Plasma Machine for Surface Treatment
Creation of Long-Lived Plasma Machine Consisting of Both Non-Transferred Arc Plasma Torch and Power Source with Deeply Dropping Characteristic for Surface Treatment of Construction Materials
Tech Area / Field
- PHY-PLS/Plasma Physics/Physics
8 Project completed
Senior Project Manager
Safronova O N
Georgian Technical University, Georgia, Tbilisi
- University of Toronto / Faculty of Applied Science and Engineering, Canada, ON, Toronto
Project summaryThe primary goal of presented Project is the creation of plasma machine with long operation life, consisting of the both non-transferred arc plasma torch with special architecture of arc-forming chamber and power source with deeply dropping characteristic having properties of a current source.
The work is devoted to development of plasma engineering and its use for technological purposes.
Being the part of above-mentioned machine, the developed construction of plasma torch has been intended for specific operations, namely the surface melting of natural stones (basalt, andesite, tuff, etc.) and man-made construction materials (concrete, ferroconcrete, bricks and so on).
The surfaces of above-mentioned materials change fully their own properties after melting and become more decorative and steady to external influences (mechanical, chemical, atmospheric, etc.).
Such technology is need for various industrial areas, mainly for construction works and manufacturing of construction materials.
The submitted plasma machine design would be a basic one, because the plasma torch might be used after small design modification for other several production and technological operations, e.g. cutting of polymeric and high-alloyed composite materials (for instance materials for body armors), cutting of non-ferrous and rare-earth metals (titanium, magnesium, etc.) of small thickness 1ё10 mm, surface spraying of various machine parts, welding of metal and dielectric materials (e.g. basalt plates), modeling of various high-temperature processes and so on.
The non-transferred plasma torches are being the most suitable for execution of above-named operations. Such plasma torches are differed from other ones by location of electrodes. Both electrodes – cathode and anode - have been mounted inside of plasma torch body. The plasma generating gas flowing through arc between electrodes is ionized and turns into the plasma without any connection with treated material. Obtained by such method high-temperature plasma discharges with high velocity and completes the above-mentioned operations.
As is obvious, the non-transferred plasma torches operate under extreme conditions. The whole electric arc burns inside torch. Thereof both the cathode and especially the anode undergo the great thermal and electric loads.
In essence, the operating lifetime of plasma torch is characterized by lifetime of anode and at present time makes up only a few hours in argon plasma atmosphere and only few decades of hours in air plasma atmosphere.
Thus, the operating life of plasma machine depends in fact on the operating life of plasma torch, namely operating life of anode. Therewith the machine operating life depends on the accurate work of the system: plasma torch - power source.
The current Project submits two methods of purpose achievement:
- Plasma torch operating life increasing.
- Elaboration and creation of special current source for joint operation with plasma torch (US Patent Nr. 4,378,522, March 29, 1983).
To increase the plasma torch’s operating life the special profile of anode’s in-chamber space is proposed in the Project. The anode’s profile corresponds to behavior of plasma electrical conductivity with growth of plasma mass-average temperature lengthwise of anode. Above-said allows to reach the following:
- both the shunt amplitude and consequently, the normal electric arc length is increased;
- the radial part of arc is increased and respectively the active gas-dynamic forces of swirling plasma flow is increased too;
- current density is decreased in the anode spot;
- the anode spot is dispersed on the larger area in comparison with ordinary cylinder anode.
Amounting to all described effects, the anode operating lifetime is increased at least 3-4 times, and besides the electric power of plasma torch is increased by 15-20% at the same invariable arc current and plasma forming gas consumption. And consequently the enthalpy and temperature of plasma flow is increased.
The characteristic of elaborated current (power) source will ensure the arc current constancy at any changes of electric arc resistance, including short circuit. By this, the plasma torch distraction is prevented at unsteady working and emergency conditions, that increases both the reliability and lifetime of plasma torch and machine in whole.
