Melting of Powder Particles in a Low Pressure Plasma Jet

1983 ◽  
Vol 30 ◽  
Author(s):  
D. Wei ◽  
D. Apelian ◽  
S. M. Correa ◽  
M. Paliwal
Keyword(s):  
Plasma Jet ◽  
Low Pressure ◽  
Navier Stokes ◽  
Temperature Dependent ◽  
Navier Stokes Equation ◽  
Free Jet ◽  
Binary Model ◽  
Proposed Model ◽  
Powder Particles ◽  
Heat And Momentum Transfer

ABSTRACTA numerical model has been developed to predict the temperature profile of particles injected in a D.C. plasma jet. The equations governing particle melting were applied to spherical powders of binary model alloys. Thermophysical properties of the gas and the powder material have been taken to be temperature dependent. In the proposed model, the latent heat of melting was taken into account by introducing apparent enthalpy as a function of the fraction of liquid formed which can be derived from equations describing non-equilibrium melting. The temperature and velocity profiles of the plasma jet used in this analysis are for a free jet (without target interference) and were calculated using the parabolic Navier-Stokes equation with a K-E turbulence model. Correction factors have been introduced to take into account non-continuum effects encountered in the low pressure environment and the results show that both heat and momentum transfer between the plasma gas and the injected particles are reduced.

Melting Powder Particles in a Low-Pressure Plasma Jet

1987 ◽  
Vol 109 (4) ◽  
pp. 971-976 ◽  
Author(s):  
D. Y. C. Wei ◽  
B. Farouk ◽  
D. Apelian
Keyword(s):  
Stokes Equations ◽  
Plasma Jet ◽  
Low Pressure ◽  
Velocity Fields ◽  
Temperature History ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
History Of ◽  
Powder Particles ◽  
Temperature And Velocity Fields

A numerical model has been developed to predict the temperature history of metal particles injected in a low-pressure (supersonic) d-c plasma jet. The temperature and velocity fields of the plasma jet are predicted by solving the parabolized compressible Navier–Stokes equations using a spatial marching scheme. Particle trajectories and heat transfer characteristics are calculated using the predicted plasma jet temperature and velocity fields. Correction factors have been introduced to take into account the noncontinuum effects encountered in the low-pressure environment. The plasma jet profiles as well as the particle/plasma interactions under different jet pressure ratios (from underexpanded to overexpanded cases) have been investigated.

A note on the solution of the Navier-Stokes equations for a spherically symmetric expansion into a very low pressure

1973 ◽  
Vol 59 (2) ◽  
pp. 391-396 ◽  
Author(s):  
N. C. Freeman ◽  
S. Kumar
Keyword(s):  
Shock Wave ◽  
Reynolds Number ◽  
Stokes Equation ◽  
Stokes Equations ◽  
Low Pressure ◽  
Navier Stokes ◽  
Spherically Symmetric ◽  
Navier Stokes Equation ◽  
Navier Stokes Equations ◽  
Type Flow

It is shown that, for a spherically symmetric expansion of a gas into a low pressure, the shock wave with area change region discussed earlier (Freeman & Kumar 1972) can be further divided into two parts. For the Navier–Stokes equation, these are a region in which the asymptotic zero-pressure behaviour predicted by Ladyzhenskii is achieved followed further downstream by a transition to subsonic-type flow. The distance of this final region downstream is of order (pressure)−2/3 × (Reynolds number)−1/3.

Analytical Solution of Hydrostatic Pocket Tilting

2016 ◽  
Vol 821 ◽  
pp. 113-119 ◽  
Author(s):  
Eduard Stach ◽  
Jiří Falta ◽  
Matěj Sulitka
Keyword(s):  
Computational Models ◽  
Load Capacity ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Detailed Model ◽  
Limit Values ◽  
Inertia Effects ◽  
Proposed Model ◽  
Machine Tool Structure

Tilting (parallelism error) of guiding surfaces may cause reduction of load capacity of hydrostatic (HS) guideways and bearings in machine tools (MT). Using coupled finite element (FE) computational models of MT structures, it is nowadays possible to determine the extent of guiding surfaces deformation caused by thermal effects, gravitational force, cutting forces and inertia effects. Assessment of maximum allowable tilt has so far been based merely on experience. The paper presents a detailed model developed for description of the effect of HS bearing tilt on the load capacity characteristics of HS guideways. The model allows an evaluation of the tilt influence on the change of the characteristics as well as determination of the limit values of allowable tilt in interaction with compliant machine tool structure. The proposed model is based on the model of flow over the land of the HS pocket under extended Navier-Stokes equation. The model is verified using an experimental test rig.

A Model for an Acoustically Driven Microbubble Inside a Rigid Tube

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Adnan Qamar ◽  
Ravi Samtaney
Keyword(s):  
Bubble Radius ◽  
Coupled Model ◽  
Tube Diameter ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Rigid Tube ◽  
Basic Model ◽  
Proposed Model ◽  
D 12 ◽  
Bubble Fragmentation

A theoretical framework to model the dynamics of acoustically driven microbubble inside a rigid tube is presented. The proposed model is not a variant of the conventional Rayleigh–Plesset category of models. It is derived from the reduced Navier–Stokes equation and is coupled with the evolving flow field solution inside the tube by a similarity transformation approach. The results are computed, and compared with experiments available in literature, for the initial bubble radius of Ro = 1.5 μm and 2 μm for the tube diameter of D = 12 μm and 200 μm with the acoustic parameters as utilized in the experiments. Results compare quite well with the existing experimental data. When compared to our earlier basic model, better agreement on a larger tube diameter is obtained with the proposed coupled model. The model also predicts, accurately, bubble fragmentation in terms of acoustic and geometric parameters.

