Stephen Dooley

Stephen Dooley
Trinity College Dublin | TCD · School of Physics

PhD

About

87
Publications
19,125
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3,487
Citations
Citations since 2017
25 Research Items
2129 Citations
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20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400

Publications

Publications (87)
Article
A novel compute intensification methodology to the construction of low-dimensional, high-fidelity “compact” kinetic models for NOX formation is designed and demonstrated. The method adapts the data intensive Machine Learned Optimisation of Chemical Kinetics (MLOCK) algorithm for compact model generation by the use of a combinatorial Latin Square me...
Preprint
Full-text available
A novel compute intensification methodology to the construction of low-dimensional, high-fidelity "compact" kinetic models for NOX formation is designed and demonstrated. The method adapts the data intensive Machine Learned Optimization of Chemical Kinetics (MLOCK) algorithm for compact model generation by the use of a Latin Square method for virtu...
Preprint
Full-text available
Chemical kinetic models are an essential component in the development and optimisation of combustion devices through their coupling to multi-dimensional simulations such as computational fluid dynamics (CFD). Low-dimensional kinetic models which retain good fidelity to the reality are needed, the production of which requires considerable human-time...
Article
Full-text available
Correction for ‘Ethanolic gasoline, a lignocellulosic advanced biofuel’ by Mícheál Séamus Howard et al. , Sustainable Energy Fuels , 2019, 3 , 409–421, https://doi.org/10.1039/C8SE00378E.
Conference Paper
Accurate low dimension chemical kinetic models for methane are an essential component in the design of efficient gas turbine combustors. Kinetic models coupled to computational fluid dynamics (CFD) and chemical reactor networks (CRN) provide quick and efficient ways to test the effect of operating conditions, fuel composition and combustor design c...
Preprint
Full-text available
Accurate low dimension chemical kinetic models for methane are an essential component in the design of efficient gas turbine combustors. Kinetic models coupled to computational fluid dynamics (CFD) provide quick and efficient ways to test the effect of operating conditions, fuel composition and combustor design compared to physical experiments. How...
Chapter
The use of ammonia in fuelling applications has been recognized as a method to support energy transition towards a zero-carbon economy. Ammonia, a chemical that contains large quantities of hydrogen, can be employed in applications that go from furnaces to aerospace engines. However, handling, power outputs, emissions and maintenance procedures sti...
Article
Full-text available
An innovative and informed methodology for the rational design and testing of anti-knock additives is reported. Interaction of the additives with OH● and HO2● is identified as the key reaction pathway by which non-metallic anti-knock additives are proposed to operate. Based on this mechanism, a set of generic design criteria for anti-knock additive...
Article
A detailed experimental methodology is outlined which allows for the measurement of quantitative ¹H and ¹³C Nuclear Magnetic Resonance (NMR) spectra of liquid hydrocarbons. Optimal experimental conditions are identified that allow for the collection of entirely quantitative ¹H and ¹³C NMR spectra, the most significant among these are shown to be th...
Article
Full-text available
A detailed systematic theoretical study of the mechanism of the homogeneous Brønsted-acid catalysis of D-glucose in aqueous solution phase ("acid hydrolysis") is reported. G4MP2 with the SMD solvation model at...
Chapter
This chapter is based on our experience in characterizing and formulating surrogate compositions to emulate prevaporized and multiphase global combustion behaviors of jet fuels. It is not our purpose here to provide an exhaustive review of the literature on this subject. Our purpose is to describe a logical thought process toward the development of...
Article
Full-text available
The chemical functional group approach is investigated to verify the fundamental applicability of low-dimensional descriptors in the prediction of global combustion behavior, as described by homogeneous reflected shock ignition delay times. Three key chemical functional groups, CH2, CH3 and benzyl-type, are used to represent n-alkyl, iso-alkyl, and...
Article
The enthalpies of formation are a critical fundamental parameter for the combustion modelling. The enthalpies of formation of the species of the high temperature combustion mechanism of the lignocellulosic biofuel, ethyl levulinate are determined by a number of methodologies. Chemical group additivity, atomization and isodesmic worked reactions are...
Article
This study presents a novel approach for the chemical representation of lignin for modelling the reaction kinetics of lignin in lignocellulosic biomass. This methodology relies on the definition of dimeric pseudo-components containing phenolic functionalities, i.e., p-hydroxyphenyl, guaiacyl and syringyl groups, as measured in real biomass and nati...
