An investigation of CO2 splitting using nanosecond pulsed corona discharge: effect of argon addition on CO2 conversion and energy efficiency

The plasma chemical splitting of carbon dioxide (CO2) to produce carbon monoxide (CO) in a pulsed corona discharge was investigated from both an experimental and a numerical standpoint. High voltage nanosecond pulses were applied to a stream of pure CO2 and its mixture with argon, and the gaseous products were identified using Fourier transform infrared spectroscopy. Due to the shape of pulses, the process of CO2 splitting was found to proceed in two phases. The first phase is dominated by ionization, which generates a high electron density. Then, during the second phase, direct electron impact dissociation of CO2 contributes to a large portion of CO production. Conversion and energy efficiency were calculated for the tested conditions. The conversions achieved are comparable to those obtained using other high pressure non-thermal discharges, such as dielectric barrier discharge. However, the energy efficiencies were considerably higher, which are favorable to industrial applications that require atmospheric conditions and elevated gas flow rates

Electrical Network-Based Time-Dependent Model of Electrical Breakdown in Water

A time-dependent, two-dimensional, percolative approach to model dielectric breakdown based on a network of parallel resistor–capacitor elements having random values, has been developed. The breakdown criteria rely on a threshold electric field and on energy dissipation exceeding the heat of vaporization. By carrying out this time-dependent analysis, the development and propagation of streamers and prebreakdown dynamical evolution have been obtained directly. These model simulations also provide the streamer shape, characteristics such as streamer velocity, the prebreakdown delay time, time-dependent current, and relationship between breakdown times, and applied electric fields for a given geometry. The results agree well with experimental data and reports in literature. The time to breakdown (tbr) for a 100 μm water gap has been shown to be strong function of the applied bias, with a 15–185 ns range. It is also shown that the current is fashioned not only by dynamic changes in local resistance, but that capacitive modifications arising from vaporization and streamer development also affect the transient behavior

2D numerical modelling of Trichel pulses in oxygen

Negative corona exhibits a self-pulsating regime when the voltage applied to the cathode is slightly above the threshold of corona discharge. These pulses, named as Trichel pulses after G. W. Trichel [1], can be easily produced in electronegative gases, like oxygen, but it has recently been shown that they can also occur in non-electronegative gases, like nitrogen or argon [2]. Trichel pulses are characterized by a short duration, of the order of tens to hundreds of nanoseconds, which makes its numerical simulation a challenging task. Frequently, only three generic species are considered in these studies: electrons, positive ions and negative ions [3, 4]. Therefore, the plasma kinetics is reduced to the fundamental processes of ionization, electron attachment and recombination

Numerical Modelling of Electrical Discharges

The problem of the propagation of an electrical discharge between a spherical electrode and a plane has been solved by means of finite element methods (FEM) using a fluid approximation and assuming weak ionization and local equilibrium with the electric field. The numerical simulation of this type of problems presents the usual difficulties of convection-diffusion-reaction problems, in addition to those associated with the nonlinearities of the charged species velocities, the formation of steep gradients of the electric field and particle densities, and the coexistence of very different temporal scales. The effect of using different temporal discretizations for the numerical integration of the corresponding system of partial differential equations will be here investigated. In particular, the so-called θ-methods will be used, which allows to implement implicit, semi-explicit and fully explicit schemes in a simple way

Multi-species simulation of Trichel pulses in oxygen

A multi-species model consisting of seven species has been implemented to simulate the generation and development of Trichel pulses in oxygen between a sphere (the cathode) and a plane (the anode). The spatial and temporal evolution of species is obtained by solving the continuity equations of species using a classical one-dimensional model of negative corona discharge. The chemical kinetics of corona discharge includes electron impact reactions (ionization, dissociative and non-dissociative electron attachment, molecular dissociation, etc.), charge transfer reactions and reactions between neutral species