Uncovering Complex Reaction Mechanisms in Combustion

Combustion chemistry, along with fluid dynamics and multi-phase physics, plays an integral role in the production of energy for transportation, and is governed by a complex network of interconnected reaction mechanisms.

Understanding the intricacies of such mechanisms, which span thousands of distinct chemical species and elementary reactions, enables the development of computational models that are employed in the design and simulation of next-generation combustion strategies focused on higher efficiency and reduced pollutant formation.

Biofuels are an alternative energy source purposed for mitigating consumption of petroleum-based fuels, namely gasoline, diesel, and aviation fuel, as well as augmenting internal combustion engine efficiency and contributing to a lower carbon-intensive transportation sector.

Most biofuels are functionalized hydrocarbons such as ethanol (H₃CCH₂OH) and butanone (H₃CC(=O)CH₂CH₃), although alkanes, aromatics, and other hydrocarbons produced from biomass are not, e.g. farnesane (2,6,10-trimethyldodecane).

Under certain combustion conditions, functional groups can impact reaction pathways that govern autoignition, which is sustained by chain-branching reactions, and reaction pathways involved in pollutant formation.

In addition to CO, NO_x, CO₂, and H₂O, byproducts of combustion include volatile organic compounds (VOC), which are implicated in health- and climate-related issues.

Globally, the transportation sector, which is driven principally by combustion, is responsible for 128 Tg per year of VOC emissions – approximately 10% compared to biogenic sources that largely produce isoprene, monoterpenes, and sesquiterpenes.

Because of the differences in molecular structure between functionalized biofuels and conventional, petroleum-derived hydrocarbons, the combustion of biofuels can alter the types of VOC emitted from the transportation sector, and understanding the ensuing impact on atmospheric chemistry is an important area in the atmospheric sciences.