesel Electro- Injector

The study of the spray of standard, five-hole, V.C.O. nozzles for D.I. diesel engine has been carried out. Several pictures of the spray have been taken using the back-light photography technique. Injected volume, feeding pressure, injection duration, spray penetration, angle and thickness, and flash delay from the start of injection have been measured both for nozzles of two different manufacturers and for a group of four injectors before and after a fatigue test of about 1500 hours running. Measurements revealed that each spray strongly depends on the needle lift, the back-pressure and the nozzle geometry and that, for the same injector, sprays are totally different from hole to hole. The causes of the most important differences have been attributed at the different hole inclination, their asymmetric feeding conditions (due to the eccentricity between needle and nozzle) and the microdefects caused by drilling operation.