Effect of piezo-driven and solenoid-driven needle opening of common-rail diesel injectors on internal nozzle flow and spray development

Abstract

A prototype piezo-driven diesel injector has been developed and characterized in terms of measured flowrate, predicted cavitating nozzle hole flow distribution, and visual spray development. Results are compared with those obtained for a conventional solenoid-driven diesel injector equipped with the same micro-sac multi-hole injection nozzle. The response time and the needle lift trace for both injectors have been predicted for injection pressures up to 1300 bar using a hydraulic simulation model. Mie spray images obtained using a high-speed camera and utilizing diffusion illumination light, have allowed estimation of the spray tip penetration and spray cone angle under a variety of back pressures. The experimental results show that the piezo-driven injector produces longer spray tip penetration and smaller spray cone angle. This has been supported by CFD simulations of the internal nozzle hole cavitating flow obtained using the transient needle profile of the solenoid- and the piezo-driven injectors. Model predictions suggest an increase in the fuel exit momentum of the piezo-driven nozzle during the opening phase of the needle, relative to those of the solenoid-driven one.

Experimental study on the effect of nozzle hole-to-hole angle on the near-field spray of diesel injector using fast X-ray phase-contrast imaging

“…as the second peak region of SW. The relationship between SW and needle lift were similar to the other experimental and simulation results [30,31]. At the OS and CS, significant SW peaks and fluctuation were observed and nozzles with larger UA had larger SW.…”

Study of the influence of the needle lift on the internal flow and cavitation phenomenon in diesel injector nozzles by CFD using RANS methods

“…In this sense, it seems clear that the injection process may affect cavitation development [14], [15], [16] since the geometry upstream the orifices changes during the opening and closing of the injector as a consequence of the variable needle lift position.…”

“…One alternative is the use of large scale models, although scale effects have been recognized to be very important [16]. For these reasons, the use of CFD tools has increased in the last years making it possible to obtain unlimited level of details about the behavior of the flow.…”

CFD Study of Needle Motion Influence on the Spray Conditions of Single-Hole Injectors

“…However, most of these studies consider two-dimensional, simplified real injector geometries, and neglect needle lift conditions. Some studies of multi-hole nozzle injectors have also been performed with consideration of the needle movement in order to study the effect of the transient opening/closing of the needle valve on the cavitating flow distribution [10,[14][15][16][17][18]. However, since many experiments are made for single-hole configurations, it is still important to gain knowledge about the dynamic behavior of the cavitation pattern and its effect on the flow at the exit for this type of injector.…”