M. Kh. Gadzhiev

Electrical breakdown voltage of transformer oil with gas bubbles

Electrical breakdown strength of liquid-gas micro bubble mixtures of transformer oil with sulfur hexafluoride and air for the case of quasi homogeneous gas inclusions distribution and 10% volumetric gas content was experimentally investigated. DC voltage up to 140 kV was applied to a 8 mm gap between hemispherical electrodes. It is shown that transformer oil bubbled with air leads to threshold breakdown voltage decrease by 34% and 19% when bubbled with sulfur hexafluoride. The stabilization effect of sulfur hexafluoride micro bubbles on the value of threshold breakdown voltage is observed.

Investigation of the argon arc binding to the lanthanated tungsten cathode

Pyrometric and spectroscopic investigations of lanthanated tungsten cathode in argon arc plasma discharge at atmospheric pressure are reported. The distribution of the surface cathode temperature was measured. Calculations and estimates of the emission current density are performed. Experimental data of the total current density are compared with the obtained results of estimation. The possible reasons for the discrepancy between the experimental and theoretical values of the total current were discussed.

A high-power low-temperature air plasma generator with a divergent channel of the output electrode

We have developed and studied a powerful high-enthalpy (H ≥ 20 kJ/g) air plasma jet generator with a divergent channel of the output electrode, which belongs to the class of dc plasmatrons with a thermionic cathode. The plasma generator possesses an efficiency of about 80% and ensures the formation of slightly divergent (2± = 12°) plasma jet with diameter D = 50 mm and a mass-average temperature of 6000–9000 K.

Effect of Stabilizing Steel Temperature in a Continuous-Caster Tundish by the Plasma Method on the Uniformity of the Mechanical Properties of Plates After Rolling

A method is described for the plasma heating of steel in the tundish of a continuous caster. Results are presented from studies of the mechanical properties of rolled products made of steel that was cast after being heated above the liquidus temperature by different amounts. The degree of superheating of the steel was stabilized by having it undergo plasma heating in the tundish. Tests of rolled products of continuouscast steel showed the positive effect of its plasma heating.

High-pressure ignition plasma torch for aerospace testing facilities

The present paper discusses the issues of implementation of high-pressure ignition plasma torch in terms of discharge phenomena in compressed gases, dense nitrogen plasma properties and stable arcing power requirements. Contact ignition has been tested in a pressure range p = 1-25 bar and has proved to be a reliable solution for pilot arc burning.

Supersonic plasmatron nozzle profiling with the real properties of high temperature working gas

The effects of real gases (excitation of vibrational degrees of freedom, dissociation and ionization) taken into account for supersonic nozzle profiling. The paper presents the method of the supersonic nozzle profiling for non-monotonic dependence of adiabatic index on temperature. The results of nozzle profile calculation for two sets of input parameters, based on independently determined specific heat for molecular nitrogen N2 and products of its thermal decomposition in the temperature range of 260–105 K and atmospheric pressure are presented. The experimental set-up based on proposed method of supersonic nozzle has been developed and manufactured. The gas velocity at different distances from the nozzle outlet has been measured. Results show the existence of the supersonic and transsonic flow regimes after the nozzle.

One more study of argon arc binding to pure tungsten cathode

Pyrometric and spectroscopic investigations of pure tungsten cathode in argon arc plasma discharge at atmospheric pressure are reported. The distribution of surface cathode temperature and the radial distribution of plasma temperature at different distance from the cathode tip were measured. We conducted a comparison between our work and other studies on arc discharges where cathodes from lanthanated (W-2% La 2 O 3 ) and thoriated (W-2% ThO 2 ) tungsten were used.

Electrical breakdown of transformer oil with sulfur hexafluoride and air bubbles

The influence of gas bubbles on the breakdown voltage of transformer oil is experimentally studied. The influence of the oil flow on the electrical characteristics of breakdown is analyzed. It is shown that sulfur hexafluoride and air bubbles decrease the breakdown voltage.

Megawatt low-temperature DC plasma generator with divergent channels of gas-discharge tract

We have developed and studied a new effective megawatt double-unit generator of low-temperature argon plasma, which belongs to the class of dc plasmatrons and comprises the cathode and anode units with divergent gas-discharge channels. The generator has an efficiency of about 80–85% and ensures a long working life at operating currents up to 4000 A.

The effect of high-enthalpy argon plasma flow on the structure and properties of YBa 2 Cu 3 O 7 – δ nanoceramics

The structure and electrical resistivity of YBa2Cu3O7 – δ-based nanostructured ceramics before and after exposure to the high-enthalpy argon plasma flow are investigated. It is demonstrated that the plasma-flow processing can strengthen the intergrain bonds in the surface layer of the ceramics and change its oxygen stoichiometry index.