Multi-jet Common Rail injection system for small Diesel engines

The diesel engine needs to be equipped with an injection system able to manage the fuel for multiple injections per cycle for meeting the future stringent emission limitations. In particular, the irregular behavior of emerging jets from multi-hole nozzle at early injection needs to be investigated to better understand non-homogeneity phenomena and their correlation to the nozzle type. This paper illustrates the results of an experimental investigation on the liquid fuel spray from a multi-jet common rail injection system both under non evaporative and evaporative conditions. Tests have been taken using a 5 hole, 0.13 mm diameter, 150° spray angle, micro-sac nozzle having a flow rate of 270 cm3/30 sec@10 MPa exploring different injection strategies. Experiments have been taken, under non evaporative conditions, injecting the fuel within stagnant inert gas, at different density, in a high-pressure optically-accessible cylindrical vessel with three large quartz windows. Under evaporative conditions, the experiments have been taken within a crank-case scavenged single-cylinder 2-stroke direct injection Diesel engine provided of optical accesses to the combustion chamber.