Why combustion reactions are useful

Here, well-to-wake GHG emissions were assessed from feedstock cultivation including fertilizer, but not land use changes , upstream transport and processing, and fuel distribution, while combustion itself was treated as carbon-neutral. Most considered pathways, e. This was not the case for Fischer Tropsch FT synthesis from gasification of cellulosic biomass. Valuable co-products such as electricity from the excess steam in the gasification FT process were assigned GHG credits.

Overall, sensitive contributions to GHG emissions were noted from fertilizers in feedstock cultivation, hydrogen consumption, and the conversion process itself. It should be noted in addition that most GHG analyses consider CO 2 , CH 4 , and N 2 O emissions, but neglect black carbon BC emitted from aircraft, although it can differ between conventional or alternative jet fuels depending on aromatic content [29].

With all suggested alternative fuels, fundamental knowledge on their combustion properties is needed, including ignition and extinction characteristics, flame development, combustion speciation, and emissions, most of which may depend sensitively on the fuel's chemical composition and the molecular nature of its compounds. One aspect of concern for future aero-engines with high compression ratios is the low-to-intermediate temperature chemistry and the potential negative temperature coefficient NTC behavior, for which studies under real engine conditions are still largely lacking [28].

Also, the development of surrogates and respective fuel models deserves attention to improve the predictability of the combustion performance. Won et al. Examined fuels included petroleum-derived jet fuel as a reference and synthetic as well as bio-derived alternatives, using e. While such analyses can prove useful in experimental screening procedures, understanding the chemical-kinetic reaction behavior of the compounds of a real fuel in applications involving turbulent multi-phase environments will need to build on substantial fundamental knowledge.

Regarding transportation and other fuels, fuel blends, and fuel—engine combinations, combustion science is needed for their critical evaluation. For pathways towards large-scale environmentally friendly fuels for future transportation, it is useful to consider the full picture, as illustrated by the few examples of lifecycle analyses above.

Chemistry is not only needed to understand the combustion process in the engine itself, but chemical knowledge is indispensable for upstream processing steps. Innovative pathways improving their environmental and greenhouse gas balance can make a substantial difference for the complete process and could be of similar or larger impact than optimizing the combustion system alone.

To avoid systemic roadblocks regarding fuels, propulsion concepts, and infrastructure, the combustion community should also feel answerable in view of the larger context and bring in their chemical and engineering expertise. The fuel spectrum that may contribute to CO 2 reduction can also provide interesting solutions for chemical energy storage and conversion between heat, power, transportation fuels, and other chemicals [32] , [33] , [34].

As a chemical building block for the C 1 compound syntheses, CO 2 might be captured preferentially from point sources, potentially from combustion systems [34]. Koj et al. They have identified about 30 LCA literature studies for respective systems described as power-to-X, power-to-fuel, power-to-gas, power-to-liquids, power-to-mobility, power-to-transport, power-to-chemicals, and power-to-heat and analyzed those in terms of potential GHG reduction and other environmental effects.

Different conversion technologies from electricity to products with their relevant process steps are illustrated in Fig. Power should preferentially be renewable but depends on the source, the integration into the system, and the full load operation hours [33].

Other inputs such as CO 2 and H 2 O and technologies for their supply, transport, and treatment separation, purification, etc. Transport, distribution, infrastructure, and storage options will also have an impact for the respective process chain. Schematic illustration of main inputs, products, processes, and technologies of different Power-to-X process chains and their classification.

Reprinted from [33] with permission from Elsevier. It is obvious from Fig. Choices of targets for the assessment, e. Nevertheless, power-to-X concepts that use available renewable or surplus electricity and available CO 2 captured from industrial processes may seem promising and deserve further attention.

Much work and creativity is needed towards viable process chains and efficient conversion steps, regarding also useful, environmentally friendly transportation fuel choices. The evaluation of their climate change impact in g CO 2 -equivalent per km considers direct emissions and those from fuel production, distribution, and other factors as well as different characteristics for the sources of electricity. Realistic choice and transparent description of conditions, regarding infrastructure as well as energy and material streams, and knowledge of the respective technological potential in the different fields — including combustion — will matter for a fair assessment of future directions.

