Xiaoyuan Zhang

King Abdullah University of Science and Technology | KAUST

Methanol is a promising renewable fuel for achieving a better engine combustion efficiency and lower exhaust emissions. Under exhaust gas recirculation conditions, trace amounts of nitrogen oxides have been shown to participate in fuel oxidation and impact the ignition characteristics significantly. Despite numerous studies that analyzed the methan...

Ammonia as a fuel offers the potential to avoid carbon emissions, but its combustion is hindered by low reactivity. Here, the extinction limits of NH3 and NH3 plus reactivity enhancers were measured in the counterflow laminar non-premixed flames. A stable NH3-N2 flame was established with an oxygen-enriched oxidizer stream, and when the fuel was bl...

In this work, we present a methodology on automatic generation of predictive lumped sub-mechanisms for normal and branched alkanes. This methodology aims at obtaining lumped reaction mechanisms that preserve the chemical behavior of each reaction class in the detailed model. To achieve this goal, detailed sub-mechanisms for combustion of alkanes ar...

Real biodiesel fuels are mixtures comprising many high molecular weight components, making it a challenge to predict their combustion chemistry with detailed kinetic models. Our group previously proposed a functional-group approach (FGMech) to model the combustion chemistry of real gasoline and jet fuels; this approach has now been extended to mode...

One of the most important problems of modern energy industry is the transition to carbon free fuels, which can mitigate the negative environmental effects. This paper presents experimental data on ammonia and ammonia/hydrogen blends oxidation in an isothermal jet-stirred reactor over the temperature of range 800–1300 K. Experiments were performed u...

Biodiesels are promising renewable fuels that can aid in the transition to carbon neutrality. The high molecular weight and complex composition of real biodiesel fuels complicate development of compact kinetic models needed for engine simulations. Our group previously proposed the functional group approach (FGMech) to model real-fuel combustion bas...

To investigate the oxidation of ammonia (NH3)/hydrogen (H2) mixtures at intermediate temperatures, this work has implemented jet-stirred reactor (JSR) oxidation experiments of NH3/H2 mixtures at atmospheric pressure and over 800-1280 K. The H2 content in the NH3/H2 mixtures is varied from zero to 70 vol% at equivalence ratios of 0.25 and 1.0. Speci...

This paper explores the low-temperature (low-T) oxidation chemistry of 2,4,4-trimethyl-1-pentene (IC8D4, diisobutylene) by using jet-stirred reactor (JSR) experiments of both IC8D4/dimethyl ether (DME) mixture and pure IC8D4 at near atmospheric pressure and low temperatures. Oxidation species are measured using synchrotron vacuum ultraviolet photoi...

The kinetics of the reactions H2NO + O2(³Σg−) → HNO(X˜1A′) + HO2 and NH2 + HO2 → NH3 + O2(³Σg−), which are, respectively, very sensitive chain-propagation and chain-termination reactions in ammonia kinetic models, have been revisited by means of high-level electronic structure and variational transition state theory calculations with the goal of im...

The evolution of hydrogen from methane decomposition in a liquid metal bubble reactor (LMBR) has become a recent subject of interest; this study examines a novel approach to hydrogen production from pyrolysis of complex hydrocarbon fuels. Modeling hydrocarbon fuel decomposition in an LMBR is executed in two stages of pyrolysis: First, primary pyrol...

This work reports investigations on laminar premixed ethylene (C2H4) flames with special interests on measurements and kinetic modeling at elevated pressures. Chemical structures of laminar premixed C2H4/O2/Ar flames at 3 and 5 atm with the equivalence ratio of 1.4 were measured with molecular beam mass spectrometry. Both the stable and reactive sp...

Low-temperature oxidation of cyclohexane is investigated in two jet-stirred reactors (JSRs) at 1.04 bar and the equivalence ratio of 0.25. Reactive hydroperoxides and highly oxygenated molecules are detected using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). The isomers of C6H10O (5-hexenal, cyclic ethers and cycloh...

In this work, pyrolysis experiments of ethyl valerate were performed in a flow reactor over 705–1051 K at low and atmospheric pressures and in a jet-stirred reactor over 633–1013 K at near-atmospheric pressure. Products were measured with synchrotron vacuum ultraviolet photoionization mass spectrometry in the flow reactor pyrolysis and gas chromato...

