Experimental and Computational Study of the Influence of Partial Needle Lift on Nozzle Flowin Diesel Fuel Injectors

Needle lift profile influence on the vapor phase penetration for a prototype diesel direct acting piezoelectric injector

“…As expected, an increase in injection pressure produces an increase in vapor penetration rates. These results agree with those previously obtained for the momentum flux and mass flow rates of this same injector by the authors in [8] [9] and the relation between mass flow rate, momentum flux and outlet velocity [25] [26].…”

“…The influence of the piezo stack charge level is clearly appreciable in Figure 5, and the effect is similar to that of the injection pressure: increasing the piezo stack charge level increases the injection rate thus increasing the vapor penetration rate. This, again, agrees to what the authors found in [9][8], where the momentum flux of the injection spray increased with the piezo stack charge level. This result is expected since the partial needle lift causes a pressure drop in the nozzle entry, and this drop is reduced as the needle lift is increased.…”

“…The study was performed using commercial Diesel fuel with a density of 812 kg/m 3 (at 70º) and kinematic viscosity of 1.9 10 -6 mm 2 /s (at 70º). The fuel was injected using with a 7-orifice nozzle (Outlet diameter D 0 = 156 µm, k-factor = 1.5 [8]) which permits full control of the needle lift position through the voltage profiles applied to the piezo stack [9]. The complete injection system is electronically controlled by the ECU and all the settings are introduced digitally.…”

“…It is known that the liquid and vapor penetration curves are not distinguishable at the first part of the injection process [18][20] [24], so the best approach was to perform a time-alignment of the vapor penetration curves with the previously obtained liquid penetration curves [9] so that they coincide with each other in the early stages of the injection process. The SOI for liquid penetration has been FUEL; Volume: 113; Pages: 257-265; DOI: 10.1016/j.fuel.2013.05.057; NOV 2013 extrapolated properly in [9], due to a much higher sampling rate along with the visualization setup permitting the visualization of the spray from the very first few millimeters.…”

“…The SOI for liquid penetration has been FUEL; Volume: 113; Pages: 257-265; DOI: 10.1016/j.fuel.2013.05.057; NOV 2013 extrapolated properly in [9], due to a much higher sampling rate along with the visualization setup permitting the visualization of the spray from the very first few millimeters.…”