Carrier Gas Injection Research Articles

Modeling of the Effect of Carrier Gas Injection on the Laminarity of the Plasma Jet Generated by a Cascaded Spray Gun

In this work, the plasma generated by the cascaded SinplexProTM plasma spray gun was studied by means of numerical simulation. Special attention is given to the laminarity of the plasma flow. The simulation part is divided into two parts: arcing simulation inside the spray gun and plasma jet simulation outside the spray gun. A laminar as well as a turbulent model is used in each case. The results show that, under the investigated conditions, the internal flow of the plasma torch can be considered as laminar with low turbulence and can, hence, be regarded as quasi-laminar flow. If carrier gas is injected into the plasma jet, the ideal laminar plasma jet is often greatly affected. However, the turbulent plasma jet with low turbulence intensity generated by the cascaded SinplexProTM plasma spray gun is less affected and can remain stable, which is beneficial to the plasma-spraying process.

Modeling of Advanced Silicon Nanomaterial Synthesis Approach: From Reactive Thermal Plasma Jet to Nanosized Particles.

A three-dimensional numerical modelling of a time-dependent, turbulent thermal plasma jet was developed to synthetize silicon nanopowder. Computational fluid dynamics and particle models were employed via COMSOL Multiphysics® v. 5.4 (COMSOL AB, Stockholm, Sweden) to simulate fluid and particle motion in the plasma jet, as well as the heat dependency. Plasma flow and particle interactions were exemplified in terms of momentum, energy, and turbulence flow. The transport of nanoparticles through convection, diffusion, and thermophoresis were also considered. The trajectories and heat transfer of both plasma jet fields, and particles are represented. The swirling flow controls the plasma jet and highly affects the dispersion of the nanoparticles. We demonstrate a decrease in both particles’ velocity and temperature distribution at a higher carrier gas injection velocity. The increase in the particle size and number affects the momentum transfer, turbulence modulation, and energy of particles, and also reduces plasma jet parameters. On the other hand, the upstream flame significantly impacts the particle’s behavior under velocity and heat transfer variation. Our findings open the door for examining thermal plasma impact in nanoparticle synthesis, where it plays a major role in optimizing the growth parameters, ensuring high quality with a low-cost technique.

Microwave remediation of oil-contaminated drill cuttings – A review

In the oil drilling process, drill cuttings are loaded to the surface by the drilling fluid. When using synthetic-based drilling fluids, drill cuttings should be subjected to a separation process for later disposal of cuttings and reuse of drilling fluid. Several techniques have been used to adapt the drilling waste disposal to the environmental legislation, including microwave thermal desorption technology. This review presents the main studies on the microwave drying remediation of drill cuttings contaminated with synthetic-based drilling fluids, with emphasis on the advantages and disadvantages of the technologies used, making a comparative analysis of the methods. Although batch remediation prototypes allow reaching low residual oil levels, it presents low processing rates and high specific energies. Alternative batch decontamination processes can be used to increase the efficiency of oil removal, such as changing the thickness and the mechanical stirring of the bed, injection of carrier gas, reduction of heating rate, etc. These prototypes are also capable of remediation of reservoir cuttings, but with higher energy costs. Continuous industrial scale prototypes also achieve low oil residual levels (<0.1%), with relatively high flow rates (100–750 kg/h) and lower energy costs, and are effective to treat both the conventional and pre-salt drill cuttings. However, despite their great commercialization potential, some adjustments are required for operation with diluted slurry and a more effective temperature control to prevent the chemical changes in the organic phase of the drilling fluids.

One-Dimensional Analysis on the Gas/Particle Flows of Cold Spray Nozzle with Carrier Gas Injection in the Diverging Part

One-Dimensional Analysis on the Gas/Particle Flows of Cold Spray Nozzle with Carrier Gas Injection in the Diverging Part

Flow characteristic of in-flight particles in supersonic plasma spraying process

In this paper, a computational model based on supersonic plasma spraying (SAPS) is developed to describe the plasma jet coupled with the injection of carrier gas and particles for SAPS. Based on a high-efficiency supersonic spraying gun, the 3D computational model of spraying gun was built to study the features of plasma jet and its interactions with the sprayed particles. Further the velocity and temperature of in-flight particles were measured by Spray Watch 2i, the shape of in-flight particles was observed by scanning electron microscope. Numerical results were compared with the experimental measurements and a good agreement has been achieved. The flight process of particles in plasma jet consists of three stages: accelerated stage, constant speed stage and decelerated stage. Numerical and experimental indicates that the H2 volume fraction in mixture gas of Ar + H2 should keep in the range of 23–26 %, and the distance of 100 mm is the optimal spraying distance in Supersonic atmosphere plasma spraying. Particles were melted and broken into small child particles by plasma jet and the diameters of most child particles were less than 30 μm. In general, increasing the particles impacting velocity and surface temperature can decrease the coating porosity.