Article
Full-text available
Ethyl levulinate (Ethyl 4-oxopentanoate) is a liquid molecule at ambient temperature, comprising of ketone and ethyl ester functionalities and is one of the prominent liquid fuel candidates that may be easily obtained from lignocellulosic biomass. The combustion kinetics of ethyl levulinate have been investigated. Shock tube and rapid compression m...
Article
Full-text available
Surrogate fuel formulation has drawn significant interest due to its relevance towards understanding combustion properties of complex fuel mixtures. In this work, we present a novel approach for surrogate fuel formulation by matching target fuel functional groups, while minimizing the number of surrogate species. Five key functional groups; paraffi...
Article
Full-text available
Autoignition propensities of ternary mixtures of bio-derived ethyl levulinate/diethyl ether/ethanol are characterised to identify diesel and gasoline suitable mixtures.
Article
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To date, a number of mechanical, electrical, thermal, and chemical approaches have been developed for storing electrical energy for utility-scale services. The only sufficiently flexible mechanism allowing large quantities of energy to be stored over long time periods is chemical energy storage in the form of carbon or hydrogen. One chemical consid...
Article
The global chemical character of complex chemical fuel mixtures is explicitly determined by evaluating the abundances of chemical functional groups present within them rather than by applying a traditional interpretation based upon molecular species composition. Statistical analyses of the relationships among each chemical functional group and spec...
Article
This study describes a lumped kinetic modelling architecture with which to simulate and predict the pyrolysis reaction kinetics of hemicellulose biopolymers. A key feature of the model is the replication of essential compositional features of biomass hemicelluloses into the chemical reaction pathways of the model. More specifically, five new model...
Presentation
Full-text available
Improved process development and design of technologies such as pyrolysis and gasification of lignocellulosic biomass can be aided greatly by advanced comprehension of their chemistry and thermal reactivity. Hemicellulose and lignin have significant chemical variations within plant species and after biomass treatment, which are outside of the capab...
Conference Paper
Full-text available
Improved process development and design of technologies such as pyrolysis and gasification of lignocellulosic biomass can be aided greatly by advanced comprehension of their chemistry and thermal reactivity. Hemicellulose and lignin have significant chemical variations within plant species and after biomass treatment, which are outside of the capab...
Article
Full-text available
Energy storage is one of the major challenges facing the world towards its challenging 2050 climate-change targets. A potential enabler of a low-carbon economy is the energy vector hydrogen. However, issues associated with hydrogen have led to consider other molecules such as ammonia as a potential candidate for chemical storage. Apart from its rel...
Article
An improved model for the prediction of ignition quality of hydrocarbon fuels has been developed using 1H Nuclear Magnetic Resonance (NMR) spectroscopy and Multiple Linear Regression (MLR) modeling. Cetane number (CN) and derived cetane number (DCN) of seventy-one pure hydrocarbons and fifty-four hydrocarbon blends were utilized as a dataset to stu...
Article
As an alternative fuel and hydrogen carrier, ammonia is believed to have good potential for future power generation. To explore the feasibility of co-firing ammonia with methane, studies involving robust numerical analyses with detailed chemistry are required to progress towards industrial implementation. Therefore, the objective of this study is t...
Conference Paper
Full-text available
Sustainable feedstocks such as lignocellulosic biomass and agricultural wastes can be integrated into platform chemical production systems via pyrolysis and gasification. These processes face challenges related to the use of low-quality biomass, with low energy densities and different chemical reactivities when compared to conventional fuels. Sophi...
Conference Paper
Full-text available
Tars are produced as vapours during gasification and their presence in the product gas is one of the main technological barriers for development of gasification and related applications. For most applications the product gas needs to be cleaned of impurities such as tars. Reliable tar measurement methods are therefore of particular importance for t...
Conference Paper
Full-text available
Thermal conversion technologies, such as pyrolysis and gasification, are efficient processes that can integrate sustainable feedstocks such as biomass into renewable energy and platform chemical production systems, through other vectors such as bio-methane, liquid biofuels, fertilisers, and heat and power. These technologies can also use a wide ran...
