A detailed chemical kinetic modeling and experimental investigation of the low‐ and high‐temperature chemistry of n‐butylcyclohexane

Abstract

Chemical kinetic models of gasoline, jet, and diesel fuels and their mixtures with bioderived fuels are needed to assess fuel property effects on efficiency, emissions, and other performance metrics in internal combustion and gas turbine engines. As these real fuels have too many fuel components to be included in a chemical kinetic model, surrogate fuels containing fewer components are used to represent them. These surrogate fuels mimic the chemical classes or molecular structures contained in the real fuel. One of the important chemical classes in gasoline, jet, and diesel fuels comprises cyclohexanes. Cyclohexanes comprise about 30% or more by weight in diesel fuel. Also, Mueller et al (Energy Fuels. 2012;26(6):3284‐3303) proposed n‐butylcyclohexane (nBCH) as a component in a nine‐component surrogate palette to represent the ignition properties, distillation curve, density, and molecular structures of a diesel certification fuel. In this work, experimental measurements of the ignition delay times (IDTs) of nBCH in a shock tube and in a rapid compression machine are reported over a wide range of temperature, pressure, and equivalence ratio important for enabling the validation of a chemical kinetic model for nBCH for combustion in diesel engines. The range of conditions are temperatures of 630–1420 K, pressures of 10, 30, and 50 bar, and equivalence ratios of 0.3, 0.5, 1.0, and 2.0 in ‘air’. A detailed chemical model is developed for nBCH to simulate its ignition at both low and high‐temperature conditions and at relevant elevated pressures. The experimentally measured IDTs are used to improve and validate the chemical kinetic model.

A comprehensive experimental and modeling study of n-propylcyclohexane oxidation

“…The combustion properties of cycloalkanes are unique, especially for their low-temperature chemistry which is different from those of n-alkanes and olefins. In particular, the negative temperature coefficient (NTC) behavior of cycloalkanes is more pronounced than that of olefins, but less than that of n-alkanes [2]. Also, the high concentration of cycloalkanes in real fuel would raise soot emissions because they can dehydrogenate and produce aromatics, which are thought to be inception sites for soot growth [3].…”

Development of a Skeletal Mechanism of a Four-Component Diesel Surrogate Fuel Using the Decoupling Method

“…The existing oxidation mechanisms of NBCH are almost large detailed mechanisms. – In this study, the reduced C4-NBCH scheme was developed based on the detailed and skeletal mechanisms reported by Mao et al, , which consists of 1802 species, 7246 reactions and 397 species, and 3465 reactions, respectively. Flux analysis for the stoichiometric NBCH–air mixture under 20 bar was performed to find the main pathways for NBCH oxidation, as shown in Figure .…”

“…In fact, the heavier alkylcyclohexane is more suitable as an alternative component of diesel than lighter alkylcyclohexane because its physical and chemical properties are closer to those of the actual fuel. Among these heavier alkylcyclohexanes, n -butylcyclohexane (NBCH) has a heavier molecular weight and reasonable molecular size, which is a good compromise. , The existing oxidation mechanisms of NBCH are almost large detailed mechanisms. , Due to the huge computation cost, it is not efficient to apply the large detailed mechanisms in engine simulation, especially in large eddy simulation (LES). The lack of a reduced mechanism has limited the further application of NBCH as one of the components of the diesel surrogate fuel in engine simulations.…”

From electronic structure to model application for alkyl cyclohexane combustion chemistry: H-atom abstraction reactions by HȮ2radical

“…35 However, the rate constants of this reaction class adopted in cycloalkane models are still based on the rate constant rules of acyclic alkanes. [36][37][38] In the current work, accurate rate constants for a series of reactions of H : O 2 radical with methyl cyclohexane (MCH), ethyl cyclohexane (ECH), n-propyl cyclohexane (nPCH), iso-propyl cyclohexane (iPCH), sec-butyl cyclohexane (sBCH), and iso-butyl cyclohexane (iBCH) were systematically calculated by combing highlevel ab initio calculations and conventional transition state theory. Four composite methods were employed to calculate the temperature-dependent thermodynamics.…”

“…35 However, the rate constants of this reaction class adopted in cycloalkane models are still based on the rate constant rules of acyclic alkanes. 36–38…”