Andrey Starikovskiy

Inactivation of bacteria using dc corona discharge: role of ions and humidity.

Here we present the results of an experimental study of the effect of ions produced in a dc corona discharge on inactivation of bacteria on the surface of agarose gel. Both positive and negative corona discharges in various gases at different humidities were studied. The measurements in air, O(2), N(2), Ar and He mixtures show that there is no inactivation in pure N(2), pure O(2) and an N(2)-H(2)O mixture. The best results were achieved in the case of direct treatment, when discharge was ignited in oxygen and water-containing mixtures. We show that neither UV radiation, ozone or H(2)O(2) nor other neutral active species alone produced by corona have an effect on bacteria viability. It is shown that the main role of charged particles may be related to the faster transport of active peroxide species-cluster ions OH(-)(H(2)O)(n) and H(3)O(+)(H(2)O)(n). The efficiency of these radicals is much higher than that of the oxygen radicals and ions (including [Formula: see text] and O(3)) and that of nitrogen and argon ions.

Application of pulsed spark discharge for calcium carbonate precipitation in hard water.

The effect of underwater pulsed spark discharge on the precipitation of dissolved calcium ions was investigated in the present study. Water samples with different calcium hardness were prepared by continuous evaporation of tap water using a laboratory cooling tower. It was shown that the concentration of calcium ions dropped by 20-26% after 10-min plasma treatment, comparing with no drop for untreated cases. A laser particle counting method demonstrated that the total number of solid particles suspended in water increased by over 100% after the plasma treatment. The morphology and the crystal form of the particles were identified by both scanning electron microscopy and X-ray diffraction. Calcite with rhombohedron morphology was observed for plasma treated cases, comparing with the round structure observed for no-treatment cases. It was hypothesized that the main mechanisms for the plasma-assisted calcium carbonate precipitation might include electrolysis, local heating in the vicinity of plasma channel and a high electric field at the tip of plasma streamers, inducing structural changes in the electric double layer of hydrated ions.

Rate of plasma thermalization of pulsed nanosecond surface dielectric barrier discharge

The paper presents a detailed explanation of the physical mechanism of the nanosecond pulsed surface dielectric barrier discharge (SDBD) effect on the flow. Actuator-induced gas velocities show near-zero values for nanosecond pulses. The measurements performed show overheating in the discharge region at fast (τ ~ 1 us) thermalization of the plasma inputed energy. The mean values of such heating of the plasma layer can reach 70, 200, and even 400 K for 7-, 12-, and 50-ns pulse durations, respectively. The emerging shock wave together with the secondary vortex flows disturbs the main flow. The resulting pulsed-periodic disturbance causes an efficient transversal momentum transfer into the boundary layer and further flow attachment to the airfoil surface. Thus, for periodic pulsed nanosecond dielectric barrier discharge DBD, the main mechanism of impact is the energy transfer to and heating of the near-surface gas layer. The following pulse-periodic vortex movement stimulates redistribution of the main flow momentum. Analysis of the experimental results of fast nonequilibrium plasma thermalization has been performed. It was shown that significant part of energy deposited into the non-equilibrium plasma at high electric field converts to translational degrees of freedom during plasma recombination.

Pulsed Multichannel Discharge Array in Water With Stacked Circular Disk Electrodes

A simple yet effective system using stacked circular disk electrodes is developed to generate pulsed multichannel discharge array in water. Images of the pulsed multichannel discharge generated in water were obtained by applying pulsed high voltage over thin circular metal disks sandwiched between a pair of dielectric disks. By stacking multiple circular disks, the present discharge array system can produce large-volume plasma desired for the treatment of a large volume of water.