Mathematical and Computer Modeling of Particles Interaction with Plasma Jet in Low Pressure Condition

1998 ◽  
Author(s):  
A. Ilyuschenko ◽  
V. Okovity ◽  
S. Kundas ◽  
V. Gurevich
Keyword(s):  
Mathematical Model ◽  
Particle Velocity ◽  
Three Dimensional ◽  
Argon Plasma ◽  
Plasma Jet ◽  
Low Pressure ◽  
Tungsten Oxides ◽  
Spraying Parameters ◽  
Powder Particles ◽  
Low Pressure Plasma Spraying

Abstract On the base of gases molecular and kinetic theory a mathematical model of interaction between powder particles and plasma jet is developed. Three-dimensional description of plasma forming gas density distribution as well as particle motion in the plasma jet are a characteristic property of the model. A software for practical realization of the mathematical model is created. Said software provides the possibility to investigate an effect of low-pressure plasma spraying parameters on particle velocity andco-ordinates in the plasma jet. Computer simulation of particle velocity for powders from aluminium and tungsten oxides in argon plasma under 60 Mbar is conducted. A "Plasma-Tecbnik" VPS unit is used for testing the developed model. Particle velocity measurement is made by a specially developed optical-electronic unit.

On the Effective Viscosity Expression for Modeling Squeeze-Film Damping at Low Pressure

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Maria F. Pantano ◽  
Leonardo Pagnotta ◽  
Salvatore Nigro
Keyword(s):  
Experimental Data ◽  
Stokes Equation ◽  
Effective Viscosity ◽  
Optimization Procedure ◽  
Low Pressure ◽  
Squeeze Film ◽  
Navier Stokes ◽  
Fluid Viscosity ◽  
Navier Stokes Equation ◽  
Squeeze Film Damping

While at high pressure, the classical Navier–Stokes equation is suitable for modeling squeeze-film damping, at low pressure, it needs some modification in order to consider fluid rarefaction. According to a common approach, fluid rarefaction can be included in this equation by substituting the standard fluid viscosity with a fictitious quantity, known as effective viscosity, for which different formulations were proposed. In order to identify which expression works better, the results obtained when either formulation is implemented inside the Navier–Stokes equation (that is then solved by both analytical and numerical means) are compared with already available experimental data. At the end, a novel expression is discussed, derived from a computer-assessed optimization procedure.

An Experimental Study of Powder Melting During Low Pressure Plasma Deposition

1983 ◽  
Vol 30 ◽  
Author(s):  
M. Paliwal ◽  
D. Apelian
Keyword(s):  
Experimental Study ◽  
High Performance ◽  
Plasma Deposition ◽  
Plasma Jet ◽  
Low Pressure ◽  
Process Variables ◽  
Plasma Gun ◽  
Pressure Plasma ◽  
Low Pressure Plasma ◽  
Powder Particles

ABSTRACTLow pressure plasma deposition (LPPD), a recent advancement in plasma spray metallizing, is currently being developed for high performance materials applications. An experimental study of particle melting within the plasma jet was pursued to identify the effect of the process variables and the material properties on the resultant deposit. In tandem the experimental results have been utilized in the development and verification of a mathematical model for the melting of powder particles during the process.Two binary iron based model alloys - Fe-20 wt% Mn and Fe-20 wt% Cu - were plasma sprayed using Ma 2.4 and Ma 3 guns. Two different methods were used to evaluate the degree of particle melting within the plasma jet. The first method intercepts the particle path in the plasma jet with a glass slide, whereas in the second method the powder particles are collected in free flight using a powder collector (resolidification of powder particles occurs before they impact the collector walls). The droplets which impacted on glass slides and the collected (using the powder collector) powder particles were studied for mode and degree of powder particle melting using scanning electron microscopy. “Sweet spot” deposits (with no relative motion between the plasma gun and the substrate) were also made for the two model alloys in different size ranges using the Ma 2.4 and Ma 3 guns. The resulting deposits were metallographically evaluated. Mode and degree of particle melting injected under different process variables as well as the resultant deposit structures are presented.

scholarly journals Simulation of 3D vortex jets in plasma torch application

2021 ◽  
Vol 2145 (1) ◽  
pp. 012021
Author(s):  
W Kongpiboolkid ◽  
R Mongkolnavin
Keyword(s):  
Plasma Torch ◽  
Gas Flow ◽  
Plasma Jet ◽  
Experimental Result ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Element Simulation ◽  
The Stability ◽  
Incompressible Navier Stokes Equation

Abstract 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.

scholarly journals Closure model for homogeneous isotropic turbulence in the Lagrangian specification of the flow field

2018 ◽  
Vol 841 ◽  
pp. 521-551
Author(s):  
Makoto Okamura
Keyword(s):  
Flow Field ◽  
Isotropic Turbulence ◽  
Longitudinal Velocity ◽  
Navier Stokes ◽  
Homogeneous Isotropic Turbulence ◽  
Closure Model ◽  
Navier Stokes Equation ◽  
Closed Set ◽  
Proposed Model ◽  
Velocity Derivative

This paper proposes a new two-point closure model that is compatible with the Kolmogorov$-5/3$power law for homogeneous isotropic turbulence in an incompressible fluid using the Lagrangian specification of the flow field. A closed set of three equations was derived from the Navier–Stokes equation with no adjustable free parameters. The Kolmogorov constant and the skewness of the longitudinal velocity derivative were evaluated to be 1.779 and$-0.49$, respectively, using the proposed model. The bottleneck effect was also reproduced in the near-dissipation range.

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