A Comprehensive Modeling Study of iso-Octane Oxidation

TLDR: In this paper, a detailed chemical kinetic mechanism has been developed and used to study the oxidation of iso-octane in a jet-stirred reactor, flow reactors, shock tubes and in a motored engine.

About: This article is published in Combustion and Flame.The article was published on 2002-05-01 and is currently open access. It has received 1279 citations till now. The article focuses on the topics: Combustion & Ignition system.

Figures

Fig. 19. Sensitivity coefficients in a JSR [10]. 0.1% iso-octane oxidation at 10 atm, 1.0, 1 s.

Fig. 5. 0.09% iso-octane oxidation in a flow reactor, 0.05, P 6 atm, T 945 K. Experimental results (points) [23] versus model predictions. Dashed line corresponds to open symbols.

Fig. 6. 0.09% iso-octane oxidation in a flow reactor, 0.05, P 6 atm, T 945 K. Experimental results (points) [23] versus model predictions for selected oxygenates. Dashed line corresponds to open symbols.

Fig. 16. F CO and E O2 formed in a CFR engine (@ 500 RPM) for iso-octane fuel, 1.0. Experimental results (points) [17] vs model predictions. Dashed line corresponds to open symbols.

Fig. 17. Sensitivity coefficients in a shock tube [7]. Stoichiometric fuel in air, P5 40 bar.

Fig. 4. 0.14% iso-octane oxidation at 12.5 atm, 1.0, 1.8 s in a PFR F O2, E CO, H2O, { Temperature rise. Experimental results (points) [22] versus model predictions. Dashed line corresponds to open symbols.

Frequently asked questions

Q1. What are the contributions in "A comprehensive modeling study of iso-octane oxidation" ?

A detailed chemical kinetic mechanism has been developed and used to study the oxidation of iso-octane in a jet-stirred reactor, flow reactors, shock tubes and in a motored engine. This range of physical conditions, together with the measurements of ignition delay time and concentrations, provide a broad-ranging test of the chemical kinetic mechanism. This mechanism was based on their previous modeling of alkane combustion and, in particular, on their study of the oxidation of n-heptane. In addition, a sensitivity analysis was performed for each of the combustion environments in an attempt to identify the most important reactions under the relevant conditions of study. 

Q2. Why have some of the expressions in their n-heptane paper been changed?

Because of recent changes in thermodynamic data, and in an attempt to improve their treatment of some of their estimated rate expressions, some of those expressions published in their n-heptane paper have been changed. 

Q3. What are the major classes of elementary reactions considered in the present mechanism?

The major classes of elementary reactions considered in the present mechanism include the following:1. Unimolecular fuel decomposition 2. H atom abstraction from the fuel 3. 

Q4. What is the reaction type that increases the reactivity of the system?

Another reaction type that increases the overall reactivity of the system is the addition of alkyl radicals to molecular oxygen, reaction type 10. 

Q5. What is the rate constant for the addition of an alkyl radical?

The rate constant for the addition of an alkyl radical has a lower A-factor and higher activation energy than for the addition of a H atom. 

Q6. How does the model predict the CCR for iso-octane?

even though the CCR for iso-octane is well reproduced by the model, it is apparent that, because the concentration of carbon monoxide formed is a direct measure of reactivity, at all compression ratios the model predicts more reactivity than is observed experimentally. 

Q7. What is the rate of addition of alkyl radicals to O2?

For 1° and 3° alkyl radical addition the authors use the Lenhardt et al. [61] measured rates of addition for n-butyl and tert-butyl radicals to O2 which are 4.52 10 12 and 1.41 1013 cm3 mol 1 s 1, respectively. 

Q8. What is the sensitivity coefficient of the reaction of hydroperoxyl radicals?

the self reaction of hydroperoxyl radicals shows a positive sensitivity coefficient as it consumes hydroperoxyl radicals which could otherwise abstract a hydrogen atom from a stable species to ultimately produce two hydroxyl radicals from one hydroperoxyl radical, as depicted in the equation array above.