Albina Tropina

Arc Modeling in a Plasmatron Channel

The mathematical model of a direct-current arc at atmospheric pressure and low currents has been proposed. This paper presents the results of 2-D simulations for an air arc within the plasmatron channel, as well as the anode, composite cathode, and external regions. The model does not employ any adjustable parameter and therefore enables direct comparison with the experiments. The model predictions were compared with the experimental data of a plasma igniter and indicated good agreement.

Comparative Analysis of Engine Ignition Systems

The experimental data of a comparative analysis of a spark-ignition system and a nanosecond-discharge-based ignition system in engines are presented. The effectiveness of the ignition systems used was evaluated on fuel consumption and exhaust-gas composition during the road and laboratory tests. It has been discovered that using a plasma-ignition system rather than a spark-ignition system considerably improves engine performance and reduces tailpipe emissions at the same time. The obtained results are analyzed based on the equilibrium calculations of combustion products and on the analytical evaluation of the flame-extinguishing-layer width near the cylinder walls of the combustion chamber.

On the Effect of Nonequilibrium Plasma on the Minimum Ignition Energy—Part 1: Discharge Model

The mathematical model of a repetitive nanosecond pulse discharge at atmospheric-pressure conditions has been presented. The influence of initial gas temperature, chemical kinetics, and vibrational nonequilibrium on the ignition of methane-air and ethylene-air mixtures has been analyzed.

Limitations on High-Spatial Resolution Measurements of Turbulence Using Femtosecond Laser Tagging

The study of the smallest scales of turbulence requires high-resolution spatially-resolved measurements of velocity. Femtosecond Laser Electronic Excitation Tagging (FLEET) provides high-spatial-resolution, minimally-invasive velocity measurements in unseeded air flows, offering both a new method for characterizing turbulence and a potential tool for studying the interaction of turbulent flow with localized energy addition. To clarify the resolution limits achievable with FLEET, we quantify the density and temperature perturbation caused by the laser-gas interaction and examine the statistics of small-scale turbulence measured with FLEET for effects of the perturbation. We combine experimental measurements with a simple numerical model of the interaction of turbulence with a density perturbation. Our results suggest that the perturbation caused by FLEET does not cause errors in velocity measurement for length scales longer than 100 microns.

Improvement of the Gas Turbine Plasma Assisted Combustor Characteristics

Theoretical and experimental investigations of the working processes in a low emission gas turbine combustor with plasma assistance have been conducted. Selected concept of a gas turbine combustor can provide higher performance, wider turn down ratios, lower emission of carbon and nitrogen oxides, demonstrate satisfactory major gravimetric and volumetric parameters. Obtained results and recommendations can be used for the gas turbine combustor operation modes modeling, geometry optimization, prospective propulsion and power generation units design and engineering.

Ignition System Based on the Nanosecond Pulsed Discharge

A new design of the compact nanosecond pulse generator based of the drift step recovery diodes as an ignition system for internal combustion engines (ICEs) has been presented. Experimental results of the comparative analysis of the standard ignition system and an ignition system on the basis of the nanosecond pulsed discharge for the four-cylinder ICE have been presented. It was shown that a nonequilibrium plasma formed by the discharge was an effective way to reduce the specific fuel consumption as well as the concentration of nitrogen oxides in the engine exhaust gases. A numerical analysis of possible mechanisms of the nonequilibrium plasma influence on the suppression of the nitrogen oxides formation has been carried out.

Dynamics of a Laser-Induced Filament Supported and Controlled by a Direct Current Discharge

†‡ A mathematical model of plasma dynamics of a laser-induced filament supported and controlled by a direct current discharge has been developed. The model we present includes Navier-Stokes, electron and vibrational temperature equations, plasma-kinetic and combustion-kinetic equations, as well as the Boltzmann equation for the electron energy distribution function. It was used to model plasma dynamics of a spark discharge guided by a femtosecond laser filament in air and methane-air mixtures. The calculated electron density and electron temperature rate decay in air are in good agreement with the published data. It was shown that despite the microns size of the laser plasma filament and electric field strength below the breakdown, we can achieve an exponential growth of the gas temperature, depending on the time delay between the initial femtosecond laser pulse and the laser guided filamentary spark discharge.

Ignition by Short Duration, Nonequilibrium Plasma: Basic Concepts and Applications in Internal Combustion Engines

ABSTRACT This article presents a brief selective overview of current trends in plasma-assisted ignition for internal combustion engines. Short duration pulsed nonequilbrium plasmas show promise for improved engine performance, including extension of the lean limit, reduction of NOX, and consistent cycle-to-cycle ignition timing. This article presents methods for achieving these improvements, including the use of lasers, microwaves, and high voltage nanosecond pulse driven discharges. These approaches can provide multiple simultaneous ignition points, optimized localization of ignition within the combustion chamber, and precise timing. A classification of nonequlibrium pulse driven ignition systems from the physical point of view and a discussion of different breakdown mechanisms are included, along with a discussion of recent laboratory and road test results.

Methane-Air Mixture Ignition by Combined Laser and Microwave Discharges

Successful ignition of hydrocarbon fuel mixtures achieving a decreased ignition delay time and an increased flame propagation speed is one key goal of plasma assisted combustion. A combination of laser and microwave discharges was proposed to both create fuel-gas mixture ionization before ignition using a laser pulse and to subsequently ignite the mixture using the microwave discharge as the thermal source. In this paper we present the modeling results of the ignition phenomenon investigations for the case of this combined laser-microwave discharge. Ignition delay times as a function of the mixture ionization level formed by a laser pulse and the microwave electric field strength are presented. The ignition mechanism of the combined laser-microwave ignition is analyzed.

Ignition Delay Time and Laminar Flame Velocity for a Combined Laser–Microwave Ignition

An analysis of the ignition delay time dependence on microwave energy input time, electric field strength, and discharge energy at high-pressure conditions is presented for a combined laser-microwave ignition. The existence of a saturation power effect at high-pressure conditions is predicted. An analytical formula for a laminar flame velocity is obtained for a case of the reaction rate dependence on vibrational temperature.