The analysis of melting and refining process for in-flight particles in supersonic plasma spraying

To understand the effect of in-flight particle behavior so as to improve the coating quality, an accurate description of transport phenomena of particles is essential. For supersonic plasma spraying (SAPS), a three-dimensional computational model is developed to describe the plasma jet coupled with the injection of carrier gas and particles. The heating and melting processes of single particle were also studied by a numerical method. The model treats the particles in the flow as discrete Lagrangian entities that exchange mass, momentum, and energy with the gas. The governing equations for the Reynolds averaged flow parameters were solved using FVM method and the continuity and momentum equations are coupled using the PISO algorithm. The velocity and temperature of the in-flight particles were measured by SprayWatch-2i, and the morphology of particles was observed by Scanning Electron Microscope (SEM). Numerical and experimental results showed that, the velocity and temperature of the in-flight particles were reached maximum at the spraying distance of 80–100 mm. Particles were melted and broken into small child particles by plasma jet. The small child particles were accelerated to higher in-flight velocity by gas flow. Particles were completely melted when the spraying distance about of 95 mm at the time of 0.35 ms. Numerical results were compared with the experimental measurements and a good agreement has been achieved.

고주파 열플라즈마 토치를 이용한 Ni 금속 입자의 나노화 공정에 대한 전산해석 연구

Numerical analysis on RF (Radio-Frequency) thermal plasma treatment of micro-sized Ni metal was carried out to understand the synthesis mechanism of nano-sized Ni powder by RF thermal plasma. For this purpose, the behaviors of Ni metal particles injected into RF plasma torch were investigated according to their diameters (), RF input power (6 ~ 12 kW) and the flow rates of carrier gases (2 and 5 slpm). From the numerical results, it is predicted firstly that the velocities of carrier gases need to be minimized because the strong injection of carrier gas can cool down the central column of RF thermal plasma significantly, which is used as a main path for RF thermal plasma treatment of micro-sized Ni metal. In addition, the residence time of the injected particles in the high temperature region of RF thermal plasma is found to be also reduced in proportion to the flow rate of the carrier gas In spite of these effects of carrier gas velocities, however, calculation results show that a Ni metal particle even with the diameter of can be completely evaporated at relatively low power level of 10 kW during its flight of RF thermal plasma torch (

A novel needle trap device with single wall carbon nanotubes sol–gel sorbent packed for sampling and analysis of volatile organohalogen compounds in air

This paper describes a new approach that combines needle trap devices (NTDs) with a newly synthesized silanated nano material as sorbent for sampling and analysis of HVOCs in air. The sol-gel technique was used for preparation of the single wall carbon nanotube (SWCNT)/silica composite as sorbent, packed inside a 21-gauge NTD. Application of this method as an exhaustive sampler device was investigated under different laboratory conditions in this study. Predetermined concentrations of each analyte were prepared in a home-made standard chamber, and the effects of experimental parameters, such as temperature, humidity, sampling air flow rate, breakthrough volume and storage time on NTD, and the sorbent performance were investigated. The proposed NTD was used in two different modes and two different injection methods, and an NTD with a side hole, a narrow neck glass liner and syringe pump assisted injection of carrier gas were applied. The NTD packed with SWCNTs/silica composite was compared to the NTD packed with PDMS and also SPME with CAR/PDMS. For four compounds, LOD was 0.001-0.01 ng mL(-1), LOQ was 0.007-0.03 ng mL(-1), and the relative standard division for repeatability of method was 2.5-6.7%. The results show that the incorporation of NTD and SWCNTs/silica composite is a reliable and effective approach for the sampling and analysis of HVOCs in air. Coupling this system to GC-MS make it more sensitive and powerful technique.

