Combustion of Ligaments and Droplets Expelled after the End of Injection in a Multi-hole Diesel Injector

Abstract

Experimental investigations were carried out to study the end of injection spray characteristics using a number of production grade multi-hole common-rail injectors. These injectors were taken from light-duty diesel vehicles that are currently in operation on the UK roads and have done different mileages. All the production injectors suffered expulsions of ligaments and droplets after the end of injection(aeoi). It is shown that injector age/mileage has very little effect on the amount of ligaments and droplets ejected from production injectors compared to injection-to-injection variations in the amount of post-injection expulsions. Brand new production injectors also show the presence of these post-injection expulsions after every injection, which is not a desired feature of the modern solenoid actuated common-rail fuel injection system. Subsequent combustion of these post-injection ligaments and droplets lasted up to 25ms after the end of fuel injection in our high pressure, high temperature experiments, and this would contribute to engine-out soot and unburned hydrocarbon (ubhc) emissions in a firing engine.