The conversion steps, fuels, and products briefly discussed above are not exhaustive. Further options of interest for combustion applications are being proposed, e. Grinberg Dana et al. The authors have compared seven synthetic fuels, namely methane, methanol, DME, ammonia, and such nitrogen-containing aqueous fuels in terms of a power-to-fuel-to-power assessment [43].

This methodology relates the available output power by the fuel's combustion to the energy required for its production considering air separation, water splitting, and fuel synthesis and distribution. While some of the proposed aqueous fuels perform quite well in this analysis [43] , their combustion reactions and efficiency are not sufficiently known, with only exemplary laboratory studies of their combustion behavior [44]. Most previously mentioned conversion schemes concern rather small molecules as energy vectors that could be also used directly as combustion fuels or in fuel combinations.

In view of rapidly needed alternatives, Schemme et al. Liquid organic hydrogen carriers LOHCs present another pathway to chemically store and handle hydrogen in liquid form without the need for dedicated and complex H 2 storage infrastructures [46]. Such LOHC systems are pairs of hydrogen-rich and hydrogen-lean compounds that can store hydrogen by repeated catalytic hydrogenation and dehydrogenation cycles without binding or releasing other substances from or to the atmosphere [46].

Hydrogen carrier molecules are typically high-boiling, and the hydrogen-rich compounds can be stored stably for extended periods and transported, also over long distances, with existing technology [46]. Hydrogen-lean molecules can be aromatic systems, with an early LOHC pair being toluene—methylcyclohexane. Catalytic steps for LOHC systems need further attention, and while stationary use has been demonstrated already at a pilot stage, mobile applications will involve further research [46].

The substances just discussed contain preferentially the elements H, C, and N. The periodic table offers more choices regarding potential combustion fuels [47 , 48]. Particularly high energy densities are available from metals that have been proposed as recyclable, zero-carbon energy carriers, including lithium, boron, magnesium, aluminum, silicon, iron, and zinc [48 , 49]. The combustion behavior of such heterogeneous systems for different applications is, however, much less understood than that of conventional liquid fuels [47].

It is beyond the scope of this article to provide a comprehensive discussion of available storage and conversion technologies. However, it should be recognized that beyond in-depth understanding of the relevant combustion systems, chemical knowledge is also required for pertinent reaction systems such as dry and steam reforming, partial oxidation, and synthesis routes.

The development and optimization of technologically viable pathways can be enhanced by interaction with the combustion community. Also, the combustion community should not leave the choice of chemicals as fuels solely to others.

High-efficiency, low-emission combustion techniques and integration of combustion into the changing energy landscape with the related conversion processes are areas deserving intense investigation.

Combustion techniques provide opportunities to produce functional materials with attractive properties, including mechanical, optical, catalytic, magnetic, and electronic characteristics that makes them interesting for various applications, e. As recently reviewed by Schulz et al. To tailor and control the properties of such materials including their composition, phase, morphology, size distribution, and further desirable characteristics, a necessary prerequisite is the fundamental understanding of the reaction process from the precursors to the particles.

This knowledge is also vital to scale up synthesis processes from the laboratory to industrial scale. Compared with conventional combustion, the chemistry of gas-phase material synthesis includes additional elements, compounds, and reactive species, with generally lesser knowledge about their reactions and kinetic parameters [50]. It is therefore highly useful to characterize the process under well-controlled laboratory conditions as shown in Fig.

Here, the authors have coupled a shock tube — a well-suited reactor to investigate the kinetics of high-temperature processes — with several in-situ diagnostic techniques including atomic resonance absorption spectroscopy ARAS , emission spectroscopy, time-resolved laser-induced incandescence TiRe-LII , extinction measurements, and high-repetition-rate time-of-flight mass spectrometry HRR-TOF-MS to provide insight into the species composition, its temporal development, and the particle growth.

