Papers by Keyword: Plasma Torch

Abstract: The manufacturing of significant products with help of laser beam welding technologies requires higher stability characteristics of such technologies; this explains the necessity to run on-line testing procedures of through pro-melting process. This type of testing can be carried out by the registration of plasma streams that occur under a work piece by through pro-melting [i.e. metal undergoes an intensive laser beam thermal processing].

Abstract: The present paper describes the determination of boundary conditions of the 10 kVA plasma reactor graphite electrode cooling. The water cooler installed on the lid of the reactor, connected in open circuit, sustains the permissible service temperatures in the analysed area of the reactor. With the monitoring of the coolant flow and temperatures at the inlet and outlet of the cooler, the heat flux necessary for the design of a closed circulation cooling circuit was determined. Software support of HTC-FC (heat transfer coefficient – natural convection) and simulation software ANSYS CFX were used to solve the design and functionality of the proposed solution. This software is designed for the numerical calculation of differential equations describing fluid flow and heat conduction with the use of the finite volume method. With the application of time-dependent boundary conditions in the simulation tool ANSYS CFX, we acquired information about the temperature distribution of the cooling medium during the operation of the described technology and also about the change in the variation of heat flux between the environment and the proposed container.

Abstract: Plasma torch is one of the most important parts for plasma arc generating system. A design of orifices in a nozzle would decide the properties of plasma arc. However, mechanisms of orifice to plasma arc are seldom discussed. In this paper, the plasma arc with two assistant orifices were analyzed by finite element method. It was concluded that the plasma arc would be further compressed in the direction parallel to two assistant orifices, but expand perpendicular to assistant orifices. Through the constriction of two assistant orifices, the shape of the plasma arc would be elliptical other than circular of the oridinary plasma arc. The torch design with two assistant orifices could be available to many fields such as plasma arc welding, especially to a welding torch with a large pressure chamber.

Abstract: The system model «high power ion beam – metal» is suggested. Regularities of impulse formation of mechanical load in the volume of metal target subjected to the action of ion beams of different component composition in the range of power density 10⁷...10¹⁰ W/cm² have been considered. The influence of generation mechanisms on the profile and amplitude-to-time parameters of shock-wave excitation is studied.

Abstract: A magneto-hydrodynamic(MHD) model of magnetic controlled DC plasma torch is presented. The model includes the Navier-Stokes and the energy equations modified by the addition of some source terms, which reflect the Lorentz force due to the self-induced and the external magnetic fields, the radiative cooling and the Joule heating. In addition, the generalized Ohm's law, and the Maxwell's equations are also modeled. The MHD model is solved with the software FLUENT . The distribution of the velocity in the torch is obtained. The results show that the larger the current size of external current-carrying solenoid coil is , the greater the radial velocity and swirl velocity in the torch outlet are.

Abstract: In this paper, some discarded circuit boards in the plasma incinerator were incinerated by the converging - extended anode channel plasma torch, whose work principle and composition was described, and two experimental results were described, finally, the percentage of four major exhaust gas (CO, NO, SO₂, O₂) was reported, showing a good prospect on treating electronic waste with using the plasma torch.

Abstract: The cold crucible technology first developed for the treatment of the high level fission products can also be used for the direct treatment of intermediate level wastes. In this case, the wastes can be under the states of liquids or solids. The first experiments carried out for the direct treatment of ionic exchange resins emphasised the requirement of very high temperature on the surface of the glass. When this surface is to cold, the unperfected oxidation lead to a glass containing inclusion such as metallic compounds coming from the reduction of species contained in the waste. Thus, the quality of the glass could be not enough to meet with some specific requirements for long term storage. For few years, the Laboratory of the Innovative Processes has been studied the capability of a cold crucible to involved plasma torches ensuring the high temperature required for a complete oxidation of a large composition of waste. The developments and the assessment of different technological ways lead to build a cold crucible fitted with a bottom inductor together with twin plasma torches above the glass bath. This is the SHIVA process. The researches carried out on this innovative technology have shown the high efficiency of the combination for the treatment of a large variety of solid wastes. The oxidation is complete and the produced glass can be easily poured in a canister. This innovative process provides new perspective of treatment for a large variety of intermediate level waste stored on the ground of nuclear facilities.

Abstract: Ablatives are heat-shielding materials used to protect aerospace substructures. These materials are sacrificial in nature and provide protection primarily through the large endothermic transformation during exposure to hyper thermal environment such as encountered in re-entry modules. The performance of certain ablatives was reported in terms of their TGA/DTA in Advanced Materials-97 (pp57-65) (1). The focus of this earlier research resided in the consolidation of interface between the refractory inclusion and the host polymeric matrix to improve thermal resistance. In the present work we explore the scope of transpiration cooling in ablative performance through flash evaporation of liquid incorporated in the host EPDM (Ethylene Propylene Diene Monomer) matrix. The compression-molded specimens were exposed separately to plasma flame (15000 C) and oxyacetylene torch (3000 C) and the back face transient temperature is recorded in situ employing a thermocouple/data logger system. Both head on impingement (HOI) and parallel flow (PF) through a central cavity in the ablator were used. It is observed that transpiration cooling is effective and yields (a) rapid thermal equilibrium in the specimen, (b) lower back face temperature and (c) lower ablation rate, compared to conventional ablatives. SEM/EDS analysis is presented to amplify the point.

Abstract: A multiple fields’ coupled model of new magnetic controlled DC plasma torch, which was used for CVD diamond film, was presented. In this model, the effects of electric field and magnetic field on the flow field and temperature field were taken into account, and the fluid dynamics equations were modified by the addition of some source terms relating to electromagnetic field, such as Lorentz force, joule heating, and radiative cooling. Conversely, the generalized ohm’s law was used to solve the current density, which reflected the effects of flow field and temperature field on the electric field and magnetic field. In addition, the rest Maxwell’s equations and external solenoid magnetic field equation were also modeled. In order to know the effect of external magnetic field on the torch, the current intensity of external solenoid was chosen to simulate its influence on the flow and heat transfer in the torch. Results show that external magnetic field plays a part in stirring the plasma, which is advantageous for the preparation of diamond film. The larger the external solenoid current intensity is, the better the uniformity of the temperature and velocity of plasma is.

Abstract: High quality diamond film wafers with different thickness are prepared by high power DC arc plasma jet CVD (DCPJ CVD) method using a CH4/Ar/H2 gas mixture. The effects of methane concentration on the growth of carbon balls in anode nozzle and arc stability are studied with theoretical analysis and experimental investigation. The results indicate that different sizes of carbon balls may rapidly grow in the anode nozzle with methane concentration higher than 2 Vol-%, symmetry and uniformity of the rotating arc are strongly affected with the occurrence of carbon balls, which will result in non-uniform deposition of diamond films over a large substrate area. The methane concentration should be controlled at a low level to keep diamond film wafers growth stable. Characterization by X-ray diffraction, Raman spectroscopy and SEM analysis are also carried out.