Combustion mechanism of nanobubbled dodecane: A reactive molecular study

Abstract

Blended fuels, created by adding methanol to ammonia or incorporating nanobubbles such as a hydrogen nanobubbles into existing fuels, offer significant opportunities for decarbonization of combustion devices. Nanobubbles (NBs), defined as gaseous cavities smaller than 1 μm in diameter, possess unique characteristics such as long-term stability, the capacity for free radical generation, and a high surface-to-volume ratio. These attributes make them potential candidates for various industrial applications, including water purification, medical engineering, and the energy and power sector. However, the fundamental understanding of the effects of NBs on chemical processes such as combustion cannot be easily captured through experimental techniques. Alternatively, reactive molecular approaches can provide a clear understanding of the impact of NBs on the combustion process. In this study, ReaxFF molecular dynamics simulations were utilized for a comparative study of the combustion of pure dodecane and hydrogen, nitrogen, and oxygen nanobubbled samples. The findings reveal that nitrogen NBs lower the activation energy to 52.89 kcal/mol for samples with a density of 0.17 g/mL by boosting the production of intermediates and radicals, which in turn increases dodecane consumption. In contrast, oxygen NBs increase the activation energy to 66.93 kcal/mol for samples with the same density, reducing dodecane consumption. At 2000 K, C2H4 is the primary product in pure, hydrogen, and oxygen nanobubbled samples, while water is the most prevalent in nitrogen nanobubbled sample at a density of 0.017 g/mL. Moreover, a temperature increase significantly enhances the thermal decomposition of the fuel in pure sample compared to nanobubbled samples. Additionally, as the density of hydrogen nanobubbled samples increases, there is a corresponding rise in fuel consumption, and water emerges as the primary product in samples with a density of 0.25 g/mL at 2000 K.