Investigation on the effect of the flow passage geometry of diesel injector nozzle on injection process parameters and engine performances

In the paper, the method based on optimization of flow passage geometry of diesel injector nozzle to improve the quality of fuel injection and atomization process has been studied. Designs of injector nozzles have been developed to enhance the quality of these processes. These nozzles' feature is the implementation of local hydraulic resistances-different grooves on the needle tip, which enhance the flow turbulence in the nozzle's flow passage. Computational fluid dynamics (CFD) simulations were performed to study the effect of the nozzle flow passage geometry on parameters of fuel flow, such as mass flow rate, velocity, turbulence, and cavitation. The influence of local hydraulic resistances on the needle tip over these parameters has been evaluated. The optimal geometry of the grooves has been chosen. Experimental studies of a four-cylinder diesel engine D-243 equipped with injectors with serial and modified nozzles have been carried out. The possibility of improving the fuel efficiency and emission performances by using the modified nozzles has been confirmed. At the maximum power condition, the use of the modified nozzles reduced the brake-specific fuel consumption from 275.2 to 270.4 g/(kW center dot h) (by 1.7%) and reduced exhaust smoke from 23.5% to 12.5% on the Hartridge scale (by 46.8%). However, at the same time, the emission of NOx increased from 1743 to 1923 ppm (by 10.3%). Moreover, there was a tendency to decrease the content of CO and unburned HC in the exhaust gases.