Article
Full-text available
Thermochemical gasification offers an attractive solution for conversion of low grade biomass and wastes. However practical experiences of the gasification processes reveal that the formation of tar is troublesome to continuous operation. Therefore tar measurement protocols and tar reduction systems are priorities in the development of effective bi...
Article
Global combustion characteristics of iso-dodecane (2,2,4,6,6-pentamethylheptane, iC12) are measured and compared to those of iso-octane (2,2,4-trimethylpentane, iC8), iso-cetane (2,2,4,4,6,8,8-heptamethylnonane, iC16) and a 50/50 molar blend of iC8/iC16. The fuels are experimentally characterized by measuring combustion property targets (derived ce...
Article
Torrefaction is suggested to be an effective method to reduce the cost of biomass provision and improve the fuel properties. In this study, both raw and torrefied Miscanthus × giganteus (M×G) were gasified in an externally heated air-blown bubbling fluidized bed (BFB) gasifier using olivine as the bed material. The effects of equivalence ratio (ER)...
Article
Full-text available
This study uses numerical modeling to provide a mechanistic discussion of the synthesis of the advanced biofuel candidates, ethyl levulinate and 5-ethoxymethylfurfural, from α/β-d-fructopyranose (d-fructose) in a condensed phase homogeneous ethanol system at 351 K catalyzed by hydrogen cations. A mechanistic comprehension is pursued by detailed mea...
Article
Full-text available
Alternatives to traditional petroleum derived transportation fuels, particularly alcohols, have been investigated increasingly over the last 5 years. Isopropanol has received little attention despite bridging the gap between smaller alcohols (methanol and ethanol) and the next generation alcohols (butyl alcohols) to be used in transportation fuels....
Article
This study challenges the assumption often postulated in the literature regarding the stoichiometric formation of formic and levulinic acids from the acid hydrolysis of hexose carbohydrates. Acid hydrolysis experiments are conducted with 2.5 wt% H2SO4 in aqueous media with a series of reactants relevant to the hydrolysis systems of hexoses; D-fruct...
Article
Typically, real jet fuels are composed primarily of normal-, iso-, and cycloalkanes, along with significant fractions of alkyl aromatics. This study elucidates fundamentally the influence of the cycloalkane functionality on the fully prevaporized global combustion kinetic behavior of a fuel mixture composed of normal- and isoparaffin and alkyl arom...
Article
Full-text available
Surrogate fuel mixtures were formulated using hydrocarbon fluids to investigate the ability of different surrogate formulations to match the sooting characteristics of a specific jet fuel (JP-8 POSF 5699). Three different surrogates were studied: two binary mixtures and a ternary mixture. The first surrogate matched the threshold soot index and ave...
Patent
Full-text available
An apparatus and method for determining the average molecular weight of a complex mixture from a plurality of test samples of the complex mixture are disclosed. The method includes a) providing a chamber having two ?xed conditions and one variable condition selected from three state variables of temperature, pressure and volume; b) intro ducing a t...
Conference Paper
Full-text available
Global combustion characteristics of one conventional jet fuel (JP-8) and four nonpetroleum alternative jet fuels (Shell Synthetic Paraffinic Kerosene (SPK), Sasol Iso- Paraffinic Kerosene (IPK), Hydrotreated Renewable Jet (HRJ Camelina and HRJ Tallow)) are experimentally examined. The ranking of the fully pre-vaporized global combustion characteri...
Conference Paper
Full-text available
The surrogate fuel concept to replicate the detailed gas phase combustion behaviors of conventional and alternative jet aviation fuels in numerical combustion models is extended and tested in specific examples of synthetic jet fuels derived from coal and natural gas, and also to the pressure and equivalence ratio dependences of the combustion respo...
Article
Full-text available
We have demonstrated previously that a (surrogate fuel) mixture of known pure hydrocarbon species that closely matches four combustion property targets (the derived cetane number (DCN), the hydrogen to carbon molar ratio (H/C), the threshold soot index (TSI), and the average molecular weight) of a specific jet fuel, displays fully prevaporized glob...
Article
The global combustion characteristics of 2,6,10-trimethyl dodecane (trimethyl dodecane), a synthetic fuel candidate species, have been experimentally investigated by measuring extinction limits for strained laminar diffusion flames at 1 atm and reflected shock ignition delays at 20 atm. The Derived Cetane Number (DCN) of trimethyl dodecane, (59.1)...
