Impact, spread, and splash dynamics of burning and non-burning fuel drops on dry and wetted surfaces

Abstract

A critical review of the literature highlighting the current progress in each scenario is presented. This study provides practical insight into pivotal problems such as fuel spray-wall interactions in combustors and engines and fire suppression techniques. An experiment is developed in which fuel drops are generated by an automated syringe pump, ignited via an arc igniter, and then proceed to collide with a solid surface under various conditions. The maximum spread factor for fuels with low impact energy collisions is studied and is shown to compare well with the literature. Crowning and secondary droplet ejection are observed for high impact energy collisions or splash events. The main focus of this work is the characterization of the radial propagation of the rim/crown upon splash. A theoretical model, derived in the literature, for radial rim/crown propagation is used and manipulated to reflect the conditions of the present experiment. The proposed model compares well with the burning and non-burning experimental points. Ethanol is the primary fuel used to demonstrate variations in impact and splash dynamics. N-Hexadecane, n-heptane, and iso-octane experiments are also reported to examine the effect of internal viscous dissipation on the dynamic impact behavior of burning drops. Fuels with lower viscosity are observed to have greater instabilities in the splash event. Burning drops are also observed to demonstrate greater instabilities compared to non-burning. Schlieren photography is implemented to visualize and verify combustion of the drops. The Schlieren images aid in characterizing the role of combustion in burning splash events.

The dynamic behaviors of burning and non-burning fuel drops interacting with a stainless steel surface are investigated in this study. Studies pertaining to the impact of water and non-burning fuel drops on various substrates have been widely explored in the literature, however, efforts to characterize burning drop interactions are practically non-existent. There is a lack of understanding for the physical mechanisms and instabilities associated with burning drop/substrate interactions. The present study focuses on three drop impact scenarios: (1) non-burning drop impact onto a dry surface, (2) non-burning drop impact onto a wetted surface or thin film, and (3) burning drop impact onto a wetted surface.