Post-spreading behavior of impacting fuel drops on stainless steel surface

Abstract

Hydrocarbon fuel drops impacting on metallic solid surfaces kept at room temperature exhibit no receding after the completion of early inertia-driven primary spreading. The experimental data of impacting drops of different fuels on a smooth stainless steel surface reveal a sluggish spreading, referred to as post-spreading, after reaching the maximum spreading diameter at the end of primary spreading. A systematic analysis involving maximum spreading factor, final spreading factor and temporal variation of post-spreading diameter of impacting fuel drops of varying Weber number is reported to describe the behavior of the post-spreading process. It is found that the dynamics of post-spreading of impacting fuel drops is different from Tanner’s spreading as the exponent n in the power law describing the temporal spreading behavior (β ∝ τn) varies with Weber number and is significantly less than 0.1. The extent of post-spreading is found to be as high as 20% of the maximum spread factor for the impact of low Weber number fuel drops. Due to the presence of post-spreading, the final spread factor of impacting fuel drops is always higher than the maximum spread factor.