Splashing of fuel drops impacting on heated solid surfaces

Abstract

Liquid drop impact on dry, solid surfaces has been studied to elucidate the role of control parameters, such as drop size, impact velocity, liquid properties, surface roughness, and wettability, on the mechanism of splashing phenomenon. It has been shown more recently that ambient gas plays a pivotal role in initiating the disintegration mechanisms leading to the ejection of secondary droplets from an impacting drop. Through systematic experiments, the role of target surface temperature in altering the morphology of a splash outcome of impacting fuel drops is investigated in the present work. It is observed that at elevated surface temperatures, the heated air film present very close to the hot surface suppresses splashing and consequently raises the splash threshold Weber number of the impacting fuel drop. For a given Weber number, the morphology of the impacting drop shifts from splashing to spreading with a rise in the surface temperature through an intermediate transition regime, characterized by the tendency of the liquid sheet to recontact the drop lamella without ejecting any secondary droplets. The experimental observations are compared with theoretical model predictions reported in the literature, and fair agreement is found in terms of both the observed splash suppression and the underlying mechanisms that govern the identified morphological regimes.