Multicomponent fuel droplet combustion investigation using magnified high speed backlighting and shadowgraph imaging

Abstract

The liquid-phase processes occurring during fuel droplet combustion are important in deciding the behaviour of the overall combustion process, especially, for the multicomponent fuel droplets. Hence, understanding these processes is essential for explaining the combustion of the multicomponent fuel droplet. However, the very fast combustion of the too small fuel droplet makes experimental investigation of these processes uneasily affordable. In the present work, a high speed backlighting and shadowgraph imaging of the multicomponent fuel droplet combustion including liquid-phase dynamics are performed. Two categories of multicomponent fuelsin which diesel is the base fuelare prepared and utilized. The first category is biodiesel/diesel and bioethanol/diesel blends, while the second category is the water-in-diesel and diesel-in-water emulsions. Specific optical setups are developed and used for tracking droplet combustion. The first setup is associated with the backlighting imaging with the resulting magnification of the droplet images being 30 times the real size. The second optical setup is used for shadowgraph imaging, with the resulting magnification being 10 times the real size. Using these setups, spatial and temporal tracking of nucleation, bubble generation, internal circulation, puffing, microexplosion, and secondary atomization during the combustion of isolated multicomponent fuel droplets are performed. Spatial and temporal tracking of the sub-droplets generated by secondary atomization, and their subsequent combustion, in addition to their overall lifetimes have also been performed. Accordingly, a comparison of the burning rate constant between the parent droplet and the resulting sub-droplets is carried out. The rate of droplet secondary atomization is higher than those obtained by relatively low imaging rate. Additionally, it is shown that during a large portion of its entire lifetime, the droplet geometry has been affected by combustion significantly.

Identifying the effect of aromatic compounds on the combustion characteristics of crude coconut oil droplet

“…The formation of H 2 O molecules has the potential to cause a natural transesterification process so that the carboxyl group on the triglyceride carbon chain breaks and separates from the fatty acids. This analysis follows previous studies, which used crude jatropha oil and palm oil droplets without additives but underwent a preheating process and magnetic field [32] to produce hot steam in the form of H 2 O molecules, which contribute to breaking the carboxyl group from fatty acids [33,34], and increase the reactivity of fuel molecules. In addition to the multi-component elements owned by CCO fuel and CvO and EO additives.…”

Combustion Phases of Evaporating Neat Fuel Droplet

“…As a result, some high temperature liquid from the surface circulated towards the core thus producing several high temperature spots within the droplet [9]. These spots initiate homogeneous nucleation of vapour bubble in small size and combines with each other as the evaporation progresses [22]. The surface of the droplet began to rupture as the bubble grows large thus forcing the liquid sub-droplet to be ejected away from the parent droplet due to pressure drop within the periphery area [14].…”

Post-Impact Characteristics of a Diesel-in-Water Emulsion Droplet on a Flat Surface Below the Leidenfrost Temperature

“…Diesel-water emulsions on the other hand represent one of the potential long term solutions to the harmful environmental impact of the diesel fuel exhaust emissions (Crookes et al, 1997;Faik & Zhang, 2018;Faik & Zhang, 2020). Emulsification is the process of mixing immiscible liquids with the help of an agent called as the emulsifier (or surfactant).…”

“…The HLB number for the latter emulsifiers ranges 0 < HLB ≤ 9 (Mollet & Grubenmann, 2001). The behaviour of fuel emulsions during combustion and associated processes such as atomization, nucleation, and micro-explosion, is the focus of a great majority of research work (Faik & Zhang, 2018). However, the intricacy of the emulsified fuel combustion, in addition to the variable nature of the engine and environmental conditions within which the fuel is working makes the analysis a bit complicated and harsh work to be accomplished (Vellaiyan and Amirthagadeswaran, 2016).…”