Kinetics of plasma assisted combustion at low reduced electric fields

The mechanism of plasma assisted ignition has been intensively discussed in recent years. Several possible mechanisms have been proposed to enhance the ignition with electrical discharges [1]. Among them, the excitation of molecules to vibrational and electronic states by plasma seems to be quite interesting due to its higher efficiency than others. The purpose of this paper is to study numerically the ignition of a hydrogen-oxygen mixture under influence of single delta oxygen (SDO, O 2 (a1Δ g )). A kinetic mechanism of the effect of singlet oxygen molecules was determined by calculating numerically the ignition characteristics. The efficiency of various electric discharges for enhancement of combustion is also presented. The ignition process was numerically simulated using the kinetic scheme given by [2], which include 12 particle species (H 2 , H, O 2 , O, O 3 , O(1D), O 2 (a1Δ g ), O 2 (b1Σ+ g ), OH, HO 2 , H 2 O 2 , H 2 O) and 80 reactions. Calculations were carried out in the zero-dimensional approximation at a fixed gas pressure.

Bacteria inactivation effect of ions generated by DC corona discharge

Summary form only given. Non-thermal plasma generated at atmospheric pressure produces a complex effect caused by reactive molecules, charges, electric fields, and ultraviolet radiation. The role of these components has been studied, and it was noticed, that inactivation efficiency highly depends on presence of charged species for room air conditions, but radiation effect in air plasma is almost always negligible. To study the role of plasma-produced charged particles, we have used DC corona discharge, where stable and uniform generation of various neutral active species and ions is possible.

Non-equilibrium plasma in liquid water -dynamics of generation and quenching

In most cases, the electric breakdown of liquids is initiated by the application of high electric field on the electrode, followed by rapid propagation and branching of plasma channels. Typically plasma is only considered to exist through the ionization of gases and typical production of plasmas in liquids has generated bubbles through heating or via cavitation and sustains the plasmas within those bubbles. The question appears: is it possible to ionize the liquid without cracking and voids formation?

Comparative Shock-Tube Study of Autoignition and Plasma-Assisted Ignition of C2-Hydrocarbons

The kinetics of ignition in C2H2:O2:Ar, C2H4:O2:Ar, C2H6:O2:Ar and C2H5OH:O2:Ar mixtures was analyzed in experiments using a shock tube with a discharge cell. Ignition delay time was measured behind a reflected shock wave after a high-voltage nanosecond discharge and in its absence. Numerical simulation was used to show the main mechanisms that lead to peculiarities of ignition properties of C2-hydrocarbons.

Plasma enhanced combustion in methane-, ethane-, propane-, and butane-air mixtures below self-ignition threshold

The paper presents results of temporal dynamics of hydroxyl radicals in premixed hydrocarbon-air flows excited by a nanosecond pulsed streamer discharge plasma below a self-ignition threshold. The experiments have been conducted for four different hydrocarbons - methane, ethane, propane and butane with equivalence ratio 0.1 at six different temperature points varying from 300 K to 800 K. Using laser induced fluorescence (LIF) technique the measurements of absolute OH radicals concentration dynamics is achieved by adjusting triggering synchronization between pulsed high voltage generator and Nd-YAG laser. The plasma was generated by sequential pulses of high-voltage (~20 kV), short pulse duration (~10 ns) and extremely short rise time (<; 1 ns) at repetition rate of 10 Hz. The high reduced electric field guarantees efficient electronic excitation and molecular dissociation, while the picosecond scale rising time greatly improves the discharge stability and helps sustaining uniform nonequilibrium plasma. The streamer discharge in premixed hydrocarbon-air flow results in extra large concentration of OH radicals and only about 10 percent increase of gas temperatures, inferred from nitrogen second positive band system spectra. The experiments gave quantitative information on the hydrocarbon reaction dynamics under self-ignition threshold with high initial concentration of radicals.

Pin-to-hole spark discharge (PHD) plasma experimental characterization and modeling

Recently, cold pin-to-hole spark discharge (PHD) plasma was reported to be successfully applied for the treatment of a human patient with complicated ulcerous eyelid wounds [1]. Such treatment was essentially salvatory for patients life: PHD plasma was shown to have healing and bactericidal effects, while other conventional medical treatments did not have an effect. In order to understand which components of spark plasma (and associated mechanisms) caused the observed biological effects, the discharge characterization is required. This will also allow optimization of the discharge and possibly finding new medical applications.