The UTC Graduate School is pleased to announce that Karah Powell will present Master’s research titled, Single Droplet Combustion of Alternative Fuels on 10/17/2024 at 2:30pm in EMCS 415D. Everyone is invited to attend.
Engineering
Chair: Dr.Shi
Co-Chair:
Abstract:
Reports from the Environmental Information Administration highlight motor gasoline, diesel, and jet fuel as major contributors to carbon dioxide emissions in the transportation sector [1]. This has spurred research into alternative fuels to reduce reliance on fossil fuels. Notable alternatives include biodiesel and its blends, which can lower emissions with minimal modifications to existing combustion systems. As biodiesel production rises, byproducts like glycerol and excess methanol or ethanol can be utilized in combustion systems. Additional notable alternative fuels include butanol and algal oil. Butanol has the potential to reduce emissions while improving combustion efficiency. Algal oil has been shown to be a promising feedstock for alternative fuels. This study will investigate both conventional fuels and alternative fuels for a comparative study of the combustion characteristics. Single droplet combustion experiments are crucial for evaluating the atomization behavior of alternative fuels. Liquid fuel is atomized into smaller droplets to enhance combustion in systems such as internal combustion engines, industrial burners, and gas turbines. Droplet combustion can be modeled using the D² law of combustion. The law indicates the droplet diameter reduces with time, the burning rate is constant, and that the droplet is spherically symmetric, thus reducing convection for simplicity. Experiments are typically performed in free fall or drop tower experiments in order to simulate zero gravity conditions to reduce the effects of convection. However, the suspended droplet method can be utilized by reducing the droplet diameter and ensuring the fibers are thin enough to not distort the droplet shape. The suspended droplet method provides valuable insights for validating computational models and assessing the scalability of alternative fuels in industrial applications. In this study, droplets were suspended on 16 µm silicon carbide fibers and ignited using two hotwire loops positioned on either side to ensure spherically symmetric combustion. A linear actuator retraction system was employed to prevent hotwire interference with the droplet’s burning process. High-speed imaging captured the combustion dynamics, while an Arduino controlled the timing of the events. The observed combustion zones included the preheating zone, swelling zone, and combustion zone. Hydrocarbon fuels and blends experienced swelling but followed the D² law of combustion in that the droplet diameter reduced with time once swelling subsided. Ethanol, methanol, and algal oil experienced micro-explosions throughout the combustion process, which deviates from the D² law. Flame characteristics and burning rates also varied between the droplets tested. The burning rate of the biodiesel blends converged as the droplet diameter increased. Blending 50% butanol into gasoline altered flame characteristics and reduced soot. Algal oil exhibited similar flame properties to gasoline. Ethanol and methanol flames extinguished upon hotwire retraction. Blending glycerol and methanol increased burn time and the occurrence of micro-explosions. Droplets with diameters of 1.0mm or less experienced an increase in micro-explosions compared to larger droplet sizes. Utilizing suspended droplet combustion allowed for a detailed examination of the combustion characteristics of various alternative fuels. By anchoring the droplets, valuable insights were gained regarding soot formation, flame properties, and burning behaviors. Future studies could enhance understanding by applying this method to emerging alternative fuels, including fuels with nanoparticle additives and algal oil blends. References [1] EIA. “U.S. Energy Information Administration (EIA) – Ap.” Eia.gov, 2018, www.eia.gov/environment/emissions/carbon/.