Plasma is gaining interest for CH4 conversion into higher hydrocarbons and H2. However, the performance in terms of conversion and selectivity toward different hydrocarbons is different for different plasma types, and the underlying mechanisms are not yet fully understood. Therefore, we study here these mechanisms in different plasma sources, by means of a chemical kinetics model. The model is first validated by comparing the calculated conversions and hydrocarbon/H2 selectivities with experimental results in these different plasma types and over a wide range of specific energy input (SEI) values. Our model predicts that vibrational-translational nonequilibrium is negligible in all CH4 plasmas investigated, and instead, thermal conversion is important. Higher gas temperatures also lead to a more selective production of unsaturated hydrocarbons (mainly C2H2) due to neutral dissociation of CH4 and subsequent dehydrogenation processes, while three-body recombination reactions into saturated hydrocarbons (mainly C2H6, but also higher hydrocarbons) are dominant in low temperature plasmas.

Plasma-Based CH4 Conversion into Higher Hydrocarbons and H2: Modeling to Reveal the Reaction Mechanisms of Different Plasma Sources.

Nd:YAG laser hardening of AISI 410 stainless steel: Microstructural evaluation, mechanical properties, and corrosion behavior

This work investigates the cut quality characteristics of SS321 using plasma arc cutting. The SS321 has a wide range of applications such as in chemical storage, exhaust manifolds of automotives and aircraft. The intricate shapes for this material are very difficult to cut using conventional machining process. Hence, plasma arc cutting is used. The input cutting parameters are cutting speed, current, stand off distance and gas pressure. For each input parameter, three levels are considered and, therefore, total numbers of experimental runs are 3 × 3 × 3 × 3 = 81. To minimize the number of runs, the Taguchi L9 orthogonal array is proposed which is having advantages of both minimum and maximum trial runs. The output parameters are surface roughness, kerf width and heat-affected zone. The experiments are carried out in Micro Step spol S.R.O. Plasma arc cutting machine. To find the best cutting parameters, the regression models are given as input of Matlab-Genetic Algorithm. The test results show that ANOVA models are significant. It is inferred that lower values of current and Standoff Distance give better surface roughness and minimum heat-affected zone.

Experimental investigation of cut quality characteristics on SS321 using plasma arc cutting

Direct current plasma torches for plasma spraying applications generate electric arc instabilities. The resulting fluctuations of input electrical power hamper a proper control of heat and momentum transfers to materials for coating deposition. This paper gives an overview of major issues about arc instabilities in conventional DC plasma torches. Evidences of arc fluctuations and their consequences on plasma properties and on material treatments are illustrated. Driving forces applied to the arc creating its motion are described and emphasis is put on the restrike mode that depends on the arc reattachment and the boundary layer properties around the arc column. Besides the arc root shown as a key region of instability, the Helmholtz oscillation is also described and accounts for the whole plasma torch domain that can generate pressure fluctuations coupled with voltage ones.

Electric Arc Fluctuations in DC Plasma Spray Torch

An investigation into the microstructure and tribological properties of rail materials with plasma selective quenching

The utility model provides a welding fixture for a craft cartridge case. The fixture is composed of a clamp (1), a clamp (2) and a clamp (3), wherein the three clamps are relatively independent. The clamp (1) comprises a fixed supporting plate, a fixed bracket, attachment bolts, fastening bolts, a link stopper and adjusting plates so that the craft cartridge case can be welded in parallel. The clamp (2) comprises an upper supporting plate, a lower supporting plate, adjusting threaded rods, fixed brackets and attachment bolts so that butt welding can be performed on the craft cartridge case perpendicularly welded in the vertical direction. The clamp (3) comprises a left supporting plate, a right supporting plate, adjusting threaded rods, fixed brackets, supporting brackets and attachment bolts so that butt welding can be performed on the craft cartridge case perpendicularly welded in the horizontal direction.

Welding fixture for craft cartridge case

The utility model discloses a method for treating inner surfaces of elbow pipes with a plasma technology. The method comprises steps as follows: a clamping cantilever of a plasma spray gun is adjusted to be similar to the to-be-treated pipes in shape; the head of the plasma spray gun moves from one end to the other end along the inner walls of the elbow pipes; the plasma spray gun rotates by a proper angle; the head of the plasma spray gun reversely moves to the initial end along the inner walls of the elbow pipes; the plasma spray gun rotates by a proper angle continuously in the original direction; the movement is repeated until the whole treatment is finished. The utility model disclosesplasma equipment for treatment with the method. The equipment mainly comprises the small plasma spray gun, a spray gun rotating device, a telescopic support arm, a bending degreeadaptation cantilever and a rotating platform. The method and the equipment for treating the inner surfaces of the elbow pipes with the plasma technology can be applied to plasma surface treatment of inner walls of arc-shaped pipes with different bend diameters, material characteristics of the inner surfaces of the elbow pipes are improved, and service lives of the elbow pipes are prolonged.

Equipment for treating inner surfaces of elbow pipes with plasma technology

The invention discloses a rotating anode plasma generator. When the plasma generator works, an anode can rotate at a preset angle in a preset direction. On one hand, the position of a plasma arc root landing point of the plasma generator on the anode is more appropriate, and the service life of the anode of the plasma generator is prolonged; on the other hand, plasma jets can change directions along with rotation of the anode, and accordingly the plasma jets at a spraying port are in an annular shape. According to the rotating anode plasma generator, the plasma jet direction at an outlet of the anode of the plasma generator is changed, the plasma generator can be especially used for quenching of plasmas on the inner surface of a bent tube, and the application range of the plasma generator in the aspect of material surface processing is widened.

Rotating anode plasma generator

The invention discloses a lateral inner powder feeding plasma spray gun structure which has a high-efficient heating mode. An anode nozzle pore canal of a spray gun adopts a three-section structure, i.e. a front compression section, an intermediate arc stabilizing powder feeding section and a rear expansion incline section. When in work, spray powder is fed through a powder feeding hole which is identical in an oblique angle of the central axis of the expansion incline section after being mixed with gas, the spray powder has the same movement direction with plasma jet, so that the spray powder can be well heated and accelerated in the plasma jet, and an effect for improving the spray quality can be realized.

Lateral inner powder feeding plasma spray gun structure

The invention discloses a method for treating an inner surface of an elbow pipe with a plasma technology. The method comprises the following steps: regulating a plasma gun clamping cantilever to be close to the shape of a pipeline to be processed; moving the head of a plasma gun from one end to the other end along the inner wall of the elbow pipe; rotating the plasma gun by a proper angle; reversely moving the head of the plasma gun to an original end along the inner wall of the elbow pipe; continuously rotating the plasma gun by a proper angle in an original direction; and repeating the previous movements until the entire processing is completed. The invention discloses plasma equipment applicable to the method for processing, and the equipment mainly comprises a small-size plasma gun, a gun rotation device, a telescopic supporting arm, a curvature degree adapting cantilever and a rotation platform. The method and the equipment for treating the inner surface of the elbow pipe with the plasma technology, which are disclosed by the invention, can be applied to the plasma surface treatment of the inner walls of pipelines with different bending radius arcs, and are good for improving the material property of the inner surface of the elbow pipe and prolonging the service life of the elbow pipe.

Method and equipment for treating inner surface of elbow pipe with plasma technology

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