CNRS Ingénierie

In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. On the basis of experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl-CH2-O-CH2-O- (1,3-dioxetane), CH3OOH (methyl hydroperoxide), HC(O)OH (formic acid), and H2O2 (hydrogen peroxide). We show that the theoretical characterization of multiple conformeric structures of some intermediates is required when interpreting the experimentally observed ionization thresholds, and a simple method is presented for estimating the importance of multiple conformers at the estimated temperature (∼100 K) of the present molecular beam. We also discuss possible formation pathways of the detected species: for example, supported by potential energy surface calculations, we show that performic acid may be a minor channel of the O2 + ĊH2OCH2OOH reaction, resulting from the decomposition of the HOOCH2OĊHOOH intermediate, which predominantly leads to the HPMF.

This work provides new temperature-dependent mole fractions of elusive intermediates relevant to the low-temperature oxidation of dimethyl ether (DME). It extends the previous study of Moshammer et al. [J. Phys. Chem. A 2015, 119, 7361–7374] in which a combination of a jet-stirred reactor and molecular beam mass spectrometry with single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation was used to identify (but not quantify) several highly oxygenated species. Here, temperature-dependent concentration profiles of 17 components were determined in the range of 450–1000 K and compared to up-to-date kinetic modeling results. Special emphasis is paid toward the validation and application of a theoretical method for predicting photoionization cross sections that are hard to obtain experimentally but essential to turn mass spectral data into mole fraction profiles. The presented approach enabled the quantification of the hydroperoxymethyl formate (HOOCH2OCH2O), which is a key intermediate in the low-temperature oxidation of DME. The quantification of this keto-hydroperoxide together with the temperature-dependent concentration profiles of other intermediates including H2O2, HCOOH, CH3OCHO, and CH3OOH reveals new opportunities for the development of a next-generation DME combustion chemistry mechanism.

Purpose: The new competitive environment characterized by innovation and constant change is forcing a new organizational behavior. This requires a digital transformation of SMEs based on collective performance determinants. SMEs have particular characteristics that differentiate them from large companies and a model that allows them to identify, leverage and develop their digital capabilities can help them to advance in digital maturity.Design/methodology/approach: An in-depth review of the existing literature on digital transformation and organizational competence was carried out on Scopus and Web of Science to identify the digital challenges faced by SMEs, and what digital capabilities they have to develop to face these challenges. In order to obtain the necessary information for the refinement of organizational competence for digital transformation model, six experts were interviewed; three of them are academics and the other three are professionals with management responsibilities in SMEs. We used semi-structured interviews, to keep the interviews focused and facilitate cross-data analysis between experts. In addition, it allowed us the possibility of analyzing new relevant aspects that could arise during the interview.Findings: As a result of this study we have developed a refined model of organizational competence for digital transformation that allows SMEs to identify and develop the digital capabilities necessary to advance in the digital transformation, refined with the opinions of six experts consulted. We were able to observe the importance of organizational learning and organizational knowledge to advance the digital transformation of SMEs.Originality/value: The developed model is useful for SME managers to know what the initial starting situation is, what the digital gaps are and to be able to plan the actions to develop the necessary digital capabilities to advance towards digital maturity.

In this paper, we propose an innovative and simple graphical framework for project control and monitoring, to integrate the dimensions of project cost and schedule with risk management, therefore extending the Earned Value methodology (EVM). EVM allows Project managers to know whether the project has overruns (over-costs and/or delays), but project managers do not know when deviations from planned values are so important that corrective actions should be taken or, in case of good performance, sources of improvement can be detected. From the concept of project planned variability, we build a graphical methodology to know when a project remains “out of control” or “within expected variability” during the project lifecycle. To this aim, we define and represent new control indexes and new cumulative buffers. Five areas in the chart represent five different possible project states. To implement this framework, project managers only need the data provided by EVM traditional analysis and Monte-Carlo simulation. We also explore the sensitivity of the methodology to control variables.