Shock tube with a variety of diagnostics for particle growth processes: a : Absorption and emission without lamp measurements for species concentration, and ignition delay time detection without spectrometer , b : time-resolved laser induced incandescence for particle size determination, c : absorption and extinction measurements for determination of species concentration, temperature, and particle formation induction times, d : high-repetition-rate time-of-flight mass spectrometer for multi-species measurements.

Similarly, Kelesidis et al. In each case, and particularly when high purity or metastable compositions are desired, in-depth understanding of the process dynamics and tight control of the synthesis conditions are essential [51]. The authors underline how the understanding of combustion synthesis has enabled progress towards scalable production routes, including control of impurities, particle size distribution, composition, and morphology.

They also highlight the importance of understanding particle dynamics and fluid mechanics for metastable product formation, and of thermophoretic sampling to understand the particle growth during the combustion process [51]. Moreover, Li et al. To describe and scale up such flame synthesis processes, computational fluid dynamics CFD simulations should include information on the combustion kinetic mechanisms [54] , and molecular modeling can assist in understanding their physico-chemical basis as a means to facilitate process design [55].

From the large number of systems and applications, some examples pertaining to energy- and fuel-related aspects may be interesting in the present context. Targeting the Fischer-Tropsch process as part of the GTL route towards cleaner fuels, a double flame spray pyrolysis technique was demonstrated to offer individual control over the properties of the catalyst and support materials, providing an alumina-supported cobalt catalyst that showed promising performance [56].

Gockeln et al. Again, the flexible operation of the double flame spray pyrolysis technique enabled control over the process by individually addressing the LTO nanoparticle size and their surface modification. With this technique, solvents or binders could be avoided, potentially improving the energy density, reducing the need for non-electrochemically-active materials, as well as complexity and costs, while providing opportunities for up-scaling [57].

Combustion processes with defined temperature, pressure, composition, and mixing properties can thus be a valuable means to provide the adjustable reaction environment for controlled synthesis of materials for multiple applications. The flexible and scalable operation of such flame reactors can offer opportunities for the energy sector, including energy storage and conversion systems. Nevertheless, the process chains must be evaluated in terms of their greenhouse gas signature, for example when using fossil-fueled, e.

Flames are especially well suited to produce carbon nanomaterials with highly attractive properties [59] , [60] , [61] , [62] , [63] , [64] , [65] , [66]. The double-faced nature of soot as both, an air pollutant and a high-tech product has been recognized, and Mulay et al.

For example, candle soot is known to be superhydrophobic, useful in water-repellant surface coatings, self-cleaning glasses, smart textiles, or oil-water separation [59 , 60]. Depending on parameters such as temperature, residence time, and wax composition, differently structured carbon materials can result, including, for example, fluorescent carbon nanoparticles and single- and multi-walled carbon nanotubes [59 , 61].

As discussed by the authors [59] , fluorescent carbon nanoparticles derived from candle soot can be used, e. Carbon materials for supercapacitor electrodes from candle soot can offer good electrochemical performance and could thus contribute to cost-effective production pathways for building blocks of high-density energy storage devices [62]. Making different carbon nanostructures in candle flames has thus come a long way since the seminal article of Liu et al.

However, understanding of the combustion parameters, in particular of the flame's reactive species composition, and of the carbon growth processes are necessary not only for using such reactive environments stably and reproducibly, but also to bring such production options from demonstration experiments into larger-scale applications.

Flames also provide opportunities to produce different two- and three-dimensional carbon structures as e. Two-dimensional materials such as graphene have received considerable attention, and well-controlled combustion conditions might permit to synthesize carbon-based 2D materials with characteristics that could be tailored for specific applications [63]. Three-dimensional structures incorporating graphene are suggested for catalysis, energy storage, and oil absorption, and flames offer appropriate reaction conditions for the fast and facile growth of such structures, as demonstrated by Qian et al.

