Time resolved measurements of the initial stages of fuel spray penetration

The period of diesel fuel spray injection from the start of injection up to 0.5 ms is investigated using ultra-high speed digital imaging. Contrary to the widely accepted idea of tip penetration exhibiting a linear dependence with time during the initial stages of spray development, the spray tip penetration is observed to follow a functional fit of the form S(t) = At3/2 right up until the tip velocity reaches its maximum value. After this, the spray tip penetration correlates well with previously established correlations found in the literature. Furthermore, the spray tip velocity immediately after start of injection is not observed to be constant but is found to be proportional to t. A collapse of the tip velocity curves is obtained when they are scaled by the peak velocity and corresponding time. Results are presented for non-evaporating diesel sprays injected into a constant volume chamber at various injection and chamber pressures.