The selective non-catalytic reduction of NO by ammonia (SNCR) has been extensively studied but no activation of ammonia oxidation by nitric oxide had been reported. Experiments performed in a jet-stirred reactor (JSR) at atmospheric pressure for various equivalence ratios (0.1–2) and initial concentrations of NH3 (500 to 1000 ppm) and NO (0 to 1000 ppm) revealed kinetic interactions similar to the so-called mutual sensitization of the oxidation of hydrocarbons and NO. The experiments were performed at fixed residence times of 100 and 200 ms, and variable temperature ranging from 1100 to 1450 K. Kinetic reaction mechanisms were used to simulate these experiments and ammonia oxidation. The most reliable model from the literature was updated (NH2 + H → NH+H2, HNO+H → NO+H2) to better predict ammonia-air burning velocities. It showed the mutual sensitization of the oxidation of ammonia and nitric oxide proceeds through several reaction pathways leading to OH production which is mainly responsible for ammonia oxidation in the current conditions: NH2 + NO → NNH + OH, NNH → N2 + H, NNH + O2 → N2 + HO2, H + O2 → OH + O, H + O2 + M → HO2 + M, and NO + HO2 → NO2 + OH.

New results on high gain observer design for networked control systems via an emulation-like approach are presented. By using a general framework and a Lyapunov approach, we derive some explicit conditions on the maximum allowable transmission interval that ensure an exponential convergence of the observation error for a large class of network protocols.

Significant amounts of unsaturated hydrocarbons, such as butene isomers, are formed as intermediate products during the oxidation of higher hydrocarbons. In this study, new experimental data were obtained for the oxidation of 1-butene and cis-2-butene. The experiments were conducted in a jet-stirred reactor in the temperature range of 900–1440 K, at atmospheric pressure, for different equivalence ratios (0.25 ≤ φ ≤ 2), and in a combustion vessel at p = 1 atm and unburned gas temperatures in the range of 300–450 K. From gas sampled in the jet-stirred reactor, concentration profiles of stable species were measured by gas chromatography and infrared spectrometry. A combustion vessel was used to determine laminar burning velocities of butene–air mixtures at atmospheric pressure and over the equivalence ratio range of 0.8–1.4. Additional data were obtained over a range of pressure (1–5 atm). A detailed chemical kinetic mechanism based on a previously proposed scheme for the oxidation of hydrocarbons was used to reproduce the present experimental data (201 species involved in 1787 reactions). The present mechanism was also tested against literature data: the structure of 1-butene premixed low pressure flat flames and 1-butene/oxygen/argon mixtures ignition delays were simulated, showing satisfactory agreement. Sensitivity analyses and reaction paths analyses were used to rationalize the results. Finally, the oxidations of cis-2-butene and trans-2-butene were compared and discussed.

New experimental results were obtained to better characterize and understand the oxidation and combustion of 1-propanol, which is a renewable alcohol usable as an alternative to petrol-derived gasoline. A pressurized jet-stirred reactor (JSR) was used to measure concentration profiles of stable species (reactants, intermediates, and final products) at 10 atm, over a range of temperatures (T = 770–1190 K) and equivalence ratios (φ = 0.35–2). A combustion bomb was used to measure burning velocities of 1-propanol/air mixtures at pressures of P = 1–10 bar and T = 423 K, over a range of equivalence ratios (0.7 ≤ φ ≤ 1.4) and at 1 bar for temperatures in the range of 323–473 K. The effects of total pressure and temperature on burning velocity were determined under stoichiometric conditions. The oxidation of 1-propanol under these conditions was modeled using a detailed chemical kinetic scheme taken from the literature and a kinetic scheme of ours was extended to the oxidation of 1-propanol. The computational results agreed reasonably well with the present set of experimental data, but the prediction of some intermediates and the burning velocities of 1-propanol/air mixtures under fuel-rich conditions could only be represented using the mechanism proposed here. Reaction path and sensitivity analyses were used to rationalize the results.