Three Dimensional Modeling of the Plasma Spray Process

Results of simulations of three-dimensional (3D) temperature and flow fields inside and outside of a DC arc plasma torch in steady state are presented with transverse particle and carrier gas injection into the plasma jet. The results show that an increase of the gas flow rate at constant current moves the anode arc root further downstream leading to higher enthalpy and velocity at the exit of the torch anode, and stronger mixing effects in the jet region. An increase of the arc current with constant gas flow rate shortens the arc, but increases the enthalpy and velocity at the exit of the torch nozzle, and leads to longer jets. 3D features of the plasma jet due to the 3D starting conditions at the torch exit and, in particular, due to the transverse carrier gas and particle injection, as well as 3D trajectories and heating histories of sprayed particles are also discussed.

Three-dimensional simulation of plasma spray: effects of carrier gas flow and particle injection on plasma jet and entrained particle behavior

As important phenomena in plasma spray, the plasma jet perturbation by the carrier gas flow and particles loading, and their effects on particle behavior are investigated. A three-dimensional computational model was developed to describe the plasma jet coupled with the orthogonal injection of carrier gas and particles. This model considered in-flight particle physical phenomena such as accelerating, heating, melting, and evaporation. The effects of carrier gas flow rates on the characteristics of plasma jet and particle spray pattern are simulated. The simulation results compare well with experimental data, for two common particle materials, NiCrAlY and ZrO2.

Three-dimensional modelling of the characteristics of long laminar plasma jets with lateral injection of carrier gas and particulate matter

A long laminar plasma jet has adjustable high-temperature region length, small temperature and velocity gradients in the axial direction, low noise emission and weak entrainment of ambient air into the jet, and thus it has potential applications in materials processing. A three-dimensional modelling approach is used in this paper to study the spatial distributions of plasma parameters in the long laminar plasma jet for the case with and without lateral injection of particulate matter and its carrier gas. The combined diffusion coefficient method is employed in the modelling to treat the diffusion of ambient air into the plasma jet. Typical computed distributions of temperature, velocity and species concentration in the jet are presented using the long laminar argon plasma jet issuing into ambient air as a calculation example. It is shown that similarly to the turbulent plasma jet case, the long laminar plasma jet has good enough stiffness to endure the impact of the laterally injected carrier gas, although the laminar jet assumes slight deflection from its original geometrical axis in the injection plane due to the action of laterally injected carrier gas. The three-dimensional effects caused by the lateral carrier-gas injection on the jet characteristics and thus on the particle moving trajectories and heating histories are shown to be appreciable. Particulate matter can be fed into the high-temperature region of the laminar plasma jet with the aid of the carrier gas.

3D modeling of plasma–particle interactions in a plasma jet under dense loading conditions

Abstract A turbulent argon plasma jet discharged into an air atmosphere is modeled for given torch input parameters. Plasma–particle interactions are also modeled by coupling Lagrangian equations describing velocity, temperature and position of the particles with an Eulerian system of equations describing the plasma flow and temperature. Results of present model are compared with both experimental and previous model results. The effects of radial injection of carrier gas and particle loading both on the plasma and particle velocities and on the temperatures are clarified. Particle loading with carrier gas locally and strongly influences the flow fields of the plasma jet. A higher mass flow rate of the carrier gas decreases the axial velocity of the plasma jet locally. In swirl jet, the weak effects of carrier gas and particle loading are distributed in larger volume. It is found that both particle velocity and temperature distributions are wider at higher particle loading than at lower particle loading in non-swirl plasma jet.

Three-dimensional flow and heat transfer in thermal plasma systems

Three-dimensional (3-D) modeling of thermal plasma systems is still a challenging problem. Modeling results recently obtained in our group are briefly presented in this paper concerning the 3-D flow and heat transfer characteristics of the thermal plasma reactor, plasma jet and non-transferred arc plasma torch. A well-validated non-commercial computer code is employed in the study. It is shown that when particulate-matter and its carrier-gas are injected into a plasma reactor through a single port at the side-wall of reactor, appreciable 3-D flow and heat transfer effects will appear and cannot be well modeled by any two-dimensional models. The 3-D effects influence the particle motion and heating within the reactor. For a plasma jet with lateral injection of carrier-gas and particles, the 3-D effects are also shown to be non-negligible. Marked 3-D special features of the flow and heat transfer within DC non-transferred arc plasma torches have been demonstrated even for the torch with completely axi-symmetrical geometrical configuration, working gas admission and electrical current connection. The predicted results are well consistent with experimental observation. Further research requirement is also discussed in this paper.

