A new era for combustion research

Abstract

Current topics in combustion chemistry include aspects of a changing fuel spectrum with a focus on reducing emissions and increasing efficiency. This article is intended to provide an overview of selected recent work in combustion chemistry, especially addressing reaction pathways from fuel decomposition to emissions. The role of the molecular fuel structure will be emphasized for the formation of certain regulated and unregulated species from individual fuels and their mixtures, exemplarily including fuel compounds such as alkanes, alkenes, ethers, alcohols, ketones, esters, and furan derivatives. Depending on the combustion conditions, different temperature regimes are important and can lead to different reaction classes. Laboratory reactors and flames are prime sources and targets from which such detailed chemical information can be obtained and verified with a number of advanced diagnostic techniques, often supported by theoretical work and simulation with combustion models developed to transfer relevant details of chemical mechanisms into practical applications. Regarding the need for cleaner combustion processes, some related background and perspectives will be provided regarding the context for future chemistry research in combustion energy science.

Molecular mass growth through ring expansion in polycyclic aromatic hydrocarbons via radical–radical reactions

“…10 and 11); these two-dimensional nanostructures resemble graphene-type layers and define molecular building blocks of graphite as detected in the L3 chondrite Khohar 36 and in Murchison 37 . The mechanism outlined here will be crucial in interpreting chemical models of combustion processes 5 and of carbon-rich circumstellar environments 4 , help explain observation of graphitized carbon grains as detected in carbonaceous chondrites 36–40 , and enrich our knowledge of the formation and evolution of carbonaceous matter in the galaxy.…”

“…However, the elucidation of the fundamental reaction pathways to polycyclic aromatic hydrocarbons (PAHs)—organic molecules composed of fused benzene rings with naphthalene (C 10 H 8 ) denoting the simplest representative—in combustion environments 1 and in the interstellar medium (ISM) 2 has posed a long-standing challenge. Sophisticated combustion 3 and astrochemical reaction networks 4 along with flame sampling studies 5 and astronomical surveys 2 reveal that PAHs represent the critical link between resonantly stabilized free radicals (RSFRs) like propargyl (C 3 H 3 • ), allyl (C 3 H 5 • ), and cyclopentadienyl (C 5 H 5 • ) 6,7 and carbonaceous nanoparticles universally referred to as soot and interstellar grains on Earth and in extraterrestrial environments, respectively 2,8,9 . Whereas on Earth, PAHs represent undesirable toxic, often carcinogenic byproducts released in incomplete combustion 10 , in the interstellar medium, PAHs embody up to 20% of the galactic carbon budget 11 and are—along with carbonaceous grains—suggested to play a central role in the formation of vital precursors to molecular building blocks of life such as amino acids 8 .…”

From atoms to aerosols: probing clusters and nanoparticles with synchrotron based mass spectrometry and X-ray spectroscopy

“…PAH growth processes are also very important in combustion chemistry 14,20,22,48 as they are precursors for soot formation. 49 With the advent of nanomaterials based on graphene, 50 fullerenes, 51 and carbon nanotubes, 52 there is also increased interest in the formation of these materials from their gas phase precursors. To elucidate ion-molecule growth dynamics in hydrocarbons, we chose mixed acetylene-ethylene clusters 53 and pure acetylene clusters.…”

Photoelectron Photoion Coincidence Spectroscopy Provides Mechanistic Insights in Fuel Synthesis and Conversion

“…117 The current research goals include controlling global combustion parameters and pollutant formation by understanding the underlying processes and enabling better numerical models with predictive value. 118 For the development of such combustion models, experimental validation data are needed, especially quantitative species data as a function of process parameters, for example, pressure, temperature, or reaction time. Detailed isomerresolved speciation data from an anisole flame measured by PEPICO spectroscopy was used for validation of a new anisole kinetic reaction mechanism by Yuan et al 119 Mass spectrometric combustion diagnostics are now standard techniques to provide quantitative speciation data in reactive environments.…”

“…Thermal conversion processes will likely remain the main method to convert the chemical energy to heat and finally electricity because they are proven to be robust and reliable . The current research goals include controlling global combustion parameters and pollutant formation by understanding the underlying processes and enabling better numerical models with predictive value …”