This paper is dedicated to vision-based modeling and control of large-dimension parallel robots driven by inextensible cables of non-negligible mass. An instantaneous inverse kinematic model devoted to vision is introduced. This model relies on the specificities of a parabolic profile hefty cable modeling and on the resulting simplified static analysis. By means of a kinematic visual servoing method, computer vision is used in the feedback loop for easier control. According to the modeling derived in this paper, measurements that allow the implementation of this visual servoing method consist of the mobile platform pose, the directions of the tangents to the cable curves at their drawing points and the cable tensions. The proposed visual servoing scheme will be applied to the control of a large parallel robot driven by eight cables. To this end, in order to obtain the aforementioned desired measurements, we plan to use a multi-camera setup together with force sensors.

Benzene and toluene were pyrolyzed under highly argon-diluted conditions at a nominal pressure of 20 bar in a single-pulse shock tube coupled to gas chromatography/gas chromatography–mass spectrometry (GC/GC–MS) diagnostics. Concentration evolutions of polycyclic aromatic hydrocarbon (PAH) intermediates were measured in a temperature range of 1100–1800 K by analyzing the post-shock gas mixtures. Different PAH speciation behaviors, regarding types, concentrations and formation temperature windows, were observed in the two reaction systems. A kinetic model was proposed to predict and interpret the measurements. Through a combination of experimental and modeling efforts, PAH formation patterns from species pools of benzene and toluene pyrolysis were illustrated. In both cases, channels leading to PAHs basically originate from the respective fuel radicals, phenyl and benzyl. Due to the higher thermal stability of benzene, the production of phenyl, and thus most PAH species, occur in higher temperature windows, in comparison to the case of toluene. In benzene pyrolysis, benzyne participates in the formation of crucial PAH species such as naphthalene and acenaphthylene. Phenyl self-recombination takes considerable carbon flux into biphenyl, which serves as an important intermediate leading to acenaphthylene through hydrogen loss and ring closure. The resonantly-stabilized benzyl is abundant in toluene pyrolysis, and its decomposition further produces other resonantly-stabilized radicals such as fulvenallenyl and propargyl. Barrierless addition reactions among these radicals are found to be important sources of PAHs. Fuel-specific pathways have pronounced effects on PAH speciation behaviors, particularly at lower temperatures where fuel depletion is not completed within the reaction time of 4.0 ms. Contributions from the commonly existing Hydrogen-Abstraction-Carbon-Addition (HACA) routes increase with the temperature in both cases.

The possibility to operate current diesel engines in dual-fuel mode with the addition of hydrogen can be limited by the variation in the combustion properties of the fuel mixture. In the present work, n-heptane was selected as a representative fuel to test the effects of hydrogen addition on the laminar flame speeds and ignition delay times. The spherical bomb technique was used to derive the laminar flame speeds of (n-heptane + hydrogen)/air mixtures (0%, 25%, and 50% hydrogen in the fuel) for an initial temperature of 294 K, pressure of 1 bar, and for equivalence ratios between 0.8 and 1.35. The results showed that average increases of 3% and 10% in the flame speeds were obtained with 25% and 50% hydrogen-enrichment, respectively, while a slight decrease of the Markstein length was obtained. Similar laminar flame speed results were predicted numerically with two kinetic models available in the literature with remarkable accuracy, especially for the Cai and Pitsch model [Cai L, Pitsch H. Combust Flame 2015; 162:1623–37]. The kinetic model was subsequently used to perform additional sensitivity and reaction pathway analyses that showed how the chemistry of n-heptane is not substantially influenced by the presence of hydrogen; while the increase in the flame speed is mainly due to the higher concentrations of radical intermediates. The ignition delay times were measured using the reflected shock tube technique for equivalence ratios equal to 0.832, 1.000, and 1.248, initial nominal pressure of 20 bar, temperatures between 730 K and 1200 K, and for different percentages of hydrogen in the fuel (20%, 50%, and 75%). The Cai and Pitsch model once again did a good job of reproducing the experimental data, indicating how at high temperatures the addition of hydrogen does not significantly affect the ignition delay; and in the NTC region (810 K–920 K) the mixtures composed of (50% n-heptane + 50% hydrogen) and (25% n-heptane + 75% hydrogen) are considerably slower than the reference n-heptane case. This is linked to the concentration of the alkane component and the related low temperature chemistry.

