scholarly journals Flow study in structure of the plasma torch for microwave plasma spray

2020 ◽  
Vol 4 (2) ◽  
pp. 56-60
Author(s):  
Muhammad Fahmi Izuwan Samion ◽  
Nur Ziana Norizat ◽  
Ahmad Redza Ahmad Mokhtar
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Plasma Spray ◽  
Plasma Torch ◽  
Gas Flow ◽  
Microwave Plasma ◽  
Microwave Oven ◽  
Outer Diameter ◽  
Flow Rates ◽  
Suitable Structure

Microwave oven induced plasma method is a novel application of microwave oven to generate plasma for coating process. It uses 2.45 GHz microwave power and only 0.8 kW input power to produce the plasma which capable of spraying all materials that are considered sprayable. However, the research regarding this microwave plasma spray are more to be discovered. Suitable structure of plasma torch is needed for microwave plasma spray that can produce laminar flow to produce desire plasma for coating application. Therefore, this paper will discuss about the suitable structure of plasma torch needed for laminar flow by Reynolds number calculation. Reynolds number calculated by applying the outlet diameter of antenna which is 2, 3 and 4 mm. From this research, Reynolds number from all outer diameter of antenna are below 2000 which indicate laminar flow. The widest plasma diameter achieved at 6.59 mm with 4 mm outlet diameter of antenna and 15 lpm working gas flow rate while the narrowest plasma diameter achieved at 1.26 mm with 3 mm outlet diameter of antenna and 10 lpm flow rates of working gas. The most acceptable condition for producing plasma plume was at 3 mm of antenna diameter with 25 lpm of Ar gas flow rates.

Optical diagnostics of a low power—low gas flow rates atmospheric-pressure argon plasma created by a microwave plasma torch

2009 ◽  
Vol 18 (2) ◽  
pp. 025030 ◽  
Author(s):  
Chuji Wang ◽  
Nimisha Srivastava ◽  
Susan Scherrer ◽  
Ping-Rey Jang ◽  
Theodore S. Dibble ◽  
...  
Keyword(s):  
Low Power ◽  
Atmospheric Pressure ◽  
Plasma Torch ◽  
Gas Flow ◽  
Microwave Plasma ◽  
Argon Plasma ◽  
Optical Diagnostics ◽  
Flow Rates ◽  
Microwave Plasma Torch

scholarly journals Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Blanke ◽  
Markus Hagenkamp ◽  
Bernd Döring ◽  
Joachim Göttsche ◽  
Vitali Reger ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Circular Ring ◽  
Flow Conditions ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

Laminar and transitional flow of drilling muds and various suspensions in circular tubes

1967 ◽  
Vol 30 (3) ◽  
pp. 449-464 ◽  
Author(s):  
Bernard Le Fur ◽  
Madeleine Martin
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Rheological Behaviour ◽  
Simple Expression ◽  
Transitional Flow ◽  
Transition Flow ◽  
Flow Rates ◽  
Circular Tubes ◽  
Head Losses ◽  
Drilling Muds

Most suspensions exhibit a rheological behaviour which cannot be represented by either Bingham's or Ostwald–De Waele's law. In studying such cases a very simple expression with only three parameters may be used. Starting with an intermediate law of this sort, this paper gives velocity profiles and head losses in laminar flow, which have been computed and plotted on diagrams in non-dimensional co-ordinates.It has been found that transition flow rates in circular tubes for data taken from the literature and from experiments conducted on drilling muds at the Institut Français du Pétrole, are efficiently predicted by an empirical criterion (Ryan & Johnson 1959) which establishes a relation between a generalized Reynolds number and a generalized Hedström number.

Characterizing the High Reynolds Number Regime for Deterministic Lateral Displacement (DLD) Devices

2017 ◽  
Author(s):  
Brian Dincau ◽  
Arian Aghilinejad ◽  
Jong-Hoon Kim ◽  
Xiaolin Chen
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Soft Lithography ◽  
Lateral Displacement ◽  
Flow Characteristics ◽  
Critical Diameter ◽  
Flow Rates ◽  
Deterministic Lateral Displacement ◽  
Array Configuration ◽  
High Reynolds

Deterministic lateral displacement (DLD) is a common name given to a class of continuous microfluidic separation devices that use a repeating array of pillars to selectively displace particles having a mean diameter greater than the critical diameter (Dc). This Dc is an emergent property influenced by pillar shape, size, and spacing, in addition to the suspending fluid and target particle properties. The majority of previous research in DLD applications has focused on the utilization of laminar flow in low Reynolds number (Re) regimes. While laminar flow exhibits uniform streamlines and predictable separation characteristics, this low-Re regime is dependent on relatively low fluid velocities, and may not hold true at higher processing speeds. Through numerical modeling and experimentation, we investigated high-Re flow characteristics and potential separation enhancements resulting from vortex generation within a DLD array. We used an analytical model and computational software to simulate DLD performance spanning a Re range of 1–100 at flow rates of 2–170 μL/s (0.15–10 mL/min). Each simulated DLD array configuration was composed of 60 μm cylindrical pillars with a 45 μm gap size. The experimental DLD device was fabricated using conventional soft lithography, and injected with 20 μm particles at varying flow rates to observe particle trajectories. The simulated results predict a shift in Dc at Re > 50, while the experimental results indicate a breakdown of typical DLD operation at Re > 70.

