We present a zero-dimensional kinetic model of CO2 splitting in non-equilibrium plasmas. The model includes a description of the CO2 vibrational kinetics (25 vibrational levels up to the dissociation limit of the molecule), taking into account state-specific VT and VV relaxation reactions and the effect of vibrational excitation on other chemical reactions. The model is applied to study the reaction kinetics of CO2 splitting in an atmospheric-pressure dielectric barrier discharge (DBD) and in a moderate-pressure microwave discharge. The model results are in qualitative agreement with published experimental works. We show that the CO2 conversion and its energy efficiency are very different in these two types of discharges, which reflects the important dissociation mechanisms involved. In the microwave discharge, excitation of the vibrational levels promotes efficient dissociation when the specific energy input is higher than a critical value (2.0 eV/molecule under the conditions examined). The calculated energy efficiency of the process has a maximum of 23%. In the DBD, vibrationally excited levels do not contribute significantly to the dissociation of CO2 and the calculated energy efficiency of the process is much lower (5%).

https://iopscience.iop.org/article/10.1088/0963-0252/23/4/045004/pdf

Splitting of CO2 by vibrational excitation in non-equilibrium plasmas: a reaction kinetics model

This paper describes a model for analyzing and predicting the temporal behavior of laser-induced incandescence (LII) from combustion-generated soot, carbon black, and other carbonaceous particles on a nanosecond time scale. The model accounts for particle heating by absorption of light from a pulsed laser and cooling by sublimation, conduction, and radiation. The model also includes mechanisms for oxidation, melting, and annealing of the particles and nonthermal photodesorption of carbon clusters from the particle surface. At fluences above 0.1 J/cm2, particle temperatures during the laser pulse are determined by the balance between absorption and sublimation, whereas at lower fluences particle temperatures do not reach the sublimation temperature, and temperatures are predominantly controlled by absorption and conduction. After the laser pulse, temperatures are predominantly controlled by conductive cooling rates. Oxidative heating may compete with conductive cooling on these time scales. Annealing of the particles to a more ordered phase of carbon is predicted to occur at fluences as low as 0.02 J/cm2. Annealing may strongly influence sublimation rates, and changes in emissivity during annealing are predicted to increase signal decay rates. Supersonic expansion of the carbon clusters sublimed from the surface is calculated to occur at fluences above 0.12 J/cm2. When compared with LII measurements recorded in a flame at atmospheric pressure, the model reproduces the shapes and relative magnitudes of LII temporal profiles over a wide range of laser fluences. Comparisons between model predictions and experimental observations suggest that the particles do not melt at laser fluences that lead to melting of bulk graphite. These comparisons also indicate that the energy released during particle annealing is much smaller than that released during annealing of neutron- or electron-irradiated graphite. Despite good agreement between model and experimental results, large uncertainties exist for input parameters used to calculate annealing rates and rates of oxidation, conduction, absorption, emission, and photolytic desorption of carbon clusters for both the initial and annealed particles.

Understanding and predicting the temporal response of laser-induced incandescence from carbonaceous particles

A complete set of V–T (vibration–translation) relaxation rates and of dissociation coefficients for the system O–O2 have been obtained by using quasiclassical trajectories on the Varandas and Pais potential energy surface. The results, averaged on a Boltzmann rotational distribution, cover the whole range of the vibrational ladder and are reproduced in closed form ready to be implemented in state-to-state kinetic models. The accuracy of the results has been tested by comparing them with available experimental and theoretical values (ASI-CAST project is acknowledged).

N-N2 state to state vibrational-relaxation and dissociation rates based on quasiclassical calculations

Recent advanced thermal interfacial materials: A review of conducting mechanisms and parameters of carbon materials

Energy related CO2 conversion and utilization: Advanced materials/nanomaterials, reaction mechanisms and technologies

Non-Equilibrium Reacting Gas Flows

Kinetic Equations and Method of Small Parameter.- State-to-State Approach.- Multi-Temperature Models in Transport and Relaxation Theory.- One-Temperature Model for Chemically Non-equilibrium Gas Mixtures.- Algorithms for the Calculation of Transport Coefficients.- Reaction Rate Coefficients.- Non-equilibrium Kinetics and its Influence on the Transport Processes Behind Strong Shock Waves.- Heat Transfer and Diffusion in a Non-equilibrium Boundary Layer.- Non-equilibrium Kinetics and Its Influence on the Parameters of Nozzle Flows.

Elena Kustova

Papers

Non-Equilibrium Reacting Gas Flows

Non-Equilibrium Reacting Gas Flows: Kinetic Theory of Transport and Relaxation Processes

State-to-state models for CO2 molecules: From the theory to an application to hypersonic boundary layers

On a correct description of a multi-temperature dissociating CO2 flow

Transport properties of a reacting gas mixture with strong vibrational and chemical nonequilibrium