Session: 11-10-01: Multiphase Flow Applications

Paper Number: 173368

The Effect of Suspended Nanoparticles on Spray Characteristics at Medium to Hight Particle Concentrations 

Iron nanoparticles have shown promise in enhancing the combustion characteristics of liquid fuels by reducing ignition delay and increasing burn rate, positioning them as a viable additive in nanofuel development. However, their influence on the spray characteristics remains underexplored. This study aims to fill this knowledge gap by investigating the effect of 40 nm iron nanoparticles on the spray behavior of ethanol, focusing on two key metrics: spray angle and sheet breakup length. To evaluate these effects, iron nanoparticles were first dispersed in ethanol across a range of concentrations from 0.25 wt% to 10 wt%, using ultrasonication to ensure homogeneous suspension and minimize agglomeration. The prepared nanofuels were then atomized using an impinging jet spray system. A high-speed camera operating at 4000 frames per second was employed to capture the temporal and spatial evolution of the spray. Image processing techniques were applied to extract quantitative values of spray angle and sheet breakup length from the recorded footage.

Viscosity and surface tension are the key physical properties that influence spray behavior and droplet formation. Specifically, surface tension affects droplet size, as instabilities caused by it cause the liquid jet or sheet to break into fine droplets. Similarly, liquid viscosity impacts droplet size and formation by affecting the energy needed to break the liquid apart. Generally, higher viscosity and surface tension lead to the creation of more spherical and larger droplets, which tend to have lower wettability and, in combustion scenarios, slower evaporation and burning rates. Therefore, the surface tension and dynamic viscosity of each fuel mixture were measured using a Wilhelmy tensiometer and rotary viscometer, respectively, to evaluate how adding nanoparticles changes the fluid's physical properties. These values were subsequently used to calculate Reynolds and Weber numbers, which are dimensionless quantities that characterize spray regimes. The measured spray metrics were then plotted as a function of both Reynolds and Weber numbers to identify underlying trends and scaling behaviors.

The results indicated that at low concentrations (0.25–1 wt%), iron nanoparticles had a negligible impact on the viscosity and surface tension of ethanol, resulting in minimal change to the spray characteristics. However, as the concentration increased beyond 5 wt%, both viscosity and surface tension exhibited significant increases. These changes led to discernible modifications in the spray behavior, with a general trend of increased spray angle and longer sheet breakup lengths. The increase in spray angle suggests enhanced atomization at higher concentrations, although it may also be indicative of particle agglomeration or altered momentum transfer dynamics.

Presenting Author: Mohsen Ghamari Wilkes University

Presenting Author Biography: Dr. Mohsen Ghamari is an associate professor of Mechanical Engineering in the department of Mechanical and Electrical Engineering at Wilkes University in Wilkes-Barre, PA. Dr. Ghamari's research is focused on nanofuels, spray and atomization, and combustion.

Authors:

Mohsen Ghamari Wilkes University
Frank Yuscavage Wilkes University