Again, the facile, one-step method may show potential for tuning physico-chemical properties of the nanoparticles and thin films. As an exciting further aspect of carbon nanoparticles from flames, their quantum dot behavior has been recently investigated systematically [66] , with an analysis of their optical bandgap, photoemission ionization energy, and electrochemical ionization behavior. The findings of these authors and earlier research summarized in their report [66] regarding the light absorption and emission properties of carbon nanoparticles from flames will have impact not only for applications in photovoltaic or electrochemical devices, but also for assessing the effects of radiative forcing from combustion-generated soot.

The apparent simplicity of combustion synthesis methods of carbon-based nanomaterials should, however, not lead to underrating the complexity of the chemical mechanisms that relate flame conditions and desired nanomaterial characteristics with catalytic, electrical, optical, magnetic, or other properties. Without understanding the physico-chemical basis, design, reliability, reproducibility, control, and scaling of such synthesis processes is left to phenomenological approaches.

Examples such as those given in this article underline that solving combustion problems and exploring combustion opportunities needs chemical understanding. Important knowledge is available from the classic physico-chemical domains, from surface science, synthesis, and reaction engineering.

Thermodynamics, for example, provides important criteria for the energetic feasibility of chemical conversion routes as well as for life-cycle analyses. Kinetics provides insight into the principles and pathways for the transition from the initial to the final state, e. Spectroscopy and microscopy provide reliable and reproducible experimental evidence for the involved phenomena not only in a laboratory system, but also in a technically representative environment.

In combination, fundamental knowledge and quantitative analysis methods from combustion chemistry can assist to conceive strategies to abate pollutants, to design fuels, to develop chemical conversion and storage routes, and to provide access to functional materials — important future fields of action for combustion science.

Combustion proceeds in a wide range of pressure, temperature, and composition and in a large variety of systems. Relevant processes may include pretreatment, delivery, and mixing of fuel and oxidizer, ignition, reaction progress for safe and efficient energy conversion, and aftertreatment.

Understanding such processes to the necessary level of detail is a prerequisite for performance optimization and control. Chemical knowledge is important for many combustion-related areas and includes diverse subjects from coal and biomass combustion to fire safety. In this chapter, selected advances and directions will be presented with a focus on gas-phase combustion.

Chemical knowledge on such systems is generated by the interplay of experiment, theory, and simulation of their characteristics and behavior by chemical-kinetic combustion models.

Many seminal investigations combine several of these aspects. The following sections should thus not be regarded as independent. A first focus will be combustion chemistry diagnostics, highlighting experimental techniques and approaches to obtain chemical information from a combustion system.

Such chemical information is important to understand the ignition and combustion behavior of conventional and alternative fuels, to understand the formation of pollutant emissions, and thus to enable design of efficient, clean combustion systems. The following two sections will then present aspects of chemically particularly complex areas, including combustion at low temperatures on the one hand and soot precursors, polycyclic aromatic hydrocarbons PAHs , and soot on the other.

The work highlighted in these two sections will also refer to the respective chemical concepts and models. Nevertheless, a final section will focus particularly on model development including selected recent work on mechanism reduction, uncertainty analysis, and data treatment. It is hoped that this overview will thus provide a flavor for the powerful methods, approaches, and developments that could also be applied in related areas beyond immediate combustion. Understanding combustion chemistry in relevant detail needs experimental information directly from the reactive system.

Multiple parameters characterize the combustion state and its development along the reaction progress, including temperature, pressure, density, velocity, mixing status, species composition, reactivity, heat release, and others, many of which can be experimentally determined. Specifically designed laboratory experiments permit access to information such as ignition delay time, flame speed, flame structure, autoignition and extinction behavior, reactive species identification, their relative or absolute concentrations, and occurrence of specific chemical reactions as a function of boundary conditions and the fuel's molecular structure.