A combined experimental and kinetic modeling study is carried out to explore the influences of added acetylene, ethylene, propylene, and propyne on the reaction schemes of benzene pyrolysis. Pyrolysis of benzene with and without the presence of the C2- or C3- unsaturated hydrocarbons (HCs) is conducted in a single pulse shock tube coupled to gas chromatography-mass spectrometry technique. A minimum of 30 species is detected in each reaction system, and their mole fraction profiles are obtained over the temperature range 1030–1800 K at a nominal pressure of 20 bar and a nominal reaction time of 4 ms. With updates based on recent theoretical studies, our ongoing detailed kinetic model with 552 species and 4958 reactions can successfully reproduce the decomposition reactivity of the fuels, formation of decomposition products, and the growth of aromatics in the pyrolysis of different fuel mixtures. Various considerations apply to all studied binary mixtures. The addition of C2- and C3- HCs to the reaction system leads to C2H2 formation, and consequently promotes the HACA mechanism starting from phenyl radical (C6H5) at relatively low temperatures. The resulted phenylacetylene, formed through C6H5+C2H2 reaction, promotes the addition-elimination reaction C6H5C2H + C6H5 leading to the enhanced and early formation of all C14H10 PAH isomers including ethynyl biphenyl, methylene-fluorene, diphenylacetylene, phenanthrene, and anthracene. It is also noteworthy that the existence of C2H2 as fuel or its production from C2H4, C3H6, and C3H4-P decomposition results in numerous compounds with ethynyl branches such as ethynyl biphenyl, diethynyl naphthalene, and ethynyl acenaphthylene. Considering the specific features of the different fuel mixtures, the addition of acetylene intensifies the HACA route leading to greater acenaphthylene formation, while naphthalene formation remains similar to the pure benzene case due to the limited H-atoms. Differently, in benzene-C2H4 co-pyrolysis, naphthalene and acenaphthylene are mainly formed through reactions between PAH radicals (phenylacetylene radical and naphthyl radical, respectively) and ethylene. Concerning benzene-C3 co-pyrolysis, indene is the major C9 species resulting from the reaction of benzene/phenyl with C3 fuels. This is an important theoretical pathway to indene which is experimentally probed here for the first time. The high concentration of indene leads to the enhanced formation of naphthalene and acenaphthylene through the reactions of indenyl radical with methyl and propargyl (C3H3) radicals, respectively. Afterwards, the naphthyl radicals participate in the formation of several larger C11–13 PAHs such as methylnaphthalene, ethynylnaphthalene and fluorene through their reactions with CH3, C2H2 and C3H4-P/C3H3, respectively.

For the first time quantitative measurements of the hydroperoxyl radical (HO2) in a jet-stirred reactor were performed thanks to a new experimental setup involving fast sampling and near-infrared cavity ring-down spectroscopy at low pressure. The experiments were performed at atmospheric pressure and over a range of temperatures (550-900 K) with n-butane, the simplest hydrocarbon fuel exhibiting cool flame oxidation chemistry which represents a key process for the auto-ignition in internal combustion engines. The same technique was also used to measure H2O2, H2O, CH2O, and C2H4 under the same conditions. This new setup brings new scientific horizons for characterizing complex reactive systems at elevated temperatures. Measuring HO2 formation from hydrocarbon oxidation is extremely important in determining the propensity of a fuel to follow chain-termination pathways from R + O2 compared to chain branching (leading to OH), helping to constrain and better validate detailed chemical kinetics models.

