This experimental work was carried out to understand the fundamental combustion characteristics of a single Heavy Fuel Oil (HFO) droplet in a thermal environment. In particular, it was explored how different variables such as droplet size, environmental temperature, and air flow rate affect parameters of engineering interest like cenosphere structure, ignition delay time (IDT) and burning time (BT). Both high speed images of the combustion phenomenon and temperature record for liquid and gas phase have been obtained for different droplet sizes. The exposition of the HFO droplet to hot oxidizing environment can lead to two different phenomena, the formation of a globules carbonaceous structure in absence of combustion, or the ignition of the vapor cloud that surround the droplet with consequent growth of a solid shell with a porous structure. Both structures found at the end of the process are called "cenosphere" literally "hollow sphere". Moreover, a physical explanation to the obtained behavior was elaborated based on previous works and observations. Unpredictable behaviors of IDT and BT with respect to the HFO droplet size were recorded. However, the trends seem to be approximately directly proportional to the droplet size.
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