Article
Gasification of Miscanthus x giganteus (MxG) was conducted in an air-blown bubbling fluidized bed (BFB) gasifier using magnesite as bed material and a moderate rate of biomass throughput (246.82–155.77 kg/m2h). The effect of equivalence ratio (ER) (0.234–0.372) and bed temperature (645–726 °C) on the performance of gasification was investigated. Th...
Article
The diffusive extinction limits of a series of methyl ester flames, from methyl formate to methyl decanoate, have been measured in the counterflow configuration. Kinetic and transport effects are decoupled by use of the transport-weighted enthalpy term and reveal that the smaller methyl esters (C2 to C4) exhibit unique behavior while methyl esters...
Article
Fundamentally, the dehydration reaction of tertiary-butanol is frequently used as an internal standard for relative rate studies of other decomposition reactions. We report here a study using radical trappers to isolate this path in tertiary-butanol pyrolysis experiments conducted in the Princeton Variable Pressure Flow Reactor. A novel technique t...
Article
A surrogate fuel is formulated in an a priori manner through a combustion property matching technique to emulate the gas phase chemical kinetic combustion phenomena of S-8 POSF 4734, an alternative aviation fuel derived from natural gas via the Fischer–Tropsch process. A fundamental concept is described which identifies n-dodecane and iso-octane as...
Article
Trimethylbenzenes have been suggested as useful components for the formulation of simple hydrocarbon mixtures that quantitatively emulate the gas-phase combustion behaviour of real liquid transportation fuels as model or surrogate fuels. To facilitate this application, various combustion properties of 1,3,5-trimethylbenzene (mesitylene) have been c...
Conference Paper
Full-text available
Reduced chemical kinetic models to predict the combustion characteristics of jet propulsion fuels are produced and tested. The parent detailed kinetic model has been developed on the basis of a surrogate fuel formulation methodology that utilizes combustion property targets measured for a particular real fuel to formulate a chemical mixture of nalk...
Article
The laminar flame speeds and premixed extinction limits of n-propylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, and toluene have been studied experimentally to assess the effects of different alkyl substitutions to the benzene ring on flame propagation and extinction. The experiments were carried out in a twin-flame counterflow setup un...
Article
A detailed kinetic model for the oxidation of the biodiesel surrogate, methyl decanoate, has been developed and tested against a broad range of experimental data. The methyl decanoate model consists of both low and high temperature oxidation chemistry. It has been constructed strictly through the extension of the chemical kinetic and thermochemical...
Article
The extinction limits of methyl butanoate, n-heptane, and methyl butanoate/n-heptane diffusion flames have been measured as a function of fuel mole fraction with nitrogen dilution in counterflow with air. On a mole fraction basis, methyl butanoate diffusion flames are observed to have a much lower extinction strain rate than n-heptane diffusion fla...
Article
A methodology for the formulation of surrogate fuels for the emulation of real fuel gas phase combustion kinetic phenomena pertinent to gas turbine combustion is described and tested. A mixture of n-dodecane/iso-octane/1,3,5-trimethylbenzene/n-propylbenzene is formulated in a predictive manner to exhibit the same gas phase combustion phenomena of a...
Article
The combustion chemistry of tertiary-butanol is studied experimentally in a high pressure flow reactor and in counterflow diffusion flames. Princeton Variable Pressure Flow Reactor results show that t-butanol does not exhibit low temperature chemistry, and thus has no negative temperature coefficient behavior under the studied conditions. The onset...
Article
The extinction limits of diffusion flames have been measured experimentally and computed numerically for fuels of three different molecular structures pertinent to surrogate fuel formulation: n-alkanes, alkyl benzenes, and iso-octane. The focus of this study is to isolate the thermal and mass transport effects from chemical kinetic contributions to...
Article
The oxidation of n-decane/oxygen/nitrogen is studied at stoichiometric conditions of 1000ppm fuel in the Princeton variable pressure flow reactor at temperatures of 520–830K and pressures of 8 and 12.5atm. The overall oxidative reactivity of n-decane is observed in detail to show low temperature, negative temperature coefficient (NTC) and hot ignit...