Pyrolysis of phenylacetylene with and without the presence of C2 hydrocarbons (acetylene or ethylene) was studied in a single-pulse shock tube coupled to gas chromatography/gas chromatography-mass spectrometry equipment for speciation diagnostics. Quantitative speciation profiles were probed from each reaction system over the temperature range of 1100–1700 K at a nominal pressure of 20 bar. A kinetic model was proposed to interpret how phenylacetylene is consumed under high-pressure pyrolytic conditions and how the resulting intermediates react to form polycyclic aromatic hydrocarbons (PAHs), and furthermore, how the extra acetylene or ethylene alter the reaction schemes. It was found that the bimolecular reaction between phenylacetylene and hydrogen atom leading to phenyl and acetylene dominates phenylacetylene decomposition throughout the temperature window. The addition/elimination reactions between phenylacetylene and phenyl not only produce hydrogen atoms to maintain the reactivity of the fuel decay, but also directly lead to the formation of several C14H10 PAH isomers including diphenylacetylene, 9-methylene-fluorene and phenanthrene. Intermediates pools, regarding both species categories and abundance, are changed by the two C2 fuels introduced into the reaction system. The added acetylene enables the Hydrogen-Abstraction-Acetylene-Addition (HACA) mechanism starting from the phenylacetylene radical to occur at relatively low temperatures. But the yielded naphthyl core does not stabilize in naphthalene due to the lack of hydrogen atoms in the reaction system, and instead, it carries on the HACA route by further combining with another acetylene molecule, ending up in acenaphthylene. Differently, the added ethylene intensifies the HACA routes by contributing to the acetylene formation, and more importantly, provides hydrogen atoms participating in the naphthalene formation from naphthyl radical.

Fuel surrogates are mixtures of a few single aliphatic and aromatic compounds representative of the main classes of hydrocarbons present in the corresponding fuels. Among these hydrocarbon classes, the cycloalkanes constitute one of the key components in several surrogate formulations. In the present investigation, the oxidation of cyclohexane and decalin has been studied based on new experimental results. The experiments were obtained using two different techniques. A heated shock tube was used to conduct ignition delay time measurements at different stoichiometric conditions, nominal pressure of around 10 bar, and temperatures between 1090 and 1860 K. Ignition delay times in the range between 10 and 1300 μs were measured from both the OH* and the CH* emission signals behind reflected shock waves for highly diluted mixtures (99% argon bath gas). Experiments were also conducted varying the dilution from 99.5% to 92.7% for specific stoichiometric conditions. In addition to the ignition studies, flame speed measurements were performed using a spherical bomb heated to 403 K. Experiments were conducted varying the equivalence ratio between 0.6 and 1.5 at an initial pressure of 1 bar. Similar experimental profiles were obtained for the two species with maximum flame speeds equal to 62.1 cm/s at Φ ≈ 1.05 for cyclohexane and 56.5 cm/s at Φ ≈ 1.07 for decalin. Both the ignition delay time and flame speed experimental results were accurately simulated using chemical kinetic models available in the literature. Subsequent modeling analyses were carried out in order to clarify the role of the single- and double-ring structures on the experimental combustion properties of the two representative compounds studied herein.

