Secondary Atomization of a Biodiesel Micro-Emulsion Fuel Droplet Colliding with a Heated Wall

Alexander E Ashikhmin,Nikita A Khomutov,Vyacheslav A Yanovsky,Maxim V Piskunov

doi:10.3390/app10020685

Alexander E Ashikhmin, Nikita A Khomutov + Show 2 more

Open Access

https://doi.org/10.3390/app10020685

Copy DOI

Abstract

Using high-speed video recording, we establish the following regimes of hydrodynamic interaction of a biodiesel micro-emulsion fuel droplet with a heated wall: deposition (including drop spreading and receding), drop hydrodynamic breakup, and rebound. Collision regime maps are plotted using a set of dimensionless criteria: Weber number We = 470–1260, Ohnesorge number Oh = 0.146–0.192, and Reynolds number Re = 25–198. The scenarios of droplet hydrodynamic disintegration are studied for transient and film boiling. We also estimate the disintegration characteristics of a biodiesel micro-emulsion droplet (mean diameter of child droplets, their number, and evaporation surface area increase due to breakup). The study establishes the effect of water proportion on the micro-emulsion composition (8–16 vol.%), heating temperature (300–500 °C), droplet size (1.8–2.8 mm), droplet velocity (3–4 m/s), rheological properties of the examined compositions, and emulsifier concentration (10.45 vol.% and 20 vol.%) on the recorded characteristics. The results show that the initial liquid surface area can be increased 2–19 times. The paper analyzes ways to control the process. The hydrodynamic disintegration characteristics of a biodiesel micro-emulsion fuel droplet are compared using 2D and 3D recording.

Highlights

In many types of internal combustion engines operating on liquid fuel, droplets of an atomized fuel flow collide with a wall
The experiments have established that the regimes and outcomes of the interaction between diesel or biodiesel fuel micro-emulsion droplets and a heated wall have critical differences from the corresponding parameters known for other liquids
Two- and three-dimensional plots were built for the main parameters of the secondary atomization of liquid droplets colliding with a heated wall for various water concentrations in the micro-emulsion (8–16 vol %), droplet heating temperatures (300–500 ◦ C), dimensions (1.8–2.8 mm), velocities (3–4 m/s) and emulsifier concentrations (10.45 vol % and 20 vol %)

Summary

Introduction

In many types of internal combustion engines operating on liquid fuel, droplets of an atomized fuel flow collide with a wall. Diesel engines often have quite a small combustion chamber, which makes the collisions of fuel droplets with the walls inevitable. The trend of miniaturization is common for engine design in general. All of this makes it especially important to understand and reliably predict the interaction of single fuel droplets with a heated surface [1]. If droplets of atomized fuel are ignited without evaporating completely, the engine demonstrates lower combustion efficiency, while emitting unburnt hydrocarbons [2]. In some engines, fuel evaporation may form gas-phase hot spots near the combustion chamber wall, which can lead to a destructive effect termed “super knock” [4]

Objectives

Results

Conclusion