Effect of Gas Density and the Number of Injector Holes on the Air Flow Surrounding Non-Evaporating Transient Diesel Sprays

The effect of ambient gas density and the number of injector holes on the characteristics of airflow surrounding non-evaporating transient diesel sprays inside a constant volume chamber were investigated using a 6-hole injector. Particle Image Velocimetry (PIV) was used to measure the gas velocities surrounding a spray plume as a function of space and time.

A conical control surface surrounding the spray plume was chosen as a representative side entrainment surface. The positive normal velocities across the control surface of single-hole injection sprays were higher than those of 6-hole injection sprays. An abrupt increase in velocities tangential to the control surface near the chamber wall suggests that the recirculation of surrounding gas is accelerated by spray wall impingement. The accumulated mass of laterally entrained gas of the single-hole injection sprays seems to be larger than that of 6-hole injection sprays mainly due to the higher positive normal velocities for the case of the single-hole injection sprays. Under the non-evaporating transient spray conditions, large differences between the total spray volume and the accumulated gas volume entrained laterally indicated that a significant portion of the gas entrainment into spray plume took place near the liquid spray tip, for the range of variables studied by the authors.