Abstract. Atmospheric oxidation chemistry and, more specifically, photooxidation show that the long-term oxidation of organic aerosol (OA) progressively erases the initial signature of the chemical compounds and can lead to a relatively uniform character of oxygenated organic aerosol (OOA). This uniformity character observed after a long reaction time seems to contrast with the great diversity of reaction mechanisms observed in the early stages of oxidation. The numerous studies carried out on the oxidation of terpenes, and more particularly on limonene for its diversity of reaction sites (endo- and oxocyclic), allow this evolution to be studied. We have selected, for their diversity of experimental conditions, nine studies of limonene oxidation at room temperature over long reaction times to be compared to the present data set obtained at elevated temperature and short reaction time in order to investigate the similarities in terms of reaction mechanisms and chemical species formed. Here, the oxidation of limonene–oxygen–nitrogen mixtures was studied using a jet-stirred reactor at elevated temperature and atmospheric pressure. Samples of the reacting mixtures were collected and analyzed by high-resolution mass spectrometry (Orbitrap) after direct injection or after separation by reverse-phase ultra-high-pressure liquid chromatography and soft ionization, i.e., (+/-) HESI and (+/-) APCI. Unexpectedly, because of the diversity of experimental conditions in terms of continuous-flow tank reactor, concentration of reactants, temperature, reaction time, mass spectrometry techniques, and analysis conditions, the results indicate that among the 1138 presently detected molecular formulae, many oxygenates found in earlier studies of limonene oxidation by OH and/or ozone are also produced under the present conditions. Among these molecular formulae, highly oxygenated molecules and oligomers were detected in the present work. The results are discussed in terms of reaction pathways involving the initial formation of peroxy radicals (RO2), isomerization reactions yielding keto-hydroperoxides, and other oxygenated intermediates and products up to C25H32O17, products which could derive from RO2 autoxidation via sequential H shift and O2 addition (C10H14O3,5,7,9,11) and products deriving from the oxidation of alkoxy radicals (produced by RO2 self-reaction or reaction with HO2) through multiple H shifts and O2 additions (C10H14O2,4,6,8,10). The oxidation of RO2, with possible occurrence of the Waddington mechanism and of the Korcek mechanism, involving H shifts is also discussed. The present work demonstrates similitude between the oxidation products and oxidation pathways of limonene under simulated atmospheric conditions and in those encountered during the self-ignition of hydrocarbons at elevated temperatures. These results complement those recently reported by Vereecken and Nozière and confirm for limonene the existence of an oxidative chemistry of the alkylperoxy radical beyond 450 K based on the H shift (Nozière and Vereecken, 2019; Vereecken and Nozière, 2020).

This work presents a comparative study on the pyrolysis of C8–C10 linear alkylbenzenes including ethylbenzene, n-propylbenzene and n-butylbenzene. Experiments were performed with highly diluted mixtures in argon containing respectively the three fuels under nearly identical conditions in a single-pulse shock tube, at a nominal pressure of 20 bar and over a temperature range of 950–1700 K. Post-shock gas mixtures were sampled and analyzed with the gas chromatographic technique so that species concentration evolutions as function of temperature were obtained for the pyrolysis of each fuel. A kinetic model was developed to interpret the similarities and differences regarding the fuel decomposition and species formation behaviors observed in the experiments. The fuel conversion of n-propylbenzene and n-butylbenzene proceeds along a similar curve, which is much faster than that of ethylbenzene. All three fuels are consumed mainly through the bond fission producing benzyl radical. The simultaneously formed C1–C3 alkyl radicals in separate cases significantly impact the fuel reactivity and the formation of small C1–C4 and monocyclic aromatic hydrocarbons. Specifically, in n-propylbenzene pyrolysis, the decomposition of ethyl radicals produces a considerable amount of hydrogen atoms, which enhances the reactivity of the reaction system and meanwhile results in relatively high production of benzene during the fuel consumption. The formation of other monocyclic aromatic hydrocarbon intermediates, such as toluene and styrene, is also influenced by fuel-related pathways. Concerning PAH formation, the kinetic schemes in the pyrolysis of linear C8–C10 alkylbenzenes are very similar, which are dominated by the reactions of benzyl and other resonantly-stabilized radicals produced from benzyl decomposition. The major PAH formation reactions are barely influenced by the fuel chemistry. The only notable fuel-specific pathway is the indene formation from 1-phenyl-2-propenyl in n-propylbenzene and n-butylbenzene pyrolysis at relatively low temperatures. Styrene is an abundant product and its reaction with phenyl is found to be an important channel of phenanthrene formation.

