The discharge with liquid non-metallic electrodes (DLNME) was investigated. The discharge burnt steadily with a DC power supply between two streams of weakly conducting liquid (tap water) in open air at atmospheric pressure. The metallic current leads were inserted into the streams and were covered by a 5 mm thick water layer. The discharge burnt in volumetric (diffuse) form with fairly high voltage (~3 kV between leads) and low current density (~0.2-0.25 A cm-2). The plasma state in the inter-electrode gap was studied by spectroscopy, microwave sounding and electrical probe technique. The rotational and vibrational temperatures of N2 electronically excited molecules were measured. The absolute radiation values of different species were obtained as a function of position in the gap. The electric field E and the concentration of charged particles were obtained. The value of parameter E/Ng was estimated (Ng being the gas concentration). The density of water vapour in the discharge column was estimated. The results obtained show that DLNME generate molecular plasma at high pressure but out of thermal equilibrium. The properties of DLNME make it promising for various engineering applications, including those in plasma chemistry.

The discharge established between two liquid non-metallic electrodes (DLNME) is investigated. This d.c. discharge burns between two streams of tap water in open air at atmospheric pressure in diffuse form. In the plasma column two zones are defined: one close to the near-cathode and the other one close to the near-anode regions of the discharge. In each zone, the composition, massic enthalpy, volumetric emissivity of N2(2+) spectral band (376-380 nm), hydrogen spectral line (Hα) and triplet oxygen spectral lines (777 nm) have been calculated in non-equilibrium conditions. The comparison with experimental results allows determining the ratio between translational temperature of electrons and that of heavy species and an upper limit of the air humidity in both zones. This type of calculation describes satisfactorily the previously obtained experimental results.

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Experimental investigations of the emission spectrum in the wavelength range 240 nm ⩽ λ ⩽ 850 nm of a discharge burning in open air between two flows of tap water (a discharge with two liquid electrodes) with direct current supply are carried out. The axial and radial distributions of spectral characteristics at different currents i and discharge lengths L (i = 40–80 mA; L = 4–8 mm) are investigated. From spectral distributions of plasma emissivity, the obtained results show that the discharge radiates mainly in the ultraviolet region of the spectrum. The main contribution to the radiation power is made by N2, OH and NO molecules. The near-electrode regions radiate most intensively. A comparison of the previously published results of the investigations of such a discharge with the present results allows us to give qualitative explanations of the regularities in the axial distributions of spectral characteristics and their dependences on current and discharge length. An estimation of the dose of irradiation of the electrode liquid (tap water) by discharge radiation, having bactericidal effect (λ ⩽ 310 nm) is made. The estimation shows that when water flows through the electrode attachment, the dose received by it is, by an order of magnitude, comparable to the dose which is necessary for sterilization.

Conference papers Accès au bibtex titre Calcul de la composition chimique dans un plasma issu de mélanges de PTFE, d'air, de cuivre et de vapeur d'eau dans le cadre d'appareillages de coupure électrique à air