Conference Paper
Full-text available
Surrogate fuel mixtures were formulated using narrow-cut solvent mixtures to match the sooting propensity of a specific jet fuel sample (JP-8 POSF 5699). To formulate the surrogate mixtures, derived cetane number (DCN), threshold soot index (TSI), hydrogen-to-carbon molar ratio, and average molecular weight were used as the combustion property targ...
Conference Paper
Full-text available
Various combustion phenomena of S-8 POSF 4734, an alternative aviation fuel derived from natural gas via the Fischer-Tropsch process are measured including: 1) The oxidative reactivity of stoichiometric mixtures of S-8 POSF 4734 in O2/N2 at 12.5 atm and 500-1050 K, for a residence time of 1.8 s at a fixed carbon content of 0.3% using a variable pre...
Conference Paper
Full-text available
A novel methodology for studying autoignition of pre-vaporized hydrocarbons at non-dilute conditions in a high-pressure flow reactor has been developed. In this methodology, the minimum equivalence ratio required for ignition at specific conditions of pressure, temperature and residence time was found. Iso-octane was vaporized with a hydrogen/oxyge...
Conference Paper
Aromatics are major components of real and surrogate jet fuels and can produce rich stabilized radicals to inhibit the mixture reativity. The laminar flame speeds of the two aromatic C9H12 isomers, n-Propylbenzene and 1,3,5-TriMethyl benzene are measured at atmospheric pressure. A kinetic model have been developed, and tested against these new expe...
Conference Paper
A numerical model for the simulation of the low temperature ignition with the flow, temperature, and species turbulent fluctuations in a high pressure counterflow diffusion flame is developed. In order to model the turbulent fluctuations, both time and space dependent perturbations are introduced. There are two types of perturbations studied in thi...
Article
Full-text available
Kinetic effects of aromatic molecular structures for jet fuel surrogates on the extinction of diffusion flames have been investigated experimentally and numerically in the counterflow configuration for toluene, n-propylbenzene, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene. Quantitative measurement of OH concentration for aromatic fuels was co...
Article
Full-text available
A detailed chemical kinetic model containing 329 species and 1888 reversible reactions has been developed to describe the oxidation of toluene and its intermediates. The model has been validated over a wide range of experimental conditions, including flow reactor, shock tube, jet-stirred reactor, and flame studies, and for toluene, phenol, benzene,...
Article
The oxidation of methyl formate (CH3OCHO), the simplest methyl ester, is studied in a series of burner-stabilized laminar flames at pressures of 22–30 Torr and equivalence ratios (Φ) from 1.0 to 1.8 for flame conditions of 25–35% fuel. Flame structures are determined by quantitative measurements of species mole fractions with flame-sampling molecul...
Conference Paper
Full-text available
The autoignition of n-propylbenzene, an aromatic compound found in crude-derived transportation fuels, has been investigated in a combined shock tube and kinetic modeling study. Ignition delay times were measured behind reflected shock waves for n-propylbenzene/air mixtures at equivalence ratios of 0.5, 1.0, and 1.5, for pressures around 11 and 21...
Conference Paper
Full-text available
The combustion chemistry of tertiary-butanol was studied experimentally in a Variable Pressure Flow Reactor and in counterflow diffusion flames. It was found that t-butanol does not exhibit low temperature chemistry, and thus has no negative temperature coefficient behavior. The onset of gas phase chemistry at high pressure occurs at ∼780 K. In the...
Article
Full-text available
Synthetic Fischer-Tropsch (F-T) fuels derived from biomass syngas are renewable fuels that can replace conventional petroleum fuels in jet engine and diesel engine applications. F-T fuels typically contain a high concentration of lightly methylated iso-alkanes, whereas petroleum derived jet and diesel fuels contain large fractions of n-alkanes, cyc...
Article
Full-text available
Alternatives to petroleum derived transportation fuels, particularly C4 alcohols (butanols), have been investigated increasingly over the last three years. One butanol isomer, teritary-butanol (derived from petroleum), is already used commercially as a gasoline octane number enhancer. Studies of tertiary-butanol (t-butanol) combustion suggest that...
Article
Full-text available
Multi dimensional Large Eddy Simulations (LES) of the fluid dynamics in the Princeton Variable Pressure Flow Reactor (VPFR) were conducted in order to study the effect of initial reactant/carrier mixing and wall catalytic reactions. The mixer/diffuser geometry and downstream cylindrical test sections were modeled with surface and gas phase reaction...