Transient characteristics of diesel sprays from a deposit rich injector

The transients of the early stage evolution of high pressure diesel sprays from a clean and a deposit rich injector were explored using high speed imaging at 24.4 kiloframes per second (kfps). Fuel was injected into a liquid that offered high density ambient conditions and, for comparison, fuel was also injected into air at less dense ambient conditions. By comparison of the evolving fuel spray from a new fuel injector to those of an injector rich in carbonaceous deposits at/in the nozzle, anomalous spray behaviour resulting from the presence of deposits becomes apparent. The fuel spray cone angle from a deposit rich injector increased by 10-140% compared to the fuel spray cone angle from a new injector. The accompanying spread in the measured angle was from 100% to 200% greater for the deposit rich case. The presence of deposits significantly affected the early stages of spray evolution, the reproducibility of the spray shape from a deposit rich injector being very low. The observed occurrence of transient radial bulging has the potential to reduce the axial momentum and reduce the combustion performance in diesel engines.