Wide distillation fuels (WDF) and gasoline/diesel blends have been proposed as new fuel formulations for advanced combustion engines. Recent studies have shown that multi-component gasoline and diesel surrogate mixtures can accurately mimic the distillation curve, functional group or hydrocarbon class distribution, average molecular weight, and oth...

Real fuels are complex mixtures of hundreds of molecules, which makes it challenging to unravel their combustion chemistry. Several approaches in the literature have helped to clarify fuel combustion, including multi-component surrogates, lumped fuel chemistry modeling, and functional-group based methods. This work presents an innovative advancemen...

Construction of kinetic models to predict real-fuel combustion properties requires significant human and computational resources. In the first of this two-part study, a functional group correlation approach called FGMech was proposed for predicting the stoichiometric parameters in lumped pyrolysis reactions. The stoichiometric parameters were imple...

Reactivity enhancement is crucial for the potential applications of ammonia (NH3) as a gas turbine fuel. Doping more reactive fuels like H2, methane and syngas is a widely adopted strategy in this field, however fundamental combustion studies of NH3/reactive fuel mixtures under gas turbine-relevant high pressure conditions are still very limited. T...

With the growing attention on ammonia (NH3) combustion, understanding NH3 and nitric oxide (NO) interaction at temperatures higher than DeNOx temperature region or even flame temperature becomes a new research need. In this work, the outwardly propagation spherical flame method was used to investigate the laminar flame propagation of NH3/NO/N2 mixt...

This work reports an experimental and kinetic modeling investigation on the laminar flame propagation of three butylbenzene isomers (n-butylbenzene, iso-butylbenzene and tert-butylbenzene)/air mixtures. The experiments were performed in a high-pressure constant-volume cylindrical combustion vessel at the initial temperature of 423 K, initial pressu...

This work reports an experimental and kinetic modeling investigation on the flow reactor pyrolysis of iso-butylbenzene and tert-butylbenzene at 0.04 and 1 atm. Pyrolysis products were detected and identified using synchrotron vacuum ultraviolet photoionization mass spectrometry, and their mole fractions versus heating temperature were measured. Hig...

In order to study the combustion chemistry of carboxyl functionality, the laminar burning velocity of acetic acid/air and propanoic acid/air mixtures was investigated in a high-pressure constant-volume cylindrical combustion vessel at 423 K, 1 atm and equivalence ratios of 0.7–1.4. Experimental results reveal that the flame propagation of propanoic...

In this work, low temperature (low-T) oxidation of 1-heptene was investigated in a jet-stirred reactor (JSR) over the temperatures of 450–800 K, 770 Torr and equivalence ratios of 0.5–2.0. The intermediates were identified and quantified using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) and gas chromatography combin...

In order to better understand the low-temperature oxidation chemistry of alkenes, 1-butene and i-butene oxidation experiments triggered by dimethyl ether (DME) were conducted in a jet-stirred reactor at 790 Torr, 500–725 K and the equivalence ratio of 0.35. Low-temperature oxidation intermediates involved in alcoholic radical chemistry and allylic...

In this work, the oxidation of ethylcyclohexane was studied in a jet-stirred reactor at 780 Torr, 480-780 K and equivalence ratios of 0.5, 1.0 and 2.0. Synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) was used for the detection of oxidation products, including a series of reactive intermediates such as cycloalkylhydroper...

This work reports the investigation on pyrolysis and laminar flame propagation of sec-butylbenzene. The pyrolysis experiments were performed in a flow reactor using synchrotron vacuum ultraviolet photoionization mass spectrometry from 780 to 1166 K at 0.04 and 1 atm. The pyrolysis products were identified and their mole fraction profiles versus the...

Flow reactor pyrolysis of iso-pentanol was conducted at 30 and 760 torr using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Pyrolysis products, especially radicals and enols, were identified and quantified. Olefins and oxygenated products (mainly aldehyde and enol) were found to be the two major product families in t...