A combined experimental and kinetic modeling study is carried out to explore the influences of acetylene and ethylene addition on the species formation from toluene pyrolysis. Experiments are conducted separately with four different argon-diluted binary toluene/C2 mixtures in a single pulse shock tube at a nominal pressure of 20 bar over a temperature range of 1150−1650 K. All the experimental mixtures contain about 100 ppm toluene and different amounts of C2 fuels (50, 216, 459 ppm acetylene and 516 ppm ethylene). Species concentrations as a function of the temperature are probed from the post-shock gas mixtures and analyzed through the gas chromatography/gas chromatography-mass spectrometry techniques. A kinetic model is developed, which successfully predicts the absolute species concentration measurements as well as the changes brought by the varied fuel compositions. With the neat fuel decomposition profiles as a reference, both fuel components exhibit increased reactivity in the pyrolysis of all studied binary mixtures, indicating the existence of obvious synergistic effects. In particular, such effects become more remarkable when increasing the initial acetylene concentration. This essentially results from the addition-elimination reaction of a toluene fuel radical and a C2 fuel molecule leading to a C9 molecule and a hydrogen atom. Indene is identified as the predominant C9 product in all studied cases, and its peak concentrations sharply increase with the initial acetylene contents in toluene-acetylene pyrolysis. On the other hand, indane, produced from the addition-elimination reaction between benzyl and ethylene, is only detected at trace levels in toluene/ethylene pyrolysis. This indicates a relatively weaker interaction between benzyl and ethylene, compared to that of benzyl and acetylene. Apart from the increased concentrations of hydrogen atoms and C9 aromatics, interactions between toluene and C2 fuels also directly result in a reduced level of C7 radicals in the reaction system. Overall, PAH species can be divided into two groups according to the way their peak concentrations varying with the initial fuel compositions. For those largely depending on benzyl reactions, such as bibenzyl, biphenylmethane, fluorene and phenanthrene, the peak concentrations decrease with the added C2 fuels. In contrast, increasing trends are observed in the peak concentrations of the PAHs which rely on indenyl as a precursor, including naphthalene, methyl-indene, benzofulvene and acenaphthalene.

To explore the potential interactions between toluene/benzyl and the common C3 combustion intermediates, toluene-propylene and toluene-propyne co-pyrolysis is studied in the current work by taking neat toluene pyrolysis as a reference. Experiments are carried out at a nominal pressure of 20 bar over a temperature range of 1050−1700 K, using a single-pulse shock tube facility coupled to the gas chromatography-mass spectrometry speciation diagnostic technique. Temperature-dependent mole fraction profiles are obtained for numerous species ranging from small-molecule products to three-ring polycyclic aromatic hydrocarbons (PAHs). A kinetic model, which has been under development in our serial works, is extended by including the interplays between toluene/benzyl and propylene/propyne chemistry. The updated model can satisfactorily predict the measurements, regarding the absolute mole fractions as well as the variation trends brought by different initial fuel compositions. Increased reactivity is observed in the conversion of toluene with the presence of propylene or propyne, while the consumption rates of the studied C3 fuels are barely influenced by toluene. Benzene formation is facilitated by the C3+C3 reactions introduced by the C3 fuels. The pyrolysis of propylene (or propyne) significantly enhances the level of C1−C3 molecules/radicals that further react with aromatic species. For instance, the reactions of benzyl+propyne result in much higher mole fractions and lower speciation temperature windows of indene and naphthalene in toluene-propylene (or propyne) co-pyrolysis. The reactions with small hydrocarbons result in reduced levels of benzyl and other C7 radicals in the reaction system in toluene- propylene (or propyne) co-pyrolysis. Consequently, for the PAHs which are mainly formed through C7+C7 reactions, such as bibenzyl and phenanthrene, the mole fractions are lowered by the addition of propylene (or propyne). Propyne has more obvious influences on the species pool of toluene pyrolysis than propylene, because the effective C7C3 interactions are mostly through the reactions between toluene/benzyl and propyne/propargyl in both cases of toluene-propylene and toluene-propyne co-pyrolysis.

The kinetics of oxidation of mixtures of iso-octane with ethanol or 1-butanol (25/75%, 50/50%, and 75/25% in vol.) were studied experimentally using a fused silica jet stirred reactor. The experiments were performed in the temperature range 770–1190 K, at 10 atm, at an equivalence ratio of 1. Kinetic modeling was performed using a reaction mechanism resulting from the merging of validated kinetic schemes for the oxidation of the components of the present mixtures (iso-octane, ethanol, and 1-butanol). Good agreement between the experimental results and the computations was observed under the present conditions. Reaction path analyses and sensitivity analyses were used to interpret the results.