Hollow needle-to-plate electrical discharge at atmospheric pressure

Abstract

Ecological applications dealing with the cleaning of flue gases, the decomposition of volatile hydrocarbons and the destruction of toxic pollutants require, in order to reach high efficiency, the use of non-thermal plasma sources. Typical sources of such non-equilibrium plasmas are barrier discharge, direct current (DC) or alternating current (AC) gliding arc, pulsed or DC corona and DC atmospheric pressure discharge stabilized by a fast gas flow (APD-GFS). In case of APD-GFS the gas flows in a rectangular channel, the top wall of which serves as the anode and the multi-needle cathode is built into the bottom wall of the channel. In order to prevent the transition to a spark and to stabilize this type of discharge the velocity of the gas should be about 100-200 m s −1 or the discharge current must be limited. To avoid the problem connected with the acceleration of the primary (polluted) gas at such a velocity, the external flow of the primary gas around the needle electrodes can be superimposed by a flow of a secondary gas through the needles. Thus the primary gas need not be accelerated to high velocity and in order to stabilize the discharge a relatively small amount of a secondary gas supplied through the needle is required. This work is therefore focused on the study of the DC APD-GFS in hollow needle-to-plane geometry. The basic electrical characteristics, magnetic noise and integral emission spectra of this type discharge with the flow of nitrogen or air through the needle are given.

Time-resolved absolute OH density of a nanosecond pulsed discharge in atmospheric pressure He–H2O: absolute calibration, collisional quenching and the importance of charged species in OH production

“…The optical emission spectra were recorded between 308 and 309 nm. The gas temperature is calculated from the Boltzmann plot of the Q 1 (5-6) and P 1 (2) lines. For each of the lines the intensity is spectrally integrated.…”

“…In environmental remediation OH is an important oxidizer for e.g. volatile organic compounds (VOC's), NO x and SO x [1,2]; in biomedical treatment OH is part of the active 'plasma cocktail' besides NO and ozone [3]; in plasmaenhanced combustion OH radicals produced by the plasma increase the combustion efficiency [4][5][6]; and in chemical synthesis OH is one of the building blocks of H 2 O 2 , which is considered as an important agent in the chemical reactivity of plasmas in and in contact with liquids [7]. To investigate the OH production mechanisms it is necessary to obtain absolute OH densities.…”

Negative Current Pulses in Atmospheric Pressure DC ElectricalDischarge

“…), in the destruction of various volatile aromatic and toxic hydrocarbons, generation and destruction of ozone (ozonizators, ionizators) etc. There is a number of possible types of electrical discharges used for a set of given applications: corona discharge [1], surface discharge [2], dielectric barrier discharge [3], discharge with ferroelectric beads [4], RF and microwave discharge [5] or some variants of atmospheric discharge enhanced by gas flow [6]. However, many physical and technological problems which need detailed explanation still remain.…”

Gas flow enhanced hollow needle to plate discharge for decomposition of volatile organic compounds

“…In this case the velocity of the gas required to stabilize the discharge is about 100 m/s. To relax these velocity requirements we proposed a new method of gas flow discharge stabilization in which the pin is substituted by hollow needle and the gas is supplied through the needle [4]. The important advantage of this proposal from the standpoint of VOC decomposition is that all the gas passes through the discharge volume and therefore is affected by plasmachemical processes.…”