Ilona Laznickova

Treatment of near-electrode regions in a simple model of blasted electric arc

The paper deals with near-electrode regions of electric arc burning in argon in an arc heater. The arc behavior is described by a mathematical model using the gas transport and thermodynamic properties and real experimental data. The near-electrode regions obey different rules than the intensively blasted arc column alone, but the integral measured data include both of them. For modelling the arc, the near-electrode regions have been previously neglected or described using the data taken from other authors who investigated just the near-electrode phenomena. Now, the influence of near-electrodes regions is tried to be excluded by procedures based just on the measured data. The obtained results are shown in comparison with the data given by other authors.

ANALYSIS OF INTENSIVELY BLASTED ELECTRIC ARC BURNING IN THE ARC HEATER'S ANODE CHANNEL

The paper deals with the description of the intensively blasted electric arc burning in Ar in the anode channel of the arc heater operated under various conditions. Directly measured experimental data (current, voltage, gas flow rate, power loss) characterize the operation of the device as a whole, but important parameters describing the electric arc inside (its geometry, temperature and voltage distribution) must be revealed using a mathematical model of the arc. An updated version of the model is introduced and used for analysis of two exemplary sets of measured data. The results are given in figures and commented.

Remarks on the design of high-temperature devices with electric Arc

The paper describes main steps of the design of high-temperature device with working gas heated by electric arc. The experimental modular-type high-temperature device has been designed and operated in various modifications by the authors. The paper summarizes useful formulas for the design and illustrates them with some typical experimentally obtained dependencies.

The Influence of Nitrogen in Ar+N2 Mixture on Parameters of High-Temperature Device with Electric Arc

The paper presents the results of numerous experiments carried out on a high temperature device consisting of an arc heater with intensively blasted electric arc and reaction chambers connected to its output. The influence of nitrogen mass concentration (up to 11 %) in working gas Ar+N2 on voltage–current characteristics, power losses of individual parts and efficiency is studied for two variants of electrical configuration of the device. A short description of the computation of necessary thermodynamic and transport properties of Ar+N2 mixture is included. The computed properties are then used for evaluation of mean temperature and velocity at certain cross-sections of the device. Conclusions can be useful for the design of high temperature devices operating with argon/nitrogenmixture.

Power loss distribution along the arc heater with intensively blasted electric arc

The paper deals with the power loss distribution along the arc heater with intensively blasted electric arc and compares the measured power loss of individual parts of the arc heater and power loss computed using a simple model of the electric arc. In previous works, the authors have presented the simple model of electric arc burning in the arc heater channel. Measured integral quantities obtained during numerous experiments served as input data of the model and attention has been focused at finding the development of the arc radius and temperature along the arc heaters channel that meets the experimentally obtained integral values as a whole. In this contribution, the arc heater is divided into several parts whose power loss is measured and computed separately. For this purpose, the arc model has been adopted to make it possible. The aim is to obtain more detailed information on processes taking place in individual parts of the arc heater. The results reveal that for the input and main part of the arc heaters anode channel the computed and measured power loss differ mutually in opposite sense. This observation raises new questions concerning the suitability of presumptions, approximations and/or simplifications used in the modelling. Further experiments and computations are needed. The conclusions can be useful for the design of similar devices, and for more precise modelling of the behavior of electric arc inside the arc heater channel.

Calculation of Arc Power Losses in the Simplified Model of Intensively Blasted Electric Arc

In previous versions of the simplified model of intensively blasted electric arc burning in argon in the arc heater’s anode channel, the authors used the constant total power loss coefficient for estimation of arc power losses in all anode channel individual parts. Using this approach, the model with relatively low computational complexity has led to very good agreement between the total computed and experimentally obtained values, but when the computed and measured power losses of individual anode channel segments have been compared, considerable differences have been revealed. In the modified model, theoretically computed net emission coefficient of argon is used in the energy equation to express the arc power losses. This way, satisfactory accordance is achieved between not only the total, but also partial measured and computed values. Exemplary results are given in figures and tables and discussed.

Experimental investigation of an arc heater operated on low gas flow rates

The paper describes the results obtained from experimental operation of the arc heater with intensively blasted electric arc. The device has been designed for investigation of decomposition of stable harmful substances and later its construction has been modified to achieve steady operation with low gas flow rates. The modification consists in reduction the anode channel diameter with a solid cylinder inserted into the input part of the channel. The paper comments the impact of the constructional modification on basic operational characteristics of the arc heater operated on argon and argon/hydrogen mixtures.

Influence of collision integrals on the electrical conductivity of a gas system

The calculation method of the electrical conductivity of the partially ionised gases is based on the Chapman-Enskog method of the kinetic theory of a multicomponent gas mixture. The electrical conductivity depends not only on the concentrations of the components but also on the collision integral values. In this paper the electrical conductivity of the gas system of dissociation and ionisation products of SF6 were calculated for some methods of the collision integral calculation that are mentioned in the literature. The hard sphere model, the Lennard-Jones potential, the polarizability method, the Coulomb interaction and the electron-neutral interactions are used.