Atomization efficiency enhancement in internal-mixing Y-jet nozzles using distinct dispersing media

Oil refining produces various petrochemical products, including ethylene, butane, diesel, jet fuel, and gasoline. These brands are generated through crude oil's fluid catalytic cracking (FCC) within reactors. Heavy fuel oil atomization is critical to this process and is responsible for forming fine sprays to enhance transfer phenomena during catalytic reactions. Oil dispersion is typically achieved in FCC units using internal-mixing nozzles, with steam as the dispersing phase. Despite ongoing rapid advances to transition towards renewable energy sources, fossil fuels and combustion processes will contribute to the global energy matrix for decades, posing significant environmental challenges. Therefore, optimizing existing processes to improve efficiency is essential. Due to its high demand and production loads, even slight improvements in oil refinery operations can substantially impact this industry's economic and environmental aspects by having larger productivity and reducing raw material consumption. Effective catalytic cracking depends heavily on adequate oil atomization, as the oil dispersion fluid dynamics directly influence subsequent reactions. However, steam-assisted atomization studies usually employ external-mixing nozzles and typically focus on flue gas analyses, neglecting the detailed fluid dynamics of the atomization process. Additionally, the mixing state using internal-mixing nozzles requires further understanding, mainly how the internal geometry affects the fluid interaction and contributes to a finer spray. Accordingly, the most applied Y-jet nozzle geometry is examined considering key geometric features. The internal flow and the external spray characteristics are explored, with correlations established to identify parameters that produce a fine spray. The aim is to investigate the effect of nozzle geometry on spray fluid dynamics and ultimately increase nozzle atomization efficiency, particularly in the steam-assisted atomization scenario. The relevance of this work for both the industry and spray research field concerns the experimental conditions approximation to industrial cases by matching dimensionless numbers, especially the Reynolds number and the Weber number of the liquid and gas. The analysis combines numerical and experimental investigations of the flow inside the nozzle, and the results are correlated with the external spray characteristics, such as the droplet sizes and velocities, spray boundary fluctuations, and mass flux distributions. The experiments use air or steam as the dispersing medium. In the latter case, the spray fluid dynamic investigation provides essential conditions for effective atomization. The primary outcome of this work concerns advancing the understanding of gas-assisted internal-mixing atomization processes and shedding some light on the liquid breakup mechanisms in the nozzle cavity. By optimizing the nozzle geometry and investigating the spray dynamics, the research contributes to enhancing atomization performance and efficiency in the petrochemical industry.