Analysis of counterbore effect in five diesel common rail injectors

The present work assesses how the nozzle geometry, particularly the counterbore which is used in gasoline direct injection, could improve the fuel mixture when injecting in diesel engines, and ultimately, increase the thermal efficiency of the engine. Five different injector's nozzles are tested using a parametric variation over counterbore dimensions. For this purpose, measurements of the rate of injection, spray momentum and non-evaporative visualization are performed. Comparison of the nozzles performance is assessed by the rate of injection and momentum, nozzle coefficients in the hydraulic part, and in terms of spray penetration and spray angle in the visualization part which describe the macroscopic characteristics of spray development. Minimal variation was found observing at the hydraulic characterization of the injectors. On the other hand, a more notable difference was found in the visualization experiments, in which the modified nozzles presented greater spray angles and smaller penetration than the original one without counterbore. This work provides an insight into the potential effects of using the popular counterbore-used in gasoline direct injection (GDI)-in a diesel injector.