As simplified in Fig. Insight gained from such partly idealized systems can serve to develop, advance, and validate transferable combustion chemistry models that bridge between fundamental chemical knowledge and practical systems behavior.

Essential contributions to characterize the chemical reaction progress in gas-phase combustion systems. Beyond gas-phase reactions, further characteristics of the combustion system may include the formation of droplets, sprays, and particles, phase changes, heat transfer, flame—wall interactions, heterogeneous reactions, and aftertreatment performance.

Challenges to investigate chemical aspects in practical combustion systems are presented, for example, by the interaction of multiple species with a turbulent flow field [67 , 68] and the reactions of multi-component conventional as well as chemically diverse future transportation fuels, with different properties and reactivity, in current and advanced engines [69] , [70] , [71] , [72] , [73].

Laser sensors and optical imaging techniques can determine relevant parameters such as temperature, pressure, and species concentrations in practical combustion systems and reactive flows [74] , [75] , [76]. Such applications span an impressive range from measurements of individual reaction rate coefficients to advanced propulsion systems [74 , 75] , often resorting to absorption and fluorescence techniques. Diagnostic advances include highly sensitive and real-time species detection in gas-phase systems [77] , [78] , [79].

Also, diagnostic techniques permit to capture temporal and spatial variations of important reactive species [80] , to probe flame—wall interactions [81 , 82] , to sample correlated temperature and velocity information with high repetition rates and spatial precision [83] , and to follow the formation and growth of soot and other particles [84 , 85]. Comprehensive reactive species information that is essential for a deeper understanding of the reaction processes as a function of temperature, pressure, fuel—oxidizer mixture, reaction time, and other system variables is often not available from laser diagnostics, but from specific methods, including mass spectrometry as a universal technique [86] , [87] , [88] , [89].

Advanced instrumentation includes synchrotron-based vacuum ultraviolet VUV photoionization PI molecular-beam mass spectrometry MBMS to determine species profiles in reactors and flames [87] , [88] , [89] , [90] , [91]. A sample of the reactive mixture at a pre-selected temperature and residence time is withdrawn from the heated JSR by a quartz probe. Schematic representation of a jet-stirred reactor that is located within an oven, all surrounded by a water-cooled stainless-steel chamber.

Molecules are sampled from the reactor through a quartz probe, ionized via single-photon ionization with vacuum-ultraviolet photons, and the respective ions are mass-selected using a reflectron time-of-flight mass spectrometer. Reprinted with permission from [92]. Copyright American Chemical Society. Such isomer-discriminating photoionization experiments have served to investigate the kinetics of individual combustion-relevant reactions [93 , 94] , to determine VUV photoionization cross sections for the quantitative detection of decisive low-temperature species such as the hydroperoxyl radical HO 2 , hydrogen peroxide H 2 O 2 , and formaldehyde H 2 CO [95] , and to detect previously elusive molecules such as Criegee intermediates [96 , 97].

Moreover, photoelectron photoion coincidence PEPICO spectroscopy, a technique that provides species-selective information from mass-selected photoionization and the coincident photoelectron spectra PES , has great potential to obtain in-depth species- and structure-selective information in complex reactive systems [98] , [99] , [] , []. The detection of intermediate species profiles with species-selective techniques is important to reveal mechanistic details and evaluate the performance of kinetic models, as shown in the examples in Figs.

Hemken et al. Since detailed reaction kinetic models for this fuel were still largely lacking, the combined experimental analysis was thought to provide a useful target for model inspection and development.

Signals are compared to the adiabatic top panel and dashed lines and vertical bottom ionization thresholds IP and photoelectron spectra PES of tert -butyl solid, red line , iso -butyl dotted, green line , 1-butyl solid, blue line , and 2-butyl dotted, yellow line.

Literature for the reference PES is given in the original article. Reprinted from [99] with the permission of AIP Publishing. The results from the two experiments are in excellent agreement, especially considering the experimental uncertainties of both independent instruments and the different cross sections of the two ionization processes for the respective quantification. Clearly, the simulation deviates significantly from the experiment in most cases, even after introduction of some modifications regarding the initial decomposition reactions and the MVK sub-mechanism [].