Three-dimensional effects of carrier gas and particle injections on the thermo-fluid fields of plasma jets

A numerical model is developed to clarify three-dimensional effects of the radial injection of carrier gas and particles on the thermo-fluid fields of the plasma jet with and without swirl. The plasma-particle two-way interactions are modelled by coupling a Lagrangian approach for particle behaviour with an Eulerian approach for plasma flow under dense loading. The effect of radial injection of the carrier gas on the flow and temperature fields of the plasma jet with and without swirl is clarified by numerical simulation. The deformations of the plasma jet thermo-fluid fields caused by dense particle loading with and without turbulent dispersion of the particles are presented. It is shown that the high mass flow rate of the carrier gas affects plasma jet fields strongly and particle turbulent dispersion can control the deformation of the plasma jet fields. The given swirl flow reduces the momentum and energy transfers between plasma and particles.

Three-dimensional modeling of the turbulent plasma jet impinging upon a flat plate and with transverse particle and carrier-gas injection

Modeling results are presented concerning the turbulent thermal plasma jet impinging normally on a substrate and with transverse injection of feedstock particles and their carrier gas from a single injection tube. The k-e two-equation model is employed to model the turbulence, and particle dispersion is studied considering the interaction between the moving particles and turbulent eddies and considering the effect on particle trajectories of the random variation of the turbulent fluctuating velocities in their magnitude and direction. A well-validated three-dimensional (3-D) computer code is used in the modeling. The 3-D effects due to the carrier gas injection on the jet flow field and thus on the particle trajectories and heating histories are shown to be appreciable. The radial location of the injection tube with respect to the plasma jet is shown to be a critical parameter for the study of 3-D effects, besides the carrier-gas/plasma stream mass flux ratio. Particle dispersion considerably widens the distribution of the particle trajectories and heating histories. In addition, although pertinent swirl number is often rather small, swirling may also affect the modeling results.

Three-dimensional simulation of a plasma jet with transverse particle and carrier gas injection

Abstract In the present paper, three-dimensional modeling results are presented concerning the turbulent thermal plasma jet with transversely injected carrier gas and metal particles at atmospheric pressure. The standard K− e model is employed for the numerical simulation of the turbulent plasma flow in coupling with the variable-property continuity, momentum and energy equations. For predicting the motion of the injected particles in the turbulent flow field, an improved particle stochastic-trajectory model is adopted in the calculation. The heating histories of the injected particles are also calculated in their moving processes. The modeling results show that including the effect of carrier gas on jet and particle behavior is very important. The plasma jet is deflected from its geometrical axis due to the transverse injection of carrier gas, and the particle trajectories are also appreciably changed by the carrier gas injection. The particles disperse around their average trajectories in the turbulent flow field.

Volatilization studies for Fe and Cd in their direct determination by inductively coupled plasma-atomic emission spectrometry using direct sample insertion or external electrothermal evaporation of powders

Abstract The object of this work was to study the evaporation and excitation processes in the analysis of powders by the direct insertion of the samples into an inductively coupled plasma (ICP) as well as by external electrothermal evaporation. The evaporation rates were monitored by using 59 Fe and 115 Cd radioactive isotopes, and the influence of various parameters such as the geometrical conditions, the carrier gas injection and the flow characteristics were investigated. The addition of thermochemical substances during direct and external evaporation was found necessary to achieve complete evaporation of Fe from the ceramic powder (Durital E90- Al 2 O 3 /SiO 2 ) and from the graphite samples.

P‐Doped Polysilicon Film Growth Technology

This paper deals with P‐doped polysilicon film growth in the and gas reaction by hot‐wall low pressure CVD technology. In P‐doped polysilicon film growth, between 600° and 650°C, the injection of carrier gas through an additional port at the exhaust vacuum pump side, which is opposite to the ports for and reaction gases, yielded uniform film thickness and resistivity, and a lower resistivity at a higher deposition rate. As the carrier, He gas, which has a long mean‐free path and a large diffusion constant, has proved effective for controlling the film thickness and resistivity distribution across the wafer. The P‐doped polysilicon film growth mechanism was explained by the Langmuir‐Hinshelwood's adsorption reaction model. The P‐doped polysilicon films, deposited on 4 in. wafers under the optimum growth condition in a batch of 50 wafers, were ±3% across the wafer and ±5% wafer to wafer in both film thickness and resistivity. A 70Å/min deposition rate was maintained for these films. After being subjected to a post heat‐treatment in an atmosphere at 1000°C for 30 min the wafers had a resistivity for 5000Å film thickness.