Shock‐tube spectroscopic water measurements and detailed kinetics modeling of 1‐pentene and 3‐methyl‐1‐butene

Abstract

To understand the effects of the chemical structure of two C 5 alkene isomers on their combustion properties, and to highlight the major chemical reactions occurring during their high-temperature oxidation, water time histories were measured behind reflected shock waves for the oxidation of 1-pentene (C 5 H 10-1) and 3-methyl-1-butene (3M1B) in 99.5% Ar. The experiments were carried out at three different equivalence ratios (φ = 0.5, 1.0, and 2.0) at pressures and temperatures ranging from 1.29 to 1.47 atm and 1 331 to 1 877 K, respectively. The H 2 O quantification extends the database for 1-pentene and provides new insights for 3M1B. These unique results were used to validate and to develop a new detailed kinetics model. Numerical predictions are presented, and the new model was able to capture the results with suitable accuracy, with 3M1B being notably more reactive than C 5 H 10-1. Sensitivity and rate-of-production analyses were performed to help explain the results. Under the present conditions, the reactivity is rapidly initiated by molecular dissociation of a fraction of the pentene isomers. The initiation phase then induces H-atom abstraction by active radicals (H, OH, O, HO 2 , and CH 3) to first produce alkenyl C 5 H 9 radicals (or an alkyl radical and an alkenyl radical by breaking a C─C bond) and subsequent, smaller fragments. The difference in terms of reactivity between the isomers is essentially due to the fact that 3M1B has one particularly weak tertiary allylic C─H bond, which allows for fast H-atom abstraction compared with 1-pentene.

Laminar Flame Speed, Ignition Delay Time, and CO Laser Absorption Measurements of a Gasoline-like Blend of Pentene Isomers

“…With regard to the laminar flame speed results, comparisons with multiple pentenes were performed in Cheng et al and Farrell et al with three (1-C 5 H 10 , 2-C 5 H 10 , and 2M2B) and four (1-C 5 H 10 , 2-C 5 H 10 , 2M1B, and 2M2B) isomers, respectively. Finally, a good range of pressures and temperatures can be found for speciation studies, and time-history profiles for both CO and H 2 O were recorded for all five pentene isomers at the exact same initial condition for the first time in a series of pentene isomers articles by the present authors. ,,, Grégoire et al developed a validated chemical kinetics mechanism encompassing all pentene isomers: some reactions have been previously modified, in particular the branched allylic C 5 H 9 species with OH and HO 2 among others, following ab initio theoretical analysis by Goldsmith et al to determine the reaction rates on the reaction of C 3 H 5 with HO 2 . For convenience, a list of these reactions is available in Supporting Information S1.…”

“…It ensures that 2-C 5 H 10 was fully decomposed, so that both fast isomers release potential key species, while 2M2B and 2M1B are consumed by 90% and 60%, respectively. Lastly, the detailed chemistry of 2M2B has been discussed in great detail in Alturaifi et al, 26 and the difference between 1-C 5 H 10 and 3M1B, the linear and branched pentenes with the C�C double bond located at the 1−2 bond site, was investigated in Gregoire et al 19 : these previous studies support and validate the behavior of Mix B and Mix C via the reactions (R4−R5) and (R8, in reverse), respectively.…”

“…Over the past few years, a large number of studies were devoted to olefins for gasoline fuel applications. More particularly, the combustion chemistry of the pentene isomers, 1-pentene (1-C 5 H 10 ), − 2-pentene (2-C 5 H 10 ), − ,− 2-methyl-1-butene (2M1B), ,− 2-methyl-2-butene (2M2B), ,,,,, and 3-methyl-1-butene (3M1B), ,, was investigated. Graphical representations of the experimental database from the literature are shown in Figure for (a) ignition delay times in shock tubes (ST) and rapid compression machines (RCM); (b) laminar flame speeds in combustion vessels; (c) speciation in flow reactors, jet-stirred reactors (JSR), and low-pressure burners (LPB); and, (d) single-pulse ST, and time-history profiles in ST. All the results are reported as functions of temperature and pressure, describing the range of experimental conditions.…”

“…Finally, a good range of pressures and temperatures can be found for speciation studies, and timehistory profiles for both CO and H 2 O were recorded for all five pentene isomers at the exact same initial condition for the first time in a series of pentene isomers articles by the present authors. 19,24,26,27 Greǵoire et al developed a validated chemical kinetics mechanism encompassing all pentene isomers: some reactions have been previously modified, in particular the branched allylic C 5 H 9 species with OH and HO 2 among others, following ab initio theoretical analysis by Goldsmith et al 28 to determine the reaction rates on the reaction of C 3 H 5 with HO 2 .…”

“…To the best of the authors’ knowledge, the combustion of blends of pentene isomers in gasoline-like proportions (and arguably in any multicomponent mixture) has never been investigated in the literature. This lack of studies where pentene isomers are combined could be problematic to fully understand their combustion chemistry since different pentene isomers share allylic radicals at all levels during the oxidation process, , inducing the possibility of having several pentene isomers after recombination of these radicals. For example, as per the model, the reaction between 2M2B + H can give several products such as C 2 H 4 + IC 3 H 7 , C 2 H 5 + C 3 H 6 , and CH 3 + IC 4 H 8 ; and the reverse of these reactions can give either 2M2B, 2M1B, or 3M1B.…”