About this Research Topic

Background

Hydrocarbon combustion whether from fossil sources or from renewable sources remains one of the main sources of particulate matter (PM or soot). PM emissions not only reduce combustion efficiency but also are known to adversely affect the environment, climate, and human health. This has led to numerous changes in emissions regulations worldwide, including more stringent standards which involve the total mass and number concentration of particles emitted. The limits imposed by emission regulations represent a challenge for the industry and thus a fundamental understanding of soot formation process is mandatory to achieve a strong reduction of PM emissions and design of cleaner and more efficient combustion systems.
The complex reaction chemistry from the fuel molecule to particle formation has motivated intense research over decades, which has been spanning among fundamental experiments and numerical simulations of real-world applications. In-depth information on the chemical composition of particulates and their interaction with different environments are as important as the knowledge of the kinetics and formation mechanisms for these particles and the development of predictive models, with the ultimate goal of understanding the relation between chemical characteristics and health effects.

As mentioned recently, challenges are manifold in connecting (i) the decomposition reactions of fuel molecules with different structures towards different intermediate species, (ii) the multitude of postulated routes contributing to polycyclic aromatic hydrocarbons (PAH) and carbon cluster formation, (iii) the process of particle inception based on this variety of precursor species and reactions, (iv) the influence of the particular combustion system conditions on particle nucleation and growth, (v) the oxidation and aging processes of the formed particles, and (vi) the effects of real emissions on radiative forcing, cloud formation, reactive processes in the environment, and health-related conditions.
Recent advances in combustion PM emission diagnostic and computational capabilities helped in improving the predictability of fundamental chemical and aerosol models for practical applications, thus tackling some of those challenges. Therefore, the goal of this issue is to display the ongoing research efforts in filling the existing gaps on particulate formation from various sources (e.g. conventional and reformulated fuels) and systems (e.g. reactors, flames, engines, spray), using both fundamental experiments and numerical simulations.

The aim of the current Research Topic is to cover promising, recent, and novel research trends in the field of combustion and aerosol science. Areas to be covered in this Research Topic may include, but are not limited to:

· Experiments on soot formation and oxidation in combustion devices (chemical reactors, engines, flames)
· Molecular modeling of the precursors in soot formation, e.g. reactive molecular dynamics (MD) simulations.
· Chemical kinetic models for predicting PAHs and soot formation from conventional and reformulated fuels combustion.
· Applications of detailed and reduced soot model to computational fluid dynamics (CFD) simulations of reacting flows (e.g. sprays, engines, flames, turbulence/chemistry interactions).
· New approaches to assess the sooting propensity of conventional and reformulated fuels, e.g. yield sooting index (YSI) experiments and predictions through computational methods (i.e. neural network and machine learning).

Keywords: Soot, Conventional and Reformulated Hydrocarbon Fuels, Engine Combustion, Kinetic Modeling, Yield Sooting Index

Important note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.

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