Russell Whitesides

Effect of Reaction Kinetics on Graphene-Edge Morphology and Composition

Abstract New simulations of graphene growth in flame environments are presented. The simulations employed a kinetic Monte Carlo (KMC) algorithm coupled to molecular mechanics (MM) geometry optimization to track individual graphenic species as they evolve. Focus was given to incorporation of five-member rings and resulting curvature and edge defects. The model code was re-written to be more computationally efficient enabling a larger set of simulations to be run, decreasing stochastic fluctuations in the averaged results. The model also included updated rate coefficients for graphene edge reactions recently published in the literature. Sensitivity analysis, enabled by the more efficient coding, confirmed the importance of the updated rates as well as providing further insight on key reactions controlling layer growth and morphology. The new KMC code was applied to simulate graphene-layer growth in the environments of laminar premixed flames. In these flame simulations, C-H ratios of evolving structures were computed and compared to those from experiment and from an alternate model.

Application of Gaseous Sphere Injection Method for Modeling Under-expanded H2 Injection

A methodology for modeling gaseous injection has been refined and applied to recent experimental data from the literature. This approach uses a discrete phase analogy to handle gaseous injection, allowing for addition of gaseous injection to a CFD grid without needing to resolve the injector nozzle. This paper focuses on model testing to provide the basis for simulation of hydrogen direct injected internal combustion engines. The model has been updated to be more applicable to full engine simulations, and shows good agreement with experiments for jet penetration and time-dependent axial mass fraction, while available – radial mass fraction data is less well predicted.

Isomer Energy Differences for the C4H3 and C4H5 Isomers Using Diffusion Monte Carlo

A new diffusion Monte Carlo study is performed on the isomers of C4H3 and C4H5 emulating the methodology of a previous study (Int. J. Chem. Kinet. 2001, 33, 808). Using the same trial wave function form of the previous study, substantially different isomerization energies were found owing to the use of larger walker populations in the present work. The energy differences between the E and i isomers of C4H3 were found to be 10.5 +/- 0.5 kcal/mol and for C4H5, 9.7 +/- 0.6 kcal/mol. These results are in reasonable accord with recent MRCI and CCSD(T) findings.

Development of Kinetic Mechanisms for Next-Generation Fuels and CFD Simulation of Advanced Combustion Engines

Predictive chemical kinetic models are needed to represent next-generation fuel components and their mixtures with conventional gasoline and diesel fuels. These kinetic models will allow the prediction of the effect of alternative fuel blends in CFD simulations of advanced spark-ignition and compression-ignition engines. Enabled by kinetic models, CFD simulations can be used to optimize fuel formulations for advanced combustion engines so that maximum engine efficiency, fossil fuel displacement goals, and low pollutant emission goals can be achieved.