Abstract

Biofuels are considered as potentially attractive alternative fuels that can reduce greenhouse gas and pol- lutant emissions. iso-Pentanol is one of several next-generation biofuels that can be used as an alterna- tive fuel in combustion engines. In the present study, new experimental data for iso-pentanol in shock tube, rapid compression machine, jet stirred reactor, and counterflow diffusion flame are presented. Shock tube ignition delay times were measured for iso-pentanol/air mixtures at three equivalence ratios, temperatures ranging from 819 to 1252 K, and at nominal pressures near 40 and 60 bar. Jet stirred reactor experiments are reported at 5 atm and five equivalence ratios. Rapid compression machine ignition delay data was obtained near 40 bar, for three equivalence ratios, and temperatures below 800 K. Laminar flame speed data and non-premixed extinction strain rates were obtained using the counterflow config- uration. A detailed chemical kinetic model for iso-pentanol oxidation was developed including high- and low-temperature chemistry for a better understanding of the combustion characteristics of higher alco- hols. First, bond dissociation energies were calculated using ab initio methods, and the proposed rate con- stants were based on a previously presented model for butanol isomers and n-pentanol. The model was validated against new and existing experimental data at pressures of 1–60 atm, temperatures of 650– 1500 K, equivalence ratios of 0.25–4.0, and covering both premixed and non-premixed environments. The method of direct relation graph (DRG) with expert knowledge (DRGX) was employed to eliminate unimportant species and reactions in the detailed mechanism, and the resulting skeletal mechanism was used to predict non-premixed flames. In addition, reaction path and temperature A-factor sensitivity analyses were conducted for identifying key reactions at various combustion conditions. ​

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Reference

S.M. Sarathy, S. Park, W. Wang, P.S. Veloo, A.C. Davis, C. Togbe, B. Weber, C.K. Westbrook, O. Park, G. Dayma, Z. Luo, M.A. Oehlschlaeger, F.N. Egolfopoulos, T. Lu, W.J. Pitz, C.-J. Sung, P. Dagaut, A comprehensive experimental and modeling study of iso-pentanol combustion, Combustion and Flame, 2013, 2712–2728.

2,5-dimethylhexane - A comprehensive combustion chemistry study of 2,5-dimethylhexane

Abstract

Iso-paraffinic molecular structures larger than seven carbon atoms in chain length are commonly found in conventional petroleum, Fischer-Tropsch (FT), and other alternative hydrocarbon fuels, but little research has been done on their combustion behavior. Recent studies have focused on either mono-methylated alkanes and/or highly branched compounds (e.g., 2,2,4-trimethylpentane). In order to better understand the combustion characteristics of real fuels, this study presents new experimental data for the oxidation of 2,5-dimethylhexane under a wide variety of temperature, pressure, and equivalence ratio conditions. This new dataset includes jet stirred reactor speciation, shock tube ignition delay, and rapid compression machine ignition delay, which builds upon recently published data for counterflow flame ignition, extinction, and speciation profiles. The low and high temperature oxidation of 2,5-dimethylhexane has been simulated with a comprehensive chemical kinetic model developed using established reaction rate rules. The agreement between the model and data is presented, along with suggestions for improving model predictions. The oxidation behavior of 2,5-dimethylhexane is compared with oxidation of other octane isomers to confirm the effects of branching on low and intermediate temperature fuel reactivity. The model is used to elucidate the structural features and reaction pathways responsible for inhibiting the reactivity of 2,5-dimethylhexane.

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C1 to C5 Alcohols - Alcohol Combustion Chemistry

Abstract

Alternative transportation fuels, preferably from renewable sources, include alcohols with up to five or even more carbon atoms. They are considered promising because they can be derived from biological matter via established and new processes. In addition, many of their physical-chemical properties are compatible with the requirements of modern engines, which make them attractive either as replacements for fossil fuels or as fuel additives. Indeed, alcohol fuels have been used since the early years of automobile production, particularly in Brazil, where ethanol has a long history of use as an automobile fuel. Recently, increasing attention has been paid to the use of non-petroleum-based fuels made from biological sources, including alcohols (predominantly ethanol), as important liquid biofuels. Today, the ethanol fuel that is offered in the market is mainly made from sugar cane or corn. Its production as a first-generation biofuel, especially in North America, has been associated with publicly discussed drawbacks, such as reduction in the food supply, need for fertilization, extensive water usage, and other ecological concerns. More environmentally friendly processes are being considered to produce alcohols from inedible plants or plant parts on wasteland. While biofuel production and its use (especially ethanol and biodiesel) in internal combustion engines have been the focus of several recent reviews, a dedicated
overview and summary of research on alcohol combustion chemistry is still lacking. Besides ethanol, many linear and branched members of the alcohol family, from methanol to hexanols, have been studied, with a particular emphasis on butanols. These fuels and their combustion properties, including their ignition, flame propagation, and extinction characteristics, their pyrolysis and oxidation reactions, and their potential to produce pollutant emissions have been intensively investigated in dedicated experiments on the laboratory and the engine scale, also emphasizing advanced engine concepts. Research results addressing combustion reaction mechanisms have been reported based on results from pyrolysis and oxidation reactors, shock tubes, rapid compression machines, and research engines. This work is complemented by the development of detailed combustion models with the support of chemical kinetics and quantum chemistry. This paper seeks to provide an introduction to and overview of recent results on alcohol combustion by highlighting pertinent aspects of this rich and rapidly increasing body of information. As such, this paper provides an initial source of references and guidance regarding the present status of combustion experiments on alcohols and models of alcohol combustion.

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A comprehensive experimental and modeling study of 2-methylbutanol combustion

Abstract

2-Methylbutanol (2-methyl-1-butanol) is one of several next-generation biofuels that can be used as an alternative fuel or blending component for combustion engines. This paper presents new experimental data for 2-methylbutanol, including ignition delay times in a high-pressure shock tube and premixed laminar flame speeds in a constant volume combustion vessel. Shock tube ignition delay times were measured for 2-methylbutanol/air mixtures at three equivalence ratios, temperatures ranging from 750 to 1250 K, and at nominal pressures near 20 and 40 bar. Laminar flame speed data were obtained using the spherically propagating premixed flame configuration at pressures of 1, 2, and 5 bar. A detailed chemical kinetic model for 2-methylbutanol oxidation was developed including high- and low-temperature chemistry based on previous modeling studies on butanol and pentanol isomers. The proposed model was tested against new and existing experimental data at pressures of 1–40 atm, temperatures of 740–1636 K, equivalence ratios of 0.25–2.0. Reaction path and sensitivity analyses were conducted for identifying key reactions at various combustion conditions, and to obtain better understanding of the combustion characteristics of larger alcohols

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