https://www.engr.colostate.edu/~marchese/combustion10/3.pdf

A Comprehensive Modeling Study of iso-Octane Oxidation

The nonaqueous rechargeable lithium–O2 battery containing an alkyl carbonate electrolyte discharges by formation of C3H6(OCO2Li)2, Li2CO3, HCO2Li, CH3CO2Li, CO2, and H2O at the cathode, due to electrolyte decomposition. Charging involves oxidation of C3H6(OCO2Li)2, Li2CO3, HCO2Li, CH3CO2Li accompanied by CO2 and H2O evolution. Mechanisms are proposed for the reactions on discharge and charge. The different pathways for discharge and charge are consistent with the widely observed voltage gap in Li–O2 cells. Oxidation of C3H6(OCO2Li)2 involves terminal carbonate groups leaving behind the OC3H6O moiety that reacts to form a thick gel on the Li anode. Li2CO3, HCO2Li, CH3CO2Li, and C3H6(OCO2Li)2 accumulate in the cathode on cycling correlating with capacity fading and cell failure. The latter is compounded by continuous consumption of the electrolyte on each discharge.

Reactions in the Rechargeable Lithium–O2 Battery with Alkyl Carbonate Electrolytes

Progress and recent trends in homogeneous charge compression ignition (HCCI) engines

Large-eddy simulation (LES) of turbulent combustion is a relatively new research field. Much research has been carried out over the past years, but to realize the full predictive potential of combustion LES, many fundamental questions still have to be addressed, and common practices of LES of nonreacting flows revisited. The focus of the present review is to highlight the fundamental differences between Reynolds-averaged Navier-Stokes (RANS) and LES combustion models for nonpremixed and premixed turbulent combustion, to identify some of the open questions and modeling issues for LES, and to provide future perspectives.

/pdf/large-eddy-simulation-of-turbulent-combustion-39umcykkan.pdf

Large-eddy simulation of turbulent combustion

Real fuels are complex mixtures of thousands of hydrocarbon compounds including linear and branched paraffins, naphthenes, olefins and aromatics. It is generally agreed that their behavior can be effectively reproduced by simpler fuel surrogates containing a limited number of components. In this work, an improved version of the kinetic model by the authors is used to analyze the combustion behavior of several components relevant to gasoline surrogate formulation. Particular attention is devoted to linear and branched saturated hydrocarbons (PRF mixtures), olefins (1-hexene) and aromatics (toluene). Model predictions for pure components, binary mixtures and multi-component gasoline surrogates are compared with recent experimental information collected in rapid compression machine, shock tube and jet stirred reactors covering a wide range of conditions pertinent to internal combustion engines (3–50 atm, 650–1200 K, stoichiometric fuel/air mixtures). Simulation results are discussed focusing attention on the mixing effects of the fuel components.

/pdf/kinetic-modeling-of-gasoline-surrogate-components-and-2opbfa4l05.pdf

Kinetic modeling of gasoline surrogate components and mixtures under engine conditions

https://www.engr.colostate.edu/~marchese/combustion10/4.pdf

A Comprehensive Modeling Study of n-Heptane Oxidation

Autoignition of isomers of pentane, hexane, and primary reference fuel mixture of n-heptane and iso-octane has been studied experimentally under motored engine conditions and computationally using a detailed chemical kinetic reaction mechanism. Computed and experimental results are compared and used to help understand the chemical factors leading to engine knock in spark-ignited engines. The kinetic model reproduces observed variations in critical compression ratio with fuel molecular size and structure, provides intermediate product species concentrations in good agreement with observations, and gives insights into the kinetic origins of fuel octane sensitivity. Sequential computed engine cycles were found to lead to stable, non-igniting behavior for conditions below a critical compression ratio; to unstable, oscillating but nonigniting behavior in a transition region; and eventually to ignition as the compression ratio is steadily increased. This transition is related to conditions where a negative temperature coefficient of reaction exists, which has a significant influence on octane number and fuel octane sensitivity.

/pdf/autoignition-chemistry-in-a-motored-engine-an-experimental-3vooee95to.pdf

Autoignition chemistry in a motored engine: An experimental and kinetic modeling study

Autoignition of the five distinct isomers of hexane is studied experimentally under motored engine conditions and computationally using a detailed chemical kinetic reaction mechanism. Computed and experimental results are compared and used to help understand the chemical factors leading to engine knock in spark-ignited engines and the molecular structure factors contributing to octane rating for hydrocarbon fuels. The kinetic model reproduces observed variations in critical compression ratio with fuel structure, and it also provides intermediate and final product species concentrations in very dose agreement with observed results. In addition, the computed results provide insights into the kinetic origins of fuel octane sensitive.

/pdf/autoignition-chemistry-of-the-hexane-isomers-an-experimental-2synhcl7k1.pdf

Autoignition Chemistry of the Hexane Isomers: An Experimental and Kinetic Modeling Study

A detailed chemical kinetic reaction mechanism is used to study the oxidation of n-heptane under several classes of conditions Experimental results from ignition behind reflected shock waves and in a rapid compression machine were used to develop and validate the reaction mechanism at relatively high temperatures, while data from a continuously stirred tank reactor (cstr) were used to refine the low temperature portions of the reaction mechanism In addition to the detailed kinetic modeling, a global or lumped kinetic mechanism was used to study the same experimental results The lumped model was able to identify key reactions and reaction paths that were most sensitive in each experimental regime and provide important guidance for the detailed modeling effort In each set of experiments, a region of negative temperature coefficient (NTC) was observed Variation in pressure from 5 to 40 bars were found to change the temperature range over which the NTC region occurred Both the lumped and detailed kinetic models reproduced the measured results in each type of experiments, including the features of the NTC region, and the specific elementary reactions and reaction paths responsible for this behavior were identified and rate expressions for these reactions were determined

/pdf/combustion-of-n-heptane-in-a-shock-tube-and-in-a-stirred-2zfpbpkt4o.pdf

P. Gaffuri

Papers

A Comprehensive Modeling Study of n-Heptane Oxidation

A Comprehensive Modeling Study of iso-Octane Oxidation

Autoignition chemistry in a motored engine: An experimental and kinetic modeling study

Autoignition Chemistry of the Hexane Isomers: An Experimental and Kinetic Modeling Study

Combustion of n-heptane in a shock tube and in a stirred reactor: A detailed kinetic modeling study