Because of the unambiguous identification and mutually supportive, quantitative experimental detection of these intermediates with two techniques, it could be concluded that further development of the model was warranted and the deviation between experiment and model was not due to experimental errors, which is the more important since MVK is a toxic species and its correct prediction would be useful []. In the previous example, the fuel radicals were not identified experimentally, and information on branching between the different possible channels was only accessible indirectly from the respective first stable decomposition products.

These are particularly important since they are at the origin of further reaction pathways and thus provide information on the expected radical pool.

However, they are hard to detect because of their reactivity and low concentrations. Although the PIE spectra in the top panel of Fig. From reference spectra of all possible butyl radicals, the branched isomers were unambiguously identified, in good agreement with the assumed major fuel destruction routes [99].

The technique has thus demonstrated excellent sensitivity and superior isomer identification potential for highly reactive species in reacting flows of chemical complexity such as a flame.

Understanding combustion processes and concurrent development of combustion models needs information in a wide range of temperatures and pressures. It is therefore important to consider multiple reaction environments with their specific target conditions and advantages for studying a given question, since they may show different sensitivity to certain species and specific reaction pathways.

Also, especially in a flame environment, uncertainties in transport and heat transfer might obscure the influence of reactions of particular interest for model development. Jet-stirred and other types of reactors [] , [] , [] , [] , shock tubes [] , [] , [] , [] , [] , [] , [] , [] , [] , and rapid compression machines RCMs [] , [] , [] offer opportunities for mechanistic investigations for fundamental and practically relevant conditions.

Different analytic methods have been used to determine important chemical information, including mass spectrometry [ , ] , Fourier-transform infrared FTIR spectroscopy [] , gas chromatography GC [] , and laser absorption [ , [] , [] , [] , [] , [] , [] , also in the mid-infrared spectral region [] , as well as cavity-enhanced laser absorption spectroscopy CEAS [ , ].

Great potential for the on-line analysis of chemical composition in highly complex mixtures is also offered by advanced two-dimensional GC techniques with flame ionization or MS detection []. The development of laser sensors enables increasingly facile, simultaneous detection and quantification of several species in reactive mixtures, including multi-species detection approaches in shock tubes [] , [] , [] , [].

As a recent example , Zhang et al. Dashed lines: simulations with a chemical-kinetic model; see original publication. The production of both species increases with temperature; observed differences between experiment and simulation might be caused by imperfections in the model or potential contributions from other absorbing intermediate species in this spectral region []. Beyond fundamental investigations, it is important to obtain information about the combustion process — including the reaction progress — for practically relevant transportation fuels and engine conditions [] , [] , [] , [] , [] , [] , [] , [] , [] , [] , [].

Ignition behavior, flame development, heat release, the effects of injection, mixing, exhaust gas recirculation EGR , and other characteristics can be monitored, often using optical diagnostic methods and chemical markers for certain process aspects. For example, laser-induced grating spectroscopy LIGS , suitable for applications in engines [ , ] , has been developed to jointly measure temperature and water concentration [].

Sampling-free in-cylinder concentration measurements have been performed with high-speed tunable diode laser absorption []. Tomographic imaging in the chemically sensitive near-IR has been demonstrated as a tracer-less means to monitor evaporation and mixing development; the results were cross-compared to planar laser-induced fluorescence PLIF measurements of naphthalene as a fuel tracer and give useful indications on combustion behavior and pollutant formation [].

In a reactivity-controlled compression ignition RCCI engine, in-situ chemical species information from single-shot PLIF of formaldehyde was used to investigate effects of the injection procedure and the interplay of autoignition, flame propagation, and heat release [].

Different ignition processes, early flame development, and cycle-to-cycle variations in heavy-duty natural-gas-fired engines were accessible with rapid-frame-rate borescopic IR imaging of water spectral lines in the 1—1. Furthermore, soot formation and in-cylinder soot oxidation were analyzed in an optical engine with high-speed extinction measurements [].

