The geometry of high-pressure pump and injector nozzles crucially influences
hydraulic behaviors (e.g., the start of injection, the pressure profiles
developed in the high-pressure line, needle lift, and injection rates) in diesel
engines. These factors, in turn, significantly impact fuel atomization, fuel–air
mixing, combustion quality, and the formation of emissions. The main geometry
parameters such as plunger diameter and the number and diameter of nozzles lead
to the system complexity, requiring careful analysis, design, and calibration.
In this study, a high-speed shadowgraph system and a high-resolution pressure
recording system were developed to capture the start of injection, spray
structure, and pressure profiles in the high-pressure line. Additionally, a
model was developed using GT-Fuel package built within the GT-Suite of
simulation tools to explore different plunger diameters and numbers and
diameters of injector nozzles. These models were validated using the pressure
profiles, fuel quantity, and start of injection timing obtained from the
experiments. This approach can either individually analyze the influence of each
parameter or assess their overall impact. The results indicate that an increase
in plunger diameter advances the start of injection (SOI). Furthermore, an
increase in the number and/or diameter of nozzles results in a higher amount of
fuel delivered per cycle. Overall, replacing an injection system with 10 mm
plungers and injectors with 7 × 250 μm nozzles with one featuring 12 mm plungers
and injectors having 8 × 300 μm nozzles can increase the fuel delivery by 1.85
fold. This approach could be useful for practical applications, including
turbocharging engines and/or designing more efficient fuel systems. Future
investigations into the high-speed shadowgraph images captured in this study
could offer additional insights into the Rayleigh–Taylor and Kelvin–Helmholtz
models concerning the primary and secondary atomization processes.