Research on the rapid combustion process of butane under microwave discharge

To study the combustion process of fuel in the microwave plasma torch, we designed a butane microwave plasma device exploiting a tungsten rod as an electrode. Through analysis of the image record by high-speed camera, we found that the discharge of butane microwave plasma torch is a cyclic process at atmospheric pressure at a frequency of around 100 Hz. During the discharge, the active particles continuously diffuse from the electrode to the outside like the bloom of the flower. Then, the variation of plasma torch of jet height and temperature with microwave power is obtained. In addition, we studied the effects of different butane flow rates on the plasma torch. The results illustrate that excessive butane will lead to carbon deposition on the electrode. All in all, this work provides a new understanding of the combustion of the microwave plasma torch, which is conducive to the further development of microwave plasma in the fields of waste gas treatment, fuel combustion, and plasma engine.

Characterization of opportunity for upgrading of the system based on arc plasma torch for thermal spaying of ceramic materials, by means of use of fuel vortex intensifier. Part I: Thermodynamic modeling of the system efficiency parameters

One of the main trends in the field of improving the modern technologies of thermal spraying, including plasma one, for functional ceramic coatings formation is the reducing the energy consumption of the process. In this regard, one of the important directions for improving these technologies is the development of their new versions, using the principle of adding inexpensive fuel-oxidizer mixtures based on hydrocarbons with air. This type of plasma-fuel type of spraying will be promising for application at the present time, first of all, in order to obtain refractory functional coatings. For this purpose, we investigated the opportunity for upgrading an industrial unit/system for plasma spraying of ceramic powder materials with arc plasma torch of 25–40 kW power by the use of experimental variant of a fuel gas-vortex intensifier. The thermodynamic assessment of possible parameters of the generated mixed flow after the torch with this fuel intensifier was carried out to estimate the applicability of this system to optimize the spraying of oxide and carbide coatings (based on the examples of Al2O3, Cr3C2 and other powders). The analysis of possible parameters of the produced flow after the torch with intensifier was performed for the cases of main C–H–O–N–Ar–Me (Me = Al, Cr) systems and additional C–H–O–Al-system to assess the potential of this system to modify the technology of oxide and carbide ceramic coatings formation. New regimes, which were analyzed in our research as the simulants of Al2O3 spraying, surpass on calculated energy efficiency characteristics (by 10–20 %) one of the new prospective spraying methods with (СO2+СH4)-plasma, as well as the conventional method of powder heating during the spraying with N2-plasma. The case of our proposed fuel assisted process (FA-APS) with liquefied petroleum gas (LPG) fuel for the heating of ceramic powders (especially, Al2O3) demonstrates the advantage of the process (in particular, on the energy efficiencies and energy consumption) in a comparison with the conventional regimes of APS of the powders (in N2 plasma of the standard torch). For the variants of the FA-APS with Al2O3 and Cr3C2 feedstock powders it was established to be potentially possible to obtain (at the moderate values of total electric energy consumption for the torch and auxiliary equipment, – near 1.8 and 1.0 kWh/(kg of product)) such high level of the process productivity on the final product as approximately 17 and 28 kg/h, respectively; at the values of required power of the torch:  28.2 and  22.3 kW.

Characterisation of a Cold Atmospheric Pressure Plasma Torch for Medical Applications: Demonstration of Device Safety

The safety and effectiveness of plasma devices are of crucial importance for medical applications. This study presents the novel design of an atmospheric plasma torch (SteriPlas) and its characterisation. The SteriPlas was characterised to ascertain whether it is safe for application on human skin. The emission spectrum discharged from the SteriPlas was shown to be the same as the emission from the MicroPlaSter Beta. The UV emitted from the SteriPlas was measured, and the effective irradiance was calculated. The effective irradiance enabled the determination of the maximum UV exposure limits, which were shown to be over two hours: significantly longer than the current two-minute treatment time. The use of an extraction system with a higher flow rate appears to reduce slightly the effective irradiance at the treatment area. The NOx and ozone emissions were recorded for both SteriPlas configurations. The NOx levels were shown to be orders of magnitude lower than their safety limits. The ozone emissions were shown to be safe 25 mm from the SteriPlas cage. A discussion of how safety standards differ from one regulatory body to another is given.

Application of functional coatings by supersonic thermal plasma flows

Development of modern high-speed technologies for thermal spraying proves that deposition of high-quality dense coatings requires velocity of sprayed particles to be 600 m/s and above. Plasma spraying is the most versatile and highly productive deposition method of various functional coatings without any limitations on the melting points of the sprayed materials. Present work describes a DC plasma torch designed for operation in a supersonic mode. The supersonic plasma torch features de Laval nozzle, utilization of air as a plasma-forming gas, and annular injection unit for delivery of the powder to the plasma jet. The comparison of NiCr and NiAl coatings deposited both in subsonic and supersonic modes are presented. Methods for further increasing the sprayed particles’velocity and the requirements for their heating temperature are proposed.

Formation of highly concentrated heterogeneous flows during plasma deposition of powder materials

Most industrial installations for plasma spraying of powder materials are equipped by nozzles with local (radial) powder input into the thermal plasma jet generated by the plasma torch. Such a local input of the sprayed material significantly perturbs the flow of the plasma jet, and causes dispersion of temperature and velocity of the particles of the sprayed powder materials. This work presents study of high-temperature heterogeneous flows generated by the electric arc plasma torch PNK - 50 with an annular (circular) input unit of powder materials with their gas-dynamic focusing developed at ITAM SB RAS. The performed experiments proved that the annular injection of a powder material guarantees the stable formation of a highly concentrated flow of thermal plasma with particles of sprayed powder materials. The comparative analysis clearly showed the advantages of annular powder input unit with its gas-dynamic focusing. In contrast to local point injection, axisymmetric annular injection practically does not disturb the jet of thermal plasma and, thus, significantly increases the efficiency of interphase exchange.

Simulation of 3D vortex jets in plasma torch application

The gas tunnel type plasma jet is an effective heat source for thermal processing applications such as plasma spraying. The key concept of gas tunnel plasma is its torch configuration, especially the role of the vortex gas flow. This is very important for the stability and energy density of the plasma jet produced. This work studied the flow of gas vortex in 3 dimensions using a finite element simulation. The simulation is based on solving partial differential equations where the incompressible Navier-Stokes equation is used as a governing equation that describes the laminar flow. The geometry of the plasma torch investigated is based on the design by A. Kobayashi. Key parameters investigated were gas pressure, velocity and profile of the vortex. It can be shown that the simulation produced results that are better matched to the experimental result than the calculation done in previous work. The simulation can also show detailed pictures of the vortex and its properties within the plasma chamber. This study could be useful in the design optimization of the plasma torch in the future.