These and other examples highlight the progress in combustion diagnostics towards real-time process monitoring and control, especially for chemically sensitive advanced engine conditions. Chemical information is also valuable to characterize engine exhaust with appropriate sensitivity in-situ , in real-time, on-board, with portable devices [] , [] , [] , [].

Such methods are especially useful to monitor real emissions as a function of driving performance, to assure compliance with regulations, and to provide a critical assessment of associated health risks. An in-depth overview of instrumentation to determine particulate emissions is given in []. Diemel et al. Results from their analysis are given in Fig. Each point corresponds to a single engine cycle. The measurements are based on tunable diode laser absorption spectroscopy TDLAS in the wavelength range of 1.

The data in Fig. Also, CO and CH 4 as indicators for incomplete combustion are found in the rich regime. Cycle-to-cycle variations are evident but with a different level of scatter for different species, which may be related to the different complexity of the selected spectral features.

The CH 4 concentrations at lean conditions should be regarded with caution because of spectral overlap with NO 2 []. Further information surrounding the combustion process in the engine can be obtained, for example on preheating and evaporation of the fuel streams [] , [] , []. Moreover, combustion diagnostics research is also directed to gas turbine combustors and furnaces, with ambitious techniques such as femtosecond two-photon LIF imaging of CO applied to piloted liquid spray flames [].

From combined detection of several chemical species, heat release can be remarkably well predicted in turbulent jet flames []. Selected results of these investigations that have combined OH and kerosene PLIF for temperature and concentration measurements from two different planes are presented in Fig. Flame characterization at two different pressures combining several PLIF channels and measurement planes.

Color coding: grey-to-white scale: OH signal; color scale top : kerosene mole fraction; color scale bottom : temperature; beige coloring bottom : OH gradient. In this series of experiments, two particle imaging velocimetry PIV systems were applied to characterize the flow field by 2D measurements of velocity in the axial x-z and radial y-z planes [] , using stereoscopic PIV in the radial measurements.

The fluorescence spectra of commercial JET A1 fuel and the contributions of mono- and di-aromatics were analyzed in high-pressure reference measurements that were used in the calibration for both, fuel mole fraction and temperature distribution. The single-shot measurements in Fig.

The characterization of industrial-type injection systems and combustion processes at elevated pressures with realistic liquid fuels is key for the design of aero-engines and transportation fuels that can significantly reduce combustion emissions. The development, monitoring, and control of low-emission combustion processes have become feasible with diagnostics methods that can analyze the combustion process and reaction progress in chemically complex laboratory systems as well as in practical applications, using chemical markers for important properties such as evaporation, mixing, flame dynamics, heat release, and pollutant formation.

Such methods, procedures, and combinations of techniques can be exploited to investigate reacting systems beyond combustion. The need to reduce emissions drives the development of high-efficiency internal combustion IC engines, particularly in the low-temperature combustion LTC regime [] , [] , [] , []. These reactions are highly exothermic which means they release energy, often in the form of heat. That's why combustion chemistry is used to heat homes and fuel cars.

Combustion reactions can sometimes be tricky to balance so if you get stuck make sure you review the content in the stoichiometry guide about balancing equations.

One interesting thing to note is that combustion reactions cannot proceed once the oxygen is depleted. Have you ever put an upside down glass over a burning candle? Check it out. You'll notice that the candle will burn for a little while longer, but as soon as all of the oxygen in the glass is consumed, the fire will disappear. Pretty neat, huh? Also, remember every combustion reaction needs a hydrocarbon as well.

In the case of candles, the hydrocarbon is the wick. Some more combustion action. Here is a nice video review if you're still feeling overwhelmed by combustion, or if you need extra help balancing combustion equations check out this video.

Ever hear of spontaneous combustion? Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter. Updated January 09, Featured Video.

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