Ammonia is attracting more and more attentions due to its role as both a carbon-free fuel for gas turbines and an effective H2 carrier. Only a limit number of investigations on the laminar flame propagation and laminar burning velocity of ammonia have been performed on elevated pressures, which were focused on ammonia/air mixtures and suffered stro...

In this work, laminar flame speeds of CH4/CO/air mixtures were measured at the unburnt temperature of 353 K and pressures from 1 to 10 atm in a high-pressure constant-volume cylindrical combustion vessel. Effects of pressure, equivalence ratio and CO content in CH4/CO mixtures on laminar flame speeds were investigated. A kinetic model for CH4/CO co...

Previous studies on sampling probe effects in the premixed flat flame showed that the temperature in the preheat zone can be lowered down to low-temperature oxidation regime (e.g., 400–800 K). In order to investigate the contribution of the low-temperature chemistry in flame-sampling experiments, a stoichiometric laminar premixed flat flame of ethy...

In order to investigate the pressure-dependent effects of carbon chain growth from methyl radical, pyrolysis experiments of butane-2,3‑dione (also known as diacetyl) were conducted both in a flow reactor over 780–1520 K at low and atmospheric pressures and in a jet-stirred reactor (JSR) over 650–1130 K at 10 bar. Identification and quantification o...

The kinetics of propanal oxidation was studied in a jet-stirred reactor (JSR) at atmospheric pressure. The investigated temperature range is from 450 to 800 K at two different equivalence ratios (0.35 and 4.0). Thanks to the synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), critical intermediates were identified, includi...

Alkylated cycloalkanes are an important chemical class in conventional fuels. Methylcyclohexane (MCH) is a simple alkylated cycloalkane that is a potential candidate to represent the naphthenic content in transportation fuel surrogates. Detailed experimental speciation data for MCH gas-phase oxidation and pyrolysis is still lacking in the literatur...

Acetaldehyde oxidation was investigated in a jet-stirred reactor at temperatures from 460 to 900 K, equivalence ratios from 0.5 to 4.0 and pressures of 710–720 Torr. Reactive intermediates under low-temperature conditions, such as methylperoxy, methylhydroperoxide and ketohydroperoxide were detected using synchrotron vacuum ultraviolet photoionizat...

Kinetic investigations into small ethyl esters lay the foundation for a good understanding of combustion properties, particularly those brought about by the ethyl ester functional group, for biodiesels in forms of fatty acid ethyl esters. A systematical study was conducted in this work, aimed at better interpreting the high-temperature reaction sch...

In this work, oxidation chemistry of methanol was investigated in laminar premixed flames. Laminar burning velocities of methanol/air mixtures at 423 K and 1–10 atm were measured in a spherical combustion vessel, extending the range of equivalence ratio up to 2.1. A stoichiometric premixed flat flame of methanol/O2/Ar at 0.04 atm was also conducted...

Diethyl ether (DEE) and its isomer n-butanol are both considered as promising fuel additives or neat biofuels. While some effects of their addition to hydrocarbon fuels under engine conditions have been reported, fundamental studies that aim at understanding the joint reaction pathways of such fuel mixtures remain quite scarce. Here, we have chosen...

In this work, laminar coflow diffusion flames fueled with methane/iso-butanol were investigated with synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Mole fractions of C2–C16 flame species, including small hydrocarbons, oxygenates and aromatics were measured along the flame centerline. The enhancement in the formation o...

Recent experiments on low-temperature oxidation of dimethyl ether (DME) at atmospheric pressure reveal much lower fuel conversion than the predictions of all published models. Consistent with previous measurements, the present work on DME oxidation in a laminar flow reactor between 400 and 1160 K at atmospheric pressure also confirmed this behavior...

Methane is probably the most frequently studied hydrocarbon fuel. Both its oxidation mechanism and its pyrolysis to higher-mass products have received considerable attention. In order to have a glance into the combustion chemistry of methane, a detailed kinetic model was developed to reproduce the fuel decomposition and the formation of benzene and...

In order to better understand the high temperature chemistry of large alcohol containing 5 carbon atoms, the pyrolysis of 2-methyl-1-butanol from 750 to 1400 K was investigated in a flow reactor at the pressures of 30 and 760 Torr. About 25 pyrolysis species including some radicals and reactive intermediates were identified and quantified using syn...