Under-Expanded Gaseous Flow at a Straight Micro-Tube Exit

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Takahiro Yoshimaru ◽  
Yutaka Asako ◽  
Toru Yamada
Keyword(s):  
Total Pressure ◽  
Gas Flow ◽  
Numerical Results ◽  
Pitot Tube ◽  
Outer Diameter ◽  
Flow Rates ◽  
Gaseous Flow ◽  
Mass Flow Rates ◽  
Tube Exit ◽  
Slight Discrepancy

This paper focuses on under-expanded gaseous flow at a straight micro-tube exit. The pitot total pressure of gas flow (jet) in the downstream region from a straight micro-tube exit was measured by a total pressure pitot tube to accumulate data for validation of numerical results. A micro-tube of 495μm in diameter and 56.3 mm in length and a total pressure pitot tube of 100 μm in outer diameter were used. The pitot total pressure was measured at intervals of 0.1 mm in both the flow and radial directions. The measurement was done for the mass flow rates of 9.71 × 10−5 kg/s and 1.46 × 10−4 kg/s. The data were accumulated for validation of the numerical results to reveal the characteristics of the under-expanded gas flow at the exit of a micro-tube. Comparisons were conducted for numerical results of corresponding cases and a slight discrepancy can be seen between numerical and experimentally measured pitot total pressures.

Low–power plasma torch method for the production of crystalline spherical ceramic particles

2001 ◽  
Vol 16 (5) ◽  
pp. 1256-1265 ◽  
Author(s):  
Chun-Ku Chen ◽  
Seth Gleiman ◽  
Jonathan Phillips
Keyword(s):  
Particle Size ◽  
Low Power ◽  
Atmospheric Pressure ◽  
Plasma Torch ◽  
Gas Flow ◽  
Microwave Plasma ◽  
Particle Density ◽  
Particle Collision ◽  
Average Particle ◽  
The Impact

A low-power, atmospheric pressure, microwave plasma torch was used to make spherical alumina particles of controlled size from irregularly shaped precursor powders. Detailed studies of the impact of operating parameters, particularly gas identity (argon or air), gas flow rates, and applied power, showed that particle size changed in a predictable fashion. The most important factor in controlling particle size appears to be precursor particle density in the aerosol stream that enters the plasma hot zone. This and other facts suggest that particle collision rate is primarily responsible for determining ultimate particle size, although atomic addition also plays a role. Reproducible volume average particle sizes ranging from 97 to 1150 μm3 were formed from precursor particles of order 14 μm3. Moreover, for the first time we report the creation of an atmospheric pressure low-power air plasma (<1 kW).

Vacuum plasma spray deposition of YSZ–NiO–Ni coatings at different Ar and H2 gas flow rates

Vacuum ◽  
2011 ◽  
Vol 86 (1) ◽  
pp. 34-38 ◽  
Author(s):  
Tomas Grinys ◽  
Sigitas Tamulevičius ◽  
Mindaugas Šilinskas
Keyword(s):  
Plasma Spray ◽  
Gas Flow ◽  
Spray Deposition ◽  
Vacuum Plasma Spray ◽  
Flow Rates ◽  
Vacuum Plasma

scholarly journals Explosive disintegration of two-component droplets in a gas flow at its turbulization

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 2983-2993
Author(s):  
Dmitrii Antonov ◽  
Pavel Strizhak
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Gas Flow ◽  
Combustion Products ◽  
Heating Time ◽  
Flue Gases ◽  
Relative Area ◽  
Heated Air ◽  
Two Component ◽  
Explosive Disintegration

The experimental results shown that the mode of droplet disintegration dominates in the laminar flow, and the intensive fragmentation is prevalent in the turbulent flow during almost the entire time of heating. Typical dependences of the time of droplet heatup before disintegration or fragmentation on the temperature, flow rate, structure and regime (laminar and turbulent) are established. The studies are conducted with heated air and flue gases to ensure the application of the research results in the technology of thermal and flame cleaning of liquids from irregular impurities. It is shown that in the flow of combustion products the droplet disintegration occurs 15-20% faster than in the air-flow. In this case, the explosive puffing is more often realized. At high-temperatures (more than 400?C) the characteristics of the explosive droplet disintegration in the studied flows are almost identical (differences in disintegration times do not exceed 5% at different flow turbulization). At lower temperatures, the disintegration times differ 3-4 times for the range Re = 2200-3400. In this case, the more Reynolds number is, the more intense is the fragmentation of two-component droplets throughout the heating time. Due to explosive disintegration of intensely evaporating two-component droplets the growth of the relative area of evaporation was 10-25 times.

Predicted Anode Arc Attachment by Local Thermodynamic Equilibrium (LTE) and Two-Temperature Arc Models in a Cascaded-Anode dc Plasma Spray Torch

2021 ◽  
Author(s):  
Rodion Zhukovskii ◽  
Christophe Chazelas ◽  
Vincent Rat ◽  
Armelle Vardelle ◽  
Ron Molz
Keyword(s):  
Thermodynamic Equilibrium ◽  
Plasma Spray ◽  
Plasma Torch ◽  
Gas Flow ◽  
Local Thermodynamic Equilibrium ◽  
Computational Domain ◽  
Dc Plasma ◽  
Arc Model ◽  
Anode Plasma ◽  
Two Temperature

Abstract Anode erosion is a common concern in dc plasma spray torches. It depends largely on the heat flux brought by the arc and the dimensions, residence time, and mode of the arc attachment to a given location on the anode wall. This paper compares anode arc attachment modes predicted by LTE (local thermodynamic equilibrium) and 2-T (two-temperature) arc models that include the electrodes in the computational domain. The analysis is based on a commercial cascaded-anode plasma torch operated at high current (500 A) and low gas flow rate (60 NLPM of argon). It shows that the LTE model predicted a constricted anode arc attachment that moves on the anode ring while the 2-T model predicted a diffuse and steady arc attachment. The comparison between the predicted and measured arc voltage indicated that the 2-T prediction is closer to the actual voltage. A post-mortem observation of a new anode ring on a plasma torch operated under the same conditions confirmed the diffuse arc attachment predicted by the 2-T arc model.

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