J. Senk

Modelling of energy processes in intensively blasted electric arc

By means of mathematical-physical model the measurements on the experimental are heater with argon as a working gas are investigated. Basic principles of the model are mass and energy conservation equations and Ohm’s law. The input data are experimentally obtained quantities of the arc current I (50÷200) A and voltage U 100 V, the mass flow rate of working gasG (up to 22 g s−1), energy losses of the anode channelPz and material functions of argon [1]. The measurements have been made on the experimental arc heater (plasmatron) [2, 3] that allows the determination of the energy losses of its individual segments.

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.

Theoretical analysis of the influence of diffusion in free jet of hot gas mixture

The theoretical analysis of the influence of diffusion on the distribution of mass fractions in free jet of hot gas mixture is based on the vector form of the continuity equation, including the diffusion member. Measured and computed quantities at the output of the are heater (temperature profile, composition, thermodynamic and transport properties of the used gas mixture) are used as the initial conditions. The influence of diffusion is analyzed using the measured temperature and velocity fields in the cross-sections of the jet along thez-axis. The approximation of radial dependencies of temperature and velocity by Gaussian function makes possible the integration in radial direction. Consequently, the two-dimensional problem in cylindrical coordinates can be transformed into the one-dimensional one. Solving the complete continuity equation, the relations for the distribution of mass fractions can be derived, including the components normally present in the surrounding environment (argon and water vapour in air).

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.

The role of radiation losses in high-pressure blasted electrical arcs

The paper deals with experiments carried out on an arc heater where the electric arc is stabilised by flowing working gas. Measured quantities (especially arc current, voltage drop, gas flow rate, and energy loss) serve as input data for a mathematical model of the arc inside a cylindrical anode channel. Previously, the losses of cathode and anode spots were assumed to be negligible in comparison with the total loss. In the new sets of experiments, a modular structure of the arc heater has made it possible to separate the losses of anode and cathode from the energy losses of the arc itself. Furthermore, the losses caused by radial conduction have been introduced into the model. The most significant change of the model concerns the computation of radiation losses of the arc. In the original model, radiation losses were taken as a portion of the total input power. In the modified model, the radiation loss is expressed using a theoretically calculated net emission coefficient of argon (by V. Aubrecht and M. Bartlova). This approach is possible due to a more precise determination of the arc net energy loss which results in flatter radial temperature profiles. Axial distribution of energy loss for the original and modified model is given in figures.