All Project participants were involved in the area of low-temperature plasma engineering and its application for technological purposes. Directly these inpiduals managed and participated in R&D topics, elaborated the various constructions of plasma torches at level of patents and author's certificates, published the scientific papers. The scientific and practical achievements were applied in industrial enterprises and defense complexes of Georgia as well as many towns of former USSR.
As a result of submitted Project implementation, the really serviceable plasma machine will be created.
The elaboration of such plasma machine will expand the range of application and will speed up the embedding process o non-transferred (independent) arc plasma torches.
The plasma machine will have a high commercial value.
On the basis of theoretical and experimental investigation of gas-dynamic, thermal and electrical processes in arc forming chamber, the new theoretical approach for anode lifetime increasing will be developed in submitted Project framework. The theoretical and experimental means will define an optimal profile of in-chamber space that will have the great scientific meaning for development of plasma engineering.
The Project foresees also the elaboration of general theoretical computational technique of plasma torches operating conditions similar to already developed ones. It is necessary for designing of torches targeted for fulfillment of various above-mentioned purposes, that has both scientific and practical meaning.
The submitted Project meets ISTC goals and enables Georgian defense scientists and specialists to redirect their capabilities on peaceful activities and to integrate them into the international scientific community.
The following scope of activities is provided for given Project:
- elaboration of theoretical and experimental procedures for increasing of plasma torch anode operating life;
- elaboration and manufacturing of innovative long-lived and high-enthalpy plasma torch;
- elaboration and manufacturing of innovative power source with deeply dropping characteristic having properties of a current source;
- creation of plasma machine consisting of innovative long-lived plasma torch for surface melting of natural stones and man-made construction materials; as well as creation of innovative current source together with whole water-gas supply system;
- investigation of primary gas-dynamic, thermal and volt-ampere characteristics of new plasma torch;
- investigation and development of optimal technological parameters and environmental improvement of surface treatment process;
- elaboration of general procedure for design of analogous plasma torches and power sources;
- preparation and processing of scientific-technical reports.
In the presented Project the role of foreign collaborators is as follows:
- information exchange during Project implementation
- review and commentaries to the quarterly, annual and final technical reports;
- joint verification of results obtained during Project implementation;
- participation in technical verification of activities carried out by ISTC personnel;
- joint participation in International meetings and conferences;
- carrying out of joint symposia and workshops.
To achieve the main goal of presented Project, i.e. to create the long-lived plasma machine consisting of both non-transferred arc plasma torch with special form of arc forming chamber and power source with deeply dropping characteristic, the following essential technical approaches and methodologies will be utilized:
- the analysis of literature sources on the novel problems of plasma flow forming, plasma torches and power sources design, as well as application of plasma machines in new technologies, will be conducted. On the base of this survey the schemes will be developed and in future the laboratory and working plasma machine will be created.
The original theoretical methods for investigation of the processes occurring in plasma torch will be developed for the purpose of establishment of optimal geometric shapes and dimensions of long-lived arc forming chamber (anode);
- to study the operating conditions of plasma torches and system: plasma torch with power source the experimental methods and theoretical procedure of design will be used.
- all stated parameters will be detected by special registering-measuring devices and apparatus.
- classical, symbolic, and graphic methods will be applied for development and investigation of innovative power source;
- to establish the technological parameters and processing conditions improvement for surface treatment of materials, the experimental methods will be applied. The special manipulator will be used for changes in pattern of position and velocity of a plasma torch relative to material treated. By means of special mixer the concentration and consumption of gas-water mixture, supplied through the additional outside nozzle of plasma torch will be controlled, depending on the incombustibility of some materials and absorption of noxious impurities which might emit at operating process. All technological parameters, namely the velocity of plasma torch, attack angle of plasma flow, distance from the nozzle exit point to treated material, will be detected directly in operating process. All experimental data will be entered in PC and the results will be computed by mathematical methods.