Structure and steady-state spray performance of an effervescent diesel injector

Abstract

We describe, for the first time, the structure and steady-state performance of an effervescent Diesel injector (EDI) having a needle and sac and being entirely contained in a conventional Diesel injector body. Experimental results help address key questions, including the single influences of needle lift, exit orifice diameter, aerator pore size, atomizing gas–liquid ratio, and injection pressure on injector performance (mean drop size, drop size distribution, and cone half-angle), as well as any coupling that results when these quantity are varied in tandem. D 32 data demonstrate that there is a small, but experimentally significant, influence of needle lift on performance when it increases from 0.025 to 0.076 mm, but no effect with a further increase to 0.318 mm. There is no significant effect of either atomizing gas-to-liquid ratio (GLR), exit orifice diameter, or aerator pore size, but injection pressure does play a key role. No coupling between the effects of needle lift and any other parameter on D 32 was observed. Drop size distribution data show that the distribution width increases at smaller needle lifts and with an increase in injection pressure—there is a small effect of exit orifice diameter at the largest GLRs. Neither GLR nor aerator pore size has any effect, nor is there any coupling between the effects of needle lift and any other parameter. Finally, spray cone angle data show that increasing needle lift from 0.025 to 0.318 mm reduces cone half-angle from 11 to 7°. Other parameters have no effect, nor is there any coupling between needle lift changes and variations in other parameters. The effects of needle lift, when they occur, are ascribed to